CircuitsArchive

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About

Mon, 01 Jan 0001 00:00:00 +0000

CircuitsArchive is a Web-based free content project to list Electronic Circuits.

An electronic circuit is an electrical circuit that also contains active electronic devices such as microprocessors, transistors or vacuum tubes.

Website History

CircuitsArchive was founded by Nicola Asuni in March 2008 as evolution of the Technick.net website. Technick.net website was previously called Nick Homepage, online since 1 March 1998.

DISCLAIMER

PLEASE BE AWARE THAT ANY INFORMATION YOU MAY FIND IN THIS WEBSITE MAY BE INACCURATE, MISLEADING OR DANGEROUS.

Audio

Mon, 01 Jan 0001 00:00:00 +0000

Batteries

Mon, 01 Jan 0001 00:00:00 +0000

Filters

Mon, 01 Jan 0001 00:00:00 +0000

Geiger Counters

Mon, 01 Jan 0001 00:00:00 +0000

Ham Radio

Mon, 01 Jan 0001 00:00:00 +0000

High Voltage

Mon, 01 Jan 0001 00:00:00 +0000

Infrared

Mon, 01 Jan 0001 00:00:00 +0000

LED

Mon, 01 Jan 0001 00:00:00 +0000

Meters

Mon, 01 Jan 0001 00:00:00 +0000

Motors

Mon, 01 Jan 0001 00:00:00 +0000

Oscillators

Mon, 01 Jan 0001 00:00:00 +0000

PC Power Supply

Mon, 01 Jan 0001 00:00:00 +0000

PIC

Mon, 01 Jan 0001 00:00:00 +0000

Repair

Mon, 01 Jan 0001 00:00:00 +0000

SmartCard

Mon, 01 Jan 0001 00:00:00 +0000

Solar

Mon, 01 Jan 0001 00:00:00 +0000

Telephone

Mon, 01 Jan 0001 00:00:00 +0000

Various

Mon, 01 Jan 0001 00:00:00 +0000

Notes on Filters

Sun, 01 Mar 1998 00:00:00 +0000

General Notes

Symbols

pi represent the Greek P value (3.14159265…)
Fc represent the cutting frequency.
Sqrt[n] represent the Square Root of number n (eg. Sqrt[2]=1.414213…)

Units of measure

Resistance [Ohm]
Capacity [F]
Frequency [Hz]

Filter’s Magnitude Response

	Highpass	Bandpass	Bandstop
GAIN
	FREQUENCY

N-Order Filter

To make a n-order filter (where n>2) you have to connect first order and second order filters in cascade (series).If n is even (4,6,8,10,…) use n/2 second order filters.If n is odd (3,5,7,9,…) use 1 first order filter and (n-1)/2 second order filters.

First Order High-Pass

Mon, 01 Jan 0001 00:00:00 +0000

First Order Low-Pass

Mon, 01 Jan 0001 00:00:00 +0000

Second Order Band-Pass

Mon, 01 Jan 0001 00:00:00 +0000

Second Order High-Pass

Mon, 01 Jan 0001 00:00:00 +0000

Second Order Low-Pass

Mon, 01 Jan 0001 00:00:00 +0000

Second Order Notch

Mon, 01 Jan 0001 00:00:00 +0000

12 Volt Toilet Tank Refiller

Sun, 01 Mar 1998 00:00:00 +0000

The 12V pump on the side of the cistern

The rev 1 circuit in action

The rev 2 circuit board

The schematic'

Introduction

A flushing toilet is something that most city dwellers take for granted, but it can be a luxury for those who live away from utility water and electricity. This circuit provides on-off pump switching for a small 12 Volt pump that is used to fill a toilet tank from an external rain water collection cistern. The 12 Volt power comes from a small solar power system. The cistern is located at ground level, so the pump is required to move the water up to the toilet tank.

13 Color LED Rainbow

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

Only a few years ago, the choice of LEDs was limited to IR, red, yellow, and green. The LED manufacturers have been busy extending the spectrum, and filling in the gaps. The latest generation of organic LEDs (OLEDs) has added some dazzling new colors to the spectrum. This circuit uses a set of 13 differently colored LEDs to generate a full color spectrum. The photo does not fully represent the colors generated due to camera limitations. The real-world display is very eye-catching. If you want to “trick out” your PC, this circuit is for you. Forget about those boring blue PC light displays.

200W ATX PC Power Supply

Sun, 01 Mar 1998 00:00:00 +0000

Here I bring you wiring diagram of PCs power supply of DTK company. This power supply has ATX design and 200W performance. I was drawed diagram, when I repaired this power supply.

This power supply circuit uses chip TL494. Similar circuit is used in the most power supplies with output power about 200W.Device use push-pull transistor circuit with regulation of output voltage.

Line voltage goes through input filter circuit (C1, R1, T1, C4, T5) to the bridge rectifier. When voltage is switched from 230V to 115V, then rectifier works like a doubler. Varistors Z1 and Z2 have overvoltage protect function on the line input. Thermistor NTCR1 limits input current until capacitors C5 and C6 are charged. R2 and R3 are only for discharge capacitors after disconnecting power supply. When power supply is connected to the line voltage, then at first are charged capacitors C5 and C6 together for about 300V. Then take a run secondary power supply controlled by transistor Q12 and on his output will be voltage. Behind the voltage regulator IC3 will be voltage 5V, which goes in to the motherboard and it is necessary for turn-on logic and for “Wake on something” functions. Next unstabilized voltage goes through diode D30 to the main control chip IC1 and control transistors Q3 and Q4. When main power supply is running, then this voltage goes from +12V output through diode D.

A very STABLE 40khz generator

Sun, 01 Mar 1998 00:00:00 +0000

A circuit that I have used before is based on the CD4060 (14stage binary counter) and a 640Khz ceramic resonator. The CD4060 is basically an oscillator and a ripple counter to divide the 640khz down to something more usable.

Here is the pinout of the CD4060 (frequencies are assuming a 640khz input signal into pins 10/11/12 - circuit shown below):

                +-\/-+ 
       160hz  1 |    | 16  Vcc 
        80hz  2 |    | 15  625hz 
        40hz  3 |    | 14  2.5khz 
       10khz  4 |    | 13  125hz 
       20khz  5 |    | 12  \ 
        5khz  6 |    | 11   >---- see sub-circuit below 
       40khz  7 |    | 10  / 
         GND  8 |    |  9  NC 
                +----+

Sub-circuit for a 640khz ceramic resonator:

AA Battery Solar Charger

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This almost trivial circuit may be used to charge a pair of AA or AAA sized rechargeable battery cells from sunlight. The circuit has been used to keep a Palm Pilot and walkman radio running perpetually. This is an unregulated charger, proper charging is achieved by placing the unit in the sun for a known amount of time, this time varies according to the battery type.

AT PC Power Supply 1

Sun, 01 Mar 1998 00:00:00 +0000

Sources

Zsolt Sebestyen (pro2sebi[at]interware.hu)

Category:PC Power Supply

AT PC Power Supply 2

Sun, 01 Mar 1998 00:00:00 +0000

Sources

Zsolt Sebestyen (pro2sebi[at]interware.hu)

Category:PC Power Supply

AT PC Power Supply 3

Sun, 01 Mar 1998 00:00:00 +0000

Sources

Zsolt Sebestyen (pro2sebi[at]interware.hu)

Category:PC Power Supply

AT PC Power Supply 4

Sun, 01 Mar 1998 00:00:00 +0000

Sources

Zsolt Sebestyen (pro2sebi[at]interware.hu)

Category:PC Power Supply

AT PC Power Supply 5

Sun, 01 Mar 1998 00:00:00 +0000

Other values not indicated on schematic are:

R31 = 1 KOhm
R35 = 100 KOhm
R40 = 3.3 KOhm
R34 = 100 KOhm
R36 = 3.3 KOhm
R39 = 8.2 KOhm
R43 = 2.2 KOhm
R25 = 1 KOhm
R20 = 3.9 KOhm
R37 = 2.2 KOhm
R55 = 56 KOhm
R26 = 2.2 KOhm
R27 = 2.2 KOhm
R28 = 1.2 KOhm
R29 = 910 Ohm
R13 = 4.2 KOhm
R24 = 2.2 KOhm
R11 = 3.3 KOhm
R12 = 3.3 KOhm
R41 = 510 Ohm
VR1 = 2 KOhm
C18 = 4.7 uF
C20 = 10 uF
C12 = 2.2 uF
C10 = 1 uF
C13 = 4.7 uF

Sources

Zsolt Sebestyen (pro2sebi[at]interware.hu)

Category:PC Power Supply

Battery Low Voltage Beeper

Sun, 01 Mar 1998 00:00:00 +0000

Photo of the assembled circuit

Schematic

Introduction

This circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn of the impending loss of power. The circuit was designed for monitoring solar systems, but it could also be useful for automotive and other 12V applications.

Big-E Stereo Parabolic Microphone

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This device is a stereo amplifier for a high sensitivity stereo parabolic microphone. It can be used for listening to distant sounds. Typical parabolic microphones are monophonic, this unit has a stereo audio path that helps produce more realistic sounding audio. The Big-E can be used with headphones or as an audio source for a stereo tape recorder or a PC sound card. This circuit also works nicely as a remote stereo audio receiver for accompanying a video surveillance system. It is capable of operating on the end of a four wire shielded cable that is more than 100 feet long. For remote operation, a set of inexpensive amplified PC speakers can be connected to the outputs for monitoring the sound.

CDV700 Geiger Counter Probe Rebuilding

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This article describes the process of rebuilding a geiger counter probe from the Victoreen CDV700 geiger counter. The process of converting the hard-wired probe to a probe with a pluggable BNC connector is also described. The probe from the model CDV700-6B is similar, but not identical, the socket is easier to access on that model.

Disassembled Geiger Counter Probe Assembly

Probe Reconstruction

The probe from my CDV700 geiger counter had a worn out probe wire, moving it would cause false clicks from the counter, or no readings at all. The remedy was to rebuild the probe assembly as follows:

Cheap 40KHz clock

Sun, 01 Mar 1998 00:00:00 +0000

Use a 40KHz Xtal and a 74C14 schmitt trigger:

              ________  <---------------- 2.2 M resistor 
          ___|  2M2   |___ 
          |  |________|   | 
          |               | 
          |               | 
          |     |\        | 
          |     | \       | 
          +-----|  O------+--------> Output 40KHz 
          |     | / 
          |     |/  gate 1 of 74C14 
          | 
          | 
        --+-- 
         XXX   40KHz Xtal 
        --+-- 
          | 
          | 
        ----- 
         --- 
          -

This circuit has worked for me in many applications. (it might be an idea to buffer the signal befor using it. (There are still 5 unused gates in the ‘C14.. :-)

Constant Temperature Circuit

Sun, 01 Mar 1998 00:00:00 +0000

This circuit is great for stabilizing VFOs and other sensitive electronic circuits.

Temperature Controller in PostScript format

Description of the temperature controller

Sources

Forrest Cook http://www.solorb.com/elect/

Category:Various

Count Accumulator for Radiation Levels (CARL)

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

The CARL device is an add-on numerical counter that plugs into the headphone jack of 1960s vintage geiger counters such as the Victoreen CDV700 and CDV700-6B. It should also work with the Lionel ENI/LENi counters, and any other geiger counter that has a headphone output pulse greater than -5V. Vintage 1960s era geiger counters don’t actually count, they use an analog meter with an integrator circuit to give short-term averaged readings of radiation detections (clicks). The CARL circuit keeps track of the total number of clicks for a period of either 60 or 600 seconds (1 or 10 minutes). This provides a way to get a statistically repeatable count of low-level radiation from sources such as radon gas, rock samples, and background radiation. The CARL circuit allows for the measurement and comparison of radioactive sources that are of levels that don’t produce measurable readings on analog geiger counter meters. As a collector of rocks, my interest in making this device was to find all of the radioactive minerals in my collection, and remove them from my living space. I found quite a few rocks that registered above the background level, fortunately, I did not find anything super-hot. I have also used the meter to compare background levels in various geographical locations.

Decoding IR Remote Controls

Sun, 01 Mar 1998 00:00:00 +0000

The origin of this posting was the question what to do with an old TV. I suggested to use the infrared remote control as an input keyboard for a microcontroller board and mentioned a piece of code I had written for the 8052 microcontroller. I was asked by some people to share my information about remote controls, so here it is:

There are at least two international standards which are used by remote controls to encode the commands, the RC5 and RECS 80 code. The RECS 80 code uses pulse length modulation. Each bit to be transmitted is encoded by a high level of the duration T followed by a low level of duration 2T representing a logical ‘0’ or 3T representing a logical ‘1’.

Detecting a telephone RING 1

Sun, 01 Mar 1998 00:00:00 +0000

Detector Schematic

                          +-------------------------- + DC power supply 
                          | 
                          ^ 
                         CR2 
                          | 
  O---C1--+--R3---+--CR3>-+-------+-------+-----> ring det logic 
                  |       |       |       | 
  phone           R2      ^       C2      R1 
  line            |      CR1      |       | 
                  |       |       |       | 
  O---------------+-------+-------+-------+----- GND 
    
  C1              .1 uf 
  CR1,CR2,CR3     1N914 
  C2              10 uF 
  R1              100K 
  R2              10K 
  R3              100K

Mostly, there is only DC or small signal AC (audio) on the phone line. C1 blocks the DC, and the R3-R2 voltage divider prevents the low level AC from having any effect.

Detecting a telephone RING 2

Sun, 01 Mar 1998 00:00:00 +0000

My computer is in the basement and this device tells me if the phone line is in use. I have inserted a N/O switch in the battery connection so that the batteries will last longer as sometime my sons spend a lot of time on the phone. Prior to using my modem I press the switch to find out if the line is busy.

                           2N3906         33K          2N3904 
          2.2 meg            /----------/\/\/\---+      /------+ 
                           |/                    |    |/       |    *** 
  Tip o--/\/\/-----+-------|   PNP               +----|  NPN   \    220 
                   \       |\                         | \      / 
                   / 330K    |                           |     \ 
                   \         |             +-------------+     | 
  Ring             |         |             |             |    --- 
      o--/\/\/-----+         |             O -           |    / \ Led 
         2.2 meg   |         |        3V                 |     | 
                   |         |             O +           |     | 
                   |         |             |             |     | 
                   +-------------------------------------+     | 
                             |             |                   | 
                             +-------------+-------------------+

Sources

Aurel Boisvert

Category:Telephone

Detecting a telephone RING 3

Sun, 01 Mar 1998 00:00:00 +0000

This circuit requires a separate 5 volt supply. The branch of the circuit that contains C1, C2 & R5, R6 is only used as a passive tap. (So you can record the line when the rest of the circuit says ‘off hook’. It can be removed if not needed. If used, it can directly drive a microphone input to a portable recoreder.

The Output of Q2 completes a path to ground when the phone lines gives an off hook reading. This can drive a relay (for a tape recorder motor) or an LED. Be sure to include a current limiting resistor if an LED is used. Also, D1 may be ommited if a non-inductive load is used (Relays and incandescent (sp?) lamps are inductive)

Detecting a telephone RING 4

Sun, 01 Mar 1998 00:00:00 +0000

The transistor is a PNP Motorola 3638 with hFE of around 100 (probably doesn’t matter). Also, you could use this with different supply voltages if you change the 220k resistor.

Also, in case anybody’s interested, I found the on-hook open-circuit voltage of my phone line to be 48.7V, and the short circuit current to be 72.8mA. This leads to the conclusion that the line has a resistance of about 670 ohms. There have been a few calls recently in sci.electronics for phone in use circuits (ie a circuit that lights a LED when an extension phone is off hook).

Digital Led Chaser

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit uses digital circuits such as a demultiplexer and a binary counter to create patterns of “moving” led lights. This basic circuit is really cool when used in the dark or to light up a sign of some sort, as it creates a cool pattern that catches the eye.

Specifications

Operating voltage: 5v Digital technology: TTL

Theory

The main part of the circuit is the demultiplexer 74ls138, we are going to connect the least significant bits of the output of the counter, that will select one of the pins of the demultiplexer as the output, lighting the led connected to it. The counter is wired only to count, and a clock pulse is needed to perform that function (the clock circuit is not included, but any will do, as long as it isn’t too noisy)

Digital/Standard Phone Line Tester

Sun, 01 Mar 1998 00:00:00 +0000

Radio Shack sells a similar device without the high current function. It detects one or two lines on an RJ-11 and tells you its polarity.

The schematic is:

      o---+--+ 
              |          | 
              \          | 
      Line 1  /680      \ / red/green LED 
              \ .5W     --- 
              |          | 
      o---+--+

The circuit for Line 2 is identical. Note that each red/green LED comes standard as reverse wired (red LED “forward”, green LED “reversed).

Based on the above, I think an appropriate modification to include a high current indicator would be: (I’ve tested it)

Expanded Scale Battery Volt Meter

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit is used to measure the voltage on a 12V (nominal) lead acid rechargeable battery system. It was specifically designed for use in solar powered systems, but is general enough that it can be used for automotive or other 12V systems. Lead acid batteries normally spend their working lifetime in the voltage range of 11-15 Volts. This meter circuit was designed to show the voltage range of 10-15V on an analog meter movement, it can be used to show the battery charge state from empty to full.

Filter Akerberg-Mossberg (AM) Second Order Bandpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Akerberg-Mossberg (AM) Second Order Highpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Akerberg-Mossberg (AM) Second Order Lowpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Akerberg-Mossberg (AM) Second Order Notch inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter Bach Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Berka-Herpy (BH) Second Order Bandpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Berka-Herpy (BH) Second Order Highpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Berka-Herpy (BH) Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Berka-Herpy (BH) Second Order Notch non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter Deliyannis Second Order Bandpass I inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Deliyannis Second Order Bandpass II inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter First Order Highpass I non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

Butterworth

 R1 = 1 / (2 · pi · Fc · C1)

See also: Notes on Filters

Category:First Order Highpass Filters

Filter First Order Highpass II non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:First Order Highpass Filters

Filter First Order Highpass III inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:First Order Highpass Filters

Filter First Order Highpass IV inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:First Order Highpass Filters

Filter First Order Lowpass I non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

Butterworth

 C1 = 1 / (2 · pi · Fc · R1)

See also: Notes on Filters

Category:First Order Lowpass Filters

Filter First Order Lowpass II non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:First Order Lowpass Filters

Filter First Order Lowpass III inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:First Order Lowpass Filters

Filter Fliege Second Order Bandpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Fliege Second Order Highpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Fliege Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Fliege Second Order Notch non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter KHN (Inverting Input) Second Order Bandpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter KHN (Inverting Input) Second Order Highpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter KHN (Inverting Input) Second Order Lowpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter KHN (Inverting Input) Second Order Notch non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter KHN (Non-Inverting Input) Second Order Bandpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter KHN (Non-Inverting Input) Second Order Highpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter KHN (Non-Inverting Input) Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter KHN (Non-Inverting Input) Second Order Notch inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter Mikhael-Bhattacharyya (MB) Second Order Bandpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Mikhael-Bhattacharyya (MB) Second Order Highpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Mikhael-Bhattacharyya (MB) Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Mikhael-Bhattacharyya (MB) Second Order Notch non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter Multiple Feedback (MFB) Second Order Bandpass I inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Filters

Filter Multiple Feedback (MFB) Second Order Bandpass II inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Multiple Feedback (MFB) Second Order Highpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Multiple Feedback (MFB) Second Order Lowpass I inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Multiple Feedback (MFB) Second Order Lowpass II inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Sallen-Key (SK) Second Order Bandpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Sallen-Key (SK) Second Order Highpass I non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

Butterworth

    C1 = C2 = C 
    R1 = Sqrt[2] / (2 · pi · Fc · C) 
    R2 = R1 / 2 = (1 / (Sqrt[2]) / (2 · pi · Fc · C)

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Sallen-Key (SK) Second Order Highpass II non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Sallen-Key (SK) Second Order Lowpass I non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

Butterworth

 R1 = R2 = R 
 C2 = Sqrt[2] / (2 · pi · Fc · R) 
 C1 = C2 /2 = (1 / (Sqrt[2]) / (2 · pi · Fc · R)

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Sallen-Key (SK) Second Order Lowpass II non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Sallen-Key (SK) Second Order Notch non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter Tow-Thomas (TT) Second Order Bandpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Tow-Thomas (TT) Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Twin-T Second Order Bandpass inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Bandpass Filters

Filter Twin-T Second Order Highpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Highpass Filters

Filter Twin-T Second Order Lowpass non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Lowpass Filters

Filter Twin-T Second Order Notch I non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Filter Twin-T Second Order Notch II non-inverting

Sun, 01 Mar 1998 00:00:00 +0000

See also: Notes on Filters

Category:Second Order Notch Filters

Geiger counter

Sun, 01 Mar 1998 00:00:00 +0000

A basic Geiger counter circuit

Geiger counters are available in all shapes and sizes, but they tend to be quite expensive to buy (typically a couple of hundred US dollars for a simple model, rising to a thousand dollars or more for a professional instrument). Building your own can be a very rewarding alternative.

The only bit that is unavoidably quite costly is the Geiger-Muller tube itself - expect to pay 50-100 US dollars. Roughly speaking, the more you pay, the larger the tube, and the better (more sensitive) the counter will be. Personally I wouldn’t bother with any tube smaller than an LND712 (ZP1400), unless I was on a very tight budget, or only interested in detecting relatively high levels of radiation. An LND712 will pick up small radioactive items such as watches & minerals quite easily. The GM tube is a specialist item, so unlikely to be in your standard electronics catalogue. However, many manufacturer-suppliers will accept individual one-off credit-card orders. I have bought tubes from LND Inc. in the US, and Alrad Instruments in the UK, for example.

Guitar Reverb Pedal Version 2

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This is my second-generation guitar reverb circuit. The output may be too high for a guitar amplifier input, try putting a 1K to 10K resistor between the output 2N3904 transistor’s emitter and the 1K/1uF junction to reduce the gain.

Specifications

Nominal battery voltage: 12V

Theory

Not finished The transformer is a standard “70 volt” audio line transformer that is often found on PA systems. The transformer adapts the dual op-amp output impedance to the reverb driver coil impedance. It also serves to isolate the ground on one side of the reverb coil from the op-amps. Without the transformer, one of the op-amp outputs may be shorted to ground at the reverb case. Some reverb tanks may not require the transformer, you may need to put a ground-isolated connector on the input.

Hands-Free Telephone

Sun, 01 Mar 1998 00:00:00 +0000

Transistor Q1 of the headset amplifier circuit amplifies the 30 mV signal, that would have gone to the earphones, to .5V, which sufficiently drives the stereo earphones. Capacitor C1 blocks any dc current from shorting back into the telephone base. Capacitor C2 provides the very important ac signal short around the amplifier. Capacitor C3 provides high-frequency rolloff characteristics and prevents the amplifier from oscillating. Capacitor C4 is a dc block to the 35-W impedance of the stereo earphones, and resistor R4 bleeds off any charge build up to prevent a popping sound when the stereo earphones are plugged into the mini-earphone jack J2. The headset amplifier has only about 2 Vdc across it. The microphone amplifier circuit is composed of transistors Q2 and Q3 in an inverted-Darlington configuration.

Hold function for Telephone

Sun, 01 Mar 1998 00:00:00 +0000

    +-------+------+      R1 = 2.2K 
    |       |      |      R2 = 1 K 
  -| SW     R      |      R3 = 47 ohms 
    |       1      |      SCR = 2N5064, TIC47, or MCR104 
    |       |      | 
    R      LED     |               Well, that's it, just remember that 
    2       |      |               the cathode of both the SCR and the 
    |       |      +- RING (Red)   LED are towards the bottom. 
    +------SCR 
    |       |      +- TIP (Green) 
    R       |      | 
    3       |      | 
    |       |      | 
    +-------+------+

Sources

figment[at]wam.umd.edu

Category:Telephone

Hot Rodding a CDV700 Geiger Counter

Sun, 01 Mar 1998 00:00:00 +0000

Solar Powered CDV700 with CARL box and yellow power LED. (not original meter)

Schematic of CDV700 modifications.

CDV700 wiring to rechargeable battery, battery jack and CARL counter box.

View of the CDV700 PC Board, note the plastic washers on the board mounting holes.

Introduction

This project involves making several modification to an early 1960s era Victoreen CDV700 or CDV600-6B geiger counter. These counters are available on E-Bay for around $50 to $100. The modifications use modern electronic parts to improve the counter’s stability, extend the run time, and add a solar recharging capability. Circuit modifications include:

HP48SX IR DECODER

Sun, 01 Mar 1998 00:00:00 +0000

INSTRUCTONS FOR THE HP48SX IR DECODER

 1) The circuit diagram is attacted to this message, as a printable  
 ASCII TTYpic. It should be printable on _any_ printer. 
 2) Construction and layout is not critical and any metohd should work. 
 I used Verowire self-fluxing wiring system. I also socketed all the IC's, 
 but that too is up to you! 
 3) De-coupling capacitors and power connections are not shown on the circuit 
 diagram. Place a 0.1uF ceramic capacitor across the power connections on each 
 IC. Also place a 10uF tantalum capacitor across the power connections close 
 to the IR transmitter. 
 4) The IR LED and IR phototransistor should be mounted on the front panel of 
 the unit. The LED goes on the Left, looking at it from outside. They must line 
 up with the ones on you HP48 for transmission to occur at all. The range of the 
 unit is about 2".  
 5) The IR LED and phototransistor are critical. I used ones available from 
 MAPLIN (see my earlier messages for the address), but the equivalents are: 
 Phototransistor Maplin YY66W (Infra Red Sensor) = TIL78 
 LED             Maplin YH70M (Infre-Red Emitter) = TIL38 
 6) The RS232 port links to the PC, not to the HP48 of course. 
 7) The circuit as given requires a +5V supply only. The MAX232 device (which 
 is expensive and hard to obtain) can be replaced by a 1488 (transmitter) 
 and 1489 (receiver) devices but then +/-12V are required for the 1488 
 8) Each section of multiple ic's is numbered. 'xx means 74lsxx. A total 
 list of ic's required is: 
 MAX232, 2*74ls393, 7425 (or 74ls25 if you can get one!), 74ls74, 74ls08, 74ls14 
 74ls04. 
 9) A list of symbols used is: (as some are non-standard to get them into 
 printable ascii) 
 -\/\/--    resistor 
 ! 
 \ 
 / 
 \    resistor 
 / 
 ! 
   
   !! 
 --!!-- capacitor 
   !! 
    !--! 
   +!  !+ 
  -!!  !!-   Quartz Crystal 
   +!  !+ 
    !--! 
 !/ 
 !     NPN transistor 
 !\! 
  - 
 \\ 
 >> 
 ! / 
 !/ 
 !\    IR phototransistor 
 ! \! 
  - 
  ! >> 
  V// 
 ---  IR LED 
  ! 
  !\ 
 -! >o-   NOT gate 
  !/ 
 -!\ 
  ! )-   AND gate 
 -!/ 
 -) 
  ) 
 -)--\ 
  )   >o-- NOR gate 
 -)--/ 
  ) 
 -) 
   +5                
   ---- 
    !                       ----------------------------- 
    !                       !                           ! 
    /                       !                 ----+     o  '74 
    \ 10k              '04  ! '04   '04   '08 /// ! --------- 
 \\ /        !\        !\   ! !\    !\            +-!D  S   ! 
 >> !--------! >o---+--! >o-+-! >o--! >o--!\        !      Q! 
 ! /         !/     !  !/     !/    !/    ! )-+     !       !o------+ 
 !/ IR       74ls14 ----------------------!/  !  +- !>  R   !       ! 
 !\  P/transistor                             !  !  ---------       ! 
 !_\!                                         !  !      o   +5      ! 
    !              ----------------------------  !      !  ----     ! 
    !              !                             !      !   !       ! 
   ---             !                             !      -----       ! 
   ///             !                             !                  ! 
            '393   !        '14                  !                  ! 
              ----------    !\                   !                  ! 
              !    R   ! +- ! >o-+     '25       !                  ! 
              !       A!-+  !/   +-----)         !                  ! 
              !        !               )         +---+              ! 
              !       B!---------------)--\    !\    !              ! 
          +---!>       !               )   >o--! >o--+              ! 
          !   !       C!---------------)--/    !/                   ! 
          !   !        !               )       '14                  ! 
          !   !       D!---------------)                            ! 
          !    ---------                                            ! 
          +-----------------------------------------------------+   ! 
                                                '393     '393   !   ! 
                 2.45MHz                       !----!   !----!  !   ! 
         '04     !--!       '04         '04    !   A!   !   A!  !   ! 
         !\     +!  !+      !\          !\     !   B!   !   B!--+   ! 
     ----! >o-+-!!  !!--+---! >o-----!--! >o---!>  C! +-!>  C!  !   ! 
     !   !/   ! +!  !+  !   !/       !  !/     !R  D!-+ !R  D!  !   ! 
     !        !  !--!   !            !         !----!   !----!  !   ! 
     !  1k    !         !  1k        !          !        !      !   ! 
     -/\/\----+  2n2    --/\/\-------!         ---      ---     !   ! 
     !           ! !                 !         ///      ///     !   ! 
     ------------! !-----------------+                          !   ! 
                 ! !                                            !   ! 
    +5                                                          !   ! 
   ----     !!        !! 4*22u                                  !   ! 
    !     +-!!-+    +-!!-+                                      !   ! 
    !     ! !! !    ! !! !                                      !   ! 
    !     !    !    !    !                                      !   ! 
    !    -------------------                                    !   ! 
    !    !  C1       C2    !  +---------------------------------)---+      
    +----!Vcc              !  !                                 ! 
   ---   !                 !  !                                 !  +5 
   ---+  !                 !  !                                 ! ---- 
    +----!+10v             !  !                                 !  !  >> 
         !                 !  !   +-----------------------------+  V // 
  PC     !                 !  !   !    '393                       --- 
 RS232   !                 !  !   !   !----!                       ! IR 
   >-----!TxO1         TxI1!--+   !   !   A!              +-/\/\---+ LED 
  Tx     !                 !      !   !   B!       2N3904 ! 56R 
         !TxO2         TxI2!      +---!>  C!            !/ 
         !                 !  +-------!R  D!----/\/\----! 
   >-----!RxI1         RxO1!--+       !----!    1k2     !\! 
  Rx     !                 !                            - ! 
         !RxI2         RxO2!                              ! 
         !                 !                             --- 
   >--+  !  -10V     Gnd   !                             /// 
  Sg  !  ------------------- 
      !       !  !!  ! 
      !       +--!!--+ 
      !          !!  ! 
     ---          +  ! 
     ///             ! 
                    --- 
                    /// 

 ------------------------------------------ 
 ------HP IR FORMAT BELOW------------------ 
 ------------------------------------------ 
 Taken from ioguide.doc, ftp from 
 ftp hpcvbbs.cv.hp.com, dir pub 
 The IR port allows half-duplex communication between  systems  at 
 2400  baud  using  pulses  of  infrared  light  instead of wires. 
 Full-duplex is not used due to the need to suppress  reflections. 
 The  format for IR transmission is similar to serial transmission 
 except that a pulse of infrared light of 52 Ns duration (nominal) 
 is used to transmit a zero-bit.  The absence of a pulse indicates 
 a one-bit or  idle  condition.   Note  that  if  the  pulses  are 
 stretched out to fill a bit time this becomes very similar to the 
 serial signal.

Source

ARD[at]siva.bris.ac.uk

Category:InfraRed

Infra Red Remote Transponder

Sun, 01 Mar 1998 00:00:00 +0000

Remote-transponder, which lets send signals from a small receiver into closed (opaque door) cabinets, and around corners, etc. Anyways, the main problem is just stray environmental noise with any slowly changing amplitude modulated IR signal (lots of 60 Hz noise, and sunlight noise). Most IR remotes work around a 40KHz carrier, so that they can just pulse this digitally, and just bandpass filter it at the receiving end. This boosts the range of unfocused IR remotes to tens of feet (around 20-30 feet). Adding two IR LEDs helps a lot, by sending out more IR signals.

Infrared Remote Control

Sun, 01 Mar 1998 00:00:00 +0000

A simple one-channel remote control. It will trigger a relay upon press of a button.

Parts List

Component	Value	Qty
Resistor [R1]	11K, ¼W	01
Resistor [R2]	1M, ¼W	01
Resistor [R3]	1K, ¼W	01
Resistor [R4, R5]	100K, ¼W	02
Potentiometer [R6]	50K	01
Capacitor [C1, C2]	0.01uF, 16V	02
Capacitor [C3]	100pF, 16V	01
Capacitor [C4]	0.047uF, 16V	01
Capacitor [C5]	0.1uF, 16V	01
Capacitor [C6]	3.3uF, 16V	01
Capacitor [C7]	1.5uF, 16V	01
Transistor [Q1]	2N2222	01
Transistor [Q2]	2N2907	01
Transistor [Q3]	NPN Phototransistor	01
Diode [D1]	1N914	01
IC [IC1]	LM308	01
IC [IC2]	567	01
LED [LED1]	Infrared LED	01
Relay	6V Relay	01
Switch [S1]	SPST Push Button	01
Battery [B1]	3V	1

Category:InfraRed

Infrared Remote Control Tester

Sun, 01 Mar 1998 00:00:00 +0000

Using a battery, a phototransistor and a visible-light LED, this simple circuit is a go/no go tester for IR remote control devices. The illumination of the LED indicates that Q1 is being modulated by IR energy.

Category:InfraRed

Infrared Remote Controller

Sun, 01 Mar 1998 00:00:00 +0000

The transmitter is built around two CMOS 555 timer ICs (TLC 555s). The transmitter generates a modulated 35-kHz IR signal. The 35-kHz carrier frequency is generated by IC2, and the 1 500-Hz modulating signal is generated by IC1. The output of IC2 drives LED1 through resistor R5; that LED provides visual indication that the transmitter is working. In addition, IC2 drives transistor Q1, which drives the two infrared LEDs (LED 2 and LED 3).

Infrared Transmitter / Detector

Sun, 01 Mar 1998 00:00:00 +0000

This circuits consist of two parts, the first part will transmit a signal upon press of a button, and the second part will detect that signal and trigger a relay…kinda like a simple remote control…

Category:InfraRed

IR Opto Detector

Sun, 01 Mar 1998 00:00:00 +0000

  This circuit converts infrared light into sound. 
  Modulated IR light, like that from remote controls, 
  IR received by the phototransistor and is amplified by 
  the LM386 IC. The IC in turn drives a small 8 Ohm 
  speaker. Unmodulated IR light, like that from an 
  incadescent light bulb, produce no sound so the 
  phototransistor also turns on an LED indicating the 
  presence of IR light. 
                        _________________ 
                        [IR Photo Trans.] 
  9Vdc----[20K RES]--+--[emit       coll]--+--[20K RES]----Gnd 
                     |  [____ base______]  | 
                     |                     +---------------------+ 
                     +--[10K Ohm Pot]--Gnd                       | 
                               ^                                 | 
      +------------------------+                                 | 
      |         LM386                                            | 
      |       +---u---+                                          | 
      |     nc|1     8|nc                                        | 
      +-------|2     7|nc                                        | 
           Gnd|3     6|9Vdc                                      | 
           Gnd|4     5|-----[+100uF-]--[8 Ohm Skeaker]--Gnd      | 
              +-------+                                          | 
                        +----------------------------------------+ 
                        | 
               [       base       ] 
        +------[emit          coll]-----[270 Ohm]---9Vdc 
        |      [Gen Pur NPN trans.] 
        | 
        +------[LED  |>| ]----Gnd 
 
  NOTES: 
  - All of the parts for this circuit are available from your 
    local Radio Shack for a few dollars. RS also has a great 
    little case for the project (# 270-294), but you better 
    build it small. 
  - My prototype used the phototransistor from the index sensor 
    of a junked floppy disk drive. Make sure you get the 
    transistor and not the IR LED, they look very simular. 
  - The transistor driving the LED can be any general purpose 
    NPN device. 2N2222 and 2N3904 are a couple of common parts 
    that will work. 
  - The LM386 amplifies the incomming signal by about 20 times. 
    The potentiometer adjusts the level of the signal feeding 
    the amplifier. Adjust the pot until amplifier starts to feed 
    back and then back it off a little. See the data sheet for 
    the LM386 for details about increasing the gain. 
  - This circuit was designed as a quick, simple tester to check 
    IR remote controls and as such was designed to use as few 
    parts and cost as little as possible. The design could be 
    improved for audio fidelity, sensitivity and gain. I'd love 
    to see any improvements you make.

Sources

John R. Schuch schuch[at]phx.mcd.mot.com

Category:InfraRed

IR Remote Extender

Sun, 01 Mar 1998 00:00:00 +0000

This circuit can be used to operate a VCR or CD player from another room. It’s really an infrared signal repeater. The signal from the remote is received and then retransmitted over wires to an infrared LED. The beam from the LED is then picked up by the receiving window on the VCR or CD player.

The visible light LED (LED1) in series with the IR unit (LED2) is used to indicate that the transmitted signal has been detected. The 100-kW trimmer potentiometer (R1) adjusts the repeater’s sensitivity. The resistor that is usually found in series with the LEDs is omitted, because the voltage reading is about 1.0 Vdc as a result of the voltage drop across the lines.

IR slotted switch sensor

Sun, 01 Mar 1998 00:00:00 +0000

There is a type of detector known as a “slotted switch” that consists of a phototransistor/LED pair mounted on a solid frame with a small air gap between the two elements. A typical circuit might be:

                o +5v     o +5v 
                |         | 
                |         | 
                \         \ 
     220 ohms   /         / 4.7K 
                \         \ 
                /         / 
                |         | 
                |         +-------> Vout 
               _|_        / 
               \ /      |/ 
              -----     |\ NPN 
                |         \ 
                |          | 
                |          | 
                |          | 
               GND        GND 
                 | air gap | 
```  

When the air gap is unobstructed, the transistor saturates, pulling Vout to ground; when the gap is blocked, the transistor cuts off and Vout is +5 volts.

Sources
-------

- Paul Hitchcock

[Category:InfraRed](/circuits/infrared)

IR Type Data Link

Sun, 01 Mar 1998 00:00:00 +0000

Category:InfraRed

Irda Adapter

Sun, 01 Mar 1998 00:00:00 +0000

This is a simple Irda adapter that can be used to connect pda’s , mobile phones and laptops etc to a desktop PC

Sources

spiralbrain[at]yahoo.com

Category:InfraRed

Irda Serial Receiver

Sun, 01 Mar 1998 00:00:00 +0000

This is a simple serial port Irda receiver.

Sources

spiralbrain[at]yahoo.com

Category:InfraRed

Isolated Telephone Interface

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit allows you to record audio from a telephone line into a tape recorder or computer soundcard. Most of the parts for this circuit can be scrounged from an old modem, with some work, it is possible to rewire the modem circuitry and use the old modem case. Note that some countries have laws that require the user of a phone recording device to notify the party on the other end of the line that they are being recorded.

Joystick electric scheme

Sun, 01 Mar 1998 00:00:00 +0000

Joystick electric scheme

Category:Various

LED Mood Light

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit makes a nice lamp that consumes little power, runs cool, and has an incredibly long lifetime. The lamp puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings.

Specifications

Operating Voltage: 12V DC
Operating Current: 80ma approx.

Theory

The current flows and the LEDs light. There are 4 series strings of LEDs in this circuit, the resistors limit the current through the LEDs and prevent them from burning up. The resistors were adjusted to get approximately 20ma through each string. Different LED colors will have different voltage drops and resulting current flows. These resistor values will work fine at 12V.

Lightning Activated Camera Shutter Trigger

Sun, 01 Mar 1998 00:00:00 +0000

This picture was taken using the circuit.

Description

This circuit is used to trigger a camera’s electronic shutter circuit when a flash of lightning is present. It has been suggested that this circuit would also work to photograph fireworks displays. The photodarlington should be set up to either look through the camera’s viewfinder or a small black tube that gives the same view as the camera’s lens. With an SLR camera, this circuit should only be used at night, daytime use will cause it to retrigger indefinitely because the viewfinder goes black then light when the photo is done, this restarts the detector. When using the circuit, be sure to stay away from sources of flickering light such as street lights and fluorescent lights, they will cause false triggering. It is normal for the circuit to activate constantly when in the presence of indoor lighting. I recommend testing the circuit by shining a flash light across the detector in a completely dark room. The original photodarlington transistor I used was a QT semiconductor model QT-L14R1. A similar part that is available from Digi-key is the Optek OP560C, part number 365-1073-ND. The VN10KM is an N channel mosfet transistor, a more common IRF520 would probably work here, but I have not tried it. The 4047 is a standard 4000 series CMOS one-shot, Digi-key sells it as part number CD4047BCN-ND. If you get any good photos using this circuit, I would love to see them.

Line voltage negative half-cycle trigged high voltage pulse generator

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit generates high voltage pulses from 230vac line voltage. The drive end’s swing comparator circuit is invented by the creator of this page. The work end is derived from stroboscope trig supply circuit. All line voltage using circuits are inherently dangerous, and this is particulary so. Do not build it.

Specifications and schematic

Input voltage 230vac 50/60Hz
Output voltage -25kV pulse (T=200uS)
Output peak current -0,4A
Output pulse energy 0,3J
Average output power 15W
Trig event control at 180…270 deg.of phase

Low Power LED Volt Meter

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This is a low power voltmeter circuit that can be used with alternative energy systems that run on 12 and 24 volt batteries. The voltmeter is an expanded scale type that indicates small voltage steps over the 10 to 16 volt range for 12 volt batteries and over the 22 to 32 volt range for 24 volt batteries. Power consumption can be as low as 14mw when operated from 12V and 160mw when operated from 24V. It is possible to set the meter to read equal steps across a variety of upper and lower voltages. The meter saves power by operating in a low duty-cycle blinking mode where the LED indicators are only on and consuming power briefly during a repeating 2 second cycle. The circuit may be switched to a high power mode where the active LED stays on at all times. Different colored LEDs may be used for the voltage level indicators, this allows the battery state to be read in the dark. With the new blue LEDs, it is possible to have a nice looking rainbow of colors using two each of red, amber, yellow, green, and blue LEDs. The circuit will also work with inexpensive and common red LEDs. If the circuit is to be used in sunlight, ultra-bright LEDs should be used, although even those may be hard to read without some kind of sun shield. Typical uses include the monitoring of portable battery operated systems and indoor wall mounted home power system charge indicators. The cost of the parts for the circuit is around $25.00 (US) and the parts are commonly available, except for the optional blue LEDs. If blue LEDS are used, expect to pay a premium for them, they cost several dollars each, compared to around 15 cents for the other colors. The blue LEDs do look nice in any case. The circuit may be built with either the CMOS ICM7555 timer or the more common bipolar 555 timer. The 7555 timer will provide much more efficient operation and should be used for systems with small batteries. The volt meter works nicely with the solar charge controller and low voltage disconnect circuits described in the home-brew section of Home Power #60 and #63.

Microprocessor RS-232 Reset

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit allows a remote microprocessor to be reset by a controlling host over a remote RS-232 or similar protocol serial line. With the use of a program loader on the remote host, a program may be downloaded and run. This allows a target processor to run different code in RAM, thus getting rid of the need to burn multiple EPROMs. The circuit is usually used for developing code on a target processor, but it can also be used for permanent applications where the target program lives on a host system’s disk. A program loader for the Z80 CPU is available below. The circuit has also been used with the Motorola 68HC11 EVB and the BUFFALO monitor program. See my Linux Cross Assemblers page for more info.

Midi Cable Optoinsulated

Sun, 01 Mar 1998 00:00:00 +0000

This circuit allows you to hook your Audio Board up to your synthesizer.

Notes

MIDI OUT connector must be connected with synthesizer MIDI IN port.
MIDI IN connector must be connected with synthesizer MIDI OUT port.

Source

Nicola Asuni

Category:MIDI

MIDI Drum

Sun, 01 Mar 1998 00:00:00 +0000

This circuit is a MIDI interface between drum pads and computer or hardware sequencer. Using this circuit you can hit pads with drumsticks and store the MIDI data in real time.

While this unit is much cheaper than commercial devices it does have some limitations:

It provides MIDI data which has to be sent to a drum/synthesiser or sound module.
The velocity byte is fixed at maximum volume and the drum selection and MIDI transmit channel are fixed at programming but can be edited afterwards in the sequencer software.

Circuit Description

MIDI to RS232 Interface

Sun, 01 Mar 1998 00:00:00 +0000

Description

This is a monodirectional MIDI to RS232 (serial) interface, it play only MIDI to personal PC “RS232”. The MIDI output connector indicated on the following picture dosen’t work because the buffer inside pic16f84 is too short.

Download the archive that contains circuit schema, description and programming files for PICS.

Components:

8 resistors 10k
4 resistors 220r
1 resistor 3k3
4 cond.Tantalie 1uF
4 cond.Ceramic 33pF
1 cond.Elett. 100uF
1 cond.Elett. 10uF
1 1n4148
2 PIC16F84A / 20 (20=max20mhZ)
1 7805
1 MAX232
1 6n136
1 connector 9pin type CANON male (rs232)
2 outlet female DIN180° (midi)
1 cable null-modem standard for PC connection (2x 9pin female):
- 2 - 3
- 3 - 2
- 5 - 5

pic16f84a connections:

1pic16F84A/20 2pic16F84A/20
PA0 OUT -> RS PA0 OUT -> MIDI
PA1 IN <- RS PA1 IN <- MIDI
PA2 DIRECT <-> PA2
PA3 DIRECT <-> PA3
PA4 DIRECT <-> PA4
PB0 DIRECT <-> PB0
PB1 DIRECT <-> PB1
PB2 DIRECT <-> PB2
PB3 DIRECT <-> PB3
PB4 DIRECT <-> PB4
PB5 DIRECT <-> PB5
PB6 DIRECT <-> PB6
PB7 DIRECT <-> PB7

Category:MIDI

Minimizing SUNs noise in IR reception

Sun, 01 Mar 1998 00:00:00 +0000

A ‘baffle’ is a perforated disk or disks spaced inside your ‘shade tube’. The idea is to trap all reflections, leaving only the light coming in on the exact axis of the tube to strike the IR Detector.

    __________________________________ 
    |        |        |        | 
  DET                                   <--- IR LIGHT 
    |        |        |        | 
    ---------------------------------- 
             ^Baff    ^Baff    ^Baff

Off-axis light, ’noise’, will be caught by the baffles and dissipated through reflection between the baffles. Paint the inside of your tube black … in fact, check into what paints/coatings are ‘black’ to IR wavelenghts. Just because a paint LOOKS black does not mean it won’t reflect IR.

Morse Code Beacon Keyer

Sun, 01 Mar 1998 00:00:00 +0000

This circuit sends morse code messages that are stored in an EPROM chip. The keyer can output either a one-shot message such as “CQ DX DE XXXX” if the start button is pushed, or it can run continuously by switching the free run switch on. The continuous mode is useful for making low power (QRP) beacons. Pressing the stop button interrupts the message. EPROMs other than the 2732 can be used if suitable changes are made to the circuit. For larger EPROMs, just ground the higher order address input lines on the EPROM chip, and wire the appropriate chip select pins for outputs enabled and chip selected.

Motorized Video Camera Mount

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This article describes a motorized, waterproof mount for a miniature video camera. If a suitable waterproof camera is used, this unit can be used outdoors.

Theory

The camera rotator circuit uses a 2716 EPROM to store a table of logic values that control the motor driver (H-bridge) circuit. The EPROM data is shown in the schematic. By using the EPROM, a large number of discrete gates are eliminated. The logic table is designed to allow the motor to turn clockwise until the clockwise limit sensor is activated. The same operation happens with counter clockwise rotation and the counter clockwise limit sensor. Inputs to the EPROM come from the limit sensors and the two control switch directions. Outputs go to the four H-bridge transistor gates. The control switch signals are buffered through the 7400 quad NAND gate, this allows for a long control wire. All of the input values are active in the low state. The H-bridge array consists of two N-channel MOSFETs and two P-channel MOSFETs. Diagonal pairs of transistors are turned on to move the motor one way or the other. If all of the transistors are off, the motor does not move. Note that the P channel transistors turn on with a 0 logic output level and the N channel transistors turn on with a 1 logic output level. There are several disallowed output states, if three or four transistors were to be turned on, the transistors would go up in smoke. Don’t do this. If the EPROM is programmed correctly, this should never happen. The voltage regulator produces 5 volts for running the logic ICs and the motor. A better H-bridge driver circuit (or IC) could be used if higher motor currents are needed, this one was sufficient, simple to build, and easy to find parts for. Note that a much simpler version of this circuit could be made by using a cross-wired center off DPDT direction switch and mechanical limit sensor switches in series with the motor power wires and with diodes across the switches. This circuit has fewer moving parts, and the sensors can fit into a smaller space than switches. The all solid state design should also last longer.

Music-On-Hold Box

Sun, 01 Mar 1998 00:00:00 +0000

U1, an LS3404 melody chip is activated when “hold” S1 is pressed, which causes SCR1 to conduct and hold the telephone line via T1, R1, and LED1. The voltage across R1 and LED1 is used to activate the melody chip. Q1 and Q2 form a restart circuit to keep the melody chip going during hold.

Category:Telephone

PC IR Remote Control

Sun, 01 Mar 1998 00:00:00 +0000

This page gives some information on a PC based IR remote control system I’ve developed for computer control of TV, video, satellite and hifi equipment etc.

I have used an IBM compatible, so the software here is for such a machine, however I guess that it is straightforward (perhaps easier) to implement this on another type of machine.

PC IR Remote Control Signals

IR remote control signals are modulated with a 40KHz carrier frequency, so for transmission or reception of the signal, the appropriate demodulation/modulation must take place.

Phone in use indicator 1

Sun, 01 Mar 1998 00:00:00 +0000

Runs off 9V battery, Plugs into phone jack, Lights an LED when any phone on the line is off-hook.

Phone Information

Measuring the voltage across the telephone line shows (typical numbers):

On Hook: 40 to 50 VDC
Off Hook: 4 to 6 VDC
Ringing: 100 VAC

The “standard” impedence of a telephone, when off-hook, is 680 ohms. Hanging a 680 ohm resistor across the telephone line will drop the voltage from 48V to about 5V, causing the line to go “active”. This is how HOLD switches work. This probably means that it is bad to load down the phone line when the phone is off hook. I wouldn’t want to hang less than a 100Kohm load across it. Should probably measure this, and see how it affects the on-hook voltage.

Phone in use indicator 2

Sun, 01 Mar 1998 00:00:00 +0000

LED will start blinking if a phone is in use.

Category:Telephone

Phone in use indicator 3

Sun, 01 Mar 1998 00:00:00 +0000

    ------+-------------+-------------+----------- pos (tip) 
          |             |             | 
          |             |            --- 
          |             |         R3 | | 
          |             |            | | 
          |             |            --- 
 zener    |             |             | 
      /------/         ---          ----- 
        /  \        R2 | |           \ / LED 
       ------          | |          ----- 
          |            ---            | 
          |             |             | 
          |     --------+----+     ---+ 
          |   |/             |   |/ 
          +---| npn1         +---| npn2 
          |   |\                 |\ 
         ---    -+                 -+ 
      R1 | |     |                  | 
         | |     |                  | 
         ---     |                  | 
          |      |                  | 
    ------+------+------------------+-------------- neg (ring)

Now here’s some logic that should work fine with the right zener and the right resistors and a couple of cheap npn’s 2n2222A’s or 2n3904’s (06’s?). If you get close to 25 volts with the new smart test boxes, a 20 volt Z may work fine. Choose R1 to limit current through Z and have enough left to turn on npn1 just enough to deprive npn2, choose R2 for that, and you will need to add a resistor R3 to protect the LED from overcurrent as needed, depending on the phone system you have!

Phone in use indicator 4

Sun, 01 Mar 1998 00:00:00 +0000

The circuit I built gives a visual indication at each extension when any extension is off-hook. It is line-powered, and the maximum number that can be used on our system is three. Since they all draw power at the same time to light the LEDs, any more indicators would cause an off-hook condition. Some changes could be made to reduce the current draw, to allow using more indicators, but the brightness of each led would suffer. The LEDs I used are tiny, but amazingly bright on just a couple milliamps. I picked them up from a surplus catalog, I can’t remember which one. If you were to use battery power for the circuit, you could use almost any number of indicators. I had use only for three, and I did not want to worry about replacing batteries. If I remember correctly, our pbx required a load of about 20 milliamps before the line failed to hang up. This circuit draws about 5 milliamps when off- hook, much less when on-hook. It senses the drop in line voltage from about 46 volts to 6 volts when an extension is picked up. The zener voltage should be well above the off-hook voltage of your system, and well below the on-hook voltage. The transistors are small high-voltage npn types I had on hand. The LED also flashes with the ring voltage. Putting a suitable MOV across the line is a good precaution to prevent lightning damage.

Phone in use indicator 5

Sun, 01 Mar 1998 00:00:00 +0000

  >>-----------------+------+---->> phone line 
                     |      | 
                     |      o 
                     |       / 
                     |      /   momentary switch 
                     |      | 
                     |      / 
                     |      \   1200 Ohm 
                     |      / 
                   -----____| 
                    / \ 
                   /___\  SCR 
                     | 
                     / 
                     \  600 Ohm 
                     / 
                     |     ^^ 
                   -----  // 
                    / \  // 
                   /___\    LED 
                     | 
                     | 
  >>-----------------+--------->> phone line

Sources

Terri Barber barber[at]beowulf.ucsd.edu

Category:Telephone

Phone in use indicator 6

Sun, 01 Mar 1998 00:00:00 +0000

                       +----+-------------+-------+-------- +9VDC 
                       |    |             |       | 
                       |    |       |\    R5      R6 
                       |    +-------|-\   |       | 
                       |    |       |  >--+      LED1 
                       |    |    +--|+/   |       v 
                       ^    |    |  |/    |       | 
                      CR2   R4   |        |      C+ 
                       |    |    |  |\    |   | / 
  <+>--R1--+--R3--+----+--> | <--+--|-\   |   |/ 
           |      |    |    |       |  >--+-B-| 
  phone    |      |    |    +-------|+/       |\ 
  line     |      |    ^    |       |/        | \ 
          R2      C1  CR1  CR3                   E+ 
           |      |    |    v       U1       Q1   | 
           |      |    |    |                     | 
  <->------+------+----+----+---------------------+-------- GND 
   
  R1,R2           1 Meg 
  R3              10 K 
  R4              1 K 
  R5              4.7 K 
  R6              470 ohm 
  C1              .005 uF 
  CR1-3           1N914 diode 
  LED1            any old led 
  Q1              2N2222 or 2N3904 
  U1              LM339 quad comparator (be sure to connect power and ground) 
  --> <--         are connected (jump) 
  ^ or v          cathode of diode 
  +               connection 
  9VDC            any old 9VDC wall transformer works nicely

Circuit description

R1 and R2 form a voltage divider, insuring that the phone line sees a high impedance load and that high voltages (such as the ring voltage) are easily dissipated by the protective diodes (CR1 and CR2). Also (obviously) they serve to divide all incoming voltages by two. Capacitor C1 filters out some of the audio signals that might otherwise make the LED flicker with speech.

Phone in use indicator 7

Sun, 01 Mar 1998 00:00:00 +0000

LED will light up if a phone is in use.

Category:Telephone

Phone Line to Audio

Sun, 01 Mar 1998 00:00:00 +0000

This circuit uses an audio coupling transformer and a capacitor.

The primary windings add in series to 500 ohms. Instead of connecting them directly together, add a cap between them. It was something like 0.047 micro farads with a 600V rating. And the secondary which is 500 ohms runs into the control room mixer.

             Tip   >------------/ II 
                                / II /-------< 
        (primary winding 1)     / II / 
                                / II / 
                   >-----X------/ II / 
                         I        II / 
           0.047 uF      =        II / -----CT   (secondary winding) 
                         I        II / 
                  >------X------/ II /          Output Side to Mixer 
                                / II /                         
        (primary winding 2)     / II / 
                                / II /-------< 
          Ring    >-------------/ II 
``

Sources
-------

- tpappas\[at\]hamp.hampshire.edu

[Category:Telephone](/circuits/telephone)

Phone rang indicator light

Sun, 01 Mar 1998 00:00:00 +0000

This, will detect the ring signal, energize the relay which latches up, and the LED comes on and stays on till you push SW.

                                                  ____ 
  tip o--CC---RR----o-D<-------o-----o------>D----^  ^----o-----+ 
                    |          |     |             SW     |     | 
                    |          |     |                    |     | 
                   \-/         |-    R||                  B-    LED 
                    Z          C     L|| ............     A     | 
                    |          |+    Y||          __.__   T+    R 
                    |          |     |         +--o   o---+     | 
                    |          |     |         |                | 
  ring o------------o----------o-----o---------o----------------+ 
      
     CC=.47 uF 200 V. capacitor 
     RR= 3k (depends on relay) 
     D = 200V diode  ( > < direction od diodes) 
     Z = 12 zener 
     RLY= any small relay 
     SW= normally closed switch 
     K = relay's contacts 
     BAT= 9 V. battery 
     R = 500 ohm (for LED) 
     C = some (10) uF capacitor

Components are not critical. It should latch on first ring, if not reduce RR. If it took too long to deenergize, reduce the C.

Phone Recorder

Sun, 01 Mar 1998 00:00:00 +0000

This recorder can be connected to the telephone lines just about any place, and no external power source is needed. The tape recorder’s switch terminals are applied to a pair of transistors, connected as Darlingtons, that are used to turn the recorder on and off. When the telephone is off-hook there’s usually about 50 Vdc across the phone thats divided over R1, R2, and R4, so that Q1’s base is negative enough to keep the recorder off. Pick up the receiver, and the voltage drops to 5 V. That leaves not quite-enough voltage on Q1’s base to keep that transistor at cutoff, so the recorder begins. Remember to keep your recorder’s switch in the on position, and depending on how many people use the telephone, remember to rewind or change tapes occasionally!

Phone to audio interface (SSI202 input)

Sun, 01 Mar 1998 00:00:00 +0000

<You have to isolate the chip from the phone line, or you’ll have all kinds of problems.

                      .22 uf              10k pot 
                       400v    ||(-----------> 
  Phone line tip  o-----)(----)||(           <---o to SSI202 input 
                              )||(           > 
  Phone line ring o-----------)||(-----------o---o ground

The transformer is a 600-ohm to 600-ohm line transformer. I use the circuit as-is, and works fine. Doesn’t take the phone off hook, you’ll need to add some circuitry for that. To set the pot, turn it down all the way, (for minimum audio into the decoder) then hold down a tone on the phone while you slowly advance the pot up until the VALID DIGIT line changes on the chip. Then advance the pot a little past that point. That should do it.

PIC Programmer

Sun, 01 Mar 1998 00:00:00 +0000

PICALL 3.1

Schematic

PCB

P16PRO

Description

As you can see, only a few standard elements are used and the hardware is very simple to build. So here are only a few words about hardware. Supply voltage can be either AC or DC. Voltage Vdd must be between 4.5 and 5.5 V. For this purpose integrated stabiliser 78L05 (Vdd=5V) is used. It has current limitation (protection) 100 mA and with this feature protects inserted PIC from damage in case something is wrong connected. Programming voltage 13V is provided with 78L08, which has pin 2 connected to Vdd (not to the ground) and on his output there is a voltage 5+8=13V. Between PC and PIC (textool) there is a one IC 74LS05 (it can be used 74LS06 or 74LS07 too - you can setup this in P16PRO). Five open collector inverters are used for turning on/off programming voltage and Vdd and for transferring data between PC and PIC. Transistors T1 and T2 are used as the switches for turning on/off supply voltage Vdd and programming voltage Vpp. LED D1 and D2 are for indication in which state the programmer is (ready the green LED lights, programming - red LED lights) On teh picture below you can see suggestion for one-sided PCB, which can be easily made by yourself. Connection between P16PRO hardware and PC can not be longer than two meters. If you have problems by programming (Programming Failure) and you have a new 486 or pentium motherboard with LTP port on motherboard, then you must connect an additional ceramic capacitor (330 to 470 pF) between ground and pin RB7 on TEXTOOL or you can add additional pull-up resistor (4k7) to ACK line and +5V.

PIC Programmer 12 parts

Sun, 01 Mar 1998 00:00:00 +0000

PIC Programmer MkV is designed to get you into PIC Programming for just a few dollars. It uses just 12 components. Most of them will be in your “junk-box” and the PC board is a small piece of matrix board. It’s the cheapest way to get started. As well as PIC PROGRAMMER MkV you will need these 4 things:

A desk-top computer with DE-9 serial port. (This programmer will not work on a lap-top computer and may not work with Vista.)
A software program called IC-Prog 105C-a and some helpful notes to guide you with setting up your computer. (This project is not suitable for In-Circuit Programming. You need to remove the chip from the project you are creating and program it in the 18 pin socket on the programmer. Eight pin chips are fitted with pin 1 aligning with pin 1 of the socket.)
A PIC chip, either PIC12F629 or PIC16F628 and
A project using one of these micros.

This will get you into producing a MICROCONTROLLER PROJECT. We have concentrated on two PIC chips. An 8 pin and 18 pin chip. The 8 pin chip can be either PIC12F629 or PIC12F675 and the 18 pin chip is PIC16F628 or PIC16F675. The programmer will work with many other chips but we are concentrating on these two types to get you started. Not only is a microcontroller project simpler than using lots of discrete chips, but it can be cheaper and easier to modify and provide a greater range of features than lots of individual chips. On top of this you can produce a project that requires a program and this can be “locked” from prying eyes. This makes it saleable and you can protect your Intellectual Property - and make money. Talking Electronics has produced a range of simple projects and provides assistance to get you into programming and creating projects that you have only “dreamed of.” Getting into microcontroller programming will change your life. But before we go any further, let’s build the programmer:

PWM DC Motor Speed Control

Sun, 01 Mar 1998 00:00:00 +0000

Circuit Description

This is a circuit for controlling the speed of small DC motors, it works nicely as a speed controller for an HO or N gauge model railroad.

Theory

The left half of the 556 dual timer IC is used as a fixed frequency square wave oscillator. The oscillator signal is fed into the right half of the 556 which is configured as a variable pulse width one-shot monostable multivibrator (pulse stretcher). The output of the one-shot is a variable width square wave pulse, the pulse width is set with the speed control pot on the control voltage input. The variable width output pulse switches the IRF521 MOSFET transistor on and off. The MOSFET amplifies the current of this signal so that it is powerful enough to control a small DC motor. The 311 comparator is used to cut off the one-shot via the reset pin when the control voltage is below a certain threshold, the 311 is also controlled by the speed control pot. The cut off circuit is necessary because the 556 one-shot circuit will always put out a small pulse, even when the control voltage is at zero.

QRP Antenna Tuner

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit is for a QRP (low power) antenna tuner, a.k.a. a transmatch, for use in the short wave amateur radio bands from 3-30 Mhz. It allows a wide variety of antennas to be connected to a low power transmitter. When the circuit is properly tuned, the maximum transmitter power will be delivered to the antenna. It is used in conjunction with a standing wave ratio (SWR) meter. This is a fairly generic antenna tuner circuit.

Remote Solar LED light

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

I created this circuit in an attempt to make the simplest possible solar powered project. It would make for an excellent science fair project, and would also serve as a good introduction to solar powered circuitry. It may also have some practical uses, such as shedding some light into a dark part of your house. The idea is simple, the solar panel converts sunlight into a trickle of electricity. The electricity is used to run a white LED.

Repair L01.1E 5464

Sun, 01 Mar 1998 00:00:00 +0000

Philips 28PW5407/01 (L01.1E AA) Fix

TV Model: Philips 28PW5407/01
Chassis Model: L01.1E AA
Symptom: Random Excessive width / Pincushion.
Problem: Bad soldering of pin 1 of component 5464 (A2 - Line Deflection).
Solution: Resolder the bad pin.

Category:Repair

SCC3 20A 12V Solar Charge Controller

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

The SCC3 is a solar charge controller, it’s function is to regulate the power flowing from a photovoltaic panel into a rechargeable battery. It features easy setup with one potentiometer for the float voltage adjustment, an equalize function for periodic overcharging, and automatic temperature compensation for better battery charging over a wide range of temperatures. The design goals of this circuit were efficiency, simplicity, reliability, and the use of field replaceable parts. A medium power solar system can be built with the SCC3, a 12V solar panel that is rated from 100 milliamps to 20 amps, and a lead acid or other rechargeable battery that is rated from 500 milliamp hours to 400 amp hours of capacity. It is advisable to match the solar panel’s maximum current to the battery’s amp-hour rating (C), a typical battery charging current is C/20, so a 100 amp hour battery should have a solar panel rating of around 5 amps. Consult the battery manufacturer’s data sheets for the best rating.

Self Powered Solar Box Furnace

Sun, 01 Mar 1998 00:00:00 +0000

(Photo 1) Solar furnace mounted on an external door

(Figure 1) Expanded parts layout

(Photo 3) Warm air exits from the output port on the top

(Photo 2) The fan pushes cold air into the input port on the bottom.

(Figure 2) Schematic.

Introduction

This project involves the construction of a self contained solar box furnace (Photo 1). I assembled the prototype with materials that I had laying around my workshop. It is suitable for heating up a small room or a detached shed. I use the furnace to warm up my garage, it takes the chill out of a fairly large space when the weather is cold, but sunny. It is possible to scale this project up to any size, a larger version, or a set of them, could be used to add a lot of supplemental heat a house. At night, the solar furnace will lose some heat due to downward convection of cold air through the box. This convection can be reduced by bringing the input port up to the level of the output port with some right-angle duct pieces. A U shaped air passage will cause cold air to become trapped in the the bottom of the box at night.

Serial-driven IR remote controller

Sun, 01 Mar 1998 00:00:00 +0000

       1.  Overview 
            This paper describes a serial infrared transmitter (SIT)  capable 
       of  generating  the infrared codes used by most current equipment that 
       incorporates an infrared remote control.  It is operated by a computer 
       through  an  asynchronous  communications port.  Driver software for a 
       computer with such a port  can  use  the  SIT  to  issue  commands  to 
       remote-controlled  equipment, and can thus act as a universal infrared 
       remote control.  Putting the equipment under computer control presents 
       many possibilities besides direct use through a menu or command line. 
            The major limitation in application of the SIT  is  that  it  can 
       only produce one carrier frequency.  Since most current equipment uses 
       a 40 KHz carrier, this is not a serious  problem.   Also,  the  device 
       does  not record the output of remote controls.  The remote codes must 
       be analyzed by other means and saved in data files. 
            The SIT is intended to use an asynchronous  serial  bitstream  to 
       modulate  an  infrared carrier in the simplest manner possible.  It is 
       operated exclusively from a computer.  It has no keypad; commands  are 
       entered  at  the  computer keyboard, or selected with a mouse or other 
       input device.  The SIT is not programmable.  The codes used to control 
       the remote equipment are stored on the computer and sent to the SIT as 
       necessary. 
            Asynchronous communication is used for  several  reasons.   Asyn- 
       chronous  ports  are available for virtually all computers.  Since the 
       asynchronous port produces a precisely timed serial  bitstream,  there 
       is  no  need for circuitry on the SIT to do that.  Also, a single byte 
       written to the computer's serial port can be used to send several bits 
       to the SIT, while a parallel port used for direct output would require 
       that a byte be written for each bit to be sent.  If  the  serial  port 
       uses  a  UART  (serial transceiver chip) with an on-board FIFO buffer, 
       several bytes can be written to it at once (up to  16  for  the  16550 
       series of UARTs), further reducing the load on the computer, which may 
       have other functions. 
            The  major  problem  with  using   an   asynchronous   port   for 
       communication  is that the infrared codes used by common equipment are 
       not asynchronous.  They are usually self-clocking bitstreams  with  no 
       start  or  stop  bits,  often with variable bit timing.  Therefore, an 
       asynchronous port cannot directly produce the  required  codes.   How- 
       ever,  carrier transitions do occur at intervals set by a fixed clock, 
       so that the codes can be synthesized if the carrier can be switched on 
       and  off at the rate set by the clock.  Although each unit has its own 
       clock rate,  the  remote  receivers  are  highly  tolerant  of  timing 
       discrepancies, so the clock rates do not need to be matched exactly. 
            Because a UART produces a bitstream that includes start and  stop 
       bits  after  every word, it cannot directly send the codes even if its 
       clock rate is set to the same clock rate used by an  infrared  remote. 
       The  SIT  circumvents  this  problem by using the UART to send one-bit 
       words.  Every data bit sent by the UART is preceded by a start bit and 
       followed by a stop bit, so each data bit takes the same amount of time 
       to send.  By using the data bit to set the state of  the  carrier  for 
       three  serial  bit  periods (until the next data bit is received), the 
       SIT lets a stream of data bits control equal periods of carrier time. 
            The UARTs used by most computers can only be set to between  five 
       and eight data bits per word.  To simulate a one-bit UART, the UART is 
       set to seven data bits per word with one start bit and one  stop  bit, 
       for  a total of nine bit times per byte written to the UART.  The byte 
       written to the UART is arranged so that  it  actually  includes  three 
       data  bits,  with the other bits always set to one or zero to simulate 
       the other start and stop bits (depicted later).   From  here  on,  the 
       term  "data  bit" will refer to the bits that control the state of the 
       carrier, three of which are written to the UART  in  each  byte.   The 
       rate at which these data bits are sent, which determines the controll- 
       able unit of carrier time, is referred to as the SIT rate. 
            The data rate used by remotes is low enough,  and  the  tolerance 
       for  timing  errors  (afforded by the self-clocking protocols) is high 
       enough, that the asynchronous port can be set  to  a  relatively  low, 
       standard  Baud  rate  and still have fine enough timing granularity to 
       operate various remote devices.  A standard Baud rate also allows  the 
       SIT  to be used from an operating system like UNIX that does not allow 
       setting the Baud rate to nonstandard values without  modifications  to 
       the  serial  driver.   The  Baud rate is selected so that the SIT rate 
       (one-third the Baud rate) is an even  enough  multiple  of  the  clock 
       rates of all of the receivers of the equipment to be operated that the 
       waveforms produced are within their tolerance.   If  the  clock  rates 
       vary  widely, the Baud rate should be selected so that the SIT rate is 
       sufficient for the equipment with the highest clock rates.  This  will 
       probably  result  in  sufficiently  fine granularity to synthesize the 
       waveforms of the remotes with lower clock rates. 
       2.  Circuit Description 
            It is relatively easy to extract the data from the one-bit  asyn- 
       chronous  protocol so that it can be used for carrier modulation.  The 
       code for a data bit can have only two forms.  It will always have  one 
       rising  edge  and one falling edge.  The rising edge will occur at the 
       start of the start bit.  The falling edge will occur after the end  of 
       the  start  bit if the data bit is a one (because a one is transmitted 
       as a low voltage by an RS232 port), or at the end of the data  bit  if 
       the data bit is a zero.  The stop bit guarantees that even if the data 
       bit is a zero, there will be a period of low voltage between  the  end 
       of the data bit and the next start bit. 
            To convert each start bit/data bit/stop  bit  into  a  continuous 
       high  or  low  voltage,  the SIT starts a one-shot timer each time the 
       data line goes high.  The one-shot is set to  1.5  serial  bit  times. 
       When  the  one-shot  finishes,  whatever  value is on the data line is 
       latched.  The latched value is used to enable or disable  the  carrier 
       transmission.   Another timer ensures that if the last bit sent to the 
       SIT inadvertantly leaves the carrier on, it is eventually turned off. 
           ___________ 
        0 |        :  |_____ 
           _____   : 
        1 |     |__:_________ 
                   ^ Latch Time 
            The SIT is  implemented  in  CMOS  so  that  it  can  be  battery 
       operated.   The  carrier disable turns off both the carrier oscillator 
       and the infrared emitters so that the SIT will be completely quiescent 
       when  not being used.  The analog parts of the design avoid DC current 
       paths, resulting in a quiescent current consumption  of  approximately 
       0.5  uA.  This makes operation from a 9V battery practical without the 
       need for trickle charging from the data line or other schemes. 
            The input signal is conditioned by resistors and diodes to  limit 
       it  to  the  range  (0,+9V).   It is inverted and cleaned up by a NAND 
       gate.  This signal is fed to a  one-shot  made  from  two  NAND  gates 
       arranged  with  feedback  so  that even if the trigger ends before the 
       timing period ends (as it will if the data bit is a one), the one-shot 
       will  continue  timing.   The  cleaned  up signal is also put on the D 
       input of a flip-flop, in addition to driving an RC network which  will 
       reset  the  flip-flop  whenever  no  data is transmitted for a certain 
       period of time (so that the transmitter will not be left on). 
            The output of the one shot is the clock for the  flip-flop.   The 
       received  data  bits  appear  at  the  outputs of the flip-flop, which 
       enable or disable an oscillator made from a  Schmitt  NAND  gate,  and 
       reset  or  allow clocking of the flip-flop that the oscillator drives. 
       The flip-flop output drives a VMOS transistor which in turn drives two 
       high-power  infrared  emitting  diodes.   The  emitters can be mounted 
       parallel to each other to obtain greater range than a  single  emitter 
       would  have,  or  can be mounted with an angle between them for better 
       coverage of multiple pieces of equipment.  They are in series,  so  no 
       more  current is used for two than would be needed for one.  The flip- 
       flop ensures that a good square wave is produced for the carrier,  and 
       avoids  the  need  for  another inverter (package or transistor) which 
       would be necessary because disabling the  oscillator  forces  it  high 
       which  would  turn  on  the N-channel VMOS transistor.  The transistor 
       also drives a visible-red emitter to provide an operating indicator. 
       3.  Transmitter Construction 
      +9 O__|/|__ __|/|______          +9 O___|/|__,---\/\/\/--+    +       O +9 
            |\|  |  |\|     _|_               |\|  |      ^ R1 |--)|--+_____| 
       O Tx      |   _____  \c/      _____         |______|   _|_470uF|     | 
       |--\/\/\--+--|     \    ,----|     \        |   _____  \c/    _|_   _|_IR 
       |   47K  +9  | U1A  |O--|    | U1B  |O--|(--+--|     \     red\ /   \ / 
       |         O--|_____/    |  ,-|_____/  1uF  +9  | U1C  |O-+    ---~~ ---~~ 
       /10  ___________________|  |                O--|_____/   |     |     | 
       \K  |   |      |   ________|_____________________________|     |    _|_IR 
       /   |  _|_     |  |   _________________________                \    \ / 
       \   /  /_\    _|__|__|_      _____         ____|____           /    ---~~ 
       /   \   |    | D  > ~Q |  ,-|     \  80KHz|    R    |     470R \     | 
       |   /1M |    |        Q|--' | U1D  |O--+--|>      ~Q|--+       /     | 
      _|_  \   |----|R  U2A   |  ,-|_____/    |  |   U2B   |  |       \     \ 
      \c/  /   |    |         |  |            /  |        D|--'       |     / 
           |___|    |_S_______|  |        20K \  |__S___Q__|    ______| 27R \ 
           | 0.1uF    |   0.001uF|            /     |   |     ||      |  1W / 
            --|(--+  _|_  ,--)|--|_____       \    _|_   -----||<-+   |     \ 
                  |  \c/  |      |     |      /    \c/        ||__|   |     | 
                 _|_     _|_     | R2  V 20K  |          VN10KM  _|_  |_____| 
          Common \c/     \c/      ---\/\/\----'                  \c/ 
            U1 is a CD4093B quad Schmitt NAND package.  U2 is a CD4013B  dual 
       D  flip-flop  package.   All  diodes  are 1N914 or equivalent.  The IR 
       emitters are XC880A or equivalent.  The LED marked "red"  can  be  any 
       visible  LED.  The transistor marked VN10KM can be any N-channel power 
       MOSFET with an ON resistance at 9V gate voltage of five ohms or  less. 
       None of the component values is critical. 
            The adjusted value of R1 should be approximately  (2e+9)/(bits/s) 
       ohms,  where (bit/s) is the Baud rate of the port the SIT is connected 
       to.  Select a pot with a somewhat higher value and adjust it until the 
       output  of U1C goes low for about 1.5x the bit time of the serial port 
       each time a data bit is sent.  Adjust R2 until the output of U1D is 80 
       KHz  when the oscillator is on.  Connect the serial line signal ground 
       to the circuit common.  Connect the serial transmit-data line  to  the 
       point  marked  Tx.  Remember to apply power to the two integrated cir- 
       cuits. 
            The serial signal, clipped to  the  power  supply  rails,  should 
       appear  at the input of U1A.  Note that the 9V supply and CMOS circui- 
       try require that the serial signal reach at least +4.5V when a zero is 
       sent  in  order  for  it  to be recognized.  Any good serial port will 
       easily satisfy this (most reach +12V  to  +15V).   The  serial  signal 
       should appear inverted at the output of U1A.  The output of U1B should 
       go high for 1.5 bit times when a one is sent, and go high for two  bit 
       times  when  a  zero is sent.  The output of U1C should go low for 1.5 
       bit times regardless of what is sent.  The data bit transmitted should 
       appear  on  the  Q  output of U2A.  When a one is sent, the oscillator 
       formed from U1D should produce an 80 KHz signal at the output of  U1D, 
       and  a  40  KHz  square  wave should appear at the Q output of U2B and 
       should be transmitted by the IR emitters.  If a sequence  of  ones  is 
       sent, the visible LED should flicker on. 
       4.  Adjustment and Operation 
            To select the SIT rate, determine the clock period of the  remote 
       codes  of the equipment to be controlled.  This is the unit of time on 
       which all carrier transitions take place.  For example, one Mitsubishi 
       remote  sends  a zero as 10 cycles of carrier followed by 30 cycles of 
       no carrier, and a one as 10 cycles of carrier followed by 70 cycles of 
       no  carrier.   The  clock  period is therefore 10 cycles of 40 KHz, or 
       1/4000 second.  Accurately creating codes for this device  requires  a 
       SIT rate of 4000 bps. 
            When all of the clock periods have been determined, select a  SIT 
       rate  that  all  of the clock periods can be approximately constructed 
       from.  Generally, just selecting the shortest clock period will  work. 
       If it doesn't, halve the period. 
            Multiply the SIT rate by three to get the approximate serial rate 
       and  then select the closest standard serial rate.  For the Mitsubishi 
       remote, the approximate serial rate is 12 Kbps.  The closest  standard 
       serial  rates are 9600 bps and 19.2 Kbps, giving SIT rates of 3200 bps 
       and 6400 bps.  Most receivers expecting a code with a clock period  of 
       1/4000  second will accept codes produced with a SIT rate of 3200 bps, 
       so a serial rate of 9600 bps would be tried first. 
            In some cases, it may not be necessary to accurately reproduce  a 
       short  pulse  sent  by  a  remote.  Some remotes send a brief, intense 
       pulse for each bit, followed by variable period of off-time.  This  is 
       used  to  extend  the  range  of  the  remote  without overdriving the 
       emitter.  A longer pulse, requiring less time  resolution,  will  also 
       work,  since  the  data  is coded in the length of the period from the 
       start of the pulse to the start of the next pulse.  For  example,  the 
       receiver for the Mitsubishi remote described above actually works fine 
       with the serial port set to 4800 bps and the SIT set  accordingly,  as 
       long  as the software driving the serial port rounds up codes that are 
       less than one data-bit-time long.  The receiver is allowing  consider- 
       able leeway: 
                  0          1 
       Expected ~___      ~_______ 
       Sent     ~~~___    ~~~______ 
            It is generally advisable to use the lowest serial port rate that 
       will work.  Although serial ports can often be set to very high rates, 
       perhaps up to 110 Kbps, the system may not actually be able  to  write 
       data  at  that  rate, especially if it has other functions.  Each word 
       will be sent at a high rate, but there will be gaps between  them,  so 
       that  the  timing  of  the code is ruined.  Under UNIX, output at high 
       rates may break up on clist (serial  driver  character  buffer)  boun- 
       daries,  so it is advantageous to ensure that an entire code fits in a 
       clist, which is typically 64 bytes long.  At higher Baud rates, it  is 
       necessary  to send more data to transmit the same code, so that a code 
       may require more than a clist can hold.  Even if a single remote  code 
       fits in a clist, a multi-code sequence may not.  It may even be longer 
       than the maximum amount of data that will  be  stored  by  the  serial 
       driver  for  tty output.  Breakup will occur if the process generating 
       output is not run again before the tty  output  buffer  is  exhausted. 
       Using the lowest Baud rate possible reduces all of these problems. 
            To use the SIT, set the serial port to the Baud rate that R1  has 
       been  adjusted  for,  and seven data bits, one start bit, and one stop 
       bit.  In the byte written to the serial port, bits one and four should 
       always  be  one  (to  create  extra  stop bits), and bits two and five 
       should always be zero (to create extra start bits).  The data bits  to 
       be  transmitted  are sent in bits zero, three, and six.  An RS232 port 
       transmits a one as a negative voltage and a zero as  a  positive  vol- 
       tage.   Data  is transmitted from low bit to high bit.  After clipping 
       to the supply rails, a one bit appears as 0V and a zero bit appears as 
       +9V. 
              ____________         ____________         ____________ 
       0     /start\ 0/lo \   1   /  2  \   3  \   4   /  5  \ 6/hi \ stop 
       1 ___/       ___________/       ___________/       ___________ 
            | start  bit 0  stop | start  bit 1  stop | start  bit 2  stop | 
            Place the SIT somewhere where the emitters can cover all  of  the 
       equipment  to  be  controlled,  preferably  in  a  position  where the 
       transmissions are not likely to  be  blocked.   If  the  equipment  is 
       stacked on shelves and the SIT is put at the front of the bottom shelf 
       with the emitters pointed up, transmission is unlikely to be  blocked. 
       However,  the transmissions will be perpendicular to the receivers, so 
       it will probably be necessary to add reflectors to make the  SIT  work 
       reliably.   Try  taping  small  pieces  of  aluminum  foil  above  the 
       receivers, either on the equipment itself or on the shelf  above  each 
       piece of equipment.  Angle the foil so as to reflect the transmissions 
       into the receivers, with the foil high enough that the  equipment  can 
       still be operated by the handheld remotes. 
       5.  Decoding Signals 
            The best way to decode the signals from an infrared remote is  to 
       digitize  and  record  them.  The data could then be directly used, or 
       could be converted to a more easily interpreted form.  The  codes  can 
       be observed with a phototransistor or photodiode, or by opening up the 
       remote control and connecting directly to the emitter leads. 
            If no means of digitizing signals is  available,  the  next  best 
       option is to use a storage oscilloscope and transcribe the codes manu- 
       ally.  If only a non-storage 'scope is available, a code  can  usually 
       be  viewed  by  holding  down  a  button on the remote.  However, some 
       remotes only send a code once, so it may be  necessary  to  repeatedly 
       press  each button to view the code for the button.  The codes tend to 
       be somewhat long, so set the 'scope  to  x10  time  magnification,  if 
       available. 
            First determine the fundamental form of the codes.  The base time 
       period  that  all  state  changes occur on will probably be relatively 
       obvious.  Don't look at the beginning or ending of the pulse train for 
       this, because the code may start or end with a sequence where the car- 
       rier is on and/or off for longer periods than it is at  any  point  in 
       the  data.   Generally, the base time period will be the length of the 
       shortest on- or off-time observed anywhere in the  code.   Record  the 
       number of carrier cycles in the base time period. 
            Once the base time period has been found, write  down  some  code 
       segments  with on-times written as 1 and off-times written as 0.  But, 
       don't consider these to be the real code  being  transmitted,  because 
       the  self-clocking protocol includes a lot of redundancy.  Codes could 
       be recorded and transmitted this way, but the transcription  would  be 
       needlessly  verbose,  and would obscure the underlying code.  Instead, 
       determine the bit encoding that is being used.  Try dividing the  code 
       segments  into  bits on zero to one transitions (points where the car- 
       rier turns on), so that each bit code consists of an on-time  followed 
       by  an  off-time.  Some remotes may use other codes (for example, Man- 
       chester coding). 
            There should be only two bit codes.  They will probably have dif- 
       ferent  lengths.   Decide  which  will be recorded as a zero and which 
       will be recorded as a one.  In  the  example  data  given  below,  the 
       shorter  code, or the one that has the shorter on-time, is taken to be 
       a zero and the other is taken to be a one.  Once the  codes  for  zero 
       and  one  have  been  determined,  the  codes  for  each button can be 
       recorded in this more compact form.  However, it may be  necessary  to 
       separately  record  a  "start"  or  "stop"  sequence  that  cannot  be 
       described using the codes for zero and 1 (though none of  the  remotes 
       described below have a stop sequence like this). 
            To further reduce the amount of data transcribed and saved, check 
       the codes sent by each button for a common prefix and/or suffix, after 
       the start and before the stop sequences, if any.  If  there  are  pre- 
       fixes and/or suffixes that are common to all of the codes, they can be 
       recorded just once.  Be very careful to start and finish  transcribing 
       the  variable  part of the code for each button at the correct points. 
       If the remote sends codes that appear to be of constant  length  after 
       conversion,  a code that comes out longer or shorter is likely to have 
       been copied incorrectly.  This is another reason to record the  actual 
       function codes instead of their transmitted forms. 
            Here are some examples.  Data bit coding is shown with on periods 
       as  ~  and  off  periods  as  _.   Start  and  stop are start and stop 
       sequences that cannot be represented with ones and  zeros.   They  are 
       given  in  the same form as the data bit codes.  Prefix and suffix are 
       the common prefix and suffix codes found.  Pause,  sleep,  and  repeat 
       are described later. 
               Mitsubishi VCR/audio/TV remote, with the VCR/audio|TV switch set 
               to VCR/audio, and the VCR-A/VCR-B/Audio select set to VCR-A. 
               Carrier: 40 KHz 
               Cycles in base time period: 10 
               0 data bit: ~___ 
               1 data bit: ~_______ 
               prefix: 1110 
               start, stop, suffix: none 
               Length of unique part of codes: 13 bits 
               Pause: 25 mS 
               Sleep: 25 mS 
               Repeat: 3 
               Kenwood Remote Control Unit RC-6010 
               Carrier: 40 KHz 
               Cycles in base time period: 22 
               0 data bit: ~_ 
               1 data bit: ~___ 
               Start: ~~~~~~~~~~~~~~~~________ 
               Prefix: 0001110111100010 
               Suffix, stop: none 
               Length of unique part of codes: 17 bits 
               Pause: 4 mS 
               Sleep: 50 mS 
               Repeat: 1 
               Sony CD Player Remote RM-D505 
               Carrier: 40 KHz 
               Cycles in base time period: 24 
               0 data bit: ~_ 
               1 data bit: ~~_ 
               Start: ~~~~_ 
               Suffix: 10001 
               Prefix, stop: none 
               Length of unique part of codes: 7 bits 
               Pause: 25 mS 
               Sleep: 60 mS 
               Repeat: 2 
            An IR receiver may help in transcribing the codes.   Radio  Shack 
       sells  the GP1U52X IR receiver/demodulator module for about $5.00.  It 
       detects 40 KHz modulated IR signals and produces a TTL and CMOS compa- 
       tible  signal, and comes with a data sheet.  It works fairly well, but 
       it should not be used for the initial analysis of  the  signals.   The 
       turn-on  and turn-off times of the GP1U52X are considerably different, 
       and vary with IR signal strength,  resulting  in  a  distorted  output 
       waveform.   However, once the bit codes have been determined, they can 
       be easily recognized in the GP1U52X output, and it makes transcription 
       easier by removing the clutter of the 40 KHz carrier. 
       6.  Driving the Transmitter 
            Once the function (button) codes, prefixes, suffixes,  start  and 
       stop  sequences,  one  and  zero  codes,  and  base  period  have been 
       recorded, the information can  be  used  to  transmit  remote  control 
       codes.   Convert  the  one, zero, start, and stop codes into interface 
       bit codes by determining how many interface bits  will  be  needed  to 
       transmit  each  of  the off-times and on-times in the codes.  For each 
       off-time and on-time, add the appropriate number of zeros or  ones  to 
       the  interface bit code being generated.  Remember that each interface 
       bit will take three serial port bit times to transmit,  and  therefore 
       will turn the carrier on or off for three serial port bit times.  Con- 
       vert the prefix and suffix into an interface  bit  code  by  replacing 
       each zero and one with the interface bit code for zero or one. 
            To transmit a function code, convert the function  code  into  an 
       interface bit code the same way the prefix and suffix were.  Construct 
       a complete code sequence by stringing together the interface bit codes 
       for  the  start  sequence,  prefix,  function  code,  suffix, and stop 
       sequence.  Convert this into data to be sent to  the  serial  port  by 
       taking  three  bits  at  a time and substituting them into the correct 
       places in a byte as described in the section on using the SIT.  It may 
       help to build a lookup table to translate the eight possible three-bit 
       values into bytes to be sent to the serial port. 
            To get the SIT to work, a few other parameters  may  have  to  be 
       recorded.   Some  equipment requires that a code be received more than 
       once before it is acted on.   If  the  SIT  is  functioning  correctly 
       (preferably  verified  by  detecting  its  output  with an IR receiver 
       module and viewing it on a 'scope), but the transmitted  codes  aren't 
       being  recognized,  hold down a button on the remote for the equipment 
       and record how long it pauses between repeating codes (if  it  repeats 
       at all).  Then try using the SIT to send codes to the equipment multi- 
       ple times, with pauses between them of the same  duration  the  remote 
       used.  It shouldn't need more than a few repeats to make it work.  The 
       time between repeats is the "pause" time given  in  the  remote  data. 
       The  number of repeats required is the value given for "repeat" in the 
       remote data (a repeat value of one means the code  only  needs  to  be 
       sent once). 
            A pause time is given for the Kenwood remote even though it  only 
       requires  one  repeat  because  for  some functions (volume up, volume 
       down, etc.) it may be useful to simulate a  continuous  button  press. 
       The  Kenwood  remote  only sends a code once, and then sends a "button 
       pressed" code until the button is released.  However, repeatedly send- 
       ing the code for the button has the same effect. 
            Another parameter that may be important is  the  length  of  time 
       that  must  pass with no code being sent before a new code can be sent 
       and be recognized as a new button press.   This  information  will  be 
       needed  to  automatically send multi-function sequences.  Determine it 
       by experimentation.  This is the "sleep"  time  given  in  the  remote 
       data. 
            Finally, check all of the codes by sending them to the equipment. 
       If  they  were  recorded  manually,  some  of them may not work due to 
       errors in transcription and will need to be re-recorded. 
  -- 
  # @(#) kenwood.dat 1.1 92/01/14 
  # John H. DuBois III 91/12/21 
  # Lines beginning with # are comments 
  name=Kenwood Remote Control Unit RC-6010 
  # Kenwood remote sensor works fine with a transmitter rate of 1600 
  # transitions/sec 
  # carrier is the carrier frequency required, in Hz. 
  # This information may be used by a driver that has access to more than 
  # one transmitter, or with a system that can set the transmitter frequency. 
  carrier=40000 
  # Transmitter codes are given as a string of 1's and 0's in the function code 
  # table.  The actual IR pulse codes emitted for each 1 and 0 are given by the 
  # value that "one" and "zero" are set to.  Each character of the values of 
  # "one" and "zero" indicates whether the 40 KHz IR transmitter is on for a unit 
  # of time.  The duration of the unit of time represented by each character of 
  # the values of "one" and "zero" is given by the value of "cycles". 
  # cycles is the number of 40 KHz cycles (25 uS periods) represented by each 
  # character in the definitions of "one" and "zero". 
  cycles=22 
  # repeat is the number of times the code should be sent 
  repeat=1 
  # pause is the length of time to wait between code repeats. 
  # It is given in the units given by the definition of "cycles" 
  # instead of in mS so that equipment that requires a very short 
  # pause can be accomodated. 
  # The Kenwood remote only sends the function code once. 
  # It then sends a button-pressed code that is the same for all buttons 
  # until the button is released. 
  # Functions for which a button would be held down (like volume up/down) 
  # continue for as long as the button-pressed code is sent. 
  # However, continually transmitting the function code also works, 
  # so no provision is made here for sending the button-pressed code. 
  # The following value is the pause between the remote code and the first 
  # transmission of the button-pressed code. 
  pause=7 
  # sleep is the length of time to wait between sending different codes, 
  # in milliseconds 
  # Actual minimum measured at 50 mS 
  sleep=65 
  # zero and one describe the waveform used to transmit a zero and one as given 
  # in the function table.  A '~' represents a period of tranmitter "on" time, 
  # during which time the emitter will be modulated by a 40 KHz square wave. 
  # For each '~',  IR pulses will be transmitted.  A '_' (underscore) 
  # represents a period of transmitter "off" time.  The period is given by the 
  # value of cycles. 
  zero=~_ 
  one=~___ 
  # start and stop give start and stop codes, if any, that cannot be described 
  # using ones and zeros as used in the function table and so cannot be given 
  # as prefixes and suffixes. 
  # start and stop are given in the same representation as zero and one. 
  # start and stop are the first and last codes transmitted (they are sent 
  # before and after prefix and suffix, respectively). 
  start=~~~~~~~~~~~~~~~~________ 
  stop= 
  # prefix and suffix give the standard preamble and postable, if any, 
  # that come immediately before and after the function code. 
  # Prefix and suffix are given in the same representation as function codes. 
  prefix=0001110111100010 
  suffix= 
  # Remote functions are given as a line of tab-separated fields: 
  # Code  Key     Word    Label   Vars    Description 
  # Code is given as a string of 0's and 1's whose meaning is 
  # in turn given by the definitions of "zero" and "one". 
  # Remote is the name of the remote that this function is for. 
  # Key and Word are the key and word that can be used to send this code. 
  # If Word is a single character, it should be the same as Key. 
  # Label is the label to put on a button representation of this function. 
  # Variable assignments that should only have effect for one function 
  # are given in the Vars field. 
  # Description is a description of what this function does. 
  # Any further fields are appended to Description preceded by a newline. 
  # A function line can be extended onto multiple lines by beginning the 
  # extension lines with a tab. 
  # The tab is included in the value, so a field boundary always exists 
  # between extention lines. 
  #Code                   Key     Word    Label           Vars    Description 
  component=amp 
  # long sleep for power to give switched components a chance to power up 
  10111001010001100       P       power   power           sleep=500 
          Tuner, amp, and switched outlet power on/off 
  # Selecting a source stops play of all other sources that are Kenwood 
  # controlled equipment 
  00101001110101100       1       tape    select tape 1   * 
          Select tape deck 1 as amp input & start play (if a Kenwood tape deck) 
  10101001010101100       2       tape2   select tape 2   * 
          Select/Unselect tape deck 2 as amp input 
  01001001101101100       c       cd      select cd       * 
          Select cd player as amp input & start play (if a Kenwood cd player) 
  00001001111101100       h       phono   select phono    * 
          Select turntable as amp input & start play (if a Kenwood turntable) 
  10001001011101100       t       tuner   select tuner    * 
          Select tuner as amp input 
  01101001100101100       v       video1  select video 1  * 
          Select video source 1 as amp input & video monitor output 
  11001001001101100       V       video2  select video 2  * 
          Select video source 2 as amp input & video monitor output 
  00111001110001100       m       mute    mute            * 
          Mute output/Unmute output 
  # Volume changing on the Kenwood amp is slow because it is electromechanical. 
  # Set sleep to 135 mS so that a bunch of volume up/downs don't accumulate 
  # in the tty output buffer!  It would be better to just wait for the buffer 
  # to drain after each write but awk can't do that. 
  01011001101001100       d       down    volume down     sleep=%135 
          Unmute output & adjust volume down (~67 steps, 135 mS/step) 
  amp:d,d,d,d,d,d,d,d,d,d,d,d,d,d,d,d,d   q       qtrdown vol 1/4 down 
          *       Set volume 1/4 further down 
  amp:q,q,q,q             D       zerovol zero volume     * 
          Set volume at zero 
  amp:u,u,u,u,u,u,u,u,u,u,u,u,u,u,u,u,u   Q       qtrup   vol 1/4 up 
          *       Set volume 1/4 further up 
  11011001001001100       u       up      volume up       sleep=%135 
          Unmute output & adjust volume up (~67 steps, 135 mS/step) 
  10100011010111000       e       eq      equalization    * 
          Graphic equalizer enabled/bypassed 
  11101011000101000       s       surround        surround        * 
          Dolby surround sound decoder on/off 
  #00010000111011110      d       disk    select disk     * 
  #       Cycle between disk 1-2-3-4-5-6-P 
  #component=cd 
  #01100000100111110      <       reverse reverse search  * 
  #01110011100011000      l       last    last selection  * 
  #10010011011011000      .       stop    stop            * 
  #11010011001011000      p       play    play/pause      * 
  #11100000000111110      >       forward forward search  * 
  #11110011000011000      n       next    next selection  * 
  #component=phono 
  #00000011111111000      .       stop    stop            * 
  #10000011011111000      p       play    play            * 
  component=tape 
  10011011011001000       p       play    play side 1     sleep=1000 
          Unpause & play side 1; repeat-play single tune if pressed in play mode. 
  00011011111001000       2       play2   play side 2     sleep=1000 
          Unpause & play side 2; repeat-play single tune if pressed in play mode. 
  00111011110001000       "       pause   pause           sleep=500 
          Pause if playing 
  # Up to 16 selections can be skipped by sending fast rev/fwd multiple times. 
  01011011101001000       <       reverse fast reverse    sleep=500 
          Wind side 1 reverse/side 2 forward; search for selection if playing 
  11011011001001000       >       forward fast forward    sleep=500 
          Wind side 1 forward/side 2 reverse; search for selection if playing 
  10111011010001000       .       stop    stop            * 
          Stop playing or winding 
  01111011100001000       R       record  record          sleep=700 
          Begin recording 
  component=tuner 
  01110001100011100       a       am      am              * 
          Select tuner as amp input and select AM reception 
  10011001011001100       s       scan    preset scan     * 
          Start/stop scanning 20 preset channels; pause 5 sec. on active stations 
  11110001000011100       f       fm      fm              * 
           Select tuner as amp input and select FM reception 
  tuner:s,s               n       next    next station    * 
          Go to next preset station 
  --

Sources

John H. DuBois III spcecdt[at]deeptht.santa-cruz.ca.us

Category:InfraRed

Seven Component Regulated LED Lamp

Sun, 01 Mar 1998 00:00:00 +0000

Circuit board installed in an automotive lamp holder, attached to a fluorescent lamp base

Introduction

This is a minimal parts lamp made with four white LEDs. It features regulated light output from 10V to around 20V and works well as a flashlight.

Specifications

Nominal Operating Voltage: 12V DC
Operating Current: 40ma

Theory

The LM317L and resistor act as a current regulator set to 40ma. Current flows from the battery through one pair of LEDs, through the regulator, through the other pair of LEDs, and back to the battery. The capacitor filters out noise on the power supply lines. The LED pairs must be matched so that the current through them is roughly equivalent. Small resistors could be placed in series with each of the four LEDs to improve the balance, but the parts count would go way up.

SmartCard PC Emulator

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This smartcard adapter follow exactly the specification ISO 7816. Also, the protocol is the “asynchronous half duplex T=0 protocol” with “active low reset” and “inverse convention” as defined in this standard. The following description may be used in order to connect computers toISO 7816 compatible chip card systems (e.g. GSM mobile phones or other pay-TV decoding systems) if they also use asynchronous transmission. For smart card systems which use synchronous transmission (e.g. most phone cards) the interface described here will need some modifications.

SmartCard PC Serial Reader / Writer (Phoenix)

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This is a Smartcard (ISO 7816) Serial Reader / Writer, also know as “Phoenix” Interface. This adapter must be connected to 9 PIN PC serial port

Electric Scheme

also connected:

pin 7=GND and pin 14=VCC of 74HC04N and 74LS04
Pin 9 and 10 of the smartcard connector are for card presence switch.

Components List

Designator	Description	Value
C9	Capacitor	27 pF 16V
C8	Capacitor	27 pF 16V
R4	Resistor	22 KOhm
R1	Resistor	220 Ohm
R2	Resistor	220 Ohm
R3	Resistor	47 KOhm
R6	Resistor	2.2 KOhm
R5	Resistor	1 MOhm
Y1	Crystal Oscillator	3.579 MHz Quartz
U3	Hex Buffer	74LS07N
U4	Hex Inverter	74HC04N
U2	+5V Powered RS-232 Driver/Receiver	MAX232
J1	Serial Connector	DSUB 9 PIN FEMALE
JP1	Smartcard Connector	ISO 7816
DS1	Red LED	RED
DS2	Green LED	GREEN
P1	2-Conductor Plug	Power Plug +9V / +12V
C4	Polarized Capacitor (Radial)	1 uF 16V
C3	Capacitor	0.1 uF 16V
C2	Capacitor	0.33 uF 16V
C5	Polarized Capacitor	1 uF 16V
C7	Polarized Capacitor	1 uF 16V
C10	Capacitor	100 pF 16V
C6	Polarized Capacitor	1 uF 16V
C1	Polarized Capacitor	470 uF 16V Elettr.
U1	Positive Voltage Regulator	7805 +5V Voltage Regulator
S1	Switch	Single-Pole, Single-Throw

IC’s Pinouts

Circuit Description

The MAX232 converts the RS-232 levels (about +10 and -10 V) to TTL voltage (0 and +5 V) and vice versa without requiring anything else than +5 V power supply. This chip contains two TTL->RS-232 and two RS-232->TTL drivers and needs four external 1 uF capacitors in order to generate the RS-232 voltage internally. The adapter electronic gets its power supply from the smartcard reader device VCC line or you can use an external 5 V supply if you wish.

Smooth Tone Clickless CW Sidetone Generator

Sun, 01 Mar 1998 00:00:00 +0000

Rev 2c prototype on OnePas OP840B circuit board

Wave form of one morse code “dit”

Introduction

This circuit is about as good as it gets for generating morse code tones. It may be used as a code practice oscillator, a tone generator for a keyer, or a sidetone oscillator for a transmitter.

Feng shuei is the Chinese art of arranging objects in buildings, it is based on many practical ideas. One important concept of feng shuei is the rounding of sharp corners. Think of this circuit as a form of electronic audio feng shuei ;-). One may think that this is a lot of circuitry just to make simple beep tones, but the real value of the circuit is that it sounds very smooth when compared to a clicky and harsh-toned square wave code oscillator. This circuit won’t hurt your ears, even with extended use.

Solar Charged LED Utility Light

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

Tired of always spending money on flashlight batteries only to have them fail just when you need them? Try this simple circuit out. It would make an excellent science fair project. The white LEDs are quite bright, they provide enough light to illuminate a small room at night. The LEDs produce a nicely focused beam. You can read by the light of this device. The box also doubles as a 12V power source and can run other small loads such as a transistor radio. This project was built with theSimpler is Better approach, the materials are common and many substitutions are possible.

Solar Current Meter

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit is used to measure the current from a solar panel. It has very low power loss for currents in the 0-10A range. It also works as a general purpose DC current meter. The circuit can be used on either the positive or negative side of a DC circuit.

Specifications

Measured Current: 0-10 Amps DC
Circuit Voltage: Will work with DC circuits at any practical voltage.
Accuracy: approximately 2%, depending on the meter movement.

Theory

The current to be measured flows through the 0.01 ohm resistor which causes a small voltage drop across the resistor. The 100 microamp meter is set up with the series 50 ohm and 500 ohm variable resistor in a voltage measurement configuration to measure this voltage drop. The 500 ohm variable resistor is used to adjust the meter’s full scale reading. The 50 ohm resistor limits the maximum current to the meter no matter what setting is on the 500 ohm resistor, this protects the meter from passing too much current and burning up. The series resistance of the meter, 500 ohm (or less) variable resistor and 50 ohm resistor should total 1000 ohms. Different meters may require a different variable resistor to achieve the 1000 ohm value.

Solar Powered Reading Lamp

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

The goal of this project was to produce a self contained reading lamp that could be used by students in developing countries for reading at night. The circuit can be used for a wide variety of lighting applications. The reading lamp consists of a small solar panel, a standard UPS style lead acid battery, and an LED circuit board. The circuit board contains a low power solar charge controller (regulator), a set of 8 white LEDs, a switch, an LED current regulator, and a low voltage disconnect circuit. The circuitry will insure a long battery life by preventing over charging and excessive discharging. The circuit was designed to work with lead acid batteries, it should also work with a string of 10 NiCd cells. Both the charge controller and LED regulator circuits can be used independently for other applications.

SPC2 6A 12V Solar Power Center

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

The SPC2 is a solar power center, it can be used to handle all of the power functions for small 12 Volt solar powered devices. It contains a photovoltaic charge controller and a low voltage load disconnect circuit. The low voltage disconnect has a load on-off switch, and a battery low voltage indicator. By using the SPC2 as the center of a solar powered device, long battery life is assured. The SPC2 can be used for powered lighting systems, radios, and other 12 Volt devices. The circuit was designed with the following goals:

Stereo Audio Isolator

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit is useful for removing ground loop hum on a remote line level audio signal line. It can be used to to connect a computer sound card to a stereo amplifier’s line input. Other uses include tapping into a line level signal for powering a remote amplifier, and removing common mode ground interference on 12 Volt audio equipment such as a car stereo. The circuit can be used in mono applications by simply ignoring the second channel.

Stereo Test Tone Generator

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

The purpose of this circuit is to create a pair of sine waves for testing stereo equipment. While it is useful for many types of audio test tone generation, the circuit is specialized for the purpose of aligning anFM Stereo Modulator, like the type used in low power FM stereo transmitters. Two tone outputs are available, the low tone has a secondary output that is 180 degrees out of phase with the primary output. The circuit is also handy for testing computer sound card inputs.

Telephone Controlled Night Light

Sun, 01 Mar 1998 00:00:00 +0000

When the telephone rings, or when the handset is lifted, the night light is turned on and remains on while the conversation takes place. When the handset is replaced in the cradle, the light remains on for about 11 s. During standby conditions, the -28Vdc bias on the phone line maintains the output of U3 in a high state. When the ac ring signal is applied to the phone line, it is processed by the ring detector U1, producing a negative output pulse at pin 2 for each ring. These pulses trigger U2, causing its output to become high and the discharge transistor to turn off. The high output of U2 activates optoisolator U4, which turns on the night light. Each ring retriggers the timer and discharges C1, preventing it from reaching the 2/3 VDD threshold level. Thus, the night light will remain on while the phone is ringing and for about 11 s after the last ring. After 11 s, C1 will be charged to the U2 threshold level (2/3 VDD) resulting in the U2 output returning to a low level and its discharge output turning on, discharging C1. The lamp will turn off if the phone is not answered.

Telephone Line Monitor (Plans)

Sun, 01 Mar 1998 00:00:00 +0000

Get yourself a low-voltage DC relay, like a 3v relay… Set it up as follows:

           Audio Isolation 
           Transformer 
   To      <--)||(---------------------+ 
              )||(                     | <==== Relay Contacts 
   Speaker <--)||(---+    +--------o/  o 
            600ohm   |    |        mmmmm DC 3v Relay Coil 
                     |    |       |     | 
    RED   -----------|----+-------+     +----------> To Dispatcher's Phone 
                     | 
    GREEN -----------+-----------------------------> To Dispatcher's Phone 
   
    |                               | 
   -+- indicates a connection,     ---  is not connected. 
    |                               |

You may have to use a Diode or two to make this telephone-line FCC clean… I’m not saying this is a clean circuit at all. It’s cheap and dirty! You may have to use a Op-Amp (Use an LM386, they’re good for speakers) on the speaker. Depends. Experiment!

Telephone Power

Sun, 01 Mar 1998 00:00:00 +0000

“If one were to try [using power from phone line], would phone company had a way of finding out?” Most assuredly. They aren’t in the business of supplying power, and they ARE in the business of finding faults in their lines. Any substantial power drain from their lines WILL be detected. If it’s large, the phone switch will conclude that you’ve dropped the phone in the bathtub or something like that, and will disconnect your line (and will check periodically to see if the drain has gone away and you can be reconnected). If it’s small, the switch will report it to the service people as a possible line problem, to be investigated before it causes a complete failure… and if they investigate and find that you’re to blame, they will probably send you a bill for time and trouble. The current you can draw without eventually having it noticed is very small.

Telephone Tap

Sun, 01 Mar 1998 00:00:00 +0000

Amplify or record a telephone call with the simple circuit shown. The 8-W secondary winding of a miniature transistor output transformer is connected in series with either of the telephone lines. The 1000-W primary winding can feed either a cassette recorder or an audio amplifier.

Category:Telephone

Temperature Controlled NICD Charger

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit is for a temperature controlled constant current battery charger. It works with NICD, NIMH, and other rechargeable cells. The circuit works on the principle that most rechargeable batteries show an increase in temperature when the cells becomes fully charged. Overcharging is one of the main causes of short cell life, hot cells pop their internal seals and vent out electrolyte. As cells dry out, they lose capacity.

TTL Pulse Reading Logic Probe

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit uses LEDs to display logic states for high, low, rising pulse, and falling pulse, it is generally useful for debugging logic circuitry.

Specifications

This circuit can monitor TTL logic levels. TTL compatible CMOS logic families can also be monitored.

Theory

The first 74LS00 gate acts as a buffer for the input logic pin. The following gates invert the signal, then further buffer it for driving the High and Low LEDs. The first 74LS123 one shot stretches out low going pulses so that they blink the Low Pulse LED for a long enough time to be visible. The second 74LS123 does the same thing for high going pulses.

Ultra Low Power LCD Indicator

Sun, 01 Mar 1998 00:00:00 +0000

Introduction

This circuit serves as an ultra-low power replacement for multiple LED on-off indicators. It also has the advantage of being easy to read in full daylight. With the parts shown, it is possible to display four bits of information. The display that I used has three digits and 2 decimal points for a total of 23 segments. Different groupings of segments can be used for the four indicators. I chose to use three squares (shown) and the three lower segments together (not shown) for the four indicators. Many other combinations could be used, one possibility would be to hard-wire numbers or letters out of each of the digits. Other LCD displays could also be used for different effects. A part that doesn’t exist as far as I know, but should, is a single pixel LCD indicator (2 wire). An LCD manufacturer could probably make a lot of money with such a part. If such a thing exists, I’d love to hear about it.

Use old phones as an intercom

Sun, 01 Mar 1998 00:00:00 +0000

Talking over the phones is easy. You put DC current through the phone and it transmits and receives audio. So two phones and a current source (about 25mA) all in series will give you a talking circuit. A suitable current source can be as simple as a 9V battery and a series resistor whose value is adjusted (with both phones offhook) till about 25mA flows. You can then bypass the battery and the resistor with a capacitor to couple the audio straight across and get a loud and clear connection.

Variations on the PWM DC Motor Speed Control

Sun, 01 Mar 1998 00:00:00 +0000

The diagrams are for 12V operation only and there are high side (common ground) and low side (common +12V) versions. The low side version is in fact, identical to the original circuit when wired for 12V operation. The low side version allows the use of higher power and more inexpensive N Channel FETs, whereas the high side version, which uses P Channel FETs is used where common ground load wiring is a requirement. The inductor on the gate side of the power MOSFET transistor can be a ferrite bead or a few turns of wire wrapped around a 10 ohm, 1/4W resistor. The purpose of this inductor is to supress RF oscillation from the MOSFET. This circuit can, in theory, switch a lot of current, an IRFZ34N MOSFET can handle over 35 Amps if connected to a proper heat sink. Inductive loads may require special care since they can generate large voltage spikes that can damage the MOSFET. Replacing the 1N4002 with a fast recovery diode may help absorb the reverse voltage kick when driving an inductive load such as a motor. Note that the pwm control has an opposite effect on these two circuits, the low side version is on with a high pin 7 output voltage and the high side version is on with a low output. In general, NMOS transistors like the IRFZ34N are lower cost and higher current compared to PMOS transistors like the IRF9540. Almost any power MOSFET transistor will work in these circuits, the load current should be lower than the transistor’s maximum rating. Note: if the circuit does not completely turn off and on when the 10K potentiometer is fully left and right, replace both of the 3.9K resistors with 3.3K resistors.

Voltage Controlled Panner Circuit

Sun, 01 Mar 1998 00:00:00 +0000

This circuit is used to convert a mono audio signal into a stereo signal that can be panned between the left and right channel by a 0-10V control signal, it is intended for analog synthesizer systems.

Voltage Controlled Audio Panner (postscript)

Description (TXT)

Sources

Forrest Cook http://www.solorb.com/elect/

Category:Audio

Wireless Telephone Eavesdropper

Sun, 01 Mar 1998 00:00:00 +0000

The IR transmitter connects to a telephone circuit, and transmits both sides of all telephone conversations to any line-of-sight location, within 40 feet. No power is taken from the central office, as long as all phones remain on-hook. The current flows through the phone and back to the central office, thereby keying their equipment. We tap into the telephone line by connecting the IR transmitter circuit in series with either the tip or ring. When the telephone is off-hook, current will flow through the diode bridge polarity protector and supply the power for the IR transmitter. The phone’s audio information is taken off the line by transformer T1. The 1000-W winding of the transformer connects to a two-stage transistor audio amplifier/modulator. A 2000-W potentiometer could be added to the input of the two-stage amplifier to control the modulation level, and another potentiometer could be added in place of R3 to adjust the IR’s idle current.