A black circuit board with many colored banana connector plugs in placed on a table. Behind it, two analogue voltage dials stand on either side of an oscilloscope stand. The oscilloscope is a cheap model, with a small LCD display and an exposed red circuit board.

Building An Analogue Computer To Simulate Neurons

March 8, 2026 by Aaron Beckendorf 2 Comments

The rapidly-improving speed and versatility of digital computers has mostly driven analogue computers out of use in modern systems, as has the relative difficulty of programming an analogue computer. There is a kind of art, though, in weaving together a series of op-amps to perform mathematical calculations; between this, a historical interest in the machines, and their rarity value, it’s no wonder that new analogue computers are being designed even now, such as [Markus Bindhammer]’s system.

The computer is built around a combined circuit board and patch panel, based on the designs included in three papers in a online library of analogue computer references. The housing around the patch panel took design cues from the Polish AKAT-1 analogue computer, including the two dial voltage indicators and an oscilloscope display, in this case an inexpensive DSO-138. The patch panel uses banana connectors and the jumper wires use stackable connectors, so several wires can be connected to the same socket.

The computer itself has a summing amplifier circuit, a multiplier circuit, an integrator, and square, triangle, and sine wave generators. This simple set of tools is enough to simulate both simple and complex math; for example, [Markus] squared five volts with the multiplier, resulting in 2.5 volts (the multiplier divides the result by ten). A more advanced example is a leaky-integrator model of a neuron, which simulates a differential equation.

We’ve covered a few analogue computers before, as well as a neuron-simulating circuit similar to [Markus]’s demonstration.

Challenge: Square A Voltage

July 1, 2025 by Al Williams 18 Comments

Your design task, should you decide to accept it: given an input voltage, square it. Ok, that’s too hard since squaring 8 volts would give you 64 volts, so let’s say the output should be 10% of the square, so 8 volts in would result in 6.4V. How do you do it? [Engineering Prof.] knows how and will show you what you can do in the video below.

The circuit uses two op amps and some transistors. However, the transistors are used in a way that depends on the temperature, so it is important to use a transistor array so they are matched and will all be at the same temperature.

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Mechanic Prince Of Tides

June 5, 2024 by Al Williams 2 Comments

Lord Kelvin’s name comes up anytime you start looking at the history of science and technology. In addition to working on transatlantic cables and thermodynamics, he also built an early computing device to predict tides. Kelvin, whose real name was William Thomson, became interested in tides in a roundabout way, as explained in a recent IEEE Spectrum article.

He’d made plenty of money on his patents related to the telegraph cable, but his wife died, so he decided to buy a yacht, the Lalla Rookh. He used it as a summer home. If you live on a boat, the tides are an important part of your day.

Today, you could just ask your favorite search engine or AI about the tides, but in 1870, that wasn’t possible. Also, in a day when sea power made or broke empires, tide charts were often top secret. Not that the tides were a total mystery. Newton explained what was happening back in 1687. Laplace realized they were tied to oscillations almost a century later. Thomson made a machine that could do the math Laplace envisioned.

We know today that the tides depend on hundreds of different motions, but many of them have relatively insignificant contributions, and we only track 37 of them, according to the post. Kelvin’s machine — an intricate mesh of gears and cranks — tracked only 10 components.

In operation, the user turned a crank, and a pen traced a curve on a roll of paper. A small mark showed the hour with a special mark for noon. You could process a year’s worth of tides in about 4 hours. While Kelvin received credit for the machine’s creation, he acknowledged the help of many others in his paper, from craftsmen to his brother.

We actually did a deep dive into tides, including Kelvin’s machine, a few years ago. He shows up a number of times in our posts.

Computer Gear With — Um — Gears

November 21, 2023 by Al Williams 10 Comments

Analog computers have been around in some form for a very long time. One very obvious place they were used was in military vehicles. While submarine fire computers and the Norden bombsight get all the press, [msylvain59] has a lesser-known example: an M13A1 ballistic computer from an M48 tank that he tears down for us in the video below.

The M48, known as a Patton, saw service from 1952 to 1987. Just looking at the mechanical linkage to the tank’s systems is impressive. But inside, it is clear this is a genuinely analog computer. The thing is built — quite literally — like a tank. What was the last computer you opened that needed a hammer? And inside, you’ll find gears, bearings, and a chain!

We don’t pretend to understand all the workings. These devices often used gears and synchros (or selsyns, if you prefer) to track the position of some external thing. But we are guessing there was a lot more to it than that. It’s probably an exciting process to see something like that designed from scratch.

We did think of the Norden when we saw this. Hard to imagine, but there were “general purpose” analog computers.

Continue reading “Computer Gear With — Um — Gears” →

Reverse-Engineering The Mechanical Bendix Central Air Data Computer

October 19, 2023 by Maya Posch 9 Comments

Before the era of digital electronic computers, mechanical analog computers were found everywhere. From the relative simplicity of bomb sights to the complexity of fire control computers on 1940s battleships, all the way to 1950s fighter planes, these mechanical wonders enabled feats which were considered otherwise impossible at the time.

One such system that [Ken Shirriff] looked at a while ago is the Bendix Central Air Data Computer. As the name suggests, it is a computer system that processes air data. To be precise, it’s the mechanism found in airplanes that uses external sensor inputs to calculate parameters like altitude, vertical speed, Mach number and air speed.

Continue reading “Reverse-Engineering The Mechanical Bendix Central Air Data Computer” →

A Modular Analogue Computer

June 12, 2023 by Jenny List 20 Comments

We are all used to modular construction in the analogue synth world, to the extent that there’s an accepted standard for it in EuroRack. But the same techniques are just as useful wherever else analogue circuits need to be configured on the fly, such as in an analogue computer. It’s something [Rainer Glaschick] has pursued, with his Flexible Analog Computer, an analogue computer made from a set of modules mounted on breadboard strips.

Standard modules are an adder and an integrator, with the adder also having inverter, comparator, and precision rectifier functions. The various functions can be easily configured by means of jumpers, and there are digital switches on board to enable or disable outputs and inputs. he’s set up a moon landing example to demonstrate the machine in practice.

We’re not going to pretend to be analogue computer experts here at Hackaday,but we naturally welcome any foray into analogue circuitry lest it become a lost art. If you’d like to experiment with analogue computing there are other projects out there to whet your appetite, and of course they don’t even need to be electronic.

A set of solderless breadboards with op amps and their functions annotated

Op-Amp Challenge: Virtual Ball-in-a-Box Responds To Your Motions

June 7, 2023 by Robin Kearey 5 Comments

With the incredible variety of projects submitted to our Op-Amp Contest, you’d almost forget that operational amplifiers were originally invented to perform mathematical operations, specifically inside analog computers. One popular “Hello World” kind of program for these computers is the “ball-in-a-box”, in which the computer simulates what happens when you drop a bouncy ball into a rigid box. [wlf647] has recreated this program using a handful of op amps and a classic display, and added a twist by making the system sensitive to gravity.

All the physics simulation work is performed by a set of TL072 JFET input op amps. Four are configured as integrators that simulate the motion of the ball in the X and Y directions, while four others serve as comparators that detect the ball’s collisions with the edges of the box and give it a push in the opposite direction. Three more op amps are connected to form a quadrature oscillator, which makes a set of sine and cosine waves that draw a circle representing the ball.

The simulator’s output signals are connected to a tiny viewfinder CRT as well as a speaker that makes a sound whenever the ball hits one of the screen’s edges. This makes for a great ball-in-box display already, but what really makes this build special is the addition of an analog MEMS accelerometer that modifies the gravity vector in the simulation.

If you tilt or shake the sensor, the virtual box experiences a similar motion, which gives the simulation a beautiful live connection to the real world. You can see the result in a demo video [wlf647] recently posted.

The whole setup is currently sitting on a solderless breadboard, but [wlf647] is planning to integrate everything onto a PCB small enough to mount on the viewfinder, turning it into a self-contained motion simulator. Analog computers are perfect for this kind of work, and while they may seem old-fashioned, new ones are still being developed.