# Analog Computer

## A modular Analog Computer Kit

Inspired by Dr. Vogels Home Brew Analog Computer , this kit consists of various 100x60 cm PCB cards which can be connected together with 2.54 mm jumpers. Each board implements a specific section of the analog computer by Dr. Vogel. Connect the various input and outputs of generators, adders, integrators and multipliers to compute different mathematical functions.

This kind of electronic computation was used for real applications in the years 1950 to 1970. You could use them to solve quite complicated differential equations and display the solution with on an oscilloscope. Two of their main disadvantages were bad calculation accuracy (due to the tolerances in non-linearities of the electronic components) and a limited value range (e.g. due to clipping of the op-amps).

Here are some simple example calculations implemented with the modules below:

Dr. Vogel has written an introduction to analog computers (German) and a description of his home brew analog computer (German).  Here are the schematics of his computer . Lots of documentation about analog computers can be found on the web pages of the Analog Computer Museum .

### Project Files This project is hosted on GitHub where you can find all Eagle Schematics and PCB files for all the circuits: https://github.com/grappendorf/analogcomputer

## +15/-15V DC-to-DC Converter

The power supply of this analog computer is +/- 15 V. A simple DC/DC-Converter transforms an input voltage of 5 V to the needed +/- 15 V. I chose an aimtec AM3N-0515D-RZ mainly because of it's availability. Input voltage range is 4.5 V to 5.5 V. Maximum output current is 100 mA.

## +/- 10 V Voltage Reference

This board supplies constant +/- 10 V voltage outputs. Together with the potentiometers, one can generate the coefficients for the calculations.

## Coefficient Potentiometers

Nothing fancy about this. Just two ten turn potentiometers connected to some pin headers.

## Triangle waveform generator

This module generates a triangular waveform with variable frequency and adjustable minimum and maximum output voltage. It also generates a derived square waveform. The amplitude of the triangular waveform can be set with the two potentiometers V+ and V-. V+ can be set anywhere between +8.4 V and +12.8 V and V- can be set anywhere between -9 V and -12.8 V. With the FREQ potentiometer the frequency can be set anywhere between about 1 Hz and 70 Hz.

## Triangle to sine waveform generator

Converts one period of a triangle wave to one period of a sine wave.

## Adder

This adder has the transfer function
f(x, y, z) = -1 * (x + y + 10 * z)

## Multiplier

This multiplier implements the transfer function
f(x+, x-, y+, y-, z) = 0.1 * (x+ - x-) * (y+ - y-) + z

## Open Amplifier

This page was last updated on 13. February 2016