# Analog Computer

1. Sep 9, 2010

### alex_da_gr8

Hello,
I am a sixth form student studying physics and I am planning on doing a project on electronic analog computation and I am stuck as to where I should begin to learn how such a system solves problems (without delving too much into too many details). I have limited knowledge on electronics but I would like to build practical example of a circuit that performs a computational/simulation task (eg: Solving a First Order Differential Equation). If this is an attainable goal, is it possible to do so using free computer software or inexpensive parts.
Thanks,
Alex

2. Sep 9, 2010

### Studiot

Welcome

You cannot hope to do analog computing without some knowledge of electronics.
Having said that, it should be accessible to a student armed with sixth form knowledge of resistors, capacitors, amplifiers and circuit theorems.

In analog computing the variable of interest is represented as a (varying) voltage. You obtain answers by taking readings or measurements of this voltage after it has been processed by the 'computer'.

The simplest form of analog computers can perform the basic 4 operations of arithmetic -addition, subtraction, multiplication and division. This can be achieved by suitable arrangements of resistors ( including variable ones) alone.

Once you introduce capacitors you gain the ability to differentiate and integrate. If you have not yet covered this in your studies then a bit of forward reading is in order.

Calculus (Integrating) with capacitor/resistor networks is pretty unfriendly and limited. this can be overcome by including the capacitor in the feedback loop of an operational amplifier.

Some more forward reading is in order, but there's tons about it

Another way of saying 'solve a differential equation' is to say 'integrate a differential equation'

In maths the output is a function from which we can calculate a table of values.

In analog computing we input voltages representing the differentials to an integrator, and measure a table of outputs to obtain a table of values.

Hope this helps and encourages. It should be a good project.

Keep us informed about how you are getting on and ask away any further questions.

3. Sep 9, 2010

### davidrit

Philbrick published a book on the subject in the 60s. I haven't seen anything that comes close to it since in terms of coverage and clarity. Some references to performance specs are outdated of course, but the principles and circuits are explained well.