Heathkit EC-1

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Thu May 1 13:23:00 2003

>From: "The Design Fort DTP" <design.fort_at_ns.sympatico.ca>
>
>I would be interested to learn more about the Heathkit EC-1 analog computer.
>So far I only found pictures and specifications on the net. Is there a
>website that actually explained how this machine worked and/or what it
>could/can do.
>Even more are there informations about "programs" that this machine could
>run?
>
>I have to admit that the "analog" times of the computer age was a bit before
>my time, but I really would love to learn more about it.
>
>Herbert
>

Hi
 The Heath kit has 9 op-amps that are connected such that
they are all inverting. It is intended to primarily model
things that are linear systems but one can add such things
as diodes to make limiting functions. They do this for one
of the example programs to put a bouncing ball on an oscilloscope
screen. Other nonlinear functions can be added.
 Although, one can model things with differentiators, these
are generally not very stable and tend to require more dynamic
range than integrators. Most linear systems can be described
as a differential equation. If one integrates the equation
a number of times, one can remove all the differentials and
be left with a number of integrals and initial constants.
These can be quickly scaled and represented by resistors
and capacitors. This modeling method can solve quite complex
problems. Things like aircraft controls to auto suspension
systems can be modeled this way. I had a friend describe
how it was used to make rail cars that wouldn't oscillate
at the same frequency as the spacing of the track joints,
over normal speed ranges. One can imagine what would happen
to the load and car if it were increasing the oscillation
on each track joint it crossed.
 I currently have a EC-1 but a while back, I needed to solve
a control system problem with an oven. There were several
factors that effected the temperature and I needed to make
sure that the system could handle these changes without oscillating
or over shooting. I found an analog modeling program called
TutSim that I used to understand the system. This is just
like using a real analog computer except it used discrete
processing to simulate the analog world. There are potential
problems doing this and one needs to understand the possible
issues.
 If you have a spice program, you can build up the equivalent
of a EC-1 in software and see how it works. It wasn't until
the late 80's someplace that digital computers became fast
enough to replace the simpler op-amps for solving these kinds
of problems. In many cases, the analog machines still have
better speed/accuracy tradeoffs.
 My biggest complaint with the EC-1 is that they needed more
binding post for the common ( 0 Volts ).
Dwight
Received on Thu May 01 2003 - 13:23:00 BST