Subject: Re: Heathkit EC-1

From: "Dwight K. Elvey" <[email-masked]>
Date: Thu May 1 13:23:00 2003

>From: "The Design Fort DTP" <[email-masked]>
>
>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

---

From: Doug Coward <[email-masked]>
Date: Fri May 2 12:53:01 2003

The Design Fort DTP wrote:
>  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?

  Most computer applications are simulations of one
kind or another, word processors, spreadsheets, drawing
programs, even a desktop GUI. Analog computers are the
masters of the art of simulation, but they are not used
for mundane simulations like these.
  Analog Computers run mathematical simulation of physical
systems. Everything from the decay of subatomic particles
to the interaction of two colliding galaxies.
  Do you want to:
 * See the results of a chemical reaction?
 * Test the design of an automobile tire?
 * Study the effects of pollution on a fish population?
 * Model blood flow through an organ?
 * Understand the effects of lowering the interest rate?
 * Fine tune the design of the Space Shuttle main engine?
 * Control flooding on a major river?
 * Explore new types of music?

 All of these are physical systems governed by mathematical
equations. 
 Analog computers are PURELY parallel and can run programs
slower than real time, real time or faster than real time.
Simulations can be halted at any point and all aspects of
the simulation can be examined. Changes can then be made
and the simulation can then be continued from the point it 
was halted or restart from the beginning. So, analog computers
can not only simulate a fixed systems, but can also test
'what if' cases very easily. 
 Analog computers can be a hardwired special purpose type or 
flexible general purpose type.
 The EC-1 with only nine amplifiers can be limiting in the
size of simulations it will handle. But analog computers
don't have the compatibility and the connectivity problem 
of digital computers. Ten EC-1s could be connected together
to form an EC-1 with 90 amplifiers. The only problem would
be if more than 9 integrators were used then a slight 
modification would have to be made to each EC-1 using an
integrator to allow one EC-1 to control the mode.
 An EC-1 can also be directly connected to another brand
of analog computer. No problem other than the mode control
of integrators.
 The lure of the EC-1 is that it a inexpensive and compact
example of vacuum tube computing. 

 The world is analog. The human mind is analog.
Digital computers make a nice hobby, and work just fine for
tasks composed of sequential steps, but they are just an 
over hyped fad.
  --Doug
=========================================
Doug Coward                
@ home in Poulsbo, WA

Analog Computer Online Museum and History Center
http://dcoward.best.vwh.net/analog
=========================================

---

From: Doug Coward <[email-masked]>
Date: Fri May 2 13:35:00 2003

Ethan wrote:
> How does a resistive sheet computer work?

  Just a quick note for now.
 Resistive sheets belong to a category of analog 
computing called network analyzers.

> In the same vein (pun intended)... how would fluidic computers
> stack up?  Digital?  Analog?  Mixed?

 Fluidics (or fluid logic) can have both analog
and digital processes. You can perform boolean
operations, but you also can have fluid amplifers.
  --Doug
=========================================
Doug Coward                
@ home in Poulsbo, WA

---

From: Doug Coward <[email-masked]>
Date: Fri May 2 17:12:00 2003

> computing called network analyzers.

  Oops, I need to correct this.
  Resistive sheets belong to a category of analog
computing called passive element computers in which 
network analyzers are probably the biggest and most
well known examples. But it also includes
* conductive sheets
* electrolytic tanks - create 3 dimensional simulations
* resistor networks 
* pin and rod systems
* resistor and capacitor network

 Passive element computers normally models a 
physical system using only passive R-L-C components,
and solve equations in which dimensions in space
are the independent variables, rather than time.

 Applications for passive element computers include
things like the simulation of
 * reception patterns of a receiving antenna
 * temperture, and pressure flow in a nozzle
 * diffusion of material at a transistor junction

 Here is an example:
  You solder together a large two dimensional matrix
of resistors (all the same value). At each node where
the resistors are soldered together you solder a capacitor
connected to ground. 
  You then apply a voltage to one corner of this 
resistor and capacitor network. As the current flows
through the network it begins to charge the capacitors.
  You now have a computer that simulates the heat flow
across a metal plate the size of your matrix, both
over distance and over time. Without the capacitors
you are simulating only over distance.

 A resistive sheet is a resistor matrix with a very
fine mesh. The finer the mesh, the better the simulation.

 "Rubber-sheet computers have been used extensively 
  to study the trajectories of electrons and gas ions
  in vacuum and gas tubes" 

  -Doug

---

From: "Dwight K. Elvey" <[email-masked]>
Date: Fri May 2 20:13:00 2003

>From: "Doug Coward" <[email-masked]>
>
>  Ethan wrote:

Hi
 This is the place to describe my method of finding
shorts on power planes. This is very much like the
resistive sheet methods.
 You place a power supply across one of the two planes
that has shorts between them, such that about one or
two amps is flowing in current limit. You place one lead
of a volt meter on the opposite plane and then probe
with the other lead on the plane with the current flowing
across it. You find a line where the meter reads zero.
Now, move the power leads to an orthogonal corners.
Again fine the line of zero volts. Where the two lines
cross, you'll find the short.
 There are variations of this method for finding shorts
between traces and even multiple shorts.
Dwight