-----Original Message----- From: vcf-midatlantic [mailto:vcf-midatlantic- bounces@lists.vintagecomputerfederation.org] On Behalf Of Herb Johnson via vcf-midatlantic Sent: 18 November 2016 15:53 To: vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> Cc: Herb Johnson <hjohnson@retrotechnology.info> Subject: [vcf-midatlantic] EAI TR20 analog computer exhibit
SVCatITC [Bill Inderrieden] posted:
I need analog math problems to be submitted, so that when the >> TR20 is restored, we'll have simulations to run on the computer. I'll make a list of what computational modules we have so you >> know what to work with, i.e. integrators, DFG's, summers, etc. The plan is to have an XY recorder and XY scope for results output.
Bill and all: I've taken the liberty to post a reply under a proper subject line that's relevant to the thread. Not "digest question blah blah" which is irrelevant and will be impractical to search back for in the future. I really encourage people who post, to use relevant subject lines, but this is up to the Moderator to enforce, (except when he doesn't).
Bill, I worked with EIA analog computers long ago, and I'm an old electrical engineer. So it's good to see this EIA TR20 will be restored and demonstrated. But very few people in the VCFed list, have any experience with analog computing or with differential equations. Fewer visitors will know this stuff.
The classic demo of these sorts of systems, is some kind of "bouncing ball" display. Everyone has seen a ball bounce, so it's familiar. There ought to be enough integrators to make a damped oscillator. Since you want a chart recorder output, the frequencies will be sub-audio.
But you might allow for a speed-up at audio rates, so an oscilloscope and speaker can demonstrate operation, without requiring the chart recorder and using up paper and ink - all points of failure, weeks and months later.
If it were my choice, I'd go "audio" so it's easier for the docents to demonstrate the unit and avoid problems with chart recorders.
That's my considerations. Something simple, familiar, and convenient to demonstrate when you aren't there. The amazing thing will be that it works, and has been preserved. We can run real programs, another day.
Herb Johnson
-- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net
I really like the car suspension problem, so typically you have a tyre which you model as a spring, a wheel which is a Mass, and the actual suspension which is a spring and damper. Then you can have parameter pots which control the parameters of the model, springiness of spring and tyre, resistance of damper, speed of car over a step. Actually, I think a problem which displays on a scope, and runs repeatedly, so that you can see that the problem parameters can be optimized quickly. This kind of shows why Analog Computers remained in use for so long after the problems could be simulated on digital computers. Dave