[sdiy] Understanding Analog Computer Schematics?
don at till.com
Wed Feb 25 07:32:10 CET 2009
> From: Aaron Lanterman <lanterma at ece.gatech.edu>
> Date: Tue, 24 Feb 2009 12:07:44 -0500
> Hmmm... Actually shouldn't the response be a quadratic and not a
> > harrybissell at wowway.com wrote:
> >> A resonant filter triggered with a pulse, followed by an absolute
> >> value circuit. Vary the Gain, the Resonance, and the Frequency ???
Um, this is an important point here... The analog computer program is
not a resonant filter through an rectifier. The idea is not to copy
the appearance of a bouncing ball, the idea is to derive the
differential equations, implement them on the analog computer, and be
impressed that the result looks much like a real boucing ball.
The analog computer program runs a parameter voltage (gravity) through
an integrator (velocity) and a second integrator (position), with some
feedback (damping). So it's not an exponentially decaying sine, it's
a quadratic, or at least a quadratic when the damping is set to zero.
(That point being made, yeah sure, then they add the absolute value
circuit, the 90-degree high frequency sine, and the ball-squash-diode
for the visual effect.)
I found the manual and schemetic for the Heath Analog Computer here:
A bouncing ball program is included at the end of the manual. But,
looking at it, I don't believe that program is correct. Additionally
there are a couple simplifications you can do so that you can include
both the quadrature ball outline oscillator and the bouncing ball
program together in the 9 opamps.
Palo Alto, California
don at till.com
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