electronics for a diy ribbon controller

Mike mgranger at greenville.infi.net
Wed Feb 25 18:00:32 CET 1998

Puentstein at aol.com wrote:
> Greetings,
> After fumbling around with a 2 foot long piece of metal, a bit of vhs tape,
> and a 9 volt battery, (for now), this hookup 'seems' to work right (measuring
> variable voltage off the tape):
>                           + --------------------meter------------------ _
>                 tape:    ____________________________  _
>                             ___________________________    >-----voltage
> source
>          metal bar :   I___________________________I  +
>  ...The tape voltage appears to change "exponentially" as in the higher up the
> tape you move your finger the quicker the voltage increases.  Is this the
> correct way to wire one of these things??   Also, how can I get an "s-trig"
> (zero resistance) whenever the tape connects with the metal?    Sorry I'm all
> questions but my objective is to learn something/build a stand alone
> controller without frying the innards of an old Moog.
> Thanks for any info, Randy

What kind of old moog do you have? The moog ribbon controller had a
separate set of contacts that ran down the length of the controller that
you could touch with your fingers to generate an s-trigger. I suppose it
would be possible to use a transistor (2N4401 or similar)with a 10K to
47k resistor from its base to the point where the ribbon voltage is
picked off. This should turn on the transistor (emitter to ground, sink
on the collector for the s-triggger) when the output voltage is over a
volt or so, and give you a circuit to ground to use for an s-trigger. 
May need to use more amplification if you don't have sufficient voltage
at the low end of the CV range.

Let me know how it works if you try it.

===Mike Granger

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