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Would this constitute abuse of a Casio?


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I've been looking online at information about the Arduino microcontroller. It is a cheap little computer, essentially, which can be wired to external components that one could build in the garage. On my list of jottings about what I might use the thing for is this: let the Arduino and its software control a device I could build in which a stepper motor wobbles a rubbery/spongy lever which would bear against the pitch-bend wheel of my CDP-230R. I would be able to specify the frequency and amplitude of the wobble. Then while playing my keyboard I would get a vibrato effect.

 

I've heard that variable resistors wear out with repeated use. Variable capacitors, on the other hand, could be twiddled millions of times without wearing out, I would think. Does anybody know how wear-resistant the pitch-bend wheel's guts are?

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By specification, many potentiometers survive less than 1000 motion cycles - in real life much more, but the fate of DJ console crossfaders (and some lousy slide pots in old Bontempis) prove that they breakdown by constant use.

It is not abuse unless a Casio is smashed and burned on stage or such demolition show crap. But why this mechanical solution if you have a microcontroller!? This is not a Hammond Novachord (1st full polyphonic tube synth, with freakish complicated mechanical timbre switch mechs). You may simply simulate a variable resistor e.g. by an optoisolator (photo transistor + LED, or LDR + incan if you want smooth (but slow) transition) or simply controlling the input through an 4066 analogue switch IC and feed it with a current produced by the Arduino.

Very likely the pitchbend potentiometer is polled like a homecomputer paddle port, i.e. a charged capacitor is polled by a digital input that counts the time until voltage drops below a threshold. (The duration is used as the detune value.) Then a current recharges the cap and everything repeats. You may easily simulate that by testing for the recharge pulse and then pull the voltage down (or up, depends on circuit) for an adjustable time through a resistor to simulate the potentiometer position. To keep the pitchbender functional, you may also wire your input parallel with the pot through a resistor. Voltage values may need to be tweaked (possibly through an op-amp, but likely a trimmer is enough).

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Yeah, feeding the headphone jack signal to an all-electronic circuit to add effects to the sound has a lot of merit. I am pretty sure I could make a circuit that puts on a tremelo effect like the old Leslie rotating speakers (i.e. an oscillating volume), and make the oscillation frequency of the amplitude be whatever I wanted it to be. But a circuit that wobbles PITCH (vibrato) is probably beyond what I would be able to whip up.

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