motorised pots

R.G. Keen keen at
Tue Jul 21 18:30:15 CEST 1998

A simplified way to do motorized pots is to scavenge the stepper motors
from half-high 5 1/4" diskette drives. Some of these have a shaft
coming out both ends. These are the ones you want. You mount the motor
on your front panel, then couple the pot shaft to the back of the motor
with 1/2" of tygon tubing and an auto hose clamp or glue. These motors
have a 1/4" shaft (matches most pots) and are 180 steps per revolution. 
Find a used computer place and you can often get a pile of these things
for a buck - or offer to haul them away if THEY'LL pay YOU!

There are single chip up-down stepper drivers to turn the pots. The
stepper solution holds its position when un powered, the double shaft
lets you mount it on a panel with standard knobs, and use the knob to
manually adjust, and the stepper chip lets you use digital control,
which presumably you want to do anyways. You can also mount the
motor/pot in an aluminum U channel with the motor inside and the pot
outside the U so that the pot is shielded from motor electrical noise.
Presumably you could also put the stepper driver chip inside the U and
have that noise shielded from delicate audio lines as well. The tubing
also prevents even any electrical contact between the two for further
noise prevention.

It's cheaper, just more assembly required than pre-motorized pots.

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