Reverseable AC motor control

[varhany]

What I have is a reversible AC induction motor (capacitor start), coupled to a gear reduction box that drives a screw, giving me linear motion. The motor has an on-board 10K position sensor potentiometer. I want to use this device to open and close the expression shutters in a pipe organ. The requirements are that the motor respond to another pot on an expression pedal in the organ's console. This means it would have to rotate the motor one way when the pedal is depressed (opened) and reverse when the pedal is closed. It would have to track whatever motion is applied to the pedal, in other words, including stopping wherever the expression stops.
I have a set of relays for reversing the motor and they are controlled by a solid-state driver circuit that is triggered through a 4N36 opto-coupler.
Anyone out there know how I might accomplish this? I am reasonably savvy in the electronics department, but this probably will take some sort of logic circuitry and I'm pretty much of a dummy in that field.
Also, I want this to be as simple as possible, so that the poor guy who follows me will be able to repair it. Most pipe organ people I know run screaming into the night when they see anything solid-state!
THANKS !!!!!!!!!!!!!!

 

[dr pepper]

Ideally you want an ac servo drive, however I'm thinking the cost would be prohibitive.

If you had a comparator circuit to compare the voltage from the pedal with the voltage from the linear actuator pot you could then use the o/p of the comparator to control your for/rev relay, and to keep the motor from continually going forwards and backwards you'd need some kind of deadband control, maybe a differential amp from both pots feeding another comparator which would give you on/off relay control with adjustable deadband.

 

[MikeMl]

Ideally you want an ac servo drive, however I'm thinking the cost would be prohibitive.

If you had a comparator circuit to compare the voltage from the pedal with the voltage from the linear actuator pot you could then use the o/p of the comparator to control your for/rev relay, and to keep the motor from continually going forwards and backwards you'd need some kind of deadband control, maybe a differential amp from both pots feeding another comparator which would give you on/off relay control with adjustable deadband.

Sort of like post #9 in this thread.

 

[varhany]

HI: Thanks so much for giving me some direction here. Are there sources online for the kinds of circuits that you describe? I'm a whole lot better at building than designing!!

Jason