Motor for Guitar Tuner

[The_Fleertz]

Hey Folks,
I am currently working on a project to make an automatic guitar tuner and I need to buy a DC servo motor. I was wondering if anyone had any suggestions for motors that would have enough torque and be easily driven using a PIC16f887 and an H-bridge. No RC servos or stepper motors are allowed.
Thanks!

 

[chuckey]

Its a gearbox thing, any electric motor would do providing its always starts and its revs/torque are matched by gears to the tuning knobs requirements. To try and do it without gears would give you a very large motor which would be difficult to mount/connect to the tuning head. A compact motor would be one that is used in model electric trains, about 15mm square X 50mm long, 12V @.5 A?.
I was thinking of how you could do this, suppose you measured the frequency, then pulsed the motor on for 100 mS, and measured the delta frequency, and repeated it a couple of times you could then work out the delta F v. motor on time, then run the motor for the required time, then repeat for a time of 10mS, for correction.
Looks like a very mechanical project to me!
Frank