Motor driver with op amps

So would this motor driver idea work?

No, that doesn't look like it would work, I think there needs to be more steering logic to properly drive the op amps into positive and negative saturation when enabled, your circuit only saturates on side or the other for positive or ground voltage, the other side is kind of 'floating' with equal voltages on both inputs.

For DC motors there are motor driver chips that include the steering logic, op amps and current amplifiers all in one package with all the details worked out. You have only to select the proper model for the voltage and current required.

Lefty

Well, I guess you could make it work.

Use a couple of 10K-or-so resistors to make a voltage divider on the "enable" line to give you a roughly 1/2Vcc input to the opamps. That'll make the comparators work the way you want.

You may need a current-limiting resistor in series with the motor.

You'll also need a fat bypass cap on the opamp power supply (It'd be even better if you weren't running it off the Arduino's Vcc, to keep the noise away from the logic power).

And protection diodes to absorb the inductive kickback when the motor is switched off.

But, even after you've done all that, you're probably not going to be able to run anything bigger than one of those little pager vibrator motors, because opamps don't have a whole lot of output drive. And maybe not even that: check the specs on the motor and the opamp.

Driver chips like the L293D are cheap and readily-available. Unless you're doing the opamp thing just for the heck of it, you're almost certainly going to be better off with one of those.

Ran

This looks promising. Does anyone have an opinion on it. I'll hopefully get around to trying it sometime soon.

Oop, I should post the link....

This looks promising (http://hades.mech.northwestern.edu/wiki/index.php/Linear_Amplifier_Motor_Driver).

Maybe I'd convert the PWM output to a steady voltage with a capacitor... or not. It's worth playing with...