I need a circuit to PWM, open loop drive a 12v dc motor. I want to use a toothed wheel with a hall effect sensor to control the speed of the brushed dc motor. I also need calibration capability within the open loop for speed adjustment. I hope this is a common application, Thus far I have not found a specific circuit for this. Thanks....JCR

 

Sure, it's very common, just do a Google search on it. However, with an open loop drive, I don't know how you expect to control the speed.

Your subject title is not very helpful; don't expect many other replies.

 

My apologies...JCR

 

If you are using a toothed wheel with a sensor to measure the RPM and thus control the PWM circuit, you will have a CLOSED VELOCITY LOOP, not an open loop. Basic tachometer feedback.