Velocity Feedback

[jmetcalf]

I am using the 7344 Motion Control and MID-7654 Servo Power Motor Drive. I am wanting to control the velocity of a P.M. DC motor; I do not care about position. I also do not have the mechanical room to fit a quad. encoder onto the motor shaft. What I am wanting to do is build a difference amp with a high common mode voltage that will measure the voltage across the motor since the voltage should be proportional to the velocity and use that voltage as the secondary (velocity) feedback (configured as an analog input and disable the primary (position) feedback.

Would this work or does anyone else have any other ideals?

--Jon

[Brian_Beal]

If I understand your setup, this is a typical dc motor speed control application. DC motor speed controllers essentially do what your proposed circuit would do. They are very inexpensive and a 0-10V input can be used to set the speed. Speed regulation is not the best though, especially at slow speed. You may want to consider using a stepper with a speed controller. Speeds are right on, and repeatable. Let me know if this is the kind of application you have, and I could give you some recommendations on hardware.

[jmetcalf]

Brian,
Thank you for the suggestion about the speed controllers. Can you give me the names of the manufactures of some DC motor speed controllers?
Buying an off the shelf solution is preferred than designing a custom circuit for my application.

As for your ideal about using stepper motors, I am trying to control existing assemblies that already have the DC motors embedded in them. What I am doing is trying to assist the M.E.s in adding control to their proof of concept models and we do not want to turn a custom circuit board and custom software for a micro-controller for each concept model.

Thanks again for your suggestion.

--Jon

[Brian_Beal]

Jon-
Minarik is the one that comes to mind. There are many others, though.

[jmetcalf]

Brian,
Thanks for the info! I will check them out.

--Jon