bs2 3 large dc motors, need reversible controller with pwm

Rov

is there a reversible speed··controller for dc motors, brused and brushless, that will handle a 40 amp motor at 12 volts?· It would be nice if it could be controlled form the stamp 2·and the controller could·generate it's own pwm based on some sort of output from the stamp.· Simultaneous use of the motors is required.·

Paul Baker

My understanding is brushless and brush motors are entirely two different beasts and are not driven the same way. For an brush motor, you can build an h bridge yourself, just get transistors that can handle the load.

Rov

Ok I've done away with the brushed motors, what kind of speed direction controller should I use for the brushless, I'm guessing I will still need something in the 40/20 amp neighborhood at 12/24 v.··· How does the controller differ between the two ??

allanlane5

This is a classical problem in robotics, and there are lots of parts created to answer it. Basically you need an H-Bridge for each motor -- this acts as a reversible switch, which allows you to apply your 12-volts forwards or backwards to get direction control.

Then you need a PWM controller to drive the H-Bridge. This provides Pulse-Width-Modulation of your 12-volts (basically on for a little, off for a little) which gives you speed control.

Now you need to size the H-Bridge to handle your voltage and current. There's lots of possibilities, google H-Bridge. And you need a PWM controller which you can talk to with the BS2 -- serial or parallel.

Post Edited (allanlane5) : 4/14/2005 5:03:20 PM GMT

Floyd

Devantech has a 20A H bridge: MD03 - 50V 20A H Bridge Motor Drive

I have not used it but just saw it yesterday while snooping around. Looks pretty versatile if not powerful enough for your needs.

http://www.robot-electronics.co.uk/shop/Motor_Controllers2008.htm

HTH, Floyd

Paul Baker

An h-bridge is used for bidirectional control of brush DC motors. An H-bridge cannot drive a brushless DC motor, the internal construction of a brushless motor is closer to a stepper motor in terms the required drive characteristics. To drive a brushless motor, feedback from the motor is required (rotor position) to derive the current drive waveforms, this is ussually do via hall effect sensors, but it can also be accomplished via encoders or Back EMF, if you want an article on the principles of BLDC control look here http://ww1.microchip.com/downloads/en/AppNotes/00901a.pdf·this article details using Back EMF to control a brushless DC motor.

Post Edited (Paul Baker) : 4/14/2005 5:03:19 PM GMT