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Topic: Motor Control (Read 1 time) previous topic - next topic

datcomputerguy

Hello, I would like to control 4 motors independently.  I am planning on using motors from VEX 2-Wire Motor 393 (http://www.vexrobotics.com/products/accessories/motion/276-2177.html) without the controller module things.  I need to be able to vary the magnitude of the motors independently of each other and also that means be able to reverse the direction of the motors.  I noticed that Stall Current:4.8A and Free Current:0.37A.

Basically my question is what should I use to do this?  Do I need Motor Drivers or Motor Controllers or what?  If someone could recommend a board for the motors I linked above that would be awesome!!!

tuxduino

Adafruit industries has a nice motor shield that supports up to 4 bi-directional dc motors, but I think its current rating is too low for you...

"4 H-Bridges: L293D chipset provides 0.6A per bridge (1.2A peak) with thermal shutdown protection, internal kickback protection diodes. Can run motors on 4.5VDC to 25VDC."

Anyway here it is:

http://www.adafruit.com/products/81

my 2 cents.

datcomputerguy

Thanks!  I was thinking about using that one but like you said I'm not sure about the current.  I got the larger of the motors because for my application the motors cannot stall so I figured I wouldn't need to worry about the stall current right?

tuxduino

I think you should play safe in case motors _do_ stall. You don't want to accidentally fry the h-bridge (or burn your fingers...) if the unexpected happens, right ? Because everybody knows it _does_ :)

dc42

L293D H-bridges are definitely not suitable for this application. This http://www.pololu.com/catalog/product/2503 is probably adequate.

Even if you never stall your motors, they will draw the stall current when you power them up, unless you power them up very gradually with PWM at a sufficiently high frequency.
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