Newsgroups: comp.robotics
Path: brunix!sgiblab!swrinde!cs.utexas.edu!utnut!cannon.ecf!chengb
From: chengb@ecf.toronto.edu (CHENG  BENJAMIN)
Subject: Trouble....DC motors
Message-ID: <CMKxAK.KF8@ecf.toronto.edu>
Sender: news@ecf.toronto.edu (News Administrator)
Organization: University of Toronto, Engineering Computing Facility
Date: Sun, 13 Mar 1994 01:25:32 GMT
Lines: 15

I have built a DC gear motor controller. It is controlled by a PC
and can turn on a set of H-bridge drivers and drive the motors.
It works fine when no load is connected to it. (I've checked it by
a voltmeter and the output voltages are normal.) However, when I
connected it to the motors, it is impossible to control. The turn-on
actions of the motors should follow the computer but they are not.
For example, when I try to command only #1 Motor to turn on but both
#1 and #2 Motors turn on simultaneously. I just suspect that there
are some back-EMF currents flowing back to the output terminals and
disturb the controller. My question is : Is there any way to avoid
it? Do I have to add some capacitors, diodes, or resistors to the
circuit? My circuit doesn't have any resistor in it and will it
create a problem? Any suggestions or comments are welcome and I will
be very appreciate that.

