Motor Controller Port Busted

[clock]

Hi,

Recently we were driving our robot around until half a hour in one moment a motor stopped working, and after checking the cables, we put that motor into another motor controller port, reconfigured the configuration file, and the robot worked fine after that. It turned out the first part on our motor controller stopped sending power for some reason. Anyone have any idea/thoughts on why a motor controller port(s) might become broken?

Clock

[mlwilliams]

I'd hook up a volt meter to the "bad" power port on the motor controller and run the "motor" at full speed. I'd expect to see the full 12+ volts from the battery. This will help you determine if it's really not sending any voltage or if there's something physically wrong with the powerpole connector that's not making good contact.

[mikets]

I'd hook up a volt meter to the "bad" power port on the motor controller and run the "motor" at full speed. I'd expect to see the full 12+ volts from the battery. This will help you determine if it's really not sending any voltage or if there's something physically wrong with the powerpole connector that's not making good contact.

Be careful how you interpret what you see. As I understand it, the way motor controllers work in general is that it actually output a 12V square wave whose duty cycle is corresponding to how fast you run the motor. If you run the motor towards full power, the square wave would have much longer ON time than OFF time. If you use a DC volt meter to check the voltage, depending on the voltmeter, you may get nothing even though it is outputting something. If you have an oscilloscope, you can hook up to the motor output of the controller and you will see what I mean. So don't throw away a motor controller only because you don't see any voltage on a DC voltmeter.

[mikets]

Be careful how you interpret what you see. As I understand it, the way motor controllers work in general is that it actually output a 12V square wave whose duty cycle is corresponding to how fast you run the motor. If you run the motor towards full power, the square wave would have much longer ON time than OFF time. If you use a DC volt meter to check the voltage, depending on the voltmeter, you may get nothing even though it is outputting something. If you have an oscilloscope, you can hook up to the motor output of the controller and you will see what I mean. So don't throw away a motor controller only because you don't see any voltage on a DC voltmeter.

BTW, if you decided to use a voltmeter anyway, try it on a known good port and if you can see voltages, then you can use it on the bad port.

[mlwilliams]

If you use a DC volt meter to check the voltage, depending on the voltmeter, you may get nothing even though it is outputting something.

Thanks for the warning about the square wave. I'd done this test earlier when we had a bad motor power wire and couldn't figure out why the motor wasn't running. I just repeated the test to be sure I remembered correctly. I unplugged a motor and read the voltage on the motor controller. With the main battery reading 12.08v on the DS I was able to see voltages from -11.97 to +11.97 and everything in between as I moved the gamepad joystick. There was no flicker; the numbers were very steady as long as the stick wasn't moving. I'm using a cheap digital meter that's probably 20 years old but hopefully the results would be the same for others. I totally agree that it would be a good idea to check a known good port to be sure there's a difference just in case the the meter doesn't read anything.