Problem with motor running when main breaker closed

[blhenze]

We're back from the regional and are trying to do some work on our robot. For some reason one of the motors starts up the second the robot is powered up. We don't understand why this is happening. Any suggestions?

[Tom Line]

Is this with the robot enabled, or disabled?

If it's disabled, you have a short on the motor side of the motor controller, or the motor controller has failed internally somehow and is sending voltage through.

If it's disabled and running, pull the fuse. If the motor stops, it's likely you've got a faulty motor controller. If it continues, you have a short on the motor side of the motor controller.

If it's enabled, work backward from the motor.

Is the light on the motor controller changing color?

If it is, you know the the controller is getting a signal to run.

This may indicate your code is telling it to run, or your pwm cable is damaged or shorted. The next step is to either replace the pwm wire, or check what your code is outputting by looking at your dashboard for that particiular output.

This is all assuming that the wiring for the motor was done correctly.... it may be that someone miswired the motor directly to the power distribution board. That would also cause this condition.

[Tristan Lall]

Follow the power path. Most likely (if the robot is disabled), you've connected the motor directly to the power distribution block, rather than having a speed controller or relay module (Victor/Jaguar/Spike) in between.

See this diagram for more details.

[Alex Cormier]

May also be the trim on the controller if it's a drive motor?

[EricVanWyk]

If it turns on immediately, it must be in your power path. Do not bother looking at your code, the cRIO, the sidecars, etc.

What are you using to control the motor? How is it wired?

Please replace your motor controller with an identical unit after checking that it is wired correctly. A likely cause is that the motor and battery terminals are swapped.

[Al Skierkiewicz]

Bernie,
If this motor is connected to a Spike, you may have fused (welded) the contacts on one of the relays.