Chief Delphi - 12V Voltage on Robot Frame (Perhaps because of a BaneBot)

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Re: 12V Voltage on Robot Frame (Perhaps because of a BaneBot)

If you have a frame short with the motor installed and it is gone when you take the motor out of the robot, it just might be you had screws that were too long and were touching wiring inside the motor. It is unusual to measure +12 volts on the frame when nothing is running. If you indeed had a positive 12 volts while the meter's other lead was on the +12 terminal of the PD, you were measuring the 24 volt supply that feeds the PD less the 12 volts of the battery. Check the insulation on the cRio.

Re: 12V Voltage on Robot Frame (Perhaps because of a BaneBot)

Quote:

Originally Posted by artdutra04 (Post 1348080)

Removing the breakers probably won't work in this situation. The breakers are single-pole on (AFAIK) the high side of the circuit. If a RS775 is case shorted, removing the breaker won't show the problem.

I would check first to make sure cRIO is isolated, then check to make sure the camera is isolated, then physically disconnect both wires leading to every RS775 (one at a time) from the M+/M- side of the speed controller, then check any custom sensors (such as Sharp IR sensors), as these in that order are the most likely causes of grounded frames.

You are correct that only the positive of the PDB board is fused and the negative terminals still have continuity even when the breaker is pulled.

However, correct me if I am wrong but unless powered and driving, if I recall correctly, the motor terminals of the motor controller should be isolated from 12V positive or negative side of the motor controller. So if the suspected shorted motor was wired correctly, pulling power by removing the breakers to the motor controller, I believe should remove the short to the frame.

Also, if the motor is shorted to its case, the actual short to the frame would change depending on which direction the motor was driven, and the voltage differential being provided to it.

If the short still exists, then its not a motor, and running though the circuits as I mentioned should help narrow it down. I would agree if they are reading a delta 12v between battery positive terminal and frame, when the robot is disabled, it means the robot chassis is shorted to battery negative terminal somewhere on the PD/CRIO/Dlink/Camera side of the system.

-Kevin

Re: 12V Voltage on Robot Frame (Perhaps because of a BaneBot)

Everyone else probably gave the right answers, but If it werent for the short, I would check to see that it was plugged into a 20 amp breaker. Without power it wont be able to send out signal to more than a few motors.

EDIT: Im reffering to digital sidecar

Re: 12V Voltage on Robot Frame (Perhaps because of a BaneBot)

If you do find it to be the RS775, the root cause is likely your gearbox-side motor mount. Any of the Mabuchi or similar motors will case short due to overheating of the enamel on the rotor shaft. You must ensure ample airflow through the front and rear air vents of the motor.

I have seen similar issues caused more than once due to this scenario. Do a continuity check from the motor housing to your chassis to confirm.