My Arduino + Raspberry Pi robot was working fine in the morning. I tested it, it ran perfectly, and then I switched it off.

Now in the evening when I'm trying to run it again, with the same batteries and everything, it just doesn't move!

I stripped it down to the motor compartment and found that when I try to run my main motor, I can see sparks through the translucent plastic on the back.

Does that mean my motor is gone?

  • $\begingroup$ To clarify - when you see sparks on the motor, can you say if the motor is actually running on its own? (Arcing in the motor is quite common, so if the motor's working there may be some fault elsewhere in the electronics or loose wiring.) $\endgroup$
    – Andy
    Commented Jul 7, 2016 at 14:55
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    $\begingroup$ @Andy yes ofc the motor is running on its own. I'm controlling it the very same way my robot does. I just removed all the wheels and gears and stuff. Wiring shouldn't be loose, all the connections are soldered $\endgroup$
    – YaddyVirus
    Commented Jul 7, 2016 at 15:01
  • $\begingroup$ Hmmm next I would check the controller itself, if you have a meter see if there's any voltage at the motor driver's output terminals (when giving stop/start commands). If not, see if anything's coming out of the controller (that is, whatever feeds the motor driver). Don't panic, it can take a while to trace these sorts of odd random faults... $\endgroup$
    – Andy
    Commented Jul 7, 2016 at 16:15
  • $\begingroup$ @Andy at this point of time I'm pretty convinced that my motor is gone. My motor driver is perfectly fine. And I can get the motor to work by giving it a bit of push, but its performance is nowhere near the power I used to get. What I am amazed about is how did it short? I mean I've been running it on the same battery, (11.1 V 3300 mAh 25 C LiPo), it works fine in the morning, and when I use the same setup several hours later, the motor just dies. $\endgroup$
    – YaddyVirus
    Commented Jul 7, 2016 at 16:52
  • $\begingroup$ Ah if you're sure it's the motor then ignore what I said about the controller :( I once burned out a motor (in a slot car - don't ask) and it was due to overloading the car. But the failure was obvious at the time - it started to lose speed rapidly. The windings were permanently damaged by excessive heat. But unless you noticed your motor doing the same thing, there must be some other cause... $\endgroup$
    – Andy
    Commented Jul 7, 2016 at 17:06

1 Answer 1


If you are using a brushed DC motor, then (hopefully) the sparks that you are seeing are a discharge between the commuter and the brushes--this is normal. Another example of this is evident in certain electric drills; under low lighting, you can see sparks through the ventilation holes. If you are interested in this, you can ask at the EE Stack Exchange, or you can grab a textbook.

As for debugging your motor, try using a different voltage supply or use a multi-meter to make sure that your battery is charged. Motors do burn out, and this may have happened, but you should check the easy things first.


I found a resource that corroborates what I am suggesting: Debugging 3-Phase Motor Failure. Your motor is not 3-Phase, but the same idea applies. Measure the winding resistance with a multi-meter. If your coil has broken internally, you will get a very large resistance (unlikely because you are seeing sparks); if you get a very small resistance, smaller than the rated value, then your coil is shorted, which might explain the sparks.

I would do these checks first, then move onto the rest of your components, but if the motor is not spinning under a verified supply voltage, it's definitely toast.

  • $\begingroup$ Batteries are up and running just fine. It's only the motor. I also noticed that the speed of the motor keeps changing randomly. Burned out maybe? $\endgroup$
    – YaddyVirus
    Commented Jul 7, 2016 at 14:52
  • $\begingroup$ It may be that the brushes are worn. If the motor has replaceable brushes you could try that. Worn brushes could increase the arcing you are observing. $\endgroup$
    – SteveO
    Commented Jul 7, 2016 at 16:31
  • $\begingroup$ @SteveO Can't open the motor. Its all in a metal cylinder $\endgroup$
    – YaddyVirus
    Commented Jul 7, 2016 at 18:31
  • $\begingroup$ @YaddyVirus Is it an old motor? $\endgroup$
    – JSycamore
    Commented Jul 7, 2016 at 22:31
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    $\begingroup$ @YaddyVirus - I would just an an asterisk ( * ) to NBCKLY's comment, "If the motor is not spinning gunder a verified supply voltage, it's definitely toast." The key point there is verified supply voltage. An almost-dead battery may read near-rated voltage when no load is applied. Try using fresh/known good batteries or a wall adapter before you discard the motor. The winding check is valid regardless, but you should expect some very low resistance, on the order of tenths to a few Ohms, if the motor's good. It generally needs to be shorted to be bad. $\endgroup$
    – Chuck
    Commented Jul 8, 2016 at 19:43

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