I’ve had an issue with motor controllers heating up in the past (to the point where I smelled some magic smoke), and it seemed that certain ports on a certain cortex fried any motor controllers that were put in it (and powered). Obviously, I didn’t test this extensively, because motor controllers are too expensive to destroy in seconds for the sake of science. But, I kept consolidating ports on this cortex with Y-cables as the ports broke one by one, until eventually I couldn’t even power 12 motors (also worth noting that the internal motor controllers in the 1 and 10 ports were broken), so I bought a new cortex in January. This seemed to fix the issue.
Now I was testing my DR4B (which is run on two high speed motors geared 1:7 externally), and it seemed to be going up and down very quickly, without any issue (I had achieved nearly neutral buoyancy with my rubber bands). I ran it up and down a couple dozen times and went to my kitchen to get some food, so it had some time to rest and wasn’t particularly struggling in the first place. I went to show my mother how the lift worked, and suddenly one side stopped working. I first checked that the motors were still plugged in (they had come unplugged earlier, but it actually lifted okay with only one motor). I noticed that the lift was actually seemingly doing worse than when one of the motors came unplugged earlier, as if the non-functioning motor was actually providing more resistance than if it simply wasn’t powered. I touched the 2-wire connection between the motor controller and the motor and it was fairly hot. SHOOT. I touched the gray part of the motor controller and it was hot as well, just like when I had this issue last season. This freaked me out, because this cortex is less than 6 months old and I didn’t want to buy a new one with the V5 coming so soon. I let it sit for a minute, then plugged it back in and it worked fine (one time up and down). I figured I shouldn’t touch it again until I got some advice from you all about how to prevent or fix this issue. The last time I had this happen, the cortex absolutely died.
I have a simple setup of a battery plugged into the cortex, which has a a lot of motor controllers in it right now from the old robot but only two plugged into my lift motors. I BELIEVE I am only powering the two ports which I am using (I am pressing the button that used to run my claw, which only had two motors). The cortex is a little dusty, but the motor controller is not. Could this come into play?
TL;DR: Motor controller heated up and associated motor stopped working. Last time, I had to replace the cortex. Any way to fix this preemptively?
Check the wires, especially where they enter the motor casing, for broken insulation/shorts. Burned out controllers 90% due to shorting out the motor at this point.
Thanks for the input. I forgot to mention that I actually checked as much of the motor as I can see, and the wire all seems fine. That doesn’t mean you are wrong, however. The short could be just inside the part of the motor that I can’t see.
Because of the nature of the motors, they will actually go into a sort of ‘braking’ mode when shorted. All the symptoms seem to point to shorted motor wires.
Don’t forget to get the rubber “strain relief” out of the way (if you still have one) to look at the wires underneath.
If I’m tossing the motor, I might as well dissect it, so why not?
Thanks for the input, guys.
Interesting thing is, I did have a shorted motor at State and it was slightly different. But I do think (can’t remember 100%) that it heated a motor controller.
When the motor shorts it will put a bunch of current and since there is no fuse outside the ptc, it pulls way more current than the motor controller can handle hence the heating up and failure of it. The motor controllers act as the fuse in a way protecting the cortex but ports 1 and 10 have the internal so if they get fried you are screwed.
I slid the grommet and revealed this lovely short! So all of y’all’s speculation was correct. Does anyone know how this kind of thing happens, especially under a grommet?
