Wednesday, September 7, 2016

ESC and/or Motor set failure and troubleshooting - Quanum Nova

As I mentioned in my previous post ... it took two Nova's and 2 years of flights, but it appears I have finally experienced my first (stock) ESC or Motor failure. The post will update as I fumble-through the troubleshooting for the first time :-)



Here are the symptoms the Quanum Nova is displaying with a failed ESC or motor:
  • On power-up, the Nova's power-up sequence of Motor & ESC twitching/ beeping is different and abnormal. It lasts a few seconds longer than normal, but finally stops.
      
  • It still allows you to Arm the aircraft. If you remember to bump the throttle on/off a few times (to make sure all props/motors spin on command) you will likely find one prop not responding properly. If you forget to test and attempt to take-off anyway, the multi-rotor will likely flip and crash.
So I start with the trouble-shooting. The is the newer Nova with the stock v1.6 ESCs. The bad esc/motor set is the Green-LED back-left (aft-port) one.

Here is something I noticed and might further help in troubleshooting.

If you disconnect only the PWM signal cable (the Dupont connector at the FC) of a "suspected bad" esc/motor-set (but leave power going to the ESC), and then power-up the Nova ...
  • The known-BAD set continues to twitch/beep constantly.
     
  • A known-GOOD set does not twitch/beep constantly. It does for it's initial test, then goes quiet like normal.
So, an indication of something. Obviously, the ESC is complaining about something. Only catch with his test is that a motor must be connected to hear the twitch/beeps but you don't actually have to power-up the motor manually (beyond what the ESC does during self-test). I also now see how shorted motors can fry and good ESC on simple power-up-and-test.

The ESC soldering, wiring, and PCB look fine. I see no blown chips or bad soldering.

I opened the motor, and the windings look good. My new LC/LCR meter (a gift) is not working properly for motor coil measurements in uH/mH, so I have another one on order. I will update this post later.

Update 1:
Ok, I got a working LC-Meter. This motor appears to be good because I am getting the following between the 3 motor pairs: 35.8, 35.6, 36.2 uH (aka mH). I took the readings with the magnet-bell removed and they were as they should be (within 10% of each other). Also, windings and magnets physically look good (nothing melted, burnt, or out-of-place).

I installed a used/working Nova v2.4 green-led-ESC. Seems motor solder-pads are in a different orientation than old v1.6 ESCs. I say that because after soldering to match the bad ESC, I still had to swap a motor wire-pair to get this motor to spin in the proper direction. It was no big-deal, but note worthy. It behaves like a good ESC/Motor set now (see above ... both tests ... connected and disconnected). I needed to program the ESCs (all-at-once) and re-do all calibrations.

Toward the end of ESC-Calibration, I observed that all motors now spin properly and turn in the proper directions. There is also a Motor Test in MissionPlanner. I like to do it from Terminal.

More repairs and updates documented here.

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