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.

Saturday, September 3, 2016

Flight Session 51 - Flying my Novas

My last few flight sessions have been with the new DT-180 drone. Some general LoS flying, but also trying to practice my FPV. Today, I thought I would take my Novas over to the school-field for some flights. Partly cloudy, 90f, and 5mph winds.

Super-Nova (newer Nova #2):

As I get to the field and get everything setup and ready for take-off ... I feel a few sprinkles. I look off in the distance, and a new dark thunder-cloud is approaching. I decide to go for it.

On power-up, I noticed that the Nova's power-up sequence of motor/esc twitch/beeping was different and abnormal. I tried again and got the same. I didn't think much more of it since it Armed ok. I likely bumped the throttle a couple of times to test motor spin, (as I usual do) but not sure. I felt a few more sprinkles so it's now or never. On take-off, it flipped over. Compass puck got cracked. Nova will still Arm, but back/left (aft-port) motor/esc set will not spin prop. Super-Nova definitely not living-up to its name. It never rained.

It took two Nova's and 2 years of flights, but it appears I have finally experienced a stock ESC or Motor failure. Caught me totally off-guard. The Nova was trying to tell me something (a few extended seconds of twitching/beeping of the ultimately non-functioning esc/motor-set on power-up) ... but I didn't understand.

Strange thing about it ... this is the newer Nova (with the v1.6 ESCs), and it 's never been crashed (well, unless you count just now when it flipped on take-off due to a non-spinning motor). Whatever component went bad here, it appears to have happened while Nova was sitting on garage shelf. Either that or it happened on initial take-off/throttle-up/amp-up.

In light of this event, I'm gonna have to add a couple of steps to my main pre-flight checklist.

- Listen for extra (abnormal) beeps/twitching from ESC/Motor sets during initial lipo connection and aircraft power-up (even if it stops after a few seconds).

- After Arming, bump the throttle on/off a few times and make sure all props/motors spin on command.

Because apparently, you can have a failure in a ESC/Motor set and it will still pass pre-arm tests and allow Arming ( basically goes un-detected). Without the pilot performing the above pre-flight observations ... there is no way to prevent a flip/crash/damage when you punch the throttle to take-off.

Current known issues:
1. Repair or replace bad motor and/or ESC in bad set
2. Repair cracked puck and do epoxy mod to reinforce.
3. Check GPS-module cable. I lost GPS for 5 mins during field testing (and it didn't appear to be an GPS-Almanac update).

Nova #1:

Only thing here is that both of my Turnigy-2700 Lipos have now puffed-up again and are apparently too large to fit into the old Nova any more (even with PDB raised-up 2mm). I used the Vant-3000 (that I usually run in the Super-Nova) instead.

The Nova flew great. All modes and Loiter. Quanum Retracts are still working fine. Flew around fast and stable. Fun flying and seems more casual than FPV. Just had the one battery that fit, but got over 12 minutes flight-time on it. GPS working OK for a 6-series. Barometer altitude reporting acceptably today on this quad.