Hi there fellow Quadplane pilots!
This is my first post in the new forum, and I’ll en-devour to respond daily.
I’ve been flying quadplanes/derivatives since the beginning of 2015 mostly with success. But over the last few months I’ve been running into issues trying to use ESC’s running the latest BLHeli and SimonK firmwares, on DYS, ZTW and Littlebee ESC hardware in particular.
- Motors run erratically, sometimes follows throttle or individual random motors cut out completely for a short period. (unflyable in hover)
- Motors and ESC’s get warm even when running without props (Same with brake/regen on or off)
- Resulting in pre-mature motor and ESC failure from overheating (mostly motor - won’t start - stutters)
- CHK Wiring/Dimensions/Plugs/Battery - all ok
- CHK ESC/Motor with PWM Servo tester - Runs ok
- CHK PXH PWM output with non-SimonK/BLHeli ESC on same motor and assembly > runs ok
- CHK with various prop combos as well as without, along with different mounting positions etc - (I suspected that maybe eddies were somehow interfering as quad is mounted on aluminium spars!) - No change
- Changed all potentially affected ESC settings and combinations with no effect - issue remained
- Pulled out hair trying to diagnose intermittent erratic faults… now bald!
Result of testing > likely issue:
For some reason the PXH to ESC PWM connection is dropping frames if the RC_SPEED is not a multiple of the ESC max Hz, which in turn causes them to cycle between max/min rapidly and makes them heat up within 30-60sec, as well as run erratic at low speeds and loosing sync.
Solution that is working so far:
Make PXH RC_SPEED 500 or 250 for 500Hz ESC’s and 300 for 600Hz ESC’s running BLHeli/SimonK.
To be safe to get it flying:
- Make sure ESC PWM mode is enabled to turn off Oneshot as this is not supported (This is disabled by default!)
- Set timing to medium and test before increasing
- Turn motor brake off and test motor/ESC temperature prior to flying when on. (This loads up the ESC/motor considerably, but typically doesn’t burn out the motor/ESC. Be careful that ESC has enough current headroom over motor max. draw)
Funnily enough, in 3.5.2 we never had any issues because Tridge set the default RC_SPEED to 300 and that worked fine with our first quadplanes running 600Hz DYS 40A ESC. But since 3.6 the PXH is running at 490Hz… Yikes some coincidence!
Anyways I hope this saves someone 6 weeks of stuffing around trying to figure out why some ESC’s don’t work properly with Pixhawk!