ESCs and motors sometimes work, sometimes not

I have a Pixhawk with a Taranis X9d and X8R on a hex using HK redbrick 50A ESCs.

Initially everything worked great. The ESCs played the tone after connecting the battery. Everything armed and flew well from the first flight.

Now I’ve added telemetry and a GPS and sometimes the ESCs do not play the tone sequence when connecting the battery. When that happens, which has become frequent, the motors don’t spin after successfully arming the FCU. I’ve also had a rough landing, but don’t see any intermittent connections, and wiggling stuff has no effect.

The situation now is:

Either all the ESCs play their tone sequence and everything works, or none of them do and it doesn’t work. The pixhawk always arms successfully.

The radio is working and I can see the radio servo values on the Mission Planner radio cal screen. This always works.

I don’t understand why this problem is intermittent and why either everything (i.e. all the ESCs and motors) work, or or none of them do.

I understand the Redbrick ESCs are cheap and I plan to replace them, but when everything works, it works and flies great.

I just wanted to clarify, If the ESCs play the tones when power is applied, everything works fine and their are no problems until the next time the battery is disconnected and then power re-applied.

Since all the ESCs behave the same way, I am assuming it is something in the PWM outputs on powerup that affects all ESCs. I’m assuming it is not as simple as power not being applied to the ESCs (this is done through the lower board which has power distribution built in), If that were intermittent, it would still be intermittent after power was applied and especially while flying.

Thanks

If you checked to see if it’s failing the “prearm checklist.”?

[quote=“dklamet”]I just wanted to clarify, If the ESCs play the tones when power is applied, everything works fine and their are no problems until the next time the battery is disconnected and then power re-applied.

Since all the ESCs behave the same way, I am assuming it is something in the PWM outputs on powerup that affects all ESCs. I’m assuming it is not as simple as power not being applied to the ESCs (this is done through the lower board which has power distribution built in), If that were intermittent, it would still be intermittent after power was applied and especially while flying.

Thanks[/quote]

Thanks for your help.

It turns out I was very, very lucky. I didn’t have any issues at all while flying. I did not look at the power because it was not intermittent while flying. Only on startup after connecting the batteries.

Though I still don’t understand how it worked as well as it did. After looking even closer today, the power wire from the battery had separated from the board, the actual pad lifted from the board, (it is the Aerosky 550 type with the lower board being the power distribution). At least it wasn’t my soldering.

Perhaps it gradually lifted, but the power must have been intermittent, though I don’t see how a connection that draws that much power could behave like that (I have an electronics background).

It was arming without any pre-arm failures. I checked the ESCs (opto), and I was thinking it was a power issue to them, but the opto line is not connected to power, so after that, I checked the voltage to the ESCs with a battery connected. Didn’t see a need to do this before, didn’t think that could possibly be the problem it it was affecting all the ESCs. However it was several volts lower than the battery. Didn’t take me long to find the issue after that.

I hadn’t done anything to stress relieve the wires where they connected to the board, which I see now was a big mistake. I didn’t use the power module, either, which I will be connecting, almost certainly on a different frame (At the price, I had a spare, but don’t think I will use it.)

Thanks again. I only feel a little foolish. :slight_smile: