PWM signal of Pixhawk cube: what is the max signal wire lenght

Dear Guys, in our analysis of a flight failure, using the Pixhawk, we see that the ardupilot software gave the right commands to the ESC/motors combination. However, it seems that these commands (PWM signals) were not giving the proper result to the ESC/motors (X80 hobbywing with only grnd and signal wire).

So one question is how long the normal PWM signal wire can be without losing the signal strength (in meters or feet)? We used shielded wire in this test for the signal cable, however the shield was not connected to the ground (we later understood it should).

Can anyone of the Px cube developers tell us how long cable can be max to ensure proper signal at the end. And what can be done to extend that length? Should we add a 5V on the rail of the motor outlets just like for the aux channels?

Hope to hear, Winfried

I’m not sure of the maximum wire length for PWM, but for any reasonable distance you will need to use CAN bus. You can get CAN nodes from mrobotics.

Great, thanks Shawn, The distance we currently use is ca 4 meter… We will have to look into that… Is there some link to info on how to install that CAN bus system? Will check, Cheers, Winfried

Actually the mro CAN nodes dont do PWM to drive an ESC. You’ll need to find others somewhere, or use CAN ESCs like the KDE Direct ones - search KDECAN on their website
and check the docs
KDE CAN ESCs — Copter documentation
and here for nodes that will drive a PWM ESC:
OlliW's Bastelseiten » UC4H: UAVCAN for Hobbyists

Either that or run the PWM wires as far as safe, then use longer motor wires. But I think even this will be problematic.

Currawong also have Can-to-PWM adapters and CAN ESCs