Hello,

We are building a new quadcopter, the relevant parts for the problem are listed bellow:

Motors: Tmotor U3 

ESC: Tmotor Air 40A (no BEC, 600Hz)

BAT: 4S

FC: Pixhawk 3DR

TX/RX: Futaba 10J / Futuba 2008SB, connected in SBUS

EDIT: Firmware(s) tested: 3.2 & 3.2.1

Note: We have had the Pixhawk since the end of 2013 and flew it very successfully before on another RIG.

The problem is quite simple, we mounted motors and ESC, we made the ESC calibration using a squid cable connected to the RX throttle. Up to here, no problems, motors are in sync and all rotating in the good direction.

Then we connect them to the Pixhawk, after some basic config we intend to arm to check the correct working of the motors. Only 2 ESC are initialized when arming, so only 2 motors run. It doesn't really matter which ones, as if we change the order of the ESC pins on the Pixhalk, other 2 ESC got activated and spin their motors. We've been testing different RC_FREQ without success. To describe the problem exaustively, we should add that sometimes, 3 ESC (randomly, or so it seems) are initialized, yet one of them quicky un-init before we can arm.

Questions:

- We've read somewhere (on this forum) that the PWM output of the Pixhawk are 3.3v instead of 5V, could this be the problem?

- Is it because our Pixhawk has an older revision (We don't really know which one btw) ?

- Did anybody reading this got this combination of FC/ESC to run?

- If not, should an incompatibility be listed?

Anyone with a beginning of an answer would help big deal!

Thanks a lot for reading.

Best regards,

Raphael

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Replies

                  • Hey!

                    It wasn't the PWM throttle value being too low :(

                    I did get all the ESC to init and motors to start in stabilize mode (was in althold before as a default mode) but 1 of them didn't start right with the others, it took him like 10sec more to init (the ESC actually, not the motor). It made a strange sound sequence before actually starting. It might be a problem with the motor/esc connection. I will have to desassemble the motor and check for any damage.

                    I tried to reproduce the 4 motors spinning without success, then I upgraded the firmware to 3.2.1 (was in 3.2.0) and we are back to the starting point. Only 2 esc init.

                    I will continu trying things see if I can at least find something else before switching to a more final solution: changing the ESC.

                    Raph

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