I currently have a USV equipped with a port and starboard thruster. We are working on transitioning from a skid steer system, to dual rudders and we are having issues with our thrusters turning off unexpectedly.
Here is a basic layout of our electrical schematic of the propulsion system:
So the pixhawk outputs a PWM (no ground necessary) to both ESCs and both ESCs are also sharing the same power source with separate fuses. Note the pixhawk is also powered from the same power source but with a regulator in between.
If the fuse blows (or positive is disconnected) going into the port ESC, both thrusters will stop working. The same thing happens if the ground is disconnected rather than the positive (or if both are disconnected). One would think that only the port ESC would stop working rather than both... right?
If the pwm going to the port ESC is disconnected, while + and/or - is also disconnected, the starboard thruster starts working again as it should. This leads me to believe that the PWM signal which should be going from the pixhawk to the starboard ESC is somehow being "drained" into the port ESC. Perhaps the giant capacitor on the non plugged in ESC is absorbing all of the signal?
My Currently Pursued Solutions:
If our theory of why this is happening is correct, then using an NPN transistor as a switch could work. If the ESC loses power, the transistor closes its gate, and the pwm line is disconnected, and thus the other thruster would work.
I am also looking into using an arduino to read the pwm from the pixhawk and output that same signal through two of its own pins, and thus isolate the PWM between the ESCs.
Ideally, I would like to be able to just output the main thrust commands through 2 of the pixhawk rc pins, but I have not figured out how to do that.
If anyone has any ideas as to the cause of this issue, or would like to verify our theory, please let me know. Thanks for any help.