Hello,
I'm thinking of fitting a 70A automotive relay between the LIPO and the ESCs, which are the standard AC2 m2mpower AC20-1.0 type without optos. In the field, the APM/IMU would then be able to boot up with the ESCs and motors isolated. The APM is powered from an external BEC, which would bypass the relay.
Once everything is booted and I have a flashing green light and GPS lock, I would then flip a switch on the top of the AC2 which would close the relay, activating the ECSs and the motors. The ESCs would then go through their beep startup sequence, and then it's ready to fly.
The purpose of this is to avoid the current difficulties with boot code generating invalid inputs to the ESCs, and I don't fancy connecting and disconnecting the ESC control wires on a powered system.
Any comments, or any downsides of doing this? The relay is not very heavy.
Thanks very much
Rob
Replies
The 4 way switch should works. I would use a 4 way inverter switch, so that you can put the ESC signal input to ground instead of leaving it high impendance.
Should be safer.
Use the best switch you will find, again, as soon as you put a switch, you can have reliability problems.
Again, this is not the best solution. The right one is to correct the PWM noise problem during boot, or better add a watchdog circuit controlling the PWM APM outputs.
I would not do this. This is the best way to destroy your ESC because of a Voltage spike when relay is opening. And this is very heavy.
I did scope tests on this, when i designed some time ago a power supply for a CNC control interface. That's why i can say you it's not the right solution.
If you want to do it, you'll need an expensive high power Transil Diode after the relay, and a low value resistor in serie, to avoid breaking the Diode. This is not something you can design without a fast digital scope. And anyway you'll loose a small amount of power in the serie resistor.
The best is to open the PWM outputs and add opto isolation if not present in the ESCs. Obviously this is a 5-10$ electronic circuit who could be sold on the store.