MOSFETs damaged due to motor stalling

[glisandro]

Hi!

Some hard landings have caused the MOSFET to stop working because the propeller/motor briefly locks up. Would it be possible to fix this issue by placing a diode on the motor pads? I understand that the Volantex V761 receiver uses this solution.

[shaise]

Sorry for the late response.
You are definitely correct! A diode should have been placed between M+ and M- contacts:

this should have eliminated back emf, specially when in PWM mode.
Not sure if this have fried the Fet or something else in the circuit.

You can use 1N5822 or SS34, for example.

What kind of DC motor are you using?

shai

[glisandro]

I installed the receiver on a Volantex Super Cub 500. It has an 8520 motor with a gearbox and a 13 cm propeller. It draws about 2.8 A at 3.8 V.

I'll try that solution and report back.

Thanks!

[shaise]

That explains why the FET fried. The fet's max current is 5 amps, so if you stall your motor it can surely draw more then 5, if the steady state is 2.8. In this case the diode will not help.
Or is it 2.8A stall current?
I use this motor: https://www.aliexpress.com/item/1005007907749148.html

[glisandro]

Okay, but it's the same MOSFET as the V761 receiver. Maybe this receiver has another form of additional protection.

I'm not sure what the solution is, but I assume it's a better FET or a propeller/motor combination that consumes less power.

[shaise]

Try the diode, perhaps this is good enough.