I have one last question about this topic.
In a similar application but with only 1 relay that control a PWM which in turn control a pump. Should I add a flyback diode to protect the PWM from the pump inductor?
The PWM is of course the cheapest one we can buy on internet.
You cannot PWM a relay, it will die soon.
I am assuming he's got a PWM source he wants to pass through a relay to run the motor forward or reverse at variable speeds.
The relays could benefit from flyback diodes but the PWM source will require those same flyback diodes if they are not already part of the PWM source circuit.
Sorry if it was not clear.
In fact, the PWM is powered with 12 volts. When powered, it produce a PWM output that drive the motor.
My relay only toggle on and off the 12 volts of the power input of the PWM. I set and forget the PWM rate with the potentiometer for example at half duty cycle. Then I turn the relay on which in turn transmit power to the PWM. This drive the motor at half-duty cycle or other preset rate.
If a flyback diode is installed. I would fix it just between the + and - prong of the motor since there is no other place.
Thank you
One must assume the PWM module is itself protected (with a diode - I can see at least one on the board) against the motor, so there will be no impulses passed through to to a relay that is switching its power input.
You would only have concerns if you were putting the reversing relays on its output to the motor.