PWM - Mosfet/motor introducing noise

[Acetronics2]

Hi,

First ...

Your diode parallelled to the mosfet must be paralleled to the MOTOR ... that will GREATLY limit the spikes ( 1N400x seems a bit Weak for this kind of motor ... try better 1N540x or a fast recovery TO220 model )

Now,

1) place a low ESR 1000µF or + capacitor as close as possible to the motor ... to lower the 12v power source impedance. ( by the way, I'm saying the mosfet could be placed close to the motor ...and the diode between motor terminals ...)

2) place a .1µF on your motor terminals

3) place a 10nF between each motor terminal and motor frame which has to be connected to circuit ground.

4) you can place a core coil ( 1mH range "big value" ) in series beetween 12 v and your 5v reg input

Alain