-1
\$\begingroup\$

I am using a FQP30N06 MOSFET to PWM a motor. When I test it with an LED and a PC fan it worked fine, but when I connected it to a big motor it just turns on by itself. I am using the analogWrite function on digital pins and 1k ohm resistor from gate to source. The Arduino ground is connected to the source, the motor is connected to drain, it’s an Arduino uno r3.

\$\endgroup\$

closed as unclear what you're asking by Andy aka, Michel Keijzers, Finbarr, laptop2d, RoyC Apr 6 '18 at 20:58

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    \$\begingroup\$ Welcome to EE.SE. We need a schematic and/or diagram please, or we cannot help you. I will clean up your text, you do the rest. \$\endgroup\$ – Sparky256 Apr 6 '18 at 2:25
  • 1
    \$\begingroup\$ Did you put a flyback diode across the motor? \$\endgroup\$ – RoyC Apr 6 '18 at 5:57
2
\$\begingroup\$

Positive surges on the drain will couple thru drain-gate capacitance; non-linearity in that capacitance will leave a net charge on the gate, perhaps of the polarity and magnitude to turn on and sustain an ON gate voltage bias.

\$\endgroup\$

Not the answer you're looking for? Browse other questions tagged or ask your own question.