Could someone tell me why I can't get this "simple", "common" circuit to work? and also, just to clear my stupidity, at what points do I put my probes to measure that the voltage actually is going from the drain to source.

I am using a fqp30n06l logic level mosfet. I am using a fixed 5v power supply to supply that 5v. I have a simple 12v motor. I need the 5v to switch on the mosfet so the 12v motor will run. I can measure voltage from gnd and the gate and it does show 5v. I do have the 5v and the 12v ground connected.

The motor by itself does run directly to the 12v battery. Just to be clear so someone can check me, the gate is the left pin, drain is the middle and right is the source. Just double checking.... and the motor is on the drain side, correct?

I've even tried it with a resistor and LED using 5v and I still can't get the LED to work either. I have many fqp30n06l that I have tried. What in the world am I overlooking? What spots can I measure? I'm sure I am overlooking something simple and stupid for what seems to be such a simple circuit.


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ If you short the drain and source of the MOSFET does the motor turn on? \$\endgroup\$
    – John D
    Sep 25, 2018 at 19:22
  • \$\begingroup\$ Are you doing this on a breadboard? \$\endgroup\$ Sep 25, 2018 at 19:27
  • \$\begingroup\$ No, when I short the drain and source (good idea btw) it still does not run. Yes, I am doing this on a breadboard.I switched breadboards and the LED version does work now, so the 1st was a bad breadboard.... \$\endgroup\$
    – mScientist
    Sep 25, 2018 at 19:48
  • \$\begingroup\$ Okay, I hard wired it using protoboard and... it works. I shall never use a breadboard again..... On another note, the motor does turn quite a bit slower than if I hook it straight to the battery, any ideas why? What would I need to look at? \$\endgroup\$
    – mScientist
    Sep 25, 2018 at 20:11
  • \$\begingroup\$ Scratch that, motor turns the same lol, brain is fried....all thanks to a breadboard... \$\endgroup\$
    – mScientist
    Sep 25, 2018 at 20:20

1 Answer 1


The answer is: Don't use a breadboard. They easily go bad. I just happened to have two and decided to make it again on the other. After duplication, it worked. My take is anything that is possibly over 1 amp don't use a breadboard. Thanks to all for the input and ideas about shorting the drain and source.


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