First time trying to control a dc brushed motor with a N-Channel MOSFET.
I believe I understand how it should work but it just isn't and I am stuck as to what to test and fix or change.
I have a small Dc brushed motor(if i connect it directly to +5V power supply it works fine) that i connected to ma IRF1010N MOSFET as per the schematics.
Arduino runs just blink code (but it also doesn't work if i manually connect gate to +5V)
However if i replace the motor with an LED it works just fine Led blinks like it should
I have tried running the motor on 12V(thinking the MOSFET was dropping the voltage too much) and it still doesn't work, but if i connect Gate to +12V for a while, it like "charges" and starts turning, but a 1 sec pulse from arduino doesn't turn it on.
What am I missing? the motor alone works, MOSFET with LED works it just when I try connecting the motor in place of the LED it doesn't work? What can i try what can I test?
Best Answer
First figure out how much current you need to make your motor move. Then look up the IV curve for the mosfet and make sure the mosfet will sink at least that amount of current at 4.5v gate voltage.
looking at the graph I see that the mosfet should pull about 1 amp. is that enough for the motor?
The mosfet most likely requires more gate voltage to turn on sufficiently. You can test this by applying 10v to the gate. At 10v gate source voltage the mosfet will be able to pull well over 10A, more than enough for most motors.
It also makes sense mentioning that the load you are trying to drive is inductive. Current will slowly increase when the mosfet is on and when it turns off it will want to continue. With no where to go it will drive the drain of the mosfet to some arbitrary high voltage. It makes sense to place a diode across the coil to absorb this high voltage pulse. The cathode will be connected to the 5v rail and the anode to mosfet drain.