Arduino DUE cant activate MOSFET FQP30N06LG?

Hi there,

I am currently using an Arduino Mega sending a PWM signal to a MOSFET FQP30N06LG to drive a DC motor from an 18V Ryobi CD-18 battery powered Drill. I am using a 19V 4.7A power supply (from old laptop) to power the drill. I also have a diode across the Motors terminals for safety. This entire circuit works perfectly with the Mega (I only need to control the speed of the motor, not direction), however I need to change the board to an Arduino DUE. This setup does not work at all with the DUE.

I have been told it is because of the 3.3V output from the DUE's pins and I would need to add a small transistor before the MOSFET. Please could someone confirm this or let me know of other solutions. If this is the way to go, then I would highly appreciate a picture of what the circuit would look like or some guidance in order to make the drill work with the DUE.

Thanks in advance,

Mike

A normal mosfet as the FQP30N06 can be viewed as a variable resistance inverserly controlled by the gate-source voltage. The higher the gate-sourec voltage the lower the Rdson resistance. If you look at the datasheet the on threshold voltage is between 2 and 4 volts. But this does not mean much since Rdson at these voltages will be quite high causing high losses and overheating of the mosfet. The Rdson of typ 0.031 is specified at Vgs = 10V. This should be considered a benchmark.

There are two ways of controlling a mosfet from 3,3V (or even 5V) device.

  • Use a driver circuit, ic or discrete. This will drive almost any mosfet or igbt
  • Use a logic level mosfet or smart power switch.

Ok thanks, I have found a pic online showing a transistor driving a MOSFET. I have attached the picture. Will this work for my application with a 19V power supply? I am going to look into those other options. For some reason there aren’t any logic level MOSFETS at the electronic stores which I am buying from.

Thanks

transistor mosfet.png

It will work but not in a good way for two reasons.

  • The circuits is inverting the signal, this can be dealt with in software
  • The 10k resistor will give quite slow switching speeds

This one will work better: http://www.piclist.org/techref/postbot.asp?by=thread&id=%5BEE%5D+discrete+MOSFET+driver&w=body&tgt=post

Awesome! thanks so much for your help. Ill try it out today and see what happens.

be aware that it is still inverting. This can be fixed in software or with an extra transistor

19V is too high a voltage for a MOSFET gate, 12V is a practical maximum. This you fix by adding a 10 or 12V zener across gate/source of the MOSFET.

Noisy 19V from a power drill will probably destroy the MOSFET completely.