How to control Speed of motor using MOFSET and potentiometer

I'm using a MOFSET IRF9540, 9V battery and 10k Potentiometer (I also have a 50k) and I want to reduce the RPM of my 3-4.5V motor for my RC car because its incredibly fast. I looked at many circuits online on how to do this but they all are using 12V batteries and 12V motors.. Adjusting my potentiometer hardly does anything but I need it to spin slower; please help me! I also have 100k ohm resistors or any kind if necessary -- I just need help building my circuit.

No arduino will be necessary for this!

This seems to be a continuation of Need help making the circuit for using a potentiometer to control small DC motor - General Electronics - Arduino Forum with the OP not believing the response.

That device is a non-logic-level p-FET, so cannot be driven from 5V logic.

A small 9V battery cannot provide enough current for a motor, not suitable.

If you have a 4.5V motor, try 3 AA cells (decent one's, not cheap ones, and preferably rechargable ones).
Motors take lots of current, even small motors.

Use a n-channel logic-level MOSFET with low-side switching - this allows using different voltages for
motor supply and logic supply.

Do not attempt to power the Arduino and motors from the same power source, you will almost
certainly be disappointed as it won't work reliably, and might cause damage even.

No arduino will be necessary for this!

Are you sure?

Then how about just using a lower voltage battery? If you run it on 2 x AA (3V) batteries it should be slower than on 9V.


If you do not want to use an Arduino.
Then a simple linear speed control may do, similar to early model railway electronic controllers, the only catch is they do not have direction change, that would mean the addition of a change over relay.
They are not as efficient as PWM type controllers.

Or PWM using LM555.

Just google dc motor control

Tom... :slight_smile: