DC brushed motor speed controller

Thread Starter


Joined Apr 24, 2010
Hello everyone,
I am looking for a quick/easy way (aside from just using a potentiometer or variac) to adjust the speed of a small brushed DC motor.

Any suggestions?

I am debating on trying PWM but i dont know which IC would be best suited.

The motor is about 2A max and 18V 18000rpm.


Joined Sep 24, 2007

As you change voltage the motor speed will change, you cane use 6 steps of 3 volts.

it depends on what you want and what type of motor you have.

Good luck

Thread Starter


Joined Apr 24, 2010
I understand that i can adjust voltage to adjust the motor speed. I was looking for something slightly less crude. Some form of PWM would be nice.

Here is the motor that I am using. http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=rs_775vcwc
I am trying to stray away from simply adjusting the voltage mainly because i would like to learn a bit about how to set up a PWM circuit. Especially when dealing with motors. The problem is that I dont know which circuits online are "good" examples and which ones are horrible...

Thread Starter


Joined Apr 24, 2010
Thank you for the links Vrainom. I will look them over. Yes I understand what pulse widths modulation is.


Joined Jun 7, 2009
virtually any PWM voltage regulator can work. A fixed reference in will produce a fixed duty cycle out. A driver may also be required to meet your power requirements. Speed regulation is a different matter.


Joined Jun 15, 2011
You are right to want to avoid just reducing the voltage with a potentiometer or some other linear means. That will just create a tremendous amount of heat and waste tons of energy when the motor is not running at full voltage.

PWM is a much more efficient method of controlling the motor speed since you aren't primarily regulating speed by converting excess voltage to heat.


Joined Jun 15, 2011
There are quite a few good 555 timer circuits that should do what you want. Just Google "555 DC motor control" and you should get some useful stuff.


Joined Feb 11, 2008
You asked for a "quick and easy way" for a small 2amp motor which would be a LM317 or LM338 on a heatsink and a pot to set the regulated voltage.

A fixed regulated DC voltage gives better speed regulation than a fixed PWM duty too, so if this is going to be run open-loop with just a pot to control it the DC regulated voltage will outperform a PWM system (apart from wasting heat).


Joined Aug 7, 2008
Or if you have some power transistors lying around , use as emitter follower, I like darlingtons & pot.& have used on several projects.