DC brushed motor speed controller

Thread Starter

oidium45

Joined Apr 24, 2010
136
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.
 

Smoke_Maker

Joined Sep 24, 2007
126
oidium45

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

oidium45

Joined Apr 24, 2010
136
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

oidium45

Joined Apr 24, 2010
136
Thank you for the links Vrainom. I will look them over. Yes I understand what pulse widths modulation is.
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
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.
 

colinb

Joined Jun 15, 2011
351
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.
 

jwilk13

Joined Jun 15, 2011
228
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.
 

THE_RB

Joined Feb 11, 2008
5,438
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).
 

Bernard

Joined Aug 7, 2008
5,560
Or if you have some power transistors lying around , use as emitter follower, I like darlingtons & pot.& have used on several projects.
 
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