DC brushed motor speed controller

Discussion in 'General Electronics Chat' started by oidium45, Sep 14, 2011.

  1. oidium45

    Thread Starter Active Member

    Apr 24, 2010
    130
    8
    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.
     
  2. Smoke_Maker

    Active Member

    Sep 24, 2007
    126
    15
    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
     
  3. oidium45

    Thread Starter Active Member

    Apr 24, 2010
    130
    8
    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...
     
  4. vrainom

    Member

    Sep 8, 2011
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  5. oidium45

    Thread Starter Active Member

    Apr 24, 2010
    130
    8
    Thank you for the links Vrainom. I will look them over. Yes I understand what pulse widths modulation is.
     
  6. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    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.
     
  7. colinb

    Active Member

    Jun 15, 2011
    351
    35
    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.
     
  8. jwilk13

    Member

    Jun 15, 2011
    228
    12
    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.
     
  9. gerty

    AAC Fanatic!

    Aug 30, 2007
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    oidium45 likes this.
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Sgt Wookie also posted a voltage controled PWM ckt some timeago- might find it in my file if interested.
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    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).
     
  12. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    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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