Pulse Width Modulation DC Motor Control

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Often, people attempt to control DC motors with a variable resistor or variable resistor connected to a transistor. While the latter approach works well, it generates heat and hence wastes power. This simple pulse width modulation DC motor control eliminates these problems. It controls the motor speed by driving the motor with short pulses. These pulses vary in duration to change the speed of the motor. The longer the pulses, the faster the motor turns, and vice versa.

Schematic

This is the schematic of the Pulse Width Modulation DC Motor Control

Parts
Part
Total Qty.
Description
Substitutions
R111 Meg 1/4W Resistor
R21100K Pot
C110.1uF 25V Ceramic Disc Capacitor
C210.01uF 25V Ceramic Disc Capacitor
Q11IRF511 MOSFETIRF620
U114011 CMOS NAND Gate
S11DPDT Switch
M11Motor (See Notes)
MISC1Case, Board, Heatsink, Knob For R2, Socket For U1

Notes

  1. R2 adjusts the speed of the oscillator and therefore the speed of M1.

  2. M1 can be any DC motor that operates from 6V and does not draw more than the maximum current of Q1. The voltage can be increased by connecting the higher voltage to the switch instead of the 6V that powers the oscillator. Be sure not to exceed the power rating of Q1 if you do this.

  3. Q1 will need a heatsink.

  4. Q1 in the parts list can handle a maximum of 5A. Use the IRF620 for 6A, if you need any higher.

  5. This circuit is not a true pulse width modulation control. Because only the frequency of pulses varies, it is really pulse frequency modulation. This works, though not as well as true PWM.

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Comments
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Jim
Pulse Width Modulation DC Motor Control
Saturday, August 13, 2011 10:15:47 AM
I've seen Pulse Width Modulation circuits that use the 555 chip. Is it possible to use those circuits with multiple N-FET to control a 70 amp motor?
Todd Winsor
Pulse Width Modulation DC Motor Control
Saturday, May 28, 2011 12:10:37 PM
I have a fishing troaling motor. I would like to control the speed of the motor. Its operating voltage is 12 to 24 VDC. Will this PWM control work ? If not---can anything be done to make it work ? Thanks !
wes clark
very slow moving motor
Wednesday, November 03, 2010 11:45:47 AM
i'm making a coyote decoy, and want to put a decoy on a motor and control it with a remote control from a old car, where can i find a reasonable motor to turn appr 8-15 rpm's while using like two d size batteries.
hassen
Pulse Width Modulation DC Motor Control
Wednesday, April 21, 2010 7:13:37 AM
i have an elevator final year project , and i want to select a dc motor. but the problem that i dont know how to control it. please can you help me. thanks
Cain
Pulse Width Modulation DC Motor Control
Wednesday, August 19, 2009 1:52:11 AM
If 24 VDC 10 AMP motor is brushed motor, you need KDS24050E, if it is brushless motor, you need KBS24051. Kelly controller is good. Their controller improves the perfomance of my motor. You can try it. Their website: newkellycontroller.com
Dave
Pulse Width Modulation DC Motor Control
Wednesday, July 08, 2009 1:41:14 PM
What is the best type of controller I can build for my 24 VDC 10 AMP motor? Im really wanting to know a most efficient design. Would it be a PWM integrated into an H-Bridge set up? Thanks all.
Jim Dandy
Pulse Width Modulation DC Motor Control
Thursday, June 25, 2009 8:33:57 AM
Definitely needs a freewheeling diode as someone else said. If there is no diode the drain voltage of the mosfet when it turns off will fly up high enough to avalanche the fet and make it run very hot. Diode will improve efficiency quite a lot. Use a schottky type for voltages up to about 50v.
sanjay
Pulse Width Modulation DC Motor Control
Wednesday, June 03, 2009 4:32:32 AM
am to make a speed controller for a dc motor 24v. This motor is 24 v 500 watts and battery is 10 amps, please send me a diagram,as fast as u can.thanks
Bruce Freeman
DC gen. to power DC motor with speed control
Saturday, May 09, 2009 8:54:45 AM
I have a small gas turbine turning a 28 volt generator/350 amps. I would like to use this to power a DC motor with some kind of speed control that I could install on a go-cart or other small vehicle. Does anyone have any suggestions or help? Thank you, Bruce
anonymous
Pulse Width Modulation DC Motor Control
Sunday, April 26, 2009 7:13:40 AM
Can anyone tell me using (appropriate terminology) how a microcontroller could be used to control the speed of a dc motor? Please would be very helpful as i have my exams coming up soon and i do not want to fail Technological studies.
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