Introduction to PWMs (Pulse Width Modulation) Motor Speed Control

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Introduction to PWMs(Pulse Width
Modulation)Motor Speed Control
In many instances it is not desirable to have a
motor run at full speed.
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Pulse Width Modulation
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What is PWM?

• PWM stands for Pulse Width Modulation
• PWM controllers switch the motor on and off in a
  series of pulses.
• Modulate means to adjust or regulate. A PWM sends
  a signal that regulates the motor- hence Pulse
  Width Modulation.

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How Do You See PWM ?
The video below shows the waveform and driven
motor
Note Motor does not begin moving until the power
level is increased enough to overcome the
friction of the drive train.
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Pictures of the Waveform?

• A. The motor is on for most of the time and only
  off a short while, so the speed is near maximum
• B. The switch is on 50 and off 50.
• C. The motor will only rotate slowly.

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High Speed Signal

• The signal at the right shows the motor on for
  most of the time, the white dips indicate when
  the motor isnt receiving power.

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Signal With The Motor Half Speed

• The signal at the right shows the motor receiving
  power half the time.

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Low Speed Signal

• The signal at the right shows the low speed
  signal which turns the motor slowly.

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Schematic of a Manually operated PWM Low Speed
Circuit
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Manual Low Speed PWM Generation
Touch Controlled Switch