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555 PWM Dimmer

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Non-Exam Extras

PWM: Pulse Width Modulation

555 Data Sheet

This circuit varies the width of Astable Pulses.
It can be used to dim a lamp or control the speed of a motor.
This technique is much more energy efficient than using a resistor to control the speed or brightness.
Little waste heat is generated by this circuit. A resistor-based dimmer can get very hot, wasting energy.

Dimmer or Motor Speed Control555 PWM Dimmer or Motor Speed Controller

Note the narrow pulses, the medium pulses and the wide pulses varying the power from about 10% to 50% and up to 90%.

Oscilloscope Measurements

555 Speed Control using the Control Voltage Pin

Instead of using a potentiometer, this could be connected to a thermistor voltage divider.

An amplifier might be needed because the voltage changes from the thermistor are small.

555 PWM using COntrol Voltage




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