Apr 182015
 

Dimmer / AC motor speed controller

If you want to control the light level of a room or if you want to control the speed of a drill or a fan (devices that use AC motors), this is the circuit you are looking for.

Many of these regulatory power circuits have an activation point and a deactivation point that do not match. This phenomenon is called hysteresis and is common on TRIACs.

How dimmer / AC motor speed controller works?

The resistor R3 and capacitor C3 are used to filter the high voltage transients that may appear on the circuit. The potentiometer P and capacitor C2 are elements necessary to trigger the triac.

Dimmer / AC motor speed controller

The triac controls the flow of alternating current to the load, switching between the conduction state and the cut-off state, during the positive and negative half cycles of power supply (110/220 VAC that comes from the electric outlet of our homes).

It should be clarified that the capacitor in an AC circuit, has out of phase voltage with respect to the original signal.

Manipulating the potentiometer, we can control the amount of current flowing to the load and thus the electrical power dissipated in it.

To correct the hysteresis of the TRIAC, a resistors R1 and R2 an capacitor C1 are used

List of circuit components for Dimmer / AC motor speed controller

  • 2  47K resistors (R1, R2)
  • 1  100 ohms resistor (R3)
  • 1  100K potentiometer (P)
  • 3  0.1 uF capacitors (uF = microfarads) (C1, C2, C3)
  • 1  TRIAC (depends on the load, 2 amps for common applications like this dimmer) (T)
  • 1  commonly used plug (110/220 Volts)

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