Dimmer Switch, General Purpose Electric Power Control

Dimmer Switch Introduction

Dimmer switch can be used to replace your electrical switch for lamps, heaters, or some types of electric motor.  Dimmer switches will control the electricity not only for on-off operation, but they are capable of operating somewhere between “on” and “off”.  Dimmer switch actually works by switching the electricity on-off rapidly, and the proportion of on and off period determine the amount of delivered power. For example when the “on” period and the “off” period is equal, the power delivered to the load is 50%.

dimmer switch circuit schematic diagram

Dimmer Switch Circuit

This dimmer switch circuit use bidirectional triode thyristor (TRIAC). The dimmer control use a potentiometer, and you must be aware that this potentiometer is not isolated from mains supply, so hazardous electric shock should be avoided by insulate the pot using the proper insulated knob. Note that the capacitor voltage rating should be higher than the mains supply voltage.

Dimmer Switch Usage

This dimmer switch circuit is not work for every devices, since it distort the sine wave shape of the electric voltage. Don’t use this dimmer circuit for audio-video system, fluorescent lamps, inductive motor (with capacitor to shift the phase emulating 3 phase power source), or synchronous motors.  You can use this dimmer switch circuit for incandescent lamps, heater, brushed electric motor (such as the motor used in drill, blender, or vacuum cleaner), or soldering iron. Basically, you can’t use the dimmer switch circuit for any device that is sensitive to the sine wave shape distortion of the electric signal, or when internal mechanism of the device regulate the power source to give a contant power to the device.

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