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Triac regulation of mains voltage

     Introduction: Triac regulation suited to regulate the power of mains appliances. It can regulate the brightness of incadescent light bulbs, halogen, dimmable energy savers, the power of heaters and other thermal appliances, engine (motor) regulation, etc. Fits as well to regulate certain types of Tesla transformer (eg SSTC). Power can be easily adjusted from 0 to 100% by simply turning the potentiometer.
     Description: Triac regulation uses the triac as a switching element. Triac is triggered at some phase by pulse to the control electrode G (Gate) and remains conductive until the line passes zero voltage. There are also some regulators made of discrete components, but as the most reliable I found the involvement of an integrated circuit U2008B. The schematic diagram below shows triac regulation circuit for 220V / 230V / 240V mains voltages. Power is adjusted by P1. If the regulations does not regulate in full range, adjust R1 or R2. The triac operates in quadrants II and III. Caution - note that the electrolytes in the diagram have positive pole at neutral. The resistors with no wattage noted are miniature. Triac Tc1 has to be sufficiently dimensioned according to the load. For higher powers, place it on the heatsink. You can use for example BT134, BT136 to 4A, BTB12 to 12A, BTA16 to 16A or BTB24 to 24A. Triac must also be rated to sufficient voltage, I recommend at least 600V.

Warning: The whole circuit is at mains voltage! To ensure safety, it is necessary to use suitable potentiometer (with plastic shaft). Metal case of triac is not isolated from the mains! Connected appliance should always be treated as live, even if the regulation is set to zero power. The appliance is still under voltage!


Schematic diagram of a triac mains power regulation with integrated circuit U2008B.


The first experiments with triac phase regulation with U2008B - dimming a light bulb.


The waveform of the output voltage to the appliance at about 25%, 50% and 75% power.


Video of triac mains power regulation - waveform on scope, dimming the incadescent bulb and regulating a motor.



Added: 6. 1. 2012
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