This is a light dimmer circuit. It has no fancy special feature, it is a a quite typical TRIAC based dimmer circuit. This circuit is only used to operate with non-inductive loads like standard light bulbs. Compared with the 120V AC above design, the triggering circuit is little bit improved. Besides that, this circuit is used to dim ligth bulb with range between 5 to 1000W. Here is the circuit:
To control the setting of the dimmer, this circuit uses potentiometer P1. To setting the dimming range this circuit uses a trimmer P2. When this circuit is run, P2 must be adjusted so P1 is in it’s maximum resistance setting the light bulb is just dimmed completely out. In this adjustment, the dimmer circuit should be dims smoothly from zero to maximum setting.
When we build this circuit we must put a small heatsink to the triac TH1. Without proper cooling it can’t withstand the full dimmer 1 kW power. If we doesn’t put small heatsink to the triac TH1, the maximum available power from the circuit is around 300W so the coil L1 must be able to withstand continuous current of at least 4.5A and it can have any value between 40 and 100 microhenries. [Circuit diagram source: bebek electronics]