The light dimmer circuit or fan regulator circuit (either case, the circuit, and design are the same, the only difference is the output load to be varied, that is, fan or light) is used to control the brightness of the light or the speed of the fan according to our desire. The objective of the circuit is to vary in intensity the brightness of the light bulb or fan speed by using a fixed source. There is no need to replace the bulb with a higher wattage one to do so. A simple Triac can do the work for you. Triacs are used in this circuit as a dimmer as they are easy to design and control, and are very much economic due to their high efficiency and low buying costs.
This is the circuit diagram of the simplest lamp dimmer or fan regulator. The circuit is based on the principle of power control using a Triac. The circuit works by varying the firing angle of the Triac. Resistors R1, R2 and capacitor C2 are associated with this. The firing angle can be varied by varying the value of any of these components. Here R1 is selected as the variable element. By varying the value of R1 the firing angle of Triac changes (in simple words, how much time should Triac conduct) changes. This directly varies the load power, since the load is driven by Triac. The firing pulses are given to the gate of Triac T1 using Diac D1.
You will get a better understanding of the light dimmer circuit by learning more about Triac.
Assemble the circuit on a good quality PCB or common board. The load whether lamp, fan or anything should be less than 200 Watts. To connect higher loads replace the Triac BT 136 with a higher Watt capacity Triac. All parts of the circuit are active with potential shock hazard. So be careful.
I advise testing the circuit with a low voltage supply (say 12V or 24V AC) and a small load (a same volt bulb), before connecting the circuit to mains.
R1 1o K 1 Watt Resistor
R2 1o0 K Potentiometer (Variable Resistance)
C1 0.1 uF (500V or above ) Polyester Capacitor
T1 BT 136 Triac
D1 DB2 Diac
Fan Regulator Circuit Diagram
BT 136Triac Necessary Data.
The light dimmer circuit explained above has been modified with the addition of a snubber circuit to improve the performance of the Triac.