LIGHT DIMMER using variable drive to control voltage

voltage control

1. Light Dimmer Voltage Control Using TRIAC Preprared By :- Ikraam Uddin Ameer (13RT1A0204) Khaja Faiyaz Ali (13RT1A0205) Mohd Ahmed Ali (13RT1A0214 ) Under the Guideance of :- ilyas bin mohammed

2. INTRODUCTION This is a standard 220V-240V AC circuit which can be used to adjust the brightness of mains light.It uses a triac,diac,flourescent Lamp and generates very little heat .That offer simplicity and high performance . The intensity of the light is determined by the proportion of the sine wave that is applied across the load

3. This circuit is designed for the 5 Hz -60 Hz sinewave to accomplish this a bilateral diac is  used to  control the circuit flow to the traic.Initially the capacitor is discharged and during each half cycle of the input the capacitor is charged to its breakover voltage, when this occurs the diac begins to conduct and discharges the capacitor through the triac gate, it allows the voltage to beapplied to the light bulb . Light dimmer circuit schematic description:

4. The intensity of the circuit can be controlled by varying the angle for the circuit .This control by rate at which the capacitor charging. And is determined by this time constant and series potentiometer the RC time constant must be 3 - 3 Ω and potentiometer lines the .1µF capacitance. The smaller the RC time constant, the quicker the capacitor reaches the breakover voltage and thus the greatest intensity of light can be seen when potentiometer is set to zero,and the greatest portion of sine wave is applied over the bulb .

5. CIRCUIT DIAGRAM

6. The Components Used : Resisitors(R1) : - 37k Ω - (0.5 Watt ) Capacitor (C1) : - 2A 104J DIAC : - DB3 TRIAC : - BT136 Variable Resistance(VR1) : - 500k Ω Lamp (L1)

7. The Working Circuit : The resister and capacitor are connected in series. The capacitor is made to charge through the 500K resistor. When the capacitor starts charging and when it reaches above the breakover voltage of DIAC, it starts conducting. Hence capacitor voltage is applied to TRIAC gate and it turns-on The charging of the capacitor can be controlled by the variable resistor. Which indirectly controls the firing delay of TRIAC.

8. Applications : It is used in controlling fan speed It is used to dim the light By changing input supply it can b used in DC motor

9. Advantages : - Simpler And Low Cost. Easy To Construct. Little Power Dessipated in resistance and TRIAC. Disadvantages :- The Circuit cannot be used for highly inducting loads. Risk of failure over the whole adjusting range . ADVANTAGES AND DISADVANTAGES

10. Assemble the circuit on a good quality PCB or common board.The load whether lamp ,fan or any thing ,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. Notes : I advice to test 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.

11. THANK YOU