Light Dimmer by using Triac (Project)

Title: Light Dimmer by using Triac.

Objectives: Dimmers are device connected to a light fixture and used to lower the brightness of light. By changing the voltage waveform applied to lower the intensity of light output.

Leaning Outcomes: i) We learn how light brightness actually controlled by using light dimmer.

 ii) We learn how dimmer circuit controlled light brightness from lower to higher brightness level.

iii) And one more one thing is that, we actually learn its working and how trice is used here for controlling it's light-brightness.

Prior Concept: Working of light dimmer circuit by using Triac.

Light Dimmer Circuit Using Triac

The Circuit shows the RC phase shift network and DIAC Controlled TRIAC for the light dimming application. The voltage applied to the gate terminal of the triac is varied by the RC arrangement involving the Resistor R3 and the capacitor C3. When the device is in off state, the rate of change or rises of voltage is limited by the series R4-C1 network that is connected across the TRIAC.

Once the input voltage if applied from the 230V power source, the capacitor C1 and C2 start charging at the rate determined by the variable resistor R2. Once the voltage across the capacitor C3 exceeds the breakdown voltage of the DIAC, it gets triggered and the DIAC start conducting and this will discharge the capacitor C3 and the gate pulse is given to the Triac.

The gate pulse turnss ON the TRIAC and the current starts flowing through the lamp. By varying the variable Resistance VRI, the rate of charging of the capacitor also gets varied, which in turn varies the voltage rate, at which the TRIAC gets triggered in both the positive and negative half cycles.

The voltage is applied to half of the AC cycle, then the light bulb will appear with less intensity when it gets the full AC voltage. Because it gets the low power to heat the filament. These light dimmer use the brightness VRI knob to control at what point each cycle to switch the light ON and OFF.

Prior concept: The basic circuit of light dimmer using TRIACis shown in the given figure and this circuit depends on phase control. The variable Resistor VRI plays as a main controller in the light dimmer circuit.

In this light dimmer circuit without any change DIAC, we can be replaced by the BC148 transistor when the transistor is used instead of DIAC, then the base terminal of the transistor not connected and remaining terminals like emitter and collector are connected without the help of polarity.

Conclusion: In light dimmer circuit by using triac we fully controlled brightness level of the light bulb according to our requirement.