Simple 220V AC Light Dimmer Circuit

This post shows you how to build a 220V AC light dimmer switch for your home lights.

This dimmer works by chopping up the electricity at just the right moment allowing you to control how bright the lights get.

Building circuits with high voltage can be dangerous.

Only do this with adult supervision and a qualified electrician should install it in your home.

This project is not recommended for beginners.

What is a AC Light Dimmer Circuit:

An electrical device called an AC light dimmer circuit is used to adjust the brightness or intensity of an AC-powered light source, usually an incandescent bulb.

A light dimmer circuits main function is to change the amount of electricity going to the light source so that users may customize the brightness to their liking.

This is accomplished by varying the voltage or current applied to the lightbulb, which regulates the quantity of light that is released.

Understanding Triac Dimmers:

Triacs commonly utilized in electronic circuits for switching AC loads operate by responding to an external DC trigger.

While they can be employed for complete switch ON and OFF procedures they are particularly popular in applications where, AC regulation is desired.

For instance, in dimmer switch circuits triacs are configured to conduct only during specific sections of the AC sine wave resulting in an output AC with a reduced average RMS value compared to the input AC.

This controlled output in turn, regulates the connected load exemplified in the common use of dimmer switches for incandescent lights.

Circuit Working:

Parts List:

Let us examine a circuit operation of an 220V AC light dimmer:

Upon feeding AC mains to the circuit, C2 charges fully after a specific delay, providing the required firing voltage to the diac.

The diac conducts triggering the triac into conduction.

However, this action also discharges the capacitor causing its charge to fall below the diacs firing voltage.

Consequently, the diac stops conducting, and so does the triac creating discrete sections in each cycle of the mains AC sine wave.

This results in a precisely tailored lower voltage output effectively controlling the light intensity.

Although C1 is not strictly necessary for resistive loads like incandescent bulb its inclusion becomes crucial for inductive loads.

Inductive loads tend to return a portion of stored energy to the supply rails, potentially disrupting C2 charging cycle.

C1 addresses this issue by providing bursts of small voltages even after C2 has completely discharged, ensuring the triac maintains the correct switching rate.

Triac dimmer circuits generate significant radio frequency RF disturbances during operation.

To eliminate this, an RC network is essential in these dimmer switches to reduce RF emissions.

Formulas:

Using a TRIAC, DIAC and additional parts a basic 220V AC light dimmer circuit requires the construction of a phase control circuit.

This kind of circuit modifies the phase angle of the AC voltage to regulate the amount of power supplied to the incandescent lightbulb.

Time Calculation:

The RC network made up of resistors and capacitors may be used to approximate the time of the phase control circuit.

The amount of delay before the TRIAC is activated is determined by the time constant 𝜏τ.

The estimated trigger delay angle, 𝛼α, for a phase control dimmer is found using the following formula:

α = 1​ / 2πfRC

where,

• The AC supply frequency denoted by f is typically 50 Hz in most countries.
• R is the resistance in the RC network, which is the total of the potentiometer and fixed resistor values.
• C is the total capacitance of C1 and C2, and f is the capacitance in farads.

The TRIAC is triggered at a certain angle during each AC cycle.

The brightness of the lightbulb may be controlled by varying the phase angle by using the potentiometer.

This circuit allows an incandescent bulb to have variable brightness by adjusting the phase angle of the AC voltage, hence providing a rudimentary dimming capability.

How to Build:

How to build a 220V AC light dimmer circuit using a triac is mentioned below:

Triac Connection:

• Connect the MT1 terminal of the triac to one of the AC mains phases live wire.
• Connect the MT2 terminal to the load incandescent bulb.
• Connect the gate of the triac through the diac to the junction of R1 and C2.
• Or simply connect the triac as shown in the diagram

Potentiometer Setup:

• Connect one end of the potentiometer to the junction of R1 and C2.
• Connect the other end of the potentiometer to the common terminal of the load.
• Connect the wiper of the potentiometer to the AC mains neutral.

C1 Connection:

• If using an inductive load connect C1 in parallel with the load, with one end connected to the junction of R1 and C2.

Power Supply:

• Connect the AC mains phase to the MT1 terminal of the triac.
• Connect the AC mains neutral to the wiper of the potentiometer.

Ground Connection (Optional):

• For safety, connect the circuit to the ground.

Testing and Adjustments:

• Power on the circuit and observe the light bulb.
• Rotate the potentiometer knob to control the light intensity.
• If the RC network is implemented, check if there is a reduction in RF disturbances.

Safety Precautions:

• It is crucial to note that all circuits discussed herein are directly connected to mains AC.
• Therefore, extreme caution must be exercised when handling these circuits while powered ON and in an uncovered condition.

Conclusion:

By carefully following this process and considering the safety precautions, you can successfully build a 220V AC light dimmer circuit with triac control.

Adjustments to the potentiometer will allow you to control the intensity of the connected incandescent bulb.

References:

TRIAC dimmer, circuit design help (resistive load)