Simple 220V AC Light Dimmer Circuit

Building a 220V AC light dimmer switch for the lights at home is explained in this post.

With the help of this dimmer one can control how bright the lights get by carefully turning off the current.

Creating high voltage circuits can be risky.

An experienced electrician should install it in ones house and should only do this under adult supervision.

Beginners should not try this project.

What is a AC Light Dimmer Circuit:

An AC light dimmer circuits are electrical devices that are used to adjust the brightness or intensity of AC powered light sources which are commonly in incandescent bulbs.

A light dimmer circuits main function is to change the amount of power that reaches the light source so that users can adjust the brightness to their desired level.

This is carried out by changing the voltage or current which is sent to the lightbulb that controls the quantity of light generated.

Understanding Triac Dimmers:

Triacs are widely employed in electronic circuits to switch AC loads.

They work by reacting to a DC trigger that is external.

Although they are often used for full switch ON and OFF operations but they are used most often in applications that need for AC regulation.

For example triacs in dimmer switch circuits are set up to only conduct during particular AC sine wave segments producing an output AC with a lower average RMS value than the input AC.

Dimmer switches for incandescent lights are common examples of how this regulated output in turn controls the connected load.

Circuit Working:

Parts List:

Let us look at how a 220V AC light dimmer circuit works:

After a certain amount of time C2 fully charges when AC mains are fed into the circuit giving the diac the necessary firing voltage.

The triac enters conduction when the diac conducts.

But this operation also discharges the capacitor which lowers its charge below the firing voltage of the diac.

As a result the diac and triac fail from working resulting in different phases inside every mains AC sine wave cycle.

As a result the light intensity is successfully controlled by a perfectly regulated lower voltage output.

C1s presence becomes essential for inductive loads even if it is not technically required for resistive loads like incandescent bulbs.

The C2 charging cycle gets interrupted by inductive loads as they frequently return some of the energy that has been stored to the supply rails.

To solve this problem C1 ensures that the triac maintains the proper switching rate by supplying brief voltage bursts even after C2 has fully drained.

During operation triac dimmer circuits produce a lot of radio frequency (RF) disturbances.

These dimmer switches must have an RC network in order to remove this and lower RF emissions.

Formulas:

A basic 220V AC light dimmer circuit requires the following process for building of a phase control circuit using a TRIAC, DIAC and other components.

This type of circuit adjusts the AC voltages phase angle to control how much power is delivered to the incandescent lightbulb.

Time Calculation:

The phase control circuits estimated duration is calculated with the resistor capacitor RC network.

The time constant 𝜏τ controls the length of delay before the TRIAC is triggered.

The following formula is used to get the estimated trigger delay angle or 𝛼α for a phase control dimmer:

α = 1​ / 2πfRC

where,

• The AC supply frequency is represented by f is around 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.

Every AC cycle triggers the TRIAC at a certain angle.

The potentiometer is used to change the phase angle which will adjust the lightbulbs brightness.

By adjusting the phase angle of the AC supply this circuit gives an incandescent light bulb changing brightness and a basic dimming capability.

How to Build:

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

The triac connection:

• Connect the triacs MT1 connection to a live wire from one of the AC main phases.
• The load incandescent bulb should be connected to the MT2 terminal.
• Through the diac connect the triacs gate to the intersection of R1 and C2.
• Or just join the triac as the diagram indicates.

Configuring a Potentiometer:

• Connect the potentiometers one end to the intersection of R1 and C2.
• Wire the opposite end of the potentiometer to the loads common terminal.
• The potentiometers wiper should be connected to the AC mains neutral.

C1 Link:

• Connect one end of C1 to the junction of R1 and C2 when using an inductive load then connect the other end to the load in parallel.

Source of Power:

• Use the triacs MT1 terminal to connect the AC mains phase.
• Connect the potentiometers wiper to the neutral AC mains.

Optional Ground Connection:

• Make sure the circuit is grounded for safety.

Testing and Modifications:

• Switch the circuit on then check the lightbulb.
• To adjust the light intensity turn the potentiometer knob.
• Verify whether there is a decrease in RF disturbances when the RC network is put into place.

Safety Measures:

• It is important to remember that every circuit covered in this article has a connection to the mains AC.
• Because of this extra care must be taken while working with these circuits when they are switched on and exposed.

Conclusion:

One may successfully construct a 220V AC light dimmer circuit with triac control by carefully following the articles directions and taking safety measures seriously.

Also one can modify the brightness of the connected incandescent lamp by using the potentiometer.

References:

TRIAC dimmer, circuit design help (resistive load)