Semiconductor dimmers switch on at an adjustable time (phase angle) after the start of each alternating-current half-cycle, thereby altering the voltage waveform applied to lamps and so changing its RMS effective value.

What is a phase cut dimmer?

“Phase-cut” dimmers work by taking the line input power (120V “house power”) and modulating the signal to reduce the power to the load. By “chopping” the signal, the load experiences a lower voltage, resulting in a lower light output.

What are the two types of phase cut dimming?

Phase-cut dimmers can operate on the leading edge (forward phase-cut) or trailing edge (reverse phase-cut) of the waveform.

How does a light dimmer circuit work?

A light dimmer works by essentially chopping parts out of the AC voltage. This allows only parts of the waveform to pass to the lamp. The brightness of the lamp is determined by the power transferred to it, so the more the waveform is chopped, the more it dims.

What are the different components in the light dimming circuit?

This light dimmer circuit is built with various electrical and electronic components like resistors R1=68 kilo ohms, R2=280 kilo ohms and R3=10 kilo ohms, variable resistors VR1=100 kilo ohms and VR2=200 kilo ohms, capacitors C1, C2 and C3=0.33 uF/400V, TRIAC is BT136 and DIAC is ER900.

How does a forward phase dimmer work?


Also known as Leading-edge dimming, it cuts each half cycle of the power signal wave (see picture below). The power is off during the initial part of each half cycle and then turns on. This type of dimmer is part of the older/traditional dimmers that we know of.

What is the difference between forward and reverse phase dimming?

Reverse phase dimming usually gives you better overall control and smooth dimming down to 5% light levels, while forward phase normally dims smoothly down to 10%. Generally works better with LED light sources and all electronic low-voltage systems.

What are the methods used to dim lighting?

The four most popular methods for dimming LED lights are described below and cover 0-10Volt dimming, PWM(Pulse Width Modulation) dimming, Forward-Phase dimming(sometimes referred to a “Triac” or Incandescent Dimming) and Reverse-Phase dimming(sometimes referred to as an ELV or Electronic Low Voltage Dimming).

What are the different types of dimmers?

Most dimmers fall into these four bulb type categories:

  • Incandescent and halogen bulbs.
  • Dimmable compact fluorescent light bulbs.
  • Magnetic Low Frequency (MLV)
  • Electronic Low Frequency (ELV)

Does a dimmer reduce voltage?

Does a dimmer switch reduce voltage? It works by changing the voltage waveform applied to the lamp, it is possible to lower the intensity of the light output.

Which device is used in light dimmer circuits?

The device that can control the intensity of light is called “light dimmer”. Variable resistors and autotransformers were used as dimmers which can adjust the load current or supply voltage.

Why TRIAC is used in light dimmer?

In the last section, we saw that a dimmer switch rapidly turns a light circuit on and off to reduce the energy flowing to a light switch. The central element in this switching circuit is a triode alternating current switch, or triac.

What is the difference between thyristor and TRIAC?

Thyristor control DC power whereas TRIAC control DC as well as AC power. A thyristor is only one mode of operation is possible while TRIAC has four different modes of operation is possible. A thyristor can operate in only one quadrant V-I characteristics while TRIAC can operate only in two quadrant V-I characteristics.

What is the difference between DIAC and TRIAC?

DIAC is an acronym for “Diode for Alternating Current”. TRIAC is an acronym for “Triode for alternating current”. It is a diode for AC that allows current in both directions when the applied voltage increase above break overvoltage.

What type of dimming is TRIAC?

Forward phase-cut dimming

Forward Phase: Forward phase-cut dimming (commonly referred to as incandescent or Triac dimming) is the most common dimming method. It’s designed for resistive or magnetic low-voltage (MLV) loads, including incandescent and halogen, but certain models allow for more usage with CFL and LED loads.

Is TRIAC same as phase dimming?

Dimmers allow you to set the level of light and save energy on the output and, when teamed with an LED light source, this energy saving can be quite substantial. Phase-cut dimmers are the most common dimming control and are often referred to as TRIAC dimmers.

What is PWM dimming?

Pulse-width modulation (PWM) is a common type of dimming used to adjust the current in white-LED driver devices. PWM dimming takes a rectangle waveform with variable positive duty cycle (D) and adjusts the LED current proportionally.

What is TRIAC dimming vs 0-10V?

0-10V light dimming also known as the 0-10V signal dimming, is an analog dimmer that distinguishes itself from the triac power supply by adding two additional 0 -10 V interfaces (+10 V and-10 V) to the 0-10 V power supply.

How do 1-10V dimmers work?

It looks a little daunting because there are more stages, but the way it works is actually quite simple. Each lamp has it’s own separate transformer (driver) to control the lights. The on/off is controlled through the mains and the level up/down is controlled on the 1-10V side of the driver.

What is a DALI dimmer?

DALI is a two-way communications protocol used to simplify lighting control in complex lighting installations. A DALI dimmer is a product that allows the DALI network to communicate with and control lighting fixtures.