What is a TRIAC dimmers? Complete Guide for Beginners

TRIAC dimmers

This guide will explain the basics of dimming LED lights with TRIAC dimmers.

Dimmable LEDs can make a huge difference to the appearance and feel of your workspace. It can be confusing to enter the world of dimmable lights, with terms such as TRIACs, thyristors and sinusoidal waves.

This article explains TRIAC dimmers in detail and gives you the knowledge to install your own dimmable led lights.

What is TRIAC Dimmers

LED Triac Dimming 101

TRIAC technology is used to dim light bulbs in various dimmer switch models. As many light dimmers as lighting technologies are available on the market. These dimmers work with CFLs (compact fluorescent light bulbs), incandescents, halogens and some LED bulbs.

The TRIAC (Triode For Alternating Current), also known as a thyristor, is a semiconductor that limits the amount of AC flow through a light. Thyristors have a unique three-electrode structure consisting of a cathode and anode. Thyristor dimmers only function if current is actively flowing through the gate.

If a current flows through the gate then the circuit will be closed and the bulb will come on. If you stop the flow of current to the gate, the bulb will go out. Standard bulbs run at maximum power due to a constant supply of electricity. A TRIAC dimmer, however, limits the current to pulses and sends them to the bulb.

It appears dim because the bulb turns on and off at hundreds of times per second. The bulb will be much darker if the electrical pulses are delayed longer. TRIAC dimmers offer a convenient and easy way to control your lighting system. You can use a dial to easily dim the lights in your home.


1.AC Dimming vs. DC Dimming

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Direct Current (DC) is the flow of electricity at a constant rate. DC dimming is as easy as connecting a light bulb to a power supply with a variable current limiter. AC (Alternating current) is a sinusoidal flow that goes from positive to negativ. DC dimmers will reduce positive current, but not negative current.

A TRIAC is a specialized circuit that dims AC devices. TRIAC dimmers utilize thyristors in order to allow AC to flow both negatively and positively. For maximum AC dimming, a TRIAC dimmer will be required.


2. Leading Edge Dimming Leading Edge Dimming

Leading-edge dimming is a technique that stops AC current flow when the sinusoidal waveform reaches 0 and restarts it as soon as it reaches its peak. TRIAC, a leading-edge dimming driver, provides light bulbs with a surge of electricity at every half AC cycle.


This is the opposite of leading edge dimming. It is only used for sensitive electronic devices like LEDs, that can be damaged by an abrupt surge of current. For marketing purposes, trailing edge dimmers have been renamed LED-Ready Dimmers. TRIAC Dimmers are available in two configurations: leading edge dimmers or trailing edge dimmers.


Types and Applications of Dimmer Switches

TRIAC dimmers can be further enhanced by installing them into different switch housings. The dimmer circuit is only capable of dimming one light at a time. When installed in a switch with multiple locations, the TRIAC dimmer can dim lights from more than one location.


The most popular light dimmer switch can accommodate a TRIAC dimmer.

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1. Single Pole Switches

A single-pole dimming switch controls one light at a given time. The switch uses a three-wire system consisting of an active (hot) wire, neutral and ground. This is the standard TRIAC dimmer. Single-pole switches are equipped with a single on/off switch and a slider dial or knob that controls brightness.

2. 3-Way/4 Way Switches

Three-way dimmers are complex electrical devices which control two or more lights from different switches. The neutral wire is replaced by two traveler cables. These traveler cables connect the three way switch to another switch at a different place.

Leading Edge lighting systems are controlled by four-way switches. Leading-edge dimming turns off AC flow when the sinusoidal waveform reaches 0 and restarts it as it reaches its peak.

TRIAC dimming driver is a cutting-edge technology that delivers a surge of electricity to light bulbs every half AC cycle.




3. Multi-Location switches

Multi-location dimmers represent an improved version of the 4-way dimmer. These switches allow you to control your lighting system in more than one location.

You can also use multiple-location switches to create zones with variable dimming. In your workspace, you can use two different dimming types simultaneously. The precision and control of these dimmers are crucial for lighting large open-concept spaces.

4. Plug-in switches

Plug-in switches must be connected to the wall socket. These switches are more like an extension cord than a dimming switch. To dim your desk or floor lamp, connect it to a plug-in switch. Dimmable LED bulbs are recommended for lamps.

Some LED lights cannot be dimmed and are therefore incompatible with dimmer switch. Plug-in switches are a great option for those who do not want to deal with the hassle of installing a permanent dimmer in their electrical socket.




5. Smart Switches

Smart dimmers are equipped with a transmitter that can be connected to your smartphone. You can control your lighting anywhere.

You can control the lighting in your home from your office, since the instructions for smart dimming are sent via the internet and wireless connection.

Smart dimmers allow you to program the time of your Luminaires. You can set up your house lights, for example, to automatically turn on around sunset using the smartphone app.


How Does a TRIAC Dimmer Work?

These dimmers combine basic electronic devices such as potentiometers and capacitors in a certain sequence to produce AC pulses.

Circuit diagrams can be confusing, but TRIAC dimming has a simple process.

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This article simplifies the complexities involved in TRIAC dimming into simple and easy to understand steps.


Step 1: Understanding Thyristors

A thyristor, a semiconductor with three electrodes, allows two-way current (positive and negative AC), to flow between the cathode and anode. This is only possible when the third electrode has been charged.

The TRIAC dimmer switches deliver a small electric burst to the gate in predetermined intervals. The gate will open and close more than 50 times per second.

So, electricity is only flowing through the thyristor intermittently and not continuously. The gate will allow more electricity to flow through the LEDs every pulse if it is activated at the start of a sinusoidal wave.

If the gate is activated towards the end the sinusoidal cycle less electricity will be sent to the LED light.

Step 2: Capacitor Automation

Capacitors, which are small electronic devices that store electrical energy and then release it after they have been fully charged, are the smallest of all electronics. TRIAC dimming switch places a small capacitance near the gate electrode.

While the capacitor charges, the gate is closed and no current can pass through to the LED light. Once the capacitor has been fully charged, the gate is triggered, turning on the light bulb.

The gate will close again once the AC wave changes from positive to negativity. The capacitor will need to be charged with negative voltage and the gate will have to be triggered again.

The capacitance of a capacitor (ability to store energy) determines its charging rate. The capacitance of larger capacitors is higher, so they will require more electricity to charge.

Step 3 – Potentiometer Control

Potentiometers are variable resistors that can be used to control the timing for the gate trigger. Potentiometers are usually in the shape of a dial or knob, similar to those on sound systems.

Potentiometers alter the resistance of TRIAC dimmers, which in turn changes the current going to the capacitor. This, in turn affects the length of the pulses from the light source.

A TRIAC dimmer does not use an intelligent digital controller. The gate trigger timing is controlled by mathematically calculated values of capacitors and resistors.

Step 4: TRIAC dimmer control

The TRIAC dimmer prevents the voltage from reaching the light source. Potentiometers and capacitors supply short pulses of current to light. The longer the pulse, the brighter and dimmer will be.

Learn more about TRIAC dimmer by watching the video:


The Pros and Con of a TRIAC Dimmer

A TRIAC dimmer (Triode For Alternating Current), is a control device widely used to regulate the output of incandescent or halogen lamps. It is important to understand the pros and cons of each type of dimmer before making decisions regarding lighting in commercial and residential settings.


1. Cost Efficient

A typical TRIAC dimming driver for small-scale illumination solutions is significantly more cost-effective than dimming technology.

A TRIAC dimmer consists of a thyristor and a potentiometer with a capacitor. The fancy designs and housing of the dimmer switches are what adds to the cost.

The low cost of dimming TRIAC switches make them a great option for small buildings, such as offices and homes.

2. High Voltage Support

TRIAC dimming controls are a good option for electrical devices that operate at high voltage. Almost all TRIAC dimming devices are rated for a few hundreds volts.

The BTA24 Triac dimmer is capable of supporting a maximum 800v at 25amps. DC LED dimmers, on the other hand, are not designed to handle this high input voltage.

3. Easy Installation

The dimmers come as single units that are easily installed in the existing wiring of your home. Most of the time, only the wall switch needs to be changed.

The convenience of these dimmers is their biggest selling point. This lowers the entry barrier for newcomers, and even novices can install these dimmers with some knowledge.

4. Reliability

A semiconductor dimmer uses a pure analog technology. It won’t be hacked or incompatible with firmware updates.

It is more difficult and time-consuming to hardwire lighting fixtures, but it is the most reliable. Hardwiring a TRIAC dimmer into a wall socket will keep it there for many years, and perform its fixed function.

5. Dimming drivers with a weaker dimming driver

TRIAC dimming device is a simple electrical device that can be used with AC LEDs.

A TRIAC LED dimming system has a smaller range than other dimming systems. This dimming technique is based on the AC voltage and is restricted to the AC cycle.

6. More Energy Efficient

A TRIAC dimmer uses a large amount of AC power, but only a small portion of that goes to the Luminaires. When dealing with high voltages there is a certain amount of power loss. This compromises the electrical efficiency in favor of broader compatibility.


Consumer Grade Dimming Solutions – TRIAC vs. PWM vs. 0-10v

TRIAC dimming does not represent the only dimming solution available on the market. PWM is another dimming technology for LEDs that has been widely adopted in recent years.

PWM dimming works similarly to a TRIAC dimmer. It turns LED lights on and then off multiple times per second to give the appearance of dimming.

TRIAC Dimming

TRIAC dimming uses an analog method to cut off the current flowing through an electrical device. Analog dimming is a physical dimming method that does not require computer software to operate the switch.

The power supply transmits a full AC signal. However, the TRIAC dimmer only allows small amounts of current to reach the light bulb. TRIAC dimming can only be done with an AC power supply.

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PWM Dimming

PWM dimming is a digital dimming technique (using a microcontroller), and a DC-alternative to TRIAC dimmers. It quickly turns on and off the power supply, resulting less current flowing to the electrical appliance.

A PWM control system has to switch on and off almost 100 times per second in order to avoid flickering lights.

DC power supplies are the only ones that can be switched from off to ON, because the current is constant. Computer hardware, such as RGB LED lighting and PC fans, commonly use a PWM dimmer.


0-10V Dimming

The 0-10V dimming (or the 1-10v dimming) method is analog, and involves a dimmer sending electrical signals between 0 and 10 volts.

The brightness is then adjusted by the receiving LED driver based on voltage. 0v is the lowest brightness and 10v the highest. This dimming technique is only compatible with LED lights that are powered by DC.

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Industrial Grade alternatives to TRIAC Dimmer

The TRIAC dimmer offers a great solution for dimmable systems. There are other lighting control systems that go beyond dimming.

Industrial-grade lighting controls provide features such as color control, lighting patterns and dimming over simple TRIAC dimmers and PWM dimmers.

Two of the most popular lighting control systems are listed below.


1. DALI Control

Digital Addressable Lighting Interface (DALI) is a digital protocol that enables a lighting control to communicate directly with each light fixture.

DALI isn’t a dimming method. DALI is a complex lighting control system that dims your lights. DALI is used for large industrial applications, such as sports stadium lighting.

Learn more about DALI lighting controls.


2. DMX Dimming

Digital Multiplex, or DXM is another digital lighting standard that allows a network of LEDs to be controlled from a central location.

DMX lighting is a user-friendly system that allows you to control the brightness, power and color of an LED source remotely. DMX is suitable for outdoor lighting.

DALI and DMX use different methods to adjust lighting. Find out more about the differences between DMX and DALI Lighting Control.


What is the best dimming solution for your lights?

The main factor that determines your choice of dimming system is the workspace. The lighting in most areas can be classified based on their size and purpose.

  • Small and Simple
  • Small and complex
  • Big and Simple
  • The Large and Complex

The term small refers to the number of fixtures and type of controls that are required. Dimming the brightness of all lights by 50% is an easy task. Dimming all lights to 50% brightness is a simple task.

For small and simple solutions, you can use any AC dimming or DC dimming system.

TRIAC dimmers offer the best retrofit solution for older homes that need to be fitted with dimmable light bulbs. DC PWM dimmers can be used to control lighting fixtures more precisely.

For large and complex lighting, you should use a DALI or DMX industrial solution.

A TRIAC LED Control System is a good choice if you’re unsure of the best dimming option. TRIAC LED control systems are AC compatible, easy to install and cost-effective. They also have a moderately flexible design.



TRIAC dimmers can dim lights reliably and consistently by limiting AC flow. A TRIAC control can be used with different dimming switches to improve the dimmer.

Once you learn the basics, this technology becomes a powerful lighting tool.