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Rojony Khatun
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Małgorzata Koperska, MD Steven Wooding
Last updated: September 19, 2025

AC 220V Fan Speed Controller Circuit Using Triac and Diac

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BT150 SCR

BT150 SCR

Medium-power silicon controlled rectifier with voltage rating ~600–800V and current handling around 12A

DB3 DIAC

DB3 DIAC

Bidirectional trigger diode with a breakover voltage of ~30V

0.1µF 400V Capacitor

0.1µF 400V Capacitor

A non-polarized film/ceramic capacitor with 0.1 microfarad capacitance and 400V voltage rating

100K Fixed Resistor

100K Variable Resistor

Adjustable resistor with 100,000 ohm resistance

2.2K Fixed Resistor 1/4W

2.2R Fixed Resistor 1/4W

A 2200-ohm resistor rated for 0.25 watts

*Please note: These are affiliate links. I may make a commission if you buy the components through these links. I would appreciate your support in this way!

AC Motor Speed Controller

Build an AC 220V fan speed controller using a triac and a diac. Easy, efficient, and safe circuit for adjusting ceiling or table fan speed.

AC fan speed controller circuit

The AC 220 V fan speed controller is designed as a triac–diac phase control device to adjust the voltage to the motor to give an efficient fan adjustment in speed, without any unnecessary heat loss.

ceiling fan speed controller

One of the applications is to use an AC 220 V fan speed controller to control the speed of a ceiling or table fan by varying the AC supply to the motor. In this circuit, a combination of a triac and a diac is used and operates on phase-angle control to control the supplied RMS voltage to the fan. This electronic design is more cost-effective, compact, and less wasteful of energy as compared to conventional resistive regulators that consume energy in the form of heat. The speed of the fan is regulated by adjusting the firing angle of the triac by using a variable resistor (potentiometer). In case of a delay in the firing angle, less power is applied to the fan, and the speed is slowed. As the angle is increased, the voltage fed to the fan increases, and the speed increases.
This is a safe and reliable controller commonly used in contemporary fan regulators. Nevertheless, it is driven by induction-type ceiling fans.

Work / Installation (Inputs → Outputs)

  • Connect the 220V AC input to the regulator circuit.
  • The diac triggers the triac based on the potentiometer setting.
  • The triac controls the conduction angle, adjusting the fan’s input voltage.
  • Output delivers variable voltage, controlling fan speed smoothly.

Testing & Final Adjustments

Upon completion, attach the controller to a ceiling or table fan. To start the test in a safe manner, set the potentiometer low and begin testing. Measure the RMS output voltage using a multimeter, and you will see that it will change as you change the knob. When the fan hums too much or stops, modify the component values (resistor/capacitor) to optimize performance. To be sure, the triac should have a heat sink to be reliable over time. Always use a safe, insulated configuration to prevent shocks of electricity. The circuit is now ready to be used on a daily basis once it has been established that it is stable.

Frequently Asked Questions - AC Motor Speed Controller:

What is a 220V fan speed controller?

It is a circuit that adjusts fan speed by controlling AC supply voltage.

Which components are used?

A triac, diac, potentiometer, resistor, and capacitor.

Is it energy efficient?

Yes, unlike resistive regulators, it saves power by phase control.

Can I use it for table fans?

Yes, it works for both ceiling and table fans.

Does it reduce fan noise?

Yes, when properly tuned, it reduces humming compared to resistive methods.

Is a heat sink needed?

Yes, for the triac to dissipate heat safely.

What voltage does it handle?

It is designed for 220V AC mains supply.

Can I use it for LED lights?

Yes, but only if the LED supports dimming.

Is it safe to install at home?

Yes, with proper insulation and protection.

What is the working principle?

Phase-angle control of AC waveform using triac and diac.

Rojony Khatun

Rojony Khatun

CalculatorToolsProject

Rojony Khatun is the creator of a free online tools website designed to simplify everyday and engineering-related calculations for students, professionals, and hobbyists. The platform offers a wide variety of basic and advanced calculators across key categories, including Electrical Calculators, Electronic Calculators, and Time & Date Calculators, helping users solve problems quickly and accurately.