Disclaimer:
This project involves working with AC mains electricity, which can be very dangerous and cause severe injury or even death if handled incorrectly. Always take extreme care when building, testing, or using AC circuits. Make sure to follow proper safety precautions, use insulated tools, and never touch the circuit when it is connected to the power supply. If you are not experienced or confident with high-voltage electronics, please seek help from a qualified professional. Safety should always be your top priority.
This project teaches you how to make a simple homemade AC light dimmer circuit. It lets you control how bright an LED bulb or fluorescent light can be by adjusting the power it gets. This kind of dimmer is called a phase-angle dimmer because it controls how long the power is supplied in each cycle of the AC electricity.
Components Required: (Affiliate Links)
- Triac-BT136 ►https://amzn.to/3ygVVwC
- Diac- DB3 ►https://amzn.to/3hwp3dB
- Potentiometer -470kΩ ►https://amzn.to/2Rhjjd2
- Capacitor-0.1µf, 400v ►https://amzn.to/3uVIK2i
- LED bulb ►https://amzn.to/3v7bANn
- AC Plug & Bulb holder ►https://amzn.to/33Qu0Ww
- Connecting wires
Circuit
Key Components of the Dimmer Circuit
- TRIAC (Triode for Alternating Current): This is the main switch. It turns on and off quickly to control power going to the light.
- DIAC (Diode for Alternating Current): This acts as a trigger for the TRIAC. It stays off until the voltage reaches a certain level, then sends a pulse to turn the TRIAC on.
- Potentiometer (Variable Resistor): This is the control knob. When you turn it, you change the resistance, which controls how fast a capacitor charges. A common value is 470 kΩ.
- Capacitor: Works with the potentiometer to create a delay. It charges at different rates depending on the knob setting. A typical value is 0.1 µF.
- AC Plug, Bulb Holder, and Load: These parts connect the dimmer circuit to the AC mains and your bulb.
Circuit
How It Works
The dimmer changes brightness by controlling when during the AC cycle power is sent to the bulb:
- At the start of each AC cycle, the capacitor begins charging through the potentiometer.
- Turning the knob changes the resistance: high resistance means slow charging, low resistance means fast charging.
- When the capacitor’s voltage reaches a specific level, the DIAC sends a pulse to the TRIAC to switch it on.
- The TRIAC then allows current to flow to the bulb for the rest of that AC half cycle.
- If the TRIAC turns on late in the cycle, the bulb gets power for a shorter time and looks dim.
- If it turns on early, the bulb gets power longer and shines brighter.
Construction and Testing
- Because this project deals with dangerous AC mains voltage, it’s safest to build it on a printed circuit board (PCB), not a breadboard.
- Always be very careful and never touch the circuit while it’s plugged in.
- When you turn the knob, you will see the bulb getting brighter or dimmer, showing how the resistance changes the light’s brightness.
Watch the full video tutorial here: How to make AC LED brightness control at Home | DIY AC light dimmer