LED Dimmer Circuit Using LM317 Voltage Regulator IC

A LED Dimmer is a circuit that works with light fixtures to control the brightness of a light. By changing the voltage waveform being applied to the lamp or LED, it is possible to lower the intensity of the light output. Although variable-voltage devices are used for various purposes, the term dimmer is generally for those electronic circuits intended to control light output; from resistive incandescent to halogen, compact fluorescent lights (CFLs), and light-emitting diodes (LEDs). In this project, we are going to design a simple LED dimmer circuit using the LM317T Regulator IC.

LM317 is a three-terminal voltage regulator IC, with a high output current value of 1.5A. The LM317 IC has many features such as current limiting, thermal protection, and safe operating area protection. It can also provide a float function for high voltage uses. If we disconnect the adjustable terminal still, LM317 will be helpful in overload protection.

Hardware Components

The following components are required to make LED Dimmer Circuit

LM317 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of LM317

LED Dimmer Circuit

Working Explanation

The above circuit is using an LM317 voltage regulator IC as a current regulator. Since the LEDs are current-driven, their brightness can be controlled by limiting their current.

Here we are adjusting the brightness of 10 super-bright white LEDs, but the number of LEDs can be increased. The 200Ω Pot controls the current/brightness of LEDs. The total output current of LM317 is 1.5A, due to which we are using a separate current limiting resistor with each LED which protects them from the maximum current output of the IC.

Applications

• They are very energy efficient and provide the inherent advantage of controlling the electricity flow across various lighting sources of your home.
• Used in devices such as mood lights, night lights & soft lights.
• Easy installation.