LCD-LED Display

PWM LED Dimmer Using NE555


  • Introduction
  • Block Diagram of LED Dimmer using 555
  • A Brief Note on 555 Timer IC
  • Circuit Diagram of PWM LED Dimmer Using 555
  • Components Required 
  • Circuit Design
  • Working of PWM LED Dimmer using 555


In this project, we will create an LED dimmer utilizing the 555 Timer IC with a PWM (Pulse Width Modulation) approach. The fundamental idea behind this circuit is to employ the 555 Timer IC to produce a PWM signal, which, in turn, is utilized to adjust the power supplied to the LEDs, thereby achieving the desired LED dimming effect.

PWM, which stands for Pulse Width Modulation, serves as a crucial technique for regulating various circuits. When it comes to dimming the LEDs in our project, we harness the power of PWM to achieve this.

By employing PWM (Pulse Width Modulation), we have the capability to adjust the amount of power supplied to a device. Consequently, by manipulating the pulse width of the signal, we can effortlessly govern the device’s behavior, whether it’s controlling the speed of a basic DC motor, altering its rotation speed, or adjusting the brightness of an LED.

Block Diagram of LED Dimmer using 555

The following image depicts the block diagram of the PWM based LED Dimmer using 555 Timer IC.

Block Diagram of LED Dimmer

To supply power to the complete circuit, including the 555 timer IC and the LEDs, a 12V DC source is employed. The 555 timer IC is utilized in conjunction with a selection of passive components to produce a PWM signal.

This generated PWM signal is subsequently directed to a cluster of LEDs, and the brightness of these LEDs can be adjusted to either high or low levels, contingent upon the Duty Cycle of the PWM Signal.

A Brief Note on 555 Timer IC

The 555 Timer is an 8-pin Integrated Circuit originally developed by Signetics and is typically enclosed in a Dual-in-Line Package. It stands as one of the most extensively utilized ICs, finding applications in timers, oscillators, and pulse generators.

The pin configuration for the 555 Timer IC is illustrated in the image below. Pin 8, designated as VCC, serves as the primary power supply input for the IC, and it accommodates an operating voltage range of 3 to 15 volts. Pins 2, 6, and 7 are respectively identified as Trigger, Threshold, and Discharge Pins.


The IC features a Reset pin situated at pin 4, responsible for resetting the entire IC. This is an active LOW pin. Pin 3, labeled as the Out pin, grants access to the IC’s output. The Control Pin is positioned at Pin 5.

The 555 Timer IC is versatile, offering operation in three distinct modes: astable, monostable, and bistable. It boasts capabilities such as timing spanning from microseconds to hours, configurable duty cycles, and adaptability to various voltage levels, among other attributes. Its applications encompass a wide array of possibilities, including lamp dimming, motor control, and joystick functionality.

Circuit Diagram of PWM LED Dimmer Using 555

Components Required 

  • 555 Timer IC 
  • 1KΩ Resistor x 6 
  • Red LEDs x 4 
  • 2N2222 NPN Transistor 
  • 0.1μF Capacitor
  • 0.01μF Capacitor
  • 50KΩ Potentiometer 
  • 1N4148 Diodes 
  • 12V Power Supply 
  • Mini Breadboard

Circuit Design

  • The 12V DC supply is given to the VCC Pin for operating voltage of 555 timer. The reset pin also directly connected to the 12V as shown in the circuit diagram. For resetting the IC, in case of an error while circuit is working, connect the RESET pin to GND for a Second and then connect it back to 12V.
  • Pin 5 or the voltage control pin is not used in this application. Hence, a decoupling capacitor of 0.01μF is connected between pin 5 and GND.
  • The Trigger pin (Pin 2) and threshold pin (pin 6) are shorted and the Wiper Terminal of the POT is connected here. Also, a 0.1μF Capacitor is connected between Pin 6 (or Pin 2) and GND. 
  • Now, one terminal of the POT is connected to anode of a Diode (preferably 1N4148) while the other terminal of the POT is connected to cathode of another diode.
  • The other ends of both these diodes are connected to the Discharge Pin i.e. Pin 7. Also, a 1KΩ Resistor is connected between Pin 7 and VCC. 
  • The OUT pin is connected to the LED panel through the transistor. 

Working of PWM LED Dimmer using 555

In this project, we employ the 555 Timer in the Astable Multivibrator Mode. The 1K Resistor, 50K POT, and 0.1F Capacitor, linked to Pins 2, 6, and 7, each fulfill a vital role.

A PWM signal is generated at the OUT Pin, namely Pin 3 of the 555 Timer IC, predicated on the timing of charge and discharge of the Capacitor. The LED panel connects to the 555’s output, sourced from Pin 3, through the intermediary of an NPN transistor (2N2222) and a 1K resistor.

LED Dimmer

The 1KΩ resistor is used to limit the base current of the transistor  and transistor is used as an amplifier to limit or enhance the current which is given to the LED panel.


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