LCD-LED Display

PWM LED Dimmer Using NE555

Outline

  • 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

Introduction

We’ll make a PWM-based LED Dimmer with the 555 Timer IC in this project. The primary premise of this circuit is to use a 555 Timer IC to generate a Pulse Width Modulation PWM signal, which is then used to alter the power given to the LEDs, resulting in the effect of LED dimming.

PWM (Pulse Width Modulation) is a technique used to regulate a variety of circuits. PWM is important if you wish to control the motor’s speed. For dimming the LEDs in our project, we use the PWM Technique.

Using PWM technique, the mount of power delivered to a device is varied and hence, if we can control the pulse width of the signal, we can easily control the device like making a simple DC Motor to rotate slow or fast or to dim the intensity 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

A 12V DC source is used to power the entire circuit including the 555 timer IC and the LEDs. The 555 timer is used to generate a PWM signal with the help of a few passive components. 

The generated PWM Signal is then applied to a bunch of LEDs and based on the Duty Cycle of the PWM Signal, the intensity of the LEDs can be high or low.  

A Brief Note on 555 Timer IC

The 555 Timer is an 8-pin Integrated Circuit that was created by Signetics and is available in a Dual-in-Line Package. It is one of the most widely used ICs, with applications including timers, oscillators, and pulse generators.

The 555 Timer IC’s pin diagram is depicted in the image below. The VCC pin on pin 8 is utilised to provide the IC with its main supply power. The operating voltage can range between 3 and 15 volts. The Trigger, Threshold, and Discharge Pins are located on pins 2, 6, and 7.

PIN DIAGRAM OF NE555 TIMER

The Reset pin on pin 4 is used to reset the entire IC. It’s a LOW Pin that’s active. The IC’s output can be accessed via the out pin, which is pin 3. The Control Pin is located on Pin 5.

The 555 Timer IC can operate in three modes: astable, monostable, and bistable. It contains characteristics such as microsecond to hour timing, configurable duty cycles, and the capacity to perform at varied voltage levels, among others. It can be used for a variety of things, including lamp dimmers, motor control, and joysticks.

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

The 555 Timer is used in this project to function in the Astable Multivibrator Mode. The 1K Resistor, 50K POT, and 0.1F Capacitor connected to Pins 2, 6, and 7 will all play a significant part.

A PWM signal is created at the OUT Pin, Pin 3 of the 555 Timer IC, based on the Capacitor’s charge and discharge timings. The led panel is connected to the output of the 555, which is taken from pin 3, via 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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