Automatic LED Blinking Circuit using 555 Timer IC – LED Flasher

Introduction:

While getting started with electronics it is good if you do some basic experiments related to 555 Timer IC. The basic experiment includes Automatic LED Blinking Circuit using 555 Timer IC. This is a simple circuit designed to explain the working and use of a 555 timer IC. This circuit is designed using a low power consumption output device, a red LED.

Some of the advanced project built using 555 Timer LED Flasher circuit are:

• Heart Shaped LED Flasher Circuit
• LED Chaser Circuit
• Flashing Police Light LED Effect
• Adjustable Auto On Off Delay Timer

Automatic LED Blinking Circuit using 555 Timer IC:

Components Required:

Circuit Diagram:

Here is a circuit diagram of Automatic LED Blinking Circuit using 555 Timer IC. Assemble the circuit in breadboard and connect the power supply, LED will automatic starts blinking.

555 Timer IC:

555 timer IC is a cheap, popular, and precise timing device used in various applications. It gets the name from the three 5KΩ resistors that are used to generate two comparator reference voltages. This IC is operated as a monostable, bistable, or astable multivibrator to produce a variety of applications.

This IC comes with a bipolar 8 pins dual in-line package. It consists of 25 transistors, 2 diodes, and 16 resistors arranged to form two comparators, flip-flops, and high current output stage.

Check the NE555 Timer Datasheet.

Pin Description
The following is the pin description of the 555 timer IC.

Pin 1-Ground: It is connected to the ground as usual. For the timer to function this pin should be connected to the ground.

Pin 2-TRIGGER: The negative input comparator No. 1. A negative pulse on this pin “sets” the internal Flip-flop when the voltage drops below 1/3Vcc causing the output to switch from a “LOW” to a “HIGH” state.

Pin 3-OUTPUT: This pin also has no special function. This pin is drawn from a PUSH-PULL configuration formed by transistors. This pin gives the output.

Pin 4-Reset: There is a flip-flop in the 555 IC timer chip. The output of the flip-flop controls the chip output at pin 3 directly. This pin is connected to Vcc for the flip-flop to stop hard resetting.

Pin 5-Control Pin: The control pin is connected from the negative input pin of comparator one. The function of this pin is to give the user direct control over the first comparator.

Pin 6-THRESHOLD: Threshold pin voltage determines when to reset the flip-flop in the timer. The threshold pin is drawn from the positive input of comparator1.

Pin 7-DISCHARGE: The discharge pin is connected directly to the Collector of an internal NPN transistor which is used to “discharge” the timing capacitor to the ground when the output at pin 3 switches “LOW”.

Pin 8-Power or VCC: This pin also has no special function. It is connected to a positive voltage.

Working of the Circuit:

555 timer IC is used here in an astable operating mode which generates a continuous output in the form of square wave via pin 3 which turns the LED on and off. Once you connect the battery to the circuit, it should flash the LED. If it doesn’t work, check the connections again.

Also, make sure that the battery is connected properly to the breadboard and that power is reaching the components of the circuit. Here you can change the flashing speed of the LED by changing the capacitor with different capacitance. If you want to add more LEDs to this flashing LED circuit, connect them parallel with the first LED using proper resistors.