Astable Multivibrator using 555 Timer

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In this tutorial, we will show you how to make an Astable Multivibrator circuit using 555 Timer IC. The astable mode is also called free-running or self-triggering mode. We can operate 555 timer IC in three different modes, but here we will operate it in astable mode only. In astable mode, the output has no fixed state, and it repeatedly switches from one state to another without the application of an external trigger.

Hardware Components

The following components are required to make Astable Multivibrator Circuit

S.NO	Component	Value	Qty
1.	Breadboard	–	1
2.	Connecting Wires	–	1
3.	Battery	9v	1
4.	IC	NE555 Timer	1
5.	Ceramic Capacitor	0.01uF	1
6.	Electrolytic Capacitor	10uF	1
7.	Resistor	1K, 100K, 220 ohm	1, 1, 1
8.	LED	5mm	1

555 IC Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer

Circuit Diagram

Working Explanation

In this circuit, we are operating 555 timers in an astable mode which works like a simple oscillator circuit that generates continuous pulses. We have connected the LED to Pin 3 of the IC, which is the output pin. LED will switch On and Off continuously and we can change the frequency of the circuit by changing the values of R1, R2, and C1.

Pins 2 and 6 of the 555 timers are connected together so that there is no need for an external trigger pulse and It will self-trigger and act as a free-running multivibrator. Pin 5 is connected to the ground using a capacitor, in order to filter out external noise from the terminal. Pin 4 is the external reset pin. If we apply low on this pin it will reset the timer, hence we have connected it to VCC.