This circuit uses the 555 timer in an Astable operating mode which generates a continuous output via Pin 3 in the form of a square wave. This turns the LED1 ON and OFF. The speed at which the LED1 is turned on and off is set by the values of R1 and R3.

Circuit Diagram:

Components Required:

  • Resistor: R1,R3= 100 Kilo ohm
  • Color Code for 100 Kilo ohm: Brown-Black-Yellow-Golden
  • R2 = 470 Ohm
  • Color Code for 470 ohm: Yellow-Violet-Brown-Golden
  • Electrolyte Capacitor: C1=10uF
  • Ceramic Capacitor: C2=104(0.1uf)
  • IC1= IC 555
  • Light Emitting Diode=LED1
  • Battery: 9 Volts



Mount IC 555 on Bread Board as shown in image.


Short the two pins of IC 555 i.e. pin 2 and pin 6 to form astable mode of operation.  This will make circuit to change its state from HIGH to LOW and LOW to HIGH continuously.

Step 3:

Connect pin 1 of IC to Ground.

Step 4:

Connect pin 8 of IC to VCC side.

Step 5:

Connect Resistor R1 of 100 Kilo Ohm to pin 8 .

Step 6:

Connect Resistor R3 of 100 Kilo Ohm between pin 6 of IC and second terminal of Resistor R1 as shown in image.

Step 7:

Connect a wire between pin 7 and junction formed by resistor R1 and R3.

Step 8:

Connect Ceramic Capacitor C2 of 0.1 uf or 104 to pin 5 of IC.

Step 9:

Connect one terminal i.e. Positive terminal of Capacitor C1 of 10uF to pin 6 of IC and  negative terminal of C1 to second terminal of C2 as shown in image.

Step 10:

Connect both capacitor’s second terminal to Ground through Black wire.

Step 11:

Connect Resistor R2 of 470 Ohm to pin 3 of IC and mount LED1 on Bread Board.


Step 12:

Connect Anode of LED to resistor R2 and Cathode to Ground.

Step 13:

Connect Battery of 9 volts to Bread Board.

When supply is given to the Circuit LED will start blinking i.e. turning ON and OFF continuously after certain interval of time decided by values of R3 and C1.