Astable Multivibrator using IC 555 timer( Square Wave Generator) with Proteus Simulation

Its a very easy task to generate a square wave. There are many methods to generate a square wave, among’st them using 555 is a method. Astable multivibrator is a very easy and very widely used method. In this thread you will learn to generate a square wave in proteus simulation using which you can apply in your circuit.

Basically it is an Astable multivbrator which means a free running multivibrator it does not have any stable state.

Pin configuration and some other useful data can be obtained from the Datasheet of lm555..click here to download datasheet of lm555. (courtesy: Texas Instruments).

YOU NEED TO INSTALL PROTEUS SOFTWARE AND HAVE BASIC KNOWLEDGE ABOUT IMPLEMENTING CIRCUITS ON PROTEUS BEFORE PROCEEDING AHEAD.

In proteus add all the components given below for your schematic

COMPONENTS REQUIRED 

1] 555 timer

2] 10k resistors

3] 10uf capacitor

4]1.1M ohm resistor

5]0.33uf capacitor

START CONNECTIONS AS PER THE CIRCUIT GIVEN BELOW

Astable multivibrtor circuit diagram
CIRCUIT DIAGRAM

U1= 10V [It is the supply voltage provided to 555]

After connecting the circuit start the simulation.

You will see the oscilloscope showing you the square wave.

Operation of Astable Multivibrator:

The frequency is independent of supply voltage because the output voltage swings between 1/3vcc and 2/3vcc. The pin no. 2 is connected to the -ve of lower comparator and pin no.6 is connected to the +ve of upper comparator. The negative pin of the upper comparator is connected to 2/3vcc and the positive pin of the lower comparator is connected to the 1/3vcc. Both 2/3vcc and 1/3vcc is internally generated because of  three 5k resistors and hence the name 555.

In Astable mode the 2nd and 6th pin are shorted. Also both the pins are connected to the vcc through resistor. Therefore the comparator compares the vcc and the internally generated voltages and sets/resets the internally flipflop hence the output switches from high and low and we get a square wave

The charge time (output high) is given by:

t1 = 0.693 (R2 + R3)C1

Discharge time (output low) by: t2 = 0.693 (R3)C1

Total period is: T = t1 + t2 = 0.693 (R2 +2R3)C1

o/p freq = 1.44/(R2+2R3)C1

OUTPUT WINDOW

astable multivibrator output window
OUTPIUT WINDOW

for the above circuit the calculated frequency is around 160khz and that what the output shows.

you can change the duty cycle by changing the capacitors or resistors.

 Learn and Explore more:

1 COMMENT

  1. […] PWM stands for pulse width modulation. The duty cycle of the PWM signal varies but the frequency remains the same. PWM signals are widely used to control intensity of the LEDs and also to control the speed of the motors. They can be used for many more applications. 555 is the basic component which can be used to generate PWM device in its Astable mode of operation. Is is easy to implement as it requires very few components. We are going to generate Pwm using 555 timer IC. Learn about working of Astable Multivibrator. […]

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