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
1] 555 timer
2] 10k resistors
3] 10uf capacitor
4]1.1M ohm resistor
START CONNECTIONS AS PER THE CIRCUIT GIVEN BELOW
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
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: