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Wednesday, October 12, 2011

To study IC 555 timer as an Astable multivibrator 555 TIMER


 To study IC 555 timer as an Astable multivibrator 555 TIMER

To study IC 555 timer as an Astable multivibrator 555 TIMER
555 TIMER

Aim:   1. To study IC 555 timer as an Astable multivibrator.
2. To study 555 timer as a Monostable multivibrator.

Apparatus:

1.      555 Timer trainer
2.      C.R.O
3.      Function generator
4.      Multimeter
5.      Connecting wires
6.      CRO probes.

Introduction:

The 555 Timer is used in number of applications; it can be used as monostable, astable multivibrators, DC to DC converters, digital logic probes, analog frequency voltage regulators and time delay circuits.

The IC 555 timer is 8-pin IC and it can operate in free-running (Astable MV) mode or in one-shot (Monostable MV) mode pin configuration is as shown in figure. It can produce accurate and highly stable time delays or oscillations.



Circuit Diagram and  model waveforms:
Monostable Multivibrator:



























Circuit Diagram:
Astable Multivibrator:
















Procedure:
Monostable Multivibrator:

1.      Connect the 555 timer trainer to the power supply mains.
2.      Connect the C.R.O at the output terminals.
3.      Apply external trigger at the trigger input terminal and give supply to trainer.
4.      Record and observe the waveforms at the output terminals and also across the capacitor.
5.      Verify with the sample output waveforms as shown in figure.
6.      Calculate the pulse width, time period of pulse (T) theoretically and verify with practical values.
7.      Now change RA value and observe out pulse width T and verify it theoretically.
T = 1.1 RAC



Astable Multivibrator:

1.      Connect the IC 555 timer trainer to power supply mains.
2.      Connect the C.R.O at the output terminals.
3.      Record and observe the waveforms at the output terminals and also across the capacitor.
4.      Verify with the Sample output waveforms as shown in figure.
5.      Calculate pulse width, time period of pulse (T) and duty cycle percentage theoretically and verify with practical values.
6.      Find the charging time tc discharging time td and totals time period T from the output waveform.
7.      Verify these values with theoretical values and calculate the % of the duty cycle.
Where Tc = 0.69 (RB+RA) C
                                                          RA = R2+R1
     Td = 0.69 (RB C
T = Tc+Td
                                                                                             f = 1/T
% of DC


Result:  







Circuit Diagram:

Integrator:


Expected waveforms:



Result:

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