Component
Timer IC-555
Resistors (1kΩ , ½ W ; 10kΩ , ½ W carbon diode)
Capacitor (0.033 µF and 0.01 µF)
CRO Probes
Bread board and Hook up wires
Instruments:
Function generator
CRO
Power Supply DC (± 15 volts)
Theory
An astale multivibrator, often called a free running multivibrator, is a rectangular wave generating circuit. Unlike the monostable multivibrator this circuit does not require an external trigger to change the state of the output, hence the name free running. However the time during which the output is either high or law is determined by the two resistors and a capacitor, which are externally connected to the 555 timer. Procedure
1. Join the circuit as shown in figure 2(a) and connect CRO between pin no. 3 and ground for output waveform.2. Switch ON the power supply i.e. Vcc and observe rectangular wave output on CRO and measure the frequency on CRO.
3. Now CRO is connected between pin no. 7 and ground terminal with CRO probe.
4. Observe the changing and discharging waveform for capacitor C, and measure the charging time (tc) and discharging time (td) , also frequency of output signal displayed.
5. Now observe the ground line by putting input coupling switch on GND position and then put the switch on DC position and adjust various knows of CRO to get stable waveform.
6. Measure the voltage across capacitor for both charging and discharging values.Also, calculate all values of the theoretical method.
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