08-09-2009, 03:50 PM
pulse generators usually allow control of the pulse repetition rate (frequency), pulse width, delay with respect to an internal or external trigger and the high- and low-voltage levels of the pulses.
COMPONENTS REQUIRED
i. Transformer 220/9V 1
ii. Diode PN 4
iii. Capacitor 1000µf/15V 1
iv. Regulator LM 7805 1
v. Capacitor 100 µf 2
vi. Capacitor 0.01 2
vi. Variable Resistance (0-1M?? 2
vii IC 555 2
viii LED 2
ix. IC Base 2
x. Resistance 330
xi. Connecting
Wires 3 m
xii. Multipurpose PCB 2
xiii. Accessories (Cabinet, cord, switches)
xiv. Relay 6v 1
Operation:
When circuit is initiated by triggering the first IC the output of it goes high. This will also indicated by the glow LED. After remaining high for certain time period output goes low which in turn trigger the other IC whose output goes high for certain time period.
depending on the resistance set between pin 7 and 8. When itâ„¢s output goes low it will trigger the first. This cycle continues. The pulse from these ICâ„¢s can be used with relay.
Setting time period:
The time period of pulse depend on the value of resistance connected between 7 and 8 pin, and value of capacitance connected to 6 pin. Here we have keep the value of capacitance constant and use variable resistance. The variable resistance on IC 1 is used to set ON time and that is on IC 2 is used to set OFF time of resultant output pulse from the circuit.
The time period is govern by the following formula:
T= 1.1*R*C
Where T=time period of output pulse of respective IC
R=variable resistance connected between pin 7 and 8
C=fixed capacitance connected to the pin 6.
The maximum ON or OFF time which can be achieved by the above circuit can be calculated as follow:
T=1.1*10*10^6*100*10^-6
= 110 sec
Since the maximum value of resistance between pin 7 and 8 is ????and that of the capacitance is
100 µf.
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