Project-01. Calling Bell circuit diagram.
Description
The circuit has been built using the basic
characteristics of transistors. A musical IC UM66 is used to generate musical
tone which is further amplified using a transistor. The charging time of the
capacitor can be controlled by the variable resistor of 100KΩ. For AC power
supply, two 470KΩ resistors is used along with a bipolar capacitor of 250V in
parallel. Then a bridge network is connected to convert AC to DC. Zener diode in parallel makes the voltage
constant. This constant voltage ensures the power source for the circuit. At
the same time it is connected with the base of the PNP transistor. When AC
supply is on the E-B is reverse biased, so no current will flow through the
Base to Collector. In this way the battery source is switched off. But if the
AC power is off the transistor becomes forward biased. So the current will
conduct through base to collector. In this way, the power source for the
circuit is automatically switched to the available power source.
Circuit Description:
There we have used a 1.0µF capacitor and two 470k resistors by replacing transformer. Then a bridge rectifier is used to supply the input voltage to the main door bell circuit. The output voltage of our supply is 4v which is required to operate the door bell. At the modified section we have used a p-n-p transistor (BC557AP),a resistor(500Ω) and two diodes(1N4001GP) which will operate the circuit in dc supply in the absence of ac supply as we predicted.
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Description
The project provides the schematic and the parts list
needed to construct a musical door bell. The door bell is operated at 1.5v-3.0v
as well as with an musical IC (UM66) to make the circuit. As a modified circuit
it is successfully operated in ac supply as well as in dc supply when ac supply
will be turned off as we required.
Circuit Description:
There we have used a 1.0µF capacitor and two 470k resistors by replacing transformer. Then a bridge rectifier is used to supply the input voltage to the main door bell circuit. The output voltage of our supply is 4v which is required to operate the door bell. At the modified section we have used a p-n-p transistor (BC557AP),a resistor(500Ω) and two diodes(1N4001GP) which will operate the circuit in dc supply in the absence of ac supply as we predicted.
Apparatus:
—
IC (UM66)
1pc
—
Speaker
(8 Ω 0.5W)
1pc
—
Diode
1N4007) 5pcs
1N4732 (Vz = 4.70V) 1pc
—
Capacitor 1µF
(bipolar) 250V 1pc
220µF 2pcs
—
Resistors 470KΩ 2pcs
100 Ω 1pc
4.7K Ω 1pc
500 Ω 1pc
—
Transistor BC 557 1pc
BC548 2pcs
