POWER SUPPLY ALARM

The circuit is designed to create alert indicating present of power supply in the mains socket.This could be used in the house,factory or working place.

The importance of this device is that it saves fuel,diesel or gas.



Operation
The device is connected to 9VDC from mains so that as soon as there is supply the circuit is powered and consequently sound the Buzzer in the circuit.
The period duration of the buzzer alarm is determined by the value of C3 and R1.The larger the value of C3 the longer the duration.

The circuit is made up of the following components

1. NE 555
2. R1 10k
3. R2 47k
4. R3 47k
5. R4 1k
6. VR1 1M
7. C1 104
8. C2 47UF
9. C3 104
10. Q1 9013 NPN
11. Relay SPST 6VDC
12. Buzzer

Note The variable resistor could be replaced with a fixed resistor of 10k resistance and would still work fine.