Battery Backup circuit, is useful for Burglar alarm systems, security camera flashing circuits and many more.
This circuit provides an alternate voltage source if the mains voltage failed. It is quite simple to wireup and effective to do. The 9V rechargeable battery gets charged if the main voltage is available, through the resistor R1.
The battery will discharges and take the load in no time, where the input voltage (12V) drops to zero.
The circuit mainly consisting of a Voltage Regulator IC 7809. The pin out of 7809 ic is shown below:-
- 7809 IC regulates the input voltage to charge the Rechargeable battery.
- The capacitor C1 filters the input ripples (if any).
- Resistor R1 limits the time to charge up the Battery.
- Diodes D1 and D2 switches the circuit for two modes (with and without mains voltage)
R1 100 ohmsD1 1N4001