electronic eye controlled security system advantages

This circuit can be divided into two parts. One is the power supply and the other is logic circuit. In the power supply 9v supply is converted to the 5v .The logic circuit operates the buzzer when any shadow falls on it.

Power supply circuit consists of battery, diode, regulators and capacitors. Initially a 9v battery is connected to the diode. Diode used here is a P-N junction diode of 1N4007 series. In this circuit 1N4007 is connected in the forward bias condition .The main purpose of the diode in this circuit is to protect the circuit from negative voltages .There is a chance of connecting battery with reverse polarities which damages the circuit. So P-N junction diode connected in the forward bias allows the current to flow only in one direction and thus the circuit can be protected .There is some voltage drop across the diode. A voltage of 0.7V is dropped across the diode.

A regulator is used for regulating the output voltage of the circuit .The regulator IC used here is 7805.78 represents the series and 05 represents the output voltage .Thus a voltage of 5v is produced at the output of the regulator .Two capacitors are used before and after the regulator .These two capacitors eliminate the ripples .Thus a constant voltage is produced at the output of the regulator, which is applied to the logic circuit.