This circuit is a simple circuit which contains 1 resistor, 1 LDR (Light Dependent Resistor) and a buzzer. When light is incident on the LDR, the resistance of LDR becomes low. Hence the total impedance of the circuit decreases which causes high current flow through the circuit.Buzzer output depends on the value of current. Therefore when light is incident ,current increases and we get buzzer output. If you can't hear the sound from buzzer increase the voltage value or decrease the value of R1.
CIRCUIT DIAGRAM :
APPLICATIONS :
We can use this circuit to protect the important things from the thieves.