Dark Dark Detecting LED Detecting LED

using using LDR andLDR and

555 Timer IC555 Timer IC

IntroductionComponentsDiscussion about key componentsCircuit diagramWorking procedureDiscussionConclusion

Contents

1.LDR2.LED3.555 TIMER IC4.RESISTORS (1k,4.7k,47 k ohm)5.CAPACITORS(1 nf,1uf)6.BATTERY(9V)6. AND SOME CONNECTING WIRE

1.555 Timer IC

LED

LDR

Circuit

Discussion1.The circuit diagram of dark detecting LED. This

circuit shows how we can convert a simple astable mode circuit to a “dark sensor”. We just need to add an LDR and a resistor in the circuit, then it simply works as dark detector.

2.A general purpose LDR is used for sensing the light.

3.When proper light is falling on the LDR its resistance is very low.

4.When there is no light the LDR resistance increases.5. At this time the IC is triggered and glows the LED attached with the circuit.

conclusion555 Timer is a highly stable device for generating

accurate time delays or oscillation. Additional terminals are provided for triggering or resetting if desired.