DESIGN AND CONSTRUCTION A SIMPLE LIGHT SENSITIVE CIRCUIT

Introduction

This is the design and construction of a light sensitive circuit which when the sensor is blocked will activate the light emitting diode at the output. The output gain depends on the non-inverting input of the operational amplifier used in this demonstration. This system is made of different component which aided in the functionality of the design.

Aim and Objective

In this paper we are to design and construct a light sensitive circuit which senses an obstruction in the sensing unit and on the output LED which is connected at the pin 6 of the operational amplifier.

Definition of important terms

1.LDR:  this is the sensitive component of the design which senses the obstruction that occurs in the sensor unit.

2.OPAMP: this is the operational amplifier which acts as a comparator calculating when the input resistance of the LDR is up to the computed Vout in the non inverting input of the comparator.

3.The regulator : is use to regulate the voltages at the non  inverting unit of the opamp

4.The LED: indicates the output level of LDR during operation.

How it works

When the devices is powered, the LDR is ready to receive signals, then when there is an obstacles in the surface of the light dependent resistor the opamp is trigged to receive its signal variation which depends on the light intensity on the surface of the LDR.

So when the obstacles moves across the LDR it blocks some parts of the LDR surface thereby creating resistances increasing the resistance of the LDR. The opamp amplifiers the received signal and compare it with the non inverting voltage and give an output which is directly proportional to the output.