Basic Electronics

Group MembersNames Roll Numbers

Mohsin Ijaz (Group Head) 110

Haziq Naeem 107

Hassan Riaz Khan 86

Muhammad Zohaib 136

Muhammad Adeel 83

Muhammad Naveed 120

Muhammad Ihsan 90

Class: BSCS-1C

Subject Teacher: Prof. Najaf

Project

Light Sensor

Introduction

Light sensor is a simple powerful concept. It

automatically switches ON lights when the sunlight

goes below the visible region of our eyes and

automatically switches OFF lights when Sunlight fall on

it (in morning), by using a sensor called LDR (Light

Dependent Resistor) which senses the light just like our

eyes.

Circuit Diagram

Components

• Light Dependent Resistor (LDR)

• Integrated Circuit (IC)

• Variable Resistor

• Resistance

• Transistor

• Diode

• Relay

Light Dependent Resistor (LDR)

A photoresistor or light-dependent resistor (LDR)

or photocell is a light-controlled variable resistor. The

resistance of a photoresistor decreases with increasing

incident light intensity. In other words, it exhibits

photoconductivity. A photoresistor can be applied in

light-sensitive detector circuits, and light- and dark-

activated switching circuits.

Integrated Circuit (IC)

• An integrated circuit or monolithic integrated circuit

(also referred to as an IC, a chip, or a microchip) is

a set of electronic circuits on one small plate

("chip") of semiconductor material, normally silicon.

• Extremely small size, small weight, reduce cost,

extremely reliable, low power consumption, easy

replacement.

• IC Terminologies: Bonding, Chip, Diffusion mask,

Encapsulation, Etching

Variable Resistor

• The resistor whose electrical resistance value can

be adjusted as per requirement by adjustable

component attached to it is called variable resistor.

• Also known as port and potentiometer.

• A variable resistor is a strip of a material such as

graphite which resists the flow of electricity. There is

a fixed terminal attached to one end of the resistor.

There is also a moving device touching the graphite

called a wiper.

Resistance

• Resistance is the opposition that a substance offers

to the flow of electric current.

• The standard unit of resistance is the ohm.

• It is defined as the ratio of the voltage applied to

the electric current which flows through it:

Transistor

• A transistor is a semiconductor device used

to amplify and switch electronic signals

and electrical power. It is composed of

semiconductor material with at least three terminals

(Collector, Base and Emitter ) for connection to an

external circuit.

• Used in Digital and analogue switch, Signal

amplifier, Power regulator and equipment

controllers.

Diode

• A diode is a specialized electronic component with

two electrodes called the anode and the cathode.

• Most diodes are made

with semiconductor materials such as silicon,

germanium.

• It also work as switch.

• Diodes can be used as rectifiers, signal limiters,

voltage regulators, switches, signal modulators,

signal mixers, signal demodulators, and oscillators.

Relay

• A relay is an electrically operated switch.

• The advantage of using a relay is that a

small current can be used to

switch on and off a circuit with a large current .

• The output from IC is send to relays which results in

its excitation and gets activated.

• When the switch is closed, current flows

and the iron rocker arm attracted to

the electromagnet that

rotate and pushes the contacts

together.

• It may have a large current flowing

through it, to operate

a powerful motor or very bright lights.

• Used to control motors, heaters, lamps

or AC circuits which themselves can

draw a lot more electrical power.

Relay

Applications

o Street lamps

o Alarm clocks

o Home lawn and Parks

o Burglar alarms

o Camera light meters

o Light intensity meters