Design of a

Colour Sensor

By:

VIVEK KR. SRIVASTAVA

Roll No. 210403

Under the guidance

of

DR. S.K. MAHNA

OUTLINE:ObjectiveColour TheorySystem IntroductionThe Optical SystemThe Electronic SystemDecoding ActionFuture Scope of the ProjectApplications

OBJECTIVE:

To design a sensor which can detect

light of different colours and is able

to differentiate between them.

COLOUR THEORY:

Primary colours are sets of colours that can

be combined to make a useful range of colours.

For human applications, 3 primary colours are

usually used, since human colour vision is

trichromatic.

A secondary colour is a colour made by

mixing two primary colours in a given colour

space.

PRIMARY AND SECONDARY COLOURS:

PRIMARY COLOUR:Primary colour can be subdivided into:

PRIMARY COLOUR

ADDITIVE SUBTRACTIVE

ADDITIVE PRIMARY:An additive colour model involves light

emitted directly from a source or

illuminant of some sort.

Combining one of these additive primary

colours with another in equal amounts

produces the additive secondary colours.

Combining all three primary lights

(colours) in equal intensities produces

WHITE.

RGB COLOUR MODEL:

An additive colour model in which RED,

GREEN, and BLUE light is added

together in various ways to reproduce a

broad array of colours.

Used in sensing, representation, and

display of images in electronic systems,

such as televisions and computers.

RGB COLOUR MODEL:

SUBTRACTIVE PRIMARY:

A subtractive colour is based on

absorption phenomenon.

Each colour is caused by subtracting (that

is, absorbing) some wavelengths of light

and reflecting the others.

This model explains the mixing of paints,

dyes, inks, and natural colourants to

create a full range of colours.

RYB COLOUR MODEL Primarily used in art and design

education, particularly painting.

SYSTEM INTRODUCTION:

BLOCK DIAGRAM

COLOUR LIGHT SOURCE

(RGB)

SENSORS(Light To Current)

SIGNAL CODITIONING OUTPUT

OPTICALCOMPONENTS

LIGHT

Light rays from a colour light source

fall on the optical components of the

Colour Sensor.

The optical components filter and

focus the rays on the optical sensors.

The output of the sensors is processed

by the electronic circuitry and the

corresponding colour output is

obtained.

THE OPTICAL SYSTEM:Photodiode Convex

lens

Colour glass filter

Hollow cylindrical pipes

10cm 10cm

OPTICAL COMPONENTS USED:

PHOTODIODE – (EG & G)

PIN Photodiode

Based on Photoelectric Effect

Converts Light to Current

CONVEX LENS (f = 5cm)

Performs the task of focusing the light

on the sensor.

OPTICAL COMPONENTS USED:

COLOUR GLASS FILTERS (Blue, Red,

Green)

Allows only single colour wavelength to

pass through it.

The optical filters used in the system are

absorption filters.

It consists of colour media like colour

glasses.

THE ELECTRONIC SYSTEM:

ELECTRONIC COMPONENTS USED:

PHOTODIODE

Connected in Reverse Bias.

Outputs current proportional to the incident

light intensity(~20µA).

OP-AMP –UA741

Connected as a trans-impedance amplifier.

Converts current into voltage.

ELECTRONIC COMPONENTS USED:

DECODER – 74HC138 3 x 8 decoderTakes 3 inputs and gives 8 outputs

VOLTAGE REGULATOR- IC 7805

Gives a fixed output voltage of 5 Volts

Need of the regulator?

The decoder IC operates on 2 to 6 Volts

The output of the op-amp can be as high as

12 volts

DECODING ACTION:INPUT OUTPUT

A2(Green)

A1(Red)

A0(Blue)

COLOUR DETECTED

0 0 0 0 1 1 1 1 1 1 1 NO COLOUR

0 0 1 1 0 1 1 1 1 1 1 BLUE

0 1 0 1 1 0 1 1 1 1 1 RED

0 1 1 1 1 1 0 1 1 1 1 MAGENTA

1 0 0 1 1 1 1 0 1 1 1 GREEN

1 0 1 1 1 1 1 1 0 1 1 CYAN

1 1 0 1 1 1 1 1 1 0 1 YELLOW

1 1 1 1 1 1 1 1 1 1 0 WHITE

FUTURE SCOPE OF THE PROJECT The system can be modified to

detect the colour of an object by sensing the light reflected by it.

The system can be interfaced with a microcontroller to detect a wide range of colour shades.

APPLICATIONS:

It can perform sorting operations:

◦ Avoids separation of medicines in

pharmaceutical industries.

◦Brick sorter

◦ In the recycling industry, sorting plastic by

colour for recycling purposes. For eg.  all

the green 7-Up bottles down one

conveyor, the clear on another and so on.

THANK YOU