M.Tech Minor project Presentation

1. Design of
a
Colour Sensor
By:
VIVEK KR. SRIVASTAVA
Roll No. 210403
Under the guidance
of
DR. S.K. MAHNA

2. OUTLINE:
 Objective
 Colour Theory
 System Introduction
 The Optical System
 The Electronic System
 Decoding Action
 Future Scope of the Project
 Applications

3. OBJECTIVE:
 To design a sensor which can detect
light of different colours and is able to
differentiate between them.

4. COLOUR THEORY:
PRIMARY AND SECONDARY COLOURS:
 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

5. PRIMARY COLOUR:
 Primary colour can be subdivided into:
PRIMARY
COLOUR
ADDITIVE SUBTRACTIVE

6. 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.

7. 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.

8. RGB COLOUR MODEL:

9. 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.

10. RYB COLOUR MODEL
 Primarily used in art and design
education, particularly painting.

11. SYSTEM
INTRODUCTION:
L
COLOUR LIGHT I OPTICAL SENSORS SIGNAL
G (Light To CODITIONING
SOURCE H
COMPONENTS OUTPUT
(RGB) T Current)
BLOCK DIAGRAM

12.  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.

13. THE OPTICAL SYSTEM:
Convex lens Colour glass filter
Photodiode
10cm 10cm
Hollow cylindrical pipes

14. 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.

15. 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.

16. THE ELECTRONIC SYSTEM:

17. 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.

18. ELECTRONIC COMPONENTS
USED:
 DECODER – 74HC138
 3 x 8 decoder
Takes 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

19. DECODING ACTION:
INPUT OUTPUT
A2 A1 A0 COLOUR
(Green) (Red) (Blue) 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

20. 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.

21. 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.