Design of aColour Sensor By: VIVEK KR. SRIVASTAVA Roll No. 210403 Under the guidance of DR. S.K. MAHNA
OUTLINE: Objective Colour Theory System Introduction The Optical System The Electronic System Decoding Action Future Scope of the Project Applications
OBJECTIVE: To design a sensor which can detect light of different colours and is able to differentiate between them.
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
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.
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: LCOLOUR LIGHT I OPTICAL SENSORS SIGNAL G (Light To CODITIONING SOURCE H COMPONENTS OUTPUT (RGB) T Current) BLOCK DIAGRAM
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.
OPTICAL COMPONENTSUSED: 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 COMPONENTSUSED: 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.
ELECTRONIC COMPONENTSUSED: 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 COMPONENTSUSED: 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
FUTURE SCOPE OF THEPROJECT 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.