Color Sensor – Working and Applications

White light is a mixture of three basic colors known as primary colors. They are red, blue and green. These colors have different wavelengths. Combinations of these colors at different proportions create different types of colors. When the white light falls on any surface, some of the wavelengths of the light are absorbed by the surface while some are reflected back based on the properties of the surface material. Colour of the material is detected when these reflected wavelengths fall on the human eye. A material reflecting wavelengths of red light appears as red. The component used to detect colors is the Color sensor.

What is a Color Sensor?

A color sensor detects the color of the material. This sensor usually detects color in RBG scale. This sensor can categorize the color as red, blue or green. These sensors are also equipped with filters to reject the unwanted IR light and UV light.

Working Principle of Color Sensor

To detect the color of material three main types of equipment are required. A light source to illuminate the material surface, a surface whose color has to be detected and the receivers which can measure the reflected wavelengths.

Colour sensors contain a white light emitter to illuminate the surface. Three filters with wavelength sensitivities at 580nm, 540nm, 450nm to measure the wavelengths of red, green and blue colors respectively.

Based on the activation of these filters, the color of the material is categorized. A light to voltage converter is also present in the sensor. The sensor responds to color by generating a voltage proportional to the detected color.

Another way of detecting color is by illuminating the material surface by Red, Blue and Green LED’s one at a time. Here the sensor contains no filters but light to voltage converter. The highest amount of light reflected back by the material surface while illuminated with the red, blue and green light is calculated to detect the color.

Applications

Colour sensors are applied to measure, detect the color of the surfaces. These sensors have a wide range of applications in industrial, medical and security systems.

Some of the applications are the light color temperature measurement, RGB LED consistency control, medical diagnosis systems, health fitness systems, industrial process control, etc…

Examples

Some of the examples of color sensors available in the market are AS73211, TCS3200, TCS3400, TCS34715, TCS34727, colorPAL from parallax, SEN-11195, Lego Mindstorms EV3, etc…

Besides RGB some color sensors can also detect different colors. IR and UV radiations are to be filtered out to determine the accurate color of the material. Sensors also contain programmable light to frequency converters. These sensors are usually very thin and can be easily interfaced with a microcontroller.

The color sensor is also opted by students for cool projects using microcontrollers like Arduino. For which of your application was color sensor useful? What are the challenges you faced while using the color sensor?