Have you ever been thinking how a robot can figure out when is light and when is darkness? The answer is simple and contains only two words – light sensor. This little and simple sensor can be used in robotics to create a vision for a robot in order to move autonomously.
A light sensor has the role to detect the light and the result is translated into output analog value. The sensor output depends by light intensity and has low or high values. The robot can be programmed to react when the light sensor detects a certain amount of light.
In some words, a light sensor is a simple robotic part that uses light sensitive materials like Galium to generate signals. When a photon hits the Galium a small signal is generated.
A light sensor is not an expensive sensor and is used widely in many fields starting with toys, robots, gadgets and appliances.
A cheap price is one of the advantages of a light sensor, but at the same time, this type of sensor cannot be used for precise light measurements. Another advantage is that the sensor is powered only when the light is sensed, otherwise the sensor has zero energy consumption. With analog output the sensor requires a converter to take the analog output and converted into digital output. This is another disadvantage of this type of sensor.
How light sensor works
Before starting the list with light sensors, I would like to write few words about how the light sensor works. As I said before, a light sensor is simple and is used for light detection. On the market are many types of sensors with slightly different way of works. At least one thing is common to all light sensors available. All of these use a photocell or photoresistor to detect the presence of light. When the light is detected by a photocell or photoresistor the value of the output signal is changed. A converter takes the analog signal and convert into digital output.
Light sensors list
In this article, I reviewed thirteen light sensors designed to be integrated in robotics projects with light detecting requirements.
01. Mini PhotocellMini Photocell is the smallest and cheapest light sensor designed by Sparkfun. The sensor changes his light resistance when the light is applied on his detecting surface. The range of resistance is between ~1k Ohm when the sensor is supposed to light, and can rise up to ~10k Ohm when the sensor is in the dark.
Mini Photocell has a low price and can be used in robotics projects with light detecting requirements and low budget.
02. SeeedStudio Light SensorSeeedStudio design a low price light sensor that uses the GL5528 photoresistor for light detection and his intensity. The resistance of the sensor decreases the value when the light intensity is high, and increase the value of resistance when the light intensity is low. Even is one of the cheapest light sensors on the market, the SeeedStudio Light Sensor returns accurate values in order to detect the intensity of light.
Integrated into robots, the sensor can be used for monitoring as well as light control robots.
03. DFRobot Light SensorDesigned and build by DFRobot the sensor works with Cds Photoresistor and change the output voltages when light intensity changes. In the dark the output value is low while in the light the analog output value is high and reaches 5 Vdc. The sensor is designed to work with an Arduino board and on the manufacturer site can be found a sample code to program the robot in order to take a decision based on sensor values.
04. Inex Light Sensor BoardDesigned by Inex, the light sensor uses an LDR (Light dependent resistor) or Photoresistor to detect the light. The output is proportional to the light intensity. With a design based on robotics integration the sensor can be integrated with microcontrollers and logic circuits due to a friendly interface.
05. Parallax QTI Light SensorThis little sensor is designed to be used in robotics projects like line following or for detection of different shades of colors. Designed by Parallax, QTI Light Sensor works using an infrared emitter / receiver and measure the infrared reflected from a surface.
It could be used with analog and digital output and has a friendly interface for any Parallax microcontrollers.