There are several types of sensors a robot can use to interact with the environment it is in. The photo above shows a sample of 6 types.
1 and 2 are touch sensors from the Vex Robotics system.The Bump Sensor and The Limit Switch They are basically push buttons that sense and object by touching it. When bumping a wall or being pushed by a moving part on the robot a digital signal is created that our microcontroller can read.
Numbers 3,4 and 5 are infrared or IR sensors, they "see" objects with an infrared light. Number 3 is the simplest, just an LED and a sensor, this could be used to sense a person moving through a doorway or in the path of a closing elevator door. The light shines and if it is not detected by the sensor we know somebody or something is in the way. Number 4 is the Sharp GP2Y0D805, a digital sensor that uses the reflectance of infrared to detect objects. If the path is clear the sensor reads one if something reflects the infrared the sensor reads 0. A similar infrared reflectance sensor is number 5, the Sharp GP2Y0A21YK0F that produces an analog output that increases as objects get closer to the sensor.
A detailed description and sample code are available on our LEARN page here. learn.rollingrobots.com/STEM/Arduino/IR-Sensor
Number 6 is the PING sensor that uses sound waves to measure distance. It is the same as SONAR used by submarines and bats to navigate in dark places. This sensor emits a sound wave that echoes off objects. We measure the distance using the speed of sound and the time it takes for the echo to return to the sensor.
Sample code and circuits for using the PING sensor with Arduino are found on our LEARN page here. learn.rollingrobots.com/STEM/Arduino/Ultrasonic-Sensor
The Robot Doc will be posting more info on how to use all these sensors on several different robotic platforms. Check back frequently or check our LEARN site. The LEARN site has several Arduino lessons right now under construction. See: learn.rollingrobots.com/STEM/Arduino
Have a question? Ask the Robot Doctor on twitter, just post it to @RollingRobots