Lets Think Robotics: Sensors

In the article “Robot – A machine with life”, we saw that sensors are integral part of robots. Robots gather the information about their surroundings with the help of sensors. Robot can gather the following information using sensors:

Distance of other object from them
Color of the other object
Temperature of other object

Based on the above information, the robot can be trained to carry out certain tasks, called as “Applications of robot”. For example, after measuring the distance from the other object, the robot can be trained for “Obstacle Avoidance” and finding it's path towards the target. Here, the distance from other object can be measured with ultrasonic sensor. Another example of Robotic Application can be “Line Follower” where the robot makes use of Color sensor/Light sensor to keep track of the line. Likewise, sensing the temperature of the other object will be required to train the robot in hazardous circumstances. We came up across three sensors until now: Ultrasonic sensor, Light Sensor and Temperature Sensor. Let us see how few of these sensors work.

What is a Sensor?

A sensor is a device which converts input from physical environment, into typically electrical or optical signal output. Specific input can be light, heat, motion, pressure etc. The output signal is generally converted to human-readable display. For example: The speedometer in a car collects wheel rotation data and calculates and displays the speed with which the car is moving. In a mercury-based glass thermometer, the input is temperature. The liquid expands and contracts in response, causing the level to be higher or lower on the marked gauge, which is human-readable.

Ultrasonic Sensor

This sensor generates ultrasonic waves (sound waves above 20KHz), by turning electrical signal into sound. The sensor then emits these sound waves. These waves strike the object surface and are reflected back to the sensor. Upon receiving the echo, sensor turns the sound waves into electrical energy which can be measured and displayed. The electrical signal generated is proportional to the difference between emitted and received sound waves. This in turn is proportional to the distance of the object from the sensor. Ultrasonic sensors are capable of detecting most objects — metal or nonmetal, clear or opaque, liquid, solid, or granular. A downside to ultrasonic sensors is that sound absorbing materials, such as cloth, soft rubber, flour and foam, make poor target objects. Ultrasonic sensors do not work in a vacuum, because sound waves cannot travel in a vacuum. Therefore ultrasonic sensors are never put on space probes or lunar rovers. It can be used for measuring wind speed and direction (anemometer), tank or channel fluid level, and speed through air or water.

Light Sensor

Light Sensor is an electronic device used to detect light. It generates an output signal indicating intensity of light. The light sensor converts light whether visible or in the infra-red parts of the spectrum into an electrical signal output. In daily life, light sensor is used for security systems as well as for home appliances like remote control. It can also be used for bar-code scanning system where the bar-code is illuminated and corresponding code is generated and fed into the computer.

These sensors, when used in Robotic world, give the robots an ability to perform similar to human being. This ability helps the robot to respond according to situation. Sensors can be classified as