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Fun with Photo-sensors

Light sensors allow your robot to read and compare light intensity. Students learn how to read inputs and cause them to change the robot’s behavior. Here are some photo-sensor activities.


BotBrain Educational Robots PhotovoreA robot that eats light? Actually photovore is what wecall a robot that seeks light. Students build it with two light sensors “looking” forward and to the sides as shown in the picture. The sensor which “sees” the most light is on the brighter side of the bot. the program turns it toward that side.

To run a competition for photovores, suspend a light in the middle of a clear area of floor about 5 feet up and darken the room. All robots start an equal distance from the brightest part of the light. The first one to the brightest spot wins.

Flashlight Remote Control

You can use the same robot and program to make the robot follow the beam of a flashlight in a darkened room. Wherever you point the light, the robot will drive.


Turn it around! A photophobe is the opposite of a photovore. It drives away from light. Turn the sensors around so they point toward the back of the robot, and reverse the logic in the program. Add a light threshold to the logic. When it gets dim enough, the robot stops moving. Shine the light at it, and it moves away again.

Light Orbiter

Another fun activity with light sensors is to try to put the robot in orbit around the light source. The configuration of sensors is similar to the Photovore. But students change the program to drive in a circle at a given distance from the light. Have different groups make their robot orbit at different distances. A roboto-planetary system!


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Robert Contaldi