All REV Robotics motors contain a built-in intermediate-level sensor called an Encoder. An Encoder, in the context of robotics, is a type of digital sensor that converts rotary motion into digital signal. These type of sensors require “decoding” to get this information into a usable form. The Control Hub and Expansion Hub have built in decoding through the “Encoder Ports” under the motor ports.

Scenarios where a sensor is needed:The robot needs to autonomously move to a specific location and stop there.The robot needs to move forward at a green signal and stop moving at a red signal.The robot has an arm that needs to be prevented from rotating too far or it may damage other parts of the robot.The robot needs to stop 1 meter away from an opaque wall.The robot needs to be able to tell how many game objects it is currently holding inside its hopper.

Sensor Basics When starting out many of the robot actions can be accomplished by turning on a motor for a specific amount of time. Eventually, these time-based actions may not be accurate or repeatable enough. As battery power drains while the robot is running and mechanisms wearing in through use can all affect time-based actions. Fortunately, there is a way to give feedback to the robot about how it is operating by using sensors; devices that are used to collect information about the robot and the environment around it.