This package includes 2 QRB1134 IR sensors to detect changes in the included encoder wheels.  It also includes a bracket with all the necessary hardware to attach the sensors to the Trekker.  The receptacle and crimps are also included for attaching the sensors the OOPic II Expansion Board (v2.x and above only).. 

The stickers attach to the  3.5" wheels or the 4.5" wheels sold with the Trekker Chassis.  When the sensors are mounted about 0.2" away from the encoder wheels it will detect the changes between the black and white lines.  The OOPic or other Microprocessor can be programmed to respond to the sensor readings to keep the Trekker on track and tell it how far its traveled.

This kit is also sold to include 4 QRB1134 IR sensors, 2 of which will be used for encoders, the other two can be used to look at the floor and determine if there are holes/edges on the floor or white/black contrasts. You can also use these four sensors for Line Following with a Trekker Line Following Bracket.

If you already have the Trekker Line Following package, then you do not need this kit, you only need the encoder brackets.

Examples of encoder code and installation instructions are included on our Trekker download page.