# Line Tracker ![](https://3510336827-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M7yGVyBrcpSR8SDSikj%2F-M871GhdSZV8jTtuSmYc%2F-M878o42wjFuFnk7h4un%2FLine%20Tracker.jpg?alt=media\&token=c588de88-199c-4519-bf98-bf0ca3d2e388) The **Line Tracker** is an analog sensor consisting of an infrared LED and an infrared light sensor. It has a single mounting hole and is designed to be mounted under the chassis of a robot. The Line Tracker allows a robot to follow a pre-marked path. The Line Tracker functions by illuminating a surface with its infrared light LED and then the infrared light sensor measures the reflected infrared radiation. Based on the reflected radiation’s intensity, the Line Tracker can determine how light or dark the surface is below the sensor. Lightly colored surfaces will reflect more infrared light than dark surfaces and will appear brighter to the sensor. This allows the sensor to detect a dark line on a pale surface, or a pale line on a dark surface. The Line Tracker is an analog sensor which means the infrared sensor will return a value anywhere between 0v and 5v of voltage to the V5 Brain depending on the reflected infrared radiation. The V5 Brain then converts this value to a percentage of reflectivity. This type of measurement requires an adequate threshold of difference between the shades of reflectivity in order to successfully follow a line. For example, the Line Tracker will not follow a strip of black electrical tape placed on the dark gray VEX Competition Field Tiles because the sensor will return percentages of reflection too close together for a threshold of difference. However, a strip of white electrical tape on the VEX Competition Field Tiles will provide a large difference in values and an adequate threshold for the robot to track the tape. ## Teams Contributed to this Article: * [BLRS](https://purduesigbots.com/) (Purdue SIGBots) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/line-tracker.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.