> For the complete documentation index, see [llms.txt](https://wiki.purduesigbots.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/line-tracker.md). # Line Tracker The Line Tracker can track "lines" and other objects using infrared LEDs ![](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 This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/line-tracker.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.