Here is the [datasheet of the reflectance sensor (CNY70)](https://www.vishay.com/docs/83751/cny70.pdf) on the module.
The Reflectance Sensor Module is a tool that used to detect contrast on a surface. It works by detecting the reflectance of a surface using infrared light and differentiating the contrast by measuring the amount of reflected light to the ratio of emitted light. The most distinguishable surface colors are black and white, as in line-following robot parkours.
The module has 3 reflectance sensors on it, positioned as left - middle - right, each sensor returns an analog value in the range of \[0, 255] to express the contrast level. This feature makes it a valuable tool to build a line follower robot system combined with PID controller.
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