AN-1049 Infared Proximity Sensor

This GreenPAK3 CMIC device is configured for an infrared proximity sensor. The design approach relies on relative changes of an objects’ IR reflected brightness as the distance varies. With the IR illumination source facing out from the detector area, the farther away an object, the less light is reflected by it. The GreenPAK3 steps through 7 increasing levels of IR illumination intensity, while the detector sensitivity remains fixed at a baseline level. As the illumination increases, the IR detector will provide a logic true output at its threshold setting, and the intensity step ups will halt. The resulting proximity is indicated linearly by a column of seven LED’s. At a distance exceeding the limits of the sensitivity of the detector, all seven LED’s are ON. As the distance to the object decreases, the number of LED’s that are ON also decreases. So with a known object, this design is also useful for simple distance/ranging.

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