Design News: Getting Started With Proximity Sensing

Jon Titus, Contributing Editor

The Vishay Semiconductors VCNL4000 reflectance proximity sensor combines an infrared (IR) LED and a photodetector with a second sensor that measures ambient light with a spectral response close to that of a human eye. The small sensor IC can detect an object out to about 20cm. Vishay suggests possible uses in smartphones, digital cameras, and tablet PCs. Other ideas include: hands-free light dimmers, pet door openers, industrial safety apparatus, etc.

The kit allows engineers to work with the small IC on a USB stick controlled by Vishay's measurement-and-control graphical user interface (GUI). I recommend the kit but with a few reservations about the quality of the accompanying manual. You must decipher many sentences and try to determine what the authors mean. I had hoped for real-world examples, which the otherwise good application information lacks.

The $35 kit worked well, and the software plotted signals from the sensor that takes into account and rejects ambient light. Software reads from or writes to 11 registers via an on-chip I2C port to set operating conditions such as LED current (10mA to 200mA), an ambient light parameter, and 16-bit ambient light and proximity values.

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