使用接近检测和环境光传感，以节省物联网设备功率

　　使用接近检测和环境光传感，以节省物联网设备功率

　　许多便携式电子设备结合环境光传感器（ALS）和接近检测器，既提高了用户体验，最大限度地降低功耗。直到最近，这些组合传感器已被限制在范围为几毫米的接近传感器，从而限制其应用到智能手机。

　　然而，许多物联网应用，包括恒温器，家用电器，办公设备，照明控制，以及其他也可以受益于电路板空间和节省功率的集成设备具有较长的检测范围。这是在Vishay Intertechnology新近出台的vcnl4100ct设计的动力。

　　本文将探讨ALS和接近传感，因为它涉及到移动和物联网设备的应用。然后介绍vcnl4100ct，描述它是如何运作的，以及如何得到它的最为你的下一个设计。

　　ALS and proximity sensors save power

　　In displays for portable devices， the ALS is used to determine the screen display intensity needed under varying light conditions. This aids screen readability and the overall user experience， while conditionally reducing power consumed by the display. Some devices， such as smartphones， also use an optical proximity detector. The sensor output can be used to disable the touchscreen function and turn off the display. This reduces the odds that a user’s ear or cheek could hang up the call， mute the speaker， or engage some other unwanted function.

　　Turning off the display while close to your face also extends battery life. If a user brings the device away from their ear to perform another task such as picking up another call， the proximity sensor will detect that action and the screen and the touch function can be re-enabled， ready for input.

　　Combining proximity and ambient light sensors into a single package has been common practice in the handheld market for several years. The integration takes advantage of the fact that photo detectors are used for both functions. For ambient light detection， the photo diode output is processed and filtered to mimic the response of the human eye. This information is then used to appropriately dim the screen. For proximity detection， an infrared emitting diode （IRED） sends out pulsed energy and a photo detector tuned to the IRED wavelength looks for that reflected energy. The combination saves valuable board space by using a single package that shares power and communication with the outside world.