Most design engineers of consumer and industrial products always look for various ways to achieve their desired goals in applications ranging from wearables to handheld devices to industrial appliances. One common thread between these applications is that they need some type of sensor(s) and actuators or decision engines to determine the actions to be taken.
Ambient light and proximity sensors (ALS/Prox sensors) are used in many of these Internet of Things (IoT) devices, home and factory automation, and handheld and wearable devices to reduce power consumption, determine screen brightness, turn on/off the screen, detect the level of the liquid in a tank, measure the proximity of the piston in a chamber, and so on.
What follows are the conventional myths that surround ALS/Prox sensor usage in various scenarios and applications—and reasons why they can all be debunked.
1. IR-based proximity sensing cannot be done under direct sunlight.
Proximity sensors can be used outdoors under direct sunlight to determine proximation. The ALS/Prox sensor detects, and subsequently cancels out, the ambient IR. It depends on the IR emitter intensity and pulse to detect the proximity. Figure 1 shows a typical ALS/Prox sensor block diagram.