Proximity sensors are literally and figuratively the often-invisible elements in systems as they react to motion, position, or a nearby presence. You can find one, or likely more, in commonplace applications:
- Printers, copiers, tablets, and home appliances
- Collision detection in robots and toys
- Proximity sensing and lighting control in offices, corridors, and public buildings
- Parking space availability in lots and garages
- Even water activation in lavatory appliances
It’s a long if not obvious list (if you make a deliberate effort to look around for them, you’ll see how many are out there, silently doing their job).
Just as proximity sensing has many applications, it can be implemented in many ways, with magnetic, capacitive, RF, and optical approaches among the most common. As always, there’s no single “best” proximity sensor, as it depends on the specifics of the installation, costs, ruggedness, use patterns, distance, potential interference, and many other factors.
The optical technique is very popular due to its ease of electrical and mechanical design-in, versatility, flexibility, RF noise immunity, low cost, low power requirements, ease of interfacing, and overall reliability. While early optically based proximity detectors used separate LEDs and photosensors, each with its respective driver or signal-conditioning circuitry, the popularity of the optical approach soon drove the development of more highly integrated and sophisticated solutions.
The latest entry is the VCNL36758 from Vishay Intertechnology. This device is a high-sensitivity proximity sensor with range up to 60 cm that incorporates an infrared (IR) LED and corresponding photosensor in a single package (Fig. 1).
