What Is a Proximity Sensor or Switch?

Proximity sensors or switches are generally used in manufacturing. These small devices are typically used in wet or dirty locations were normal switching apparatus cannot be used. Some proximity sensors are found on automobiles. Automobile proximity sensors are used as a warning device to identify objects or persons in the driver's blind spot when backing up the vehicle.

Significance

A proximity sensor typically will operate whenever it comes in close range of a metal object. This metal object can be a manufactured part or a small metal lever that is tripped or moved during a particular operation. When the proximity switch senses the metal it will turn itself on or off, or change its state, like a common household light switch.

Function

The proximity sensor is a self-contained electronic switch. It typically consists of three wires. One wire is a low feeding voltage of 36 volts or less, a common or neutral wire and the switch wire. The sensor must have some form of power in which to operate the internal circuitry of the switch. A common ground wire must also be used to complete the electrical path of the circuit. The switch wire conducts power from the feeding power circuit back into a control circuit. This switch wire typically activates a remote relay which in turn can power another device.

Types

The sensor is typically round and cylindrical in design. It can range in size from a small diameter pencil to the size of a large tube of caulking. The proximity switch can also be in the form of a square or rectangular box shape. Regardless of size and shape these sensors will activate to either an "on" or "off" switching state.

Features

There are two types of states for the proximity sensor. A normally closed or always "on" and the normally open or always "off" state. A normally closed sensor maybe used as a safety that will open the circuit when activated. During the open state, the switch will shut off any electrical circuit that is going through the sensors internal switching apparatus. A normally open sensor will close or turn on a circuit whenever it senses the metal object of lever. This type of switch can be used for automation as it can control other devices upon activation.

Benefits

A larger and more sophisticated sensor is now used on vehicles. This type of sensor bounces an internal signal off of objects, and then can read the amount of time it takes from sending that signal to receiving it back. The shorter the duration of time in sending to receiving that signal, the closer an object is to the sensor face. These proximity sensors are used to identify objects or persons that maybe too close to the rear blind area of a moving car or truck.