How to Wire an Inductive Proximity Switch

by G.K. Bayne; Updated September 26, 2017

Inductive proximity switches or sensors are used in industrial applications for sensing a metal part. When the metal part moves into close proximity of the sensor an internal switch is either opened or closed. The sensor is always labeled as N.O. (normally opened) or N.C. ( normally closed). This designation identifies the precondition of the switch and when actuated will reverse its condition. In other words, a normally open sensor when tripped will then close completing an electrical circuit. The same for a normally closed switch as it will open upon the sensor being triggered. A proximity switch is generally powered by a direct current source of low voltage in the range of 12 VDC to 36 VDC.

Items you will need

  • Proximity switch
  • Crescent wrench
  • Wire strippers
  • Small wire nuts
Step 1

Identify the type of proximity sensor or switch you need to install. Whether that condition is a NO or NC type. You should also confirm the power requirements of the sensor so you will not damage the power source or the device it is controlling.

Step 2

Install the proximity switch into the receiving hole of the mechanical device using the crescent wrench. You should have two large nuts to secure the switch into place. One nut should be placed on either side of the holding plate. Generally this hole will be a slotted opening either horizontal or vertical in nature. The purpose for the oblong opening is to fine tune the alignment for the metal lever the switch is electrically identifying.

Step 3

Use the wire strippers and reveal approximately ½ inch of the bare copper on the insulated power feed and switch wires on both the proximity switch and the wires coming from the control panel. There should be three identified colored wires. Depending on the manufacturer, the black wire will be the power or switch common. The brown wire is the power feed wire and the blue wire is the switch wire. Individual specifications or blue prints should be checked to proper connection of the wiring.

Step 4

Connect the wires in the following order by finger twisting the bare ends together and covering the bare connection with the small wire nut. The black common should be connected to the power feed common of the control power system. The brown wire will tied to the power feed voltage, 12VDC to 36 VDC, depending on the type of switch. The blue wire will be connected to the device that is being electrically controlled, usually a small electric relay.

Step 5

Fine tune adjust the proximity switch with the crescent wrench by loosening the holding nuts and set the gap between the end of the sensor and the metal actuation lever. There will be two identification lights on the sensor. The green LED represents power to the switch and the yellow LED indicates a state of the switch being engaged or tripped.

Step 6

Set the proper gap and test the switch circuit by manually raising and lowering the metal lever. Adjust the gap so the metal lever can never physically come in contact to the sensor end. Direct metal contact will damage the switch.

Warnings

  • When choosing a proximity switch keep in mind the conditions the switch will be placed in as certain environments can damage a very expensive sensor.