Proximity Switches

Probably a magnetic reed switch.

It will in this case just be an on/off function.

Current will either flow or not and the control panel will recognise this.

Hi Sakthi, welcome to the forum. Proximity switches come in many different forms, and use different techniques to detect a object:

They can be inductive, optical, capacitive and ultrasonic proximity switches.

The reed switch, mentioned by Portugalphilip, opens or closes when a magnet is close enough to activate the "tongue" of the reed switch.

This works only with magnetic materials and for detections of ample millimeters.

While the other types may detect and switch proximities of other bodies, materials, liquids and even foam. (The choice may be critical) All the mentioned types may come in 2 or 3 wire versions. The 3 wire versions contain electronics inside and have a +, -, and a output wire. The configuration can be NPN or PNP, or relay output - and some universal PNP/NPN types come with 4 wires.

Your question:

2 wires to the controller means that the sensing element is a 2 wire type.

It connects to the controller. This type has no electronics in it - only a component (or group) that is part of the sensor/controller electronics and gets it life from that part.

Sensitivity and other parameters are controlled by the controller.

Hope this helps. D

consider that sensor(proximity switch) which is connected to controllers takes 8.5vdc for its operation.we are having only two wires from controller to sensor..then how it takes that voltage and how it gives return feedback makes controller NC to NO and NO to NC????

You are talking about a wired remote controller, that is supposed to give this voltage to the sensor.

Compare with a bulb and a dimmer in one box - to move the bulb out the box, you extend the 2 wires and bring the bulb away from the box.

Your sensor is a different component, that is a part of the electronic controller.

The change in property, albeit current, voltage, frequency will affect the controller that is designed to provide closed or open contact results, either potential free or with a practical output signal for further processing e.g. in PLC or CNC applications.

The controller can have threshold, sensitivity and calibration adjustable set points. If you provide more specs. we can give more details, but I kept it universal now.

Two wire proximity switches are usually connected in series with your relay coil that is the terminal A1 of the relay. Your other relay coil terminal A2 is usually is connected to the negative of the power source or to the neutral line.

At normal stage, when the proximity switches is not actuated by the actuator, the power supply that feed to the proximity switches, that is the "RED" (+) wire, actually, power up your proximity switches thru the negative wire, "Blue" wire or sometime it is a "Black" wire and back to the negative of the power supply thru the relay coils.

The current that flow from the proximity switches is very low in which it will not able to energize your relay. When the actuator that actuated your proximity switches, the proximity will conduct a full current thru the proximity switches and fully energize your relays.

Example below is the proximity switches connection