How to use proximity switches as inputs

Hai, Dear,

New guest, very interested site,

My question is, how can I connect Inductive proximity switches as in put and please tell me what are analog inputs and how can I connect to the inputs

You typically connect a proximity switch to a DC discrete input, just as you would a mechanical switch. The only caution is that you hae to watch sinking and sourcing. I usually use sinking inputs on the PLC and a sourcing prox.

Analog inputs are used with things like pressure transmitters, and the signal is proportional to the measured variable. For example, if you have a 0-200 psig pressure transmitter with a 4-20 mA output, at 0 psi you have 4 mA, at 100 psi you have 12 mA, and at 200 psi you have 20 mA.

There are a variety of analog signals available. Your PLC analog input card catalog or manual should show connections for various sensor types.

asha6965,

If you're new to proxy's here are a couple tips to follow:

1] Three basic power types: AC , DC-NPN , DC-PNP . You will have to match the proxy power type & voltage to your PLC input. Also, there are N.O. , N.C. & N.O.N.C. or SPDT outputs.

2] Proxy's usually have a rating for Leakage Current . This is a minnimum current that HAS to flow through the circuit to turn off the proxy when it is supposed to be off.

With good PLC's Leakage Current is not usually an issue as the manufacturers make the inputs with resistors to account for this. With cheap, off-brand PLC's and some "smart relays" & micro-PLC's you will have to add an external resistor, pilot light or relay to satisfy the current requirement or the proxy will always be ON.

Proximity sensors can have both digital and analog outputs.

Digital sensors have an output that swithes when the distance to the object is close enough.
The output can be 110VAC SINK, 110VAC SOURCE, 24VDC PNP, 24VDC NPN or other.
You wrote "proximity switch", so that would be a digital sensor.

Analog sensors have an output the changes with the distance to the object.
The output can be 0-10V, 4-20mA or other.

How to connect to an analog input on the PLC would depend on the exact type of both sensor and PLC.

Please advise a suetable hardware

Dear friends,

I am interested to develop one programme with my windows 98 PC. I wish to controle motors throgh my Pc. Which type of hardware I have to provide and for controlling 3 motor operation ( conveyors) with up & down lemit switch operation. Please advise me the complete procedure to make a programme with plc

Dear asha6965,

Your question is pretty open ended, kind of like asking, "how should I decorate my living room" without ever meeting you, but I'll take a little stab at it. First of all, if you are going to use a plc, you will not be controlling motors through your Pc. Your computer will be used to program the plc and then monitor it. You stated that you will need to control 3 motors using some limit switches but you will probably need several more switches or sensors like start and stop buttons, etc. If you can give us more details as to what you are trying to accomplish and your plc preferences and budget constraints, we can give you more details.

P.S. Are you sure this isn't a homework problem?

Tough times?

Please advise me the complete procedure to make a programme with plc

Click to expand...

Sure sounds like a homework assignment and if I were your instructor, well, let's just say it would not sit well with me.