Pepperl Fuchs NPN inductive proximity switch

javelin
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09 Apr 2018 03:04 #108639 by javelin

Pepperl Fuchs NPN inductive proximity switch was created by javelin

Hello everyone. New here and brand new to the CNC world. I may have messed up, I dont know so any input would be of help.

I purchased a set of Pepperl + Fuchs NPN inductive proximity switches. Part of my issue is a lack of education on how it works and how to install the hardware side of things to the 7i76e. From looking online concerning these things and the other information on limit switches it seems to be information overload to my brain.

I do understand it has been said that PNP switches work better, yet I have what I have for the moment. Does anyone here have any experience with this specific switch and its wiring or the best way to go about setting it up to the 7i76e? Based on the documents from the company I have seen would I need an external component of some kind? If so what should I look for when it comes to the 7i76e?

Here is a link to the technical data sheet for the sensor: Limit Switch

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Clive S
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09 Apr 2018 07:37 #108644 by Clive S

Replied by Clive S on topic Pepperl Fuchs NPN inductive proximity switch

I believe you will need a weak pull up resistor on the inputs to get those to work. The PNP type will just work without.

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rodw
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09 Apr 2018 08:28 #108646 by rodw

Replied by rodw on topic Pepperl Fuchs NPN inductive proximity switch

I made the same mistake. Assuming you are using 24V as field power, a 2.2k pullup resistor fixes the problem and I've never had a problem.

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javelin
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09 Apr 2018 11:15 - 09 Apr 2018 11:22 #108650 by javelin

Replied by javelin on topic Pepperl Fuchs NPN inductive proximity switch

rodw wrote:
I made the same mistake. Assuming you are using 24V as field power, a 2.2k pullup resistor fixes the problem and I've never had a problem.

Would some of these work? Resistor

Or would it require 2.2k 1w? 2.2k 1w resistor

Last edit: 09 Apr 2018 11:22 by javelin. Reason: Clarification

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rodw
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09 Apr 2018 11:30 #108651 by rodw

Replied by rodw on topic Pepperl Fuchs NPN inductive proximity switch

Sorry, I forgot to say 1 W resistors but you are on the right track.

Those prices seem pretty expensive. I pay AUD $0.24 each at my local electronics store. What does Mouser/Element14/RS Components offer?

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rodw
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09 Apr 2018 11:32 #108652 by rodw

Replied by rodw on topic Pepperl Fuchs NPN inductive proximity switch

MIght be a couple more than you need

www.amazon.com/Uxcell-a11101900ux0055-Me...ywords=2.2k+resistor

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javelin
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09 Apr 2018 11:46 #108653 by javelin

Replied by javelin on topic Pepperl Fuchs NPN inductive proximity switch

Thanks for all the help guys. I checked Mouser but I couldnt find what I needed there as the filters kept returning no results, but the amazon bulk buy listed was perfect. Just have to wait until they can get here.

I appreciate all the help. Also from what I understand I will need to use the in-not pin when wiring to the mesa. I will work on identifying those and in the meantime getting everything else running.

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rodw
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09 Apr 2018 12:30 #108655 by rodw

Replied by rodw on topic Pepperl Fuchs NPN inductive proximity switch

Once you get your prox sensors installed, you will be able to watch in halshow when you trigger them and work out if you need the -not signal.

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javelin
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09 Apr 2018 12:38 #108656 by javelin

Replied by javelin on topic Pepperl Fuchs NPN inductive proximity switch

Ahhh okay. Thank you so much.

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andypugh
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10 Apr 2018 13:56 #108739 by andypugh

Replied by andypugh on topic Pepperl Fuchs NPN inductive proximity switch

javelin wrote:
I do understand it has been said that PNP switches work better,

Well, it depends...

NPN can be useful if you have 5V inputs but the sensors need 7 to 32 Volts (as is often the case). As an NPN functions as a "switch to gnd" device it is safe to connect it to 5V (it either allows the pin to float high, or shorts it to Gnd, both of which are safe).

PNP is useful if your field-power is high enough to drive the sensors. The issue with NPN and the 7i76 is that the input are active-high, they sense voltage above gnd and are pulled low when unconnected.
With the pull-up resistor connected from the pin to +24V you have, in effect, a potential divider circuit. With the switch open it is 2.2K to +24V and (the pull-down resistance) to 0V so the pin sees some significant fraction of 24V. With the pin closed the bottom resistance is 0 ohms, so the input is pulled low.

Also be aware that the style of sensor with the plastic end exposed can not be buried in metal. There are others with the threaded outer all the way to the end, these can be buried in metal, and that can be handy for installing in retrofits (you can bury them in the parts and sense holes)

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