Proximity Switches

Ok

Following on from the thread the other day regarding these inductive proximity switches. And after you have pulled yourselves back together after reading Jonathon build thread which im sure is going to be the topic of this week....

TL-W5MC1 5mm Inductive Proximity Sensor Detection Switch NPN DC 5-24V | eBay

Ive got the one on Y working, using the below wiring, however as im running two on the X (for autosquare) Im having problems with interference and I wonder if im missing a diode or something to stop feedback from one to the other?

essentially, if I wire just one... say just to pin 11 its fine, but as soon as I put two in place (ie to pin 12 aswell) I notice false positives on pin 11 if you follow?

If I do need a diode? or an additional component id be grateful for a recommendation
Attachment 9898

Your diagram is wrong... the connection to the bob is from the other side of the load resistor, not gnd.

But I think you are using these incorrectly. If these are NPN the load resistor is from output to + supply, not output to gnd. And the load resistor needs to be smaller than 100k, exact value depending on whther bob inputs are opto-isolated or not.

I found this Attachment 9903 when I was looking for info on the proximity sensors I've got. Still haven't got around to fitting them though.

Hope it helps.

You might find this interesting:- Three-Wire Sensors
It explains a little of how they operate ..Clive

thankyou all for your posts, I have the sensors working now... and auto-squaring

:-D

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Originally Posted by kingcreaky

thankyou all for your posts, I have the sensors working now... and auto-squaring

:-D

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So what was the problem? Your resistors are 10k, not 100k. I think the sensors you have are not open collector, since they worked without any resistor which implies they have an internal resistor. Putting the 10k resistor from the output signal to ground reduces the output voltage to the 5V required by the breakout board since it forms a potential divider with the other resistor.

Yes your right, for a start I got the resistor flavour wrong in my diagram... and I was taking signal from wrong place.

its now like this... and it works

(incidently) if you measure across the grey spots, or the green spots you get 4.97v high, and 0.01v low

Attachment 9908

Whats the supply voltage?

These are open collector NPN sensors so your BOB must have pullup resistors and the external resistors are not needed.

Diagram attached shows how to use both PNP and NPN open collector proximity sensors.

Attachment 9915

I'm starting to look at switch options for my design - are you using these proximity switches for homing?...are they accurate enough on a repeatable basis for that (ie, tool changes, flipping work piece etc)?

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Originally Posted by CraftyGeek

I'm starting to look at switch options for my design - are you using these proximity switches for homing?...are they accurate enough on a repeatable basis for that (ie, tool changes, flipping work piece etc)?

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In my opinion yes, sheerly because there is no mechanical parts. I cant talk from too much experience with flipping work etc but they were recommended to me by another forum member who does.

Thanks, i'm liking the look of this approach & I have basic electronics knowledge with plenty of soldering experience so should be easy enough to get them running - any chance of a pic showing how you've got one attached to your machine?

What are you using for limits?

limits switches are for girls!!! the 'limit' is where the ballnut slams into the bearing housing :encouragement:

no pictures im afraid, however they are very simple... wave something metal infront of it... and it triggers

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Originally Posted by kingcreaky

limits switches are for girls!!! the 'limit' is where the ballnut slams into the bearing housing :encouragement:

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. . . .Ah ah obviously not bent a ballscrew yet Matt or ripped the teeth of a timing Belt..:sorrow:

Crafty Just buy some cheap-ish micro switches for limits and wire in series. Also arrange them so they get triggered by running over the switch and not into it. Same goes for Home/Proximity switches.

Also If you want to keep wiring and number of switches down then just have 1 limit switch per axis that travels with that Axis and gets tripped by some fixed but adjustable brackets at each end.

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Originally Posted by JAZZCNC

Crafty Just buy some cheap-ish micro switches for limits and wire in series. Also arrange them so they get triggered by running over the switch and not into it. Same goes for Home/Proximity switches.

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That's pretty much what I did on my last crappy MDF machine...although the micro switches were a smidge too cheap :tongue:
They've been retired...i'll be getting some new ones when the time comes.

I've got six nice inductive sensors, four of these and two of these. I'm not sure if and how I could use the last ones as they have only two connections. Do I need additional circuitry to be able to use them?

The four you have are Normally Open type, the preferred type for limit switches is Normally Closed.
Also take note when you mount them, if you notice they use brass, stainless, polypropylene mounts.
The last two may be normally closed, it does not say, some of these just change a voltage level so that the input decides if it's on or off.

This manual shows the wiring arrangements but obviously for their own board.
http://cnc4pc.com/Tech_Docs/C31R1_USER_MANUAL_REV1.pdf

You could wire the sensors so they operate the coil of a N/C relay then use the relay contacts as inputs to your breakout board but it's a backward as you have introduced more things to go wrong.

Personally I would replace them all for 3 wire N/C type.

If I use them only for homing with additional limit micro-switches will I have any issues being PNP?

PNP is the most common type used so you should have no issues.

Technical FAQs | Knowledge Base

yours are 5-10v so you should not require extra resistors as in this discussion but it makes interesting reading
http://www.mycncuk.com/forums/genera...-required.html

@paulus:
You can't use the 2-wire ones directly, they need additional circuitry ( see here for more info)

Here is a diagram showing how to use the 3-wire ones
Attachment 9915


@EddyCurrent - not sure I agree PNP are more common...

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Originally Posted by irving2008

@EddyCurrent - not sure I agree PNP are more common...

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No me either.!!. . . . Must took the thoughts straight from my Mind. .:smiley_simmons:

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Originally Posted by irving2008

@EddyCurrent - not sure I agree PNP are more common...

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Mabe on the other side of the pond.
Not arguing because it doesn't matter but;

I've just done an inductive proximity sensor product search on Pepperl & Fuchs website
No. of products NPN 74
No. of products PNP 207

Same again but RS online
No. of products NPN 54
No. of products PNP 208


Edit: Just noticed the 2 wire ones are NAMUR type, this is quite a good document
http://www.simeks.biz.tr/resimler/pd...ciklamalar.pdf
Maybe the last time I used them (which is quite a number of years ago now :upset:) the PLC had input cards designed for them, although I've never been a fan of 2 wire type.