Proximity Switches

[Jonathan]

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

:-D

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.

[kingcreaky]

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

[irving2008]

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.

[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)?

[kingcreaky]

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)?

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.

[CraftyGeek]

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?

[kingcreaky]

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

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

[paulus.v]

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?

[EddyCurrent]

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.