Proximity Switches

[Clive S]

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

[kingcreaky]

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

:-D

[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.