Mesa Cards and Inductive Proximity Switches

Skippy1 wrote: Had the sensor hanging as far out of the tool holder as I could, as the instructions said that if it was adjacent to, or shrouded by metal, it reduces the sensitivity

There are "shielded" and "unshielded" types. if the threaded sleeve extends all the way to the end then the prox is "shielded" and these are a lot easier to work with in a machine tool.

I have a few of them embedded in actual slideways in places that never see any swarf using a hole drilled in the mating part as a target.
picasaweb.google.com/lh/photo/PtEG4xP6Ic...pFm0?feat=directlink shows a couple in my milling machine prior to being wired up.

Thanks for the tip Andy - that's a top idea.

I purchased a pair of the Omron M5 threaded tube PNP shielded type, (E2E-X1B1) and tested them. They have a really crisp on/off point on the approach and retract, repeatable to about a thou'.

As suggested, I plan to bury them in the carriage cross-slide dovetail in drilled and tapped passages. Once I conform the travel limits, I'll drill corresponding 5mm divots in the mating part.

Cheers, Steve

PCW wrote: for 7I76 (and 7I77,7I70,7I66,7I84) inputs,
PNP type proximity switches are the best
(no external components)

Damn, I have a 7i76e and I've been collecting NPN proximity switches. Can someone tell me what external components are required and where they should be connected on a 24 volt NPN proximity switch? I'm guessing a pullup resistor or something is required. What value resistor?

Reading the manual, it sounds like the inputs on the expansion connectors are 5V logic with pull-up (whereas the GPIO is 32V inputs with pull-down) so it might make sense to interface the proximity switches to the expansion connector rather than the terminal blocks.

But see what PCW says about this, it might be a terrible idea.

Using the expansion connector pins directly will work with NPN proximity switches
(the expansion port pins have pull-ups to 5V)

_BUT_ if you make a wiring mistake (connecting to >7V or < -0.5V) even for a microsecond
or you have a EMI issue and large voltage spikes on the wiring, you will damage the FPGA

Safer to use the field inputs with a 2K 1 W pullup to 24V