pnp sensors, pull down resistors, and NC limit switches with mesa 7i96s

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03 Apr 2024 03:53 #297484 by jg00163206
Greeting fellow linuxcnc peeps, I am building a milling macnine and i have a few questions about limits switch wiring that someone might be able to clear up for me. i get conflicting info on hear sometimes and unless you ask the question with the hardware you are using, its hard to get a straight answer by reading other peoples configs and try to figure out if it will work for my setup so here goes.
im using a mesa 7i96s with pnp proximity sensors for the max limit and NC limit switches for the min on each axis. with these sensors i want to "sink" them to ground. do i need a resistor on the input to make that work or is the resistors on the mesa board suficient? the way i have it wired currently(but not connected to the board yet) is +24vdc==>input common terminal==>+side of prox sensor. black(signal) wire==> inputs. - side of prox sensor==> -24vdc. and the NC limits are just connected on side to +24vdc and the other side to the inputs on the mesa 7i96s. im just looking for a sanity check before i plug this all in and it seems like im missing something. any help or reading materials would be of great help and greatly appreciated.

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03 Apr 2024 04:59 - 03 Apr 2024 05:01 #297486 by PCW
For PNP  sensors, the 7I96S input common connects
to the 24V supplies negative terminal. They therefore pull
the inputs toward the negative when undriven. No
additional resistors are needed.

For switches the, one side connects to +24V and the other
to a 7I96S input.
Last edit: 03 Apr 2024 05:01 by PCW.
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03 Apr 2024 14:14 #297507 by jg00163206
for the outputs on the 7i96s, A and B. does it matter what one is + and -? i realize it can be configured in HAL at a later time, but for the initial wiring, does it matter? thank you BTW. you are a godsend and this site would not be possible without your (and everyones) contributions.

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03 Apr 2024 16:28 #297513 by PCW
The A/B on 7I96S outputs 4 and 5 are interchangeable (non-polarized)
Outputs 0..3 _are_ polarized so you must wire them appropriately

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05 Apr 2024 00:36 #297613 by jg00163206
thank you very much. i connected the limit switches to the mesa 7i96s the way you recommended and i now have the lights on the iputs lite up and they are working correctly. for the outputs, 0..3, i don't want to assume anything so i'll have to ask, A+, and B-?

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05 Apr 2024 01:08 #297617 by PCW
The low current (100 mA)  7I96S outputs are non-polarized
so work either way (that is, you can swap A/B without
any problem)
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05 Apr 2024 16:15 #297652 by jg00163206
if i understand you correctly, and i use the term understand loosley, the non-polarized #4 &5, does not matter polarity, and can go +/- -/+ and you can switch between the two. for the low current outputs, once i designate one output as positive or negetive they all have to all be that way or can the polarities be mixed and matched as with the "high current" relay outputs? i wish the manual went into a little more detail on the inputs and outputs. its kind of vague in some areas.

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05 Apr 2024 16:51 #297653 by PCW
Not sure what you mean by "mixed and matched"

Outputs 4 and 5 are non-polarized (A and B are interchangeable)

Outputs 0..3 are polarized (you need to pay attention to the + and -
and wire external circuits accordingly)

 

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07 Apr 2024 01:59 #297735 by jg00163206
is there a way i can get these limit switches to be off normally? as it is right now, they are lite up like a christmas tree and when i trigger them, they turn off. how can i get them so they are off and they turn on when they are triggered?

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07 Apr 2024 03:41 - 07 Apr 2024 13:30 #297739 by PCW
Its actually better to run them in that (Normally Closed) mode
so a broken wire causes a fault rather than being undetected.
Last edit: 07 Apr 2024 13:30 by PCW.

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