Sourcing Input NI 9401

[Olli_]

Hi!

I want to connect an NI9401 configured as Input to a SPS so that the SPS can give informations to the Input. The SPS is just a relay, so that the Input must be "Sourcing" to provide a 5V level. (so, if the relay is open the Input shows "true", and when the relay closes it connects the Input to the "Com" so that the input shows "false")

Is this possible? On the NI Homepage Product Information is the NI 9401 declared as "5 V/TTL, sinking/sourcing digital I/O", but I have no idea how I can configure it as sourcing Input (in LabView)? I use the NI9401 in a cRIO.

If it is not possible, has anybody another idea how to solve my problem?

Also: Where can I get a more detailed technical information than just the small "Operating Instructions and Specifications" on the NI-Page, which is not very detailed...

Thanks!

[ludhaber]

I have the EXACT same question. I would like to take advantage of the on-board pull-up in a digital input operation so I can determine the state of a switch without external power. If this can be set up, it would be tremendous time and energy saver in my application. I have a call in to NI support on this as well. If I hear back, I will post again.

Cheers;

Ludwig

[K C]

Hi,

This module does not have a pull-up resistor but a pull-down. See page 7.

If you want to connect a relay contact to an input use the 'Dev 2' situation on page 9. Use a 1k resistor..

You can also connect the relay contact in series with the resistor to the input to 'invert' the situation.

[mknix]

Hi,

I'am digging-out this old thread instead of opening a new one, hoping KC is still there, or someone else can help me...

I'am not clear with the explanation above.

On page 9, dev 2 circuit, as mentionned by KC, I don't know what the 5V suply is.

Is it an external power source? Or can we use another IO from the module, set as output to provide these 5 volts?

update link to the manual : NI 9401 manual

In my case, the contact is comming from the output of an PC817 photocoupler, so only open / close contact, no power suply available...

Hope it's clear, thanks in advance

antoine

[K C]

Hi Antoine,

I am always still here.

The 5V supply mentioned in the diagram at page 12 is an external one.

In your case connecting the output from an optocoupler to this digital input you need an external power source.

Or use another device with sourcing inputs.

Or your suggestion use a output from this module to power the opto output.

Kees

[mknix]

OK very clear, Thanks a lot !

[PghFool]

So why in the world is the 9401 listed as being a sourcing input?  Isn't a sourcing input one that has a pull-up resistor in it?  NI makes a big deal about distinguishing sourcing and sinking inputs and outputs in their cDAQ course (which is good) but then their hardware specifications don't say (see the spec sheet for the 9401), or appear to be misleading (see https://www.ni.com/en-us/shop/select/c-series-digital-module, which says is can be a sourcing input).