I/O Port and Voltage Levels

davieo · January 2005

Greetings,

I am working on a project that will be receiving feedback (and possibly controlling) some power windows. I want to use an I/O to track the feedback from the window controller, but it outputs 24VDC at high. From what I have read on the NI series, they see high at 3.5-5VDC. Does anyone have a suggesstion about how I can handle this short of having my electronics tech build something to bleed off to 4-5VDC when seening 24VDC?

Thanks,
Dave Ohlendorf
ACE Programmer

Spire_Jeff · January 2005

I could be wrong, but I believe that a dry contact closure is recommended, even tho the unit can handle up to 5v. If it does work with dry contact closure, this could be easily accomplished with a relay switch from Radio Shack that is activated by 24VDC.

Hope this helps,

Jeff

DHawthorne · February 2005

The I/O ports can work on a "wet" closure, as stated, at 3-5 VDC, or, a dry closure between the input and ground. In your case, I would use a relay as suggested rather than trying to drop the output voltage with a resistor; I prefer to isolate my devices - you never know when you might introduce a strange voltage differential and what it might do to things. Then you can just flip the n/o contacters between ground and the port, and you are done.

Thomas Hayes · February 2005

I'm with Jeff and Dave on this one. Isolate the 24VDC, its better to fry a relay than the controller. I use a similiar design which interfaces with a card swipe system and will only allow access to the TP if you are cleared by the security computer.

Chip Moody · February 2005

Originally posted by Thomas Hayes
I use a similiar design which interfaces with a card swipe system and will only allow access to the TP if you are cleared by the security computer.

Jeeze... I've got to find some cool clients like yours. Haven't had the pleasure of working with anything nearly as slick as that!

- Chip

I/O Port and Voltage Levels

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