5mA from PXI-6723 too low to drive relay

[Daddy-O]

I know this has been posted before for other DAQ boards, but I haven't seen a definitive solution in my travels around the Forums.  I am trying to short a 12V line (part of my unit under test) to ground. I am trying to accomplish this using my analog out lines, by switching a relay. Being that the relay seems to switch at about 12mA, and my PXI-6723 only generates about 4.9mA, well...

I cannot spend more money and buy a switch card (even though that would be simplest). Does anyone know of a relay that can run on less that 10VDC and say.... 4mA??  All I have been able to find with coil current that low, requires 24 or 48VDC. (Many hours of research). I am hoping someone else ran into the same problem and has a part number handy!

I am also trying to avoid building a transistor circuit to increase the current, because I have 40 of these lines, independent of each other with which to contend.

OR... is there a programmatic way for me to "short" these two lines together, that doesn't require an NI Switch card?

Chris

[Ed W]

Hi,

Thank you for posting to the NI forums.  While the analog outputs may not be sufficient for driving your relay, the digital outputs can provide up to 24mA per channel.  Post back if you have further questions.

Best regards,

Ed W.

Applications Engineer

National Instruments

[Daddy-O]

Thanks Ed, I will have to try that route sometime. I ended up just borrowing a switch card from my other station for this application. It will be very helpful in the future to know the limitations of the digital outs as well!!

[wana be prog]

If you are having trouble driving relays with either the digital or analog, use a transistor, like a 2n4401.  This should give you enough boost to drive the relays.

Cheers

[JÞB]

Daddy-O

I hate to break it to you this way but, you have got to burn enough power to generate a field that can move that relay contact against the mechanical resistance.  Simple Newtonian physics.  You need a driver.  The ULN2003 is a fairly low-cost solution.

Take care- don't break any more laws of physics.

Jeff

[Dennis_Knutson]

wana be prog and Jeff,

Did either of you notice that the thread you are responding to is close to two years old?