DAQ as a Relay

[ASU]

Can I use a DAQ card to act as a relay?

Basically, i have 14 lines that can be controlled by either a logic 5V or ground. Can a DAQ with digital I/Os do the same thing and if so what basic card could do the trick

thanks

newbie darryl

[Wayne.C]

Darryl,

Digital I/O are a great way to drive 0 and 5 volts.  What you need to keep in mind is that each DAQ I/O has limits as to how much current it can sink or source.  There will also be an overall limit for the card.  Another thing to consider is what kind of load are you driving?  If it is inductive, you will need to add snubbers across the inductive loads. 

Another one that gets overlooked a lot is the idle/unconfigured state of the digital I/O's.  You need to consider how your external device is going to react to not having any input ( open ) or say a tri-stated w/weak pullup DAQ output.  These kinds of situations happen when say a cable is not connected between the DAQ card and the external device or if the cable is connected to the card, but your LV vi is not running.

[ASU]

Thanks for your response and help.

Basically I have a motor driver ( p/n 40105 [www.hsi-inc.com] for reference) that can be controlled externally with logic highs and lows. So i'm assuming thesnubber circuit is n/a here. Also I believe without a signal it defualts to a high.

[Wayne.C]

ASU,

It sounds like any DAQ device with enough digital I/O should work.  Would probably want a device with a couple of counters to use for clock generation.  Suggest you look at some of the pulse generation examples that ship with NI.

Next step is to consider the rest of your application.  Any need for analog I/O?  If so, what voltage levels.