Using a PCI-6229 to switch 12 relays

[m610]

In my next project I'll be using the PCI-6229 for analog I and O plus digital I and O plus controlling 12 relays.  My question is about the current capacity of the PCI-6229 when driving these relays.

The input of each relay is a diode bridge so polarity and using a protection diode should not be an issue.  But, it takes 23 mA (nominal) to turn on each relay.  The specs on the PCI-6229 DIO channel are 24 mA max (very close!) and 448 mA total.

1. I'm really close the the max current.  Will that cause problems, shorten the life of the board, generate too much heat?

2. What exactly is a channel, in the present context.  It that the same as an I/O line?

3. My total current for the relays is in the 276 mA range, and while I'll need more for the other DIO lines, I'm well below the limit for the total current.  But, are there any issues with driving this much current that I should be aware of.  I know it is not much, but I prefer to drive TTL-type currents from a multifunction board like this. I prefer these boards just handle signals, not do the work.

Thanks.

[Wayne.C]

m610,

Consider using a driver such as ULN2003A to drive relays.  While I'm sure that NI has done extensive life testing of their hardware at elevated temp and rated loads, it doesn't hurt to use a little caution.

[m610]

Very helpful.  Thanks.  I'm probably going to have to build an interface board from DIO anyway andthese will do nicely.

That data sheet didn't say anything about total power dissipation for the package.