Relay board?

[JÞB]

Kit no- But Axicom has some nice hi-rel relays and any ULN2008 driver makes the front end (throw side) effective. 

[AnalogKid2DigitalMan]

How about using solid state relays (SSR)?. Most can be driven directly from a digital output. Also provides optical isolation between the DAQ and the load. No need for protection diodes since there is no coil. No contacts to wear out either. About as easy as a roll your own application can get. I have used them for years with no problems.

AC types can also be specified with zero-crossing turn ons- they turn the load on when the AC sine wave is at zero volts, providing an electrically cleaner switching of the load.

-AK2DM

[chuggins143]

Sounds interesting.... got a good source for SSR?

C

[AnalogKid2DigitalMan]

Major SSR (and coil/contact relays) companies that come to mind are: Omron, Crydom, Magnetcraft, Opto22, and Teledyne.

I generally order from Allied Electronics, Newark, and DigiKey, there are gobs of suppliers available.

-AK2DM

[chuggins143]

The info is much appreciated!

C

[JÞB]

Going back through the thread.  The SSR idea seams apt for this application. They offer better life expectancy but lower isolation (R off @ 10M).  for switching motor loads this is fine- for mutliplexing signals for metering stick with the EM relays to avoid the undesired loading.