Multifunction DAQ

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I have a PCI-6503 and need to drive a motor that runs at 125V, 0.9A. I was thinking to use a ULN2003 Darlington array and a Omron G5NB-1A DC5 relay to handle this. The realy has a coil voltage of 5 VDC and current 40 mA. Will this work? I just want to make sure I do not damage the board with this configuration.




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A coil voltage of 5V is exactly what you want.  The 6503 outputs a digital signal from 0-5V and the coil voltage is simply saying that the relay doesn't want to be controlled by anything larger than 5V.  So the relay control portion of this project should work just fine.  I am not familiar with the Darlington so cannot speak for it.

Jason Daming
Applications Engineer
National Instruments
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You are right on the money!   The ULN2003 works for me every time I use it.  Just remember to add in the 5V supply that will source the darlington output current.  I don't recommend using the 5V off the 6503 for this as it can introduce noise.  Moreover, and most importantly, whatever supply you use may be damaged in the case that the ULN2003 is overloaded or miswired.  You don't want this to happen to your calibrated device! 


Good Luck!

"Should be" isn't "Is" -Jay
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Thank you guys for the replies. I was really thinking to take the +5V from the pin 49 of 6503. It is fused and has a max current of 1A so I thought it would work fine with the G5NB coil which pulls max 40mA. If I could do this it would be great because the whole thing will be very compact and I won't need an external powder supply.


Jeff, if the +5V coming from 6503 is fused, why shouldn't this work? My application is extremely simple, I have only 2 DI and 1 DO (this motor that I need to control).


Thanks again,


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Yes- it's fused.  So when it blows (not if- it's better to design for likely failure modes) you have to open the PC and replace the fuse.  Then you've violated the calibration of the DAQ so you need to send it out for cal and a functional test.  Your looking a a couple days down time + recalibration costs.  A good external PS with overload protection runs a lot cheaper.  e.g Lambda DPP25-5 @$48.00.  


The system should run off the DAQ 5V.  If you are willing to accept the risks and increased repair costs.


Good Luck

"Should be" isn't "Is" -Jay
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