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Using a NI 9476 to drive a relay

Hi all,

 

I have a quick question regarding the use of a NI 9476 to drive a relay, which is a sourcing DO module that can take anywhere from 6V to 36V and source 250 mA/ch.

 

The NI 9476 will be powered with an external 20V power supply (Unfortunately, this is the only one I have) and I will be driving two relays using one output from the NI9476. The relay I'm using is: G2RL-1A-E DC12, which has a 12V coil voltage and a 33.3mA coil current resulting from a 360Ohm coil resistance.

 

Since 20V output of the NI9476 is much greater than the 12V coil voltage, the relay will draw too much current and kill itself. I was wondering whether I could get around this issue by just adding a 250Ohm resistor in front of the relay and stepping the output down to 12V. (250Ohm resistor + 360Ohm relay coil resistance).

 

Also, I read that the NI9477 (a sinking DO module) requires the use of a flyback diode when driving relays. Does the 9476 have to have similar provisions?

Thank you!

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lets make this simple...just use a LM7812 with a ULN2003( which has 'flyback diode' protection built in)...

 

Spoiler
12v relay uln.png

 

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Thank you for the answer! Interesting....

 

In this application, wouldn't I need a sinking DO? (Meaning that I would need the NI9477 isntead of the NI9476).

 

Also, what are the benefits of this application instead of my resistor? (Out of curiosity)

 

Thanks!

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@Pegasixi wrote:

Thank you for the answer! Interesting....

 

In this application, wouldn't I need a sinking DO? (Meaning that I would need the NI9477 isntead of the NI9476).

 

Also, what are the benefits of this application instead of my resistor? (Out of curiosity)

 

Thanks!


yes, tie the gnds together with your Daq

 

benefits are your current load does not effect the regulated voltage, on the other hand..it would effect your resistor drop

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According to the Getting Started Guide, you need a Flyback Diode.   https://www.ni.com/pdf/manuals/373964h.pdf

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