Relay control

[hughes265]

Hi All,

Was looking for some advice on driving a relay using Digital output from the NI USB 6002.

As I understand from the manual/spec this is an open collector output. Am I correct in thinking each output can only sink 4mA?

My understanding of the open collector output is that I can use an external voltage source ie. 12V connected through an external pull up resistor and sink to ground through the output. However I have to respect the sink current of the open collector output, but this seems low at 4mA.

[crossrulz]

You have to respect the transistor that is being used to drive that signal low.  In this case, it is a really small transistor that is rated for 5V and 4mA.

You might want to look at using a USB-6525, which is designed to handle the industrial signal levels.

[hughes265]

Hi,

I'm specifically trying to avoid that solution in this application, thanks for the recommendation though.

If I were to add a relay driver such as the ULN2003 or an opto-isloator maybe I could operate relays this way.

Have you any advice or thoughts on this method?

[crossrulz · Accepted solution]

I have not gone those routes before.  But looking at the data sheet for the ULN2003, it should work just fine for you.

[hughes265]

Thanks for your help.

I have also found a lot now on the forums if searching for NI usb and ULN6003. 

This is indeed the way forward and the solution I require. 

[LUCA_CARRARO]

Hi,

I solved with this TOSHIBA Photocoupler 6N139.

Greetings Luca.