NI 9476 | load current

[-Heathcliff-]

Hello everybody

I have a question about digital output module NI 9476. This has 32 digital outputs. I have read the "Getting Started Guide", but it does not answer all the questions about the output current. I realize that a single output can deliver 250mA and you could use several in parallel for the same consumer. Also that all 4 Vsup inputs are connected to each other I have read in a forum thread.

Now to my questions:
- Do the outputs limit the currents to 250mA with a protective circuit? (or do I have to secure each output individually)
- What current must I use to secure the supply line (Vsup)?

Thank you very much in advance

[Tomasz_Kowalczyk]

Hello,

@-Heathcliff- Are the questions mentioned still bothering you? Have you already managed to find a solution?

Regards,

[-Heathcliff- · Accepted solution]

Hello Tomasz

Thanks for asking. Yes the problem is solved. The power consumption of each DO is limited to 250mA. In addition, according to NI Support, it is possible to connect Vsup directly to a general existing control current fuse of 10A in my application. (of course considering other wiring aspects)
I have decided to install a 2A-fuse to which Vsup will be connected. All my cDAQ signals go to the DUTs via interface relays or isolation amplifiers. (Protection of the cDAQ, as also defective devices must be checked for diagnostic purposes)

I did not know that under manuals there are 2 different documents
- http://www.ni.com/pdf/manuals/373964c_02.pdf (as data sheet, wrongly referred to by me as the Getting Started Guide)
- http://www.ni.com/pdf/manuals/373964h (as a Getting Started Guide)
Now I know it 😉

The Getting Started Guide describes the following:

Page 16/17: "I/O Protection"
The NI 9476 is protected against overcurrent, inrush, and shortcircuit conditions in accordance with IEC 61131-2. Each channel on the NI 9476 has circuitry that protects it from voltage and current surges resulting from short circuits. Caution The NI 9476 can be damaged under overvoltage and reverse bias voltage conditions. Checking the voltage specifications for all devices that connect to the NI 9476. Excessive current through a DO pin causes the channel to go into an overcurrent state. In an overcurrent state, the channel cycles off and on until the short circuit is removed or the current returns to acceptably low level. Each channel has a status line that indicates in software the channel is in an overcurrent state.

Thank you and best regards