Physically Testing Digital Outs with LEDs

[LabViewNubie]

I have a PCI-DIO-96 and am currently trying to learn Labview. I am wanting to physically connect a few (not 96) LEDs so I can play with the

digital outs. What is the best way to do this? I do not have a strong electrical background and do not want to fry my computer. Thanks

LabVIEW gurus!

                                                                                                                                                                                        -- Matt

[Sandra_T]

Hello Matt,

Thank  you for posting to this forum. It looks like you are trying to test your digital outs channels.

A good way to do this is to go into Measurement and Automation Explorer. Under Device and Interfaces, find your device. You can then click on the Test Panel to use the utility to read and write to your ports.

For information on the connector and connections, take a look at the user manual of the PCI-DIO-96

PCI-DIO-96/PXI-6508/PCI-6503 User Manual
https://www.ni.com/docs/en-US/bundle/pci-dio-96-pxi-6508-pci-6503-feature/resource/374938b.pdf
Chapter 3 is on Signal Connection and there is a figure of the Pin Assignments for this hardware.

In your post you mentioned connecting LEDs to your digital outs. Checking Appendix A of the User Manual, you will be able to get the Input and Output specs.
This card can source a maximum of 2.5mA. If you try to draw anything more then that amount of current (<2 kΩ load at 5 V output) you can seriously damage your card. This card is used as a logic device and if you try to current drive LEDs which have low impedance and may require high currents this may be an issue. Check the specs for your LEDs.

Please take a look at the documentation that I have included. This should get your started with your application. Let us know if you have any additional questions or comments.

Have a good one!

Regards,
  Sandra T.
Applications Engineer | National Instruments

[Buechsenschuetz]

Low-current LEDs usually need a current of 3mA. You can also run them with current limited to 2.5mA as it is available from your board, the LED just will be not quite as bright as when running on 3mA but the difference will be hardly noticeable.

You connect the anode of the LED (long wire) to the output you want to check and the cathode (short wire) to the GND terminal of the board. The LED should light up as soon as the output is in the physical high state.

[Buechsenschuetz]

I just checked the specs of this board and found that it will source 4mA with an output voltage of 3 to 5V in high state. Red LEDs typically need something around 2 to 2.3V at 3mA to light up. I would recommend a resistor (to limit the output current) in series with the LEDs (no matter into which connection you insert the resistor, I would recommend the anode connection). The LEDs will not be as bright as they are supposed to be but you should be able to see a clear indication.

[LabViewNubie]

Thousands of thank you's Sandra T. and Buechsenschuetz!

I'll rig up something this weekend! I'm learning G pretty rapidly, but I still want to actually SEE some physical output from the code. I don't know why, just the way my mind is programmed I guess.

 -- Matt

[Buechsenschuetz]

Ooops... I just found that I forgot to indicate the value of the resistor recommended. I would suggest a 1kOhm resistor. Due to possible variations of high output voltage the LED will light up more or less bright but in any case you should be able to see the state of the outputs.