NI ELVIS---DAQ--Digital Out

[SK0480]

Hello

Iam using an NI Elvis board... it has a built in DAQ board.....Iam trying to test the digital output port....Iam actually writiing a boolean array to the digital output port...I want to test the signal at the DIO using LEDS...How will I need to connect the LEDS to the DIO port.....

Thanks

[Matt.M]

Hello,

First, I'm not sure what kind of LED you are using, but according to the specifications the P0 lines can only source 16mA and the PFI lines can only source 24mA.  I have attached the table where I found this information.  You can find all other specifications of the ELVIS II here.

Most LEDs require more current than this board can source, so you would need to use an LED driver of some sort.

Regards,

Matt M.

[SK0480]

OK well what Iam doing is using the digital write from the labview to write 1D boolean array to the digital port of my ELVIS II board....

Now Iam just trying to verify whether Iam getting the signals at that port or not,,,so I bought some red LEDs which are like standard LEDs and I connected it to the digital I/O but I dont see anythign.....

so can I using something like darlington transistor to drive the LEDS.....

I also see that there are some built in LEDS in the NI ELVIS board, is there anyway I can use those to check the signals comming from the digital port,, if so what would be the procedure...I even went to the measurement and automation explorer and used the test panels to turn on and off the bits in the port....but I just do not know how to verify if the signal is infact comming into the lines in the port.

Thanks

SK

[Matt.M]

No, you wouldn't use a darlington pair.  You would use a circuit like the one I have attached below.  Except instead of a switch connecting 5V to the gate of the transistor, you would connect your digital channel output to the gate.  You choose the value of R based on how much current you want to flow through the LED.  The data sheet for your LEDs should say what the max current is.  

In the data sheet it should also state what the voltage drop across the LED is.

Use the equation: R = (Vdd - Vdrop)/I

Regards,

Matt M.