How to Monitor Motherboard LED Output Signals

[Big Ben]

Hi, I hope somebody can answer this question for me.

I am looking for ways to monitor 64 PC motherboards' LED signals (electrically), 4 LED signals per motherboard total 256 channels needed i guess.

What do i use? Digital I/O or a DAQ?

I need to be able to group the signals into groups of 4 to ID the M/B and from the state of these signals interface with my program to trigger some other response.

Sorry but i am really noob in this.

[lhaoxian]

Hi Ben,

For high channel count DIO applications, such as your application, I believe NI DIO 650x cards should be more suitable, such as the NI-6509, which can have up to 96 5V TTL/CMOS channels. 

In terms of software, there should not be any issue. You can monitor all the channels from your program (such as within LabVIEW) and then use the result to trigger other parts of your program. There are example programs that comes installed with the NI-DAQmx driver that you can refer to.

Best regards,

Victor

NI ASEAN 

[memoryleak]

Ben -

      Victor's solution is better than what I was going to propse so I wont bother 😉  I do, however, recommend you take a voltmeter to your LEDs with respect to GND and figure out what voltage is driving them.  It looks like the 6509 reads high at 2V and low at 0.8V.  Depending on how the LED circuit was designed, this may (likely) or may not be enough.

LED circuit image stolen from robotroom.com:

In your case, your computer is supplying the power to the LED, and it could be from the 3.3, 5 or 12 volt rail.  The resistor may be before or after the LED.  Additionally, they could be doing something more exotic that doesn't involve a resistor (like a current controlled LED driver) but that's less likely than a simple resistor-LED combination.

The voltage drop across the LED depends on the color, but is generally around 0.9 - 1.4V.  This *could* be a problem, but it's entirely likely that the source of the LED voltage is just a 5V signal and you might get to measure the voltage before the resistor.

So the answer is... "it depends" 😉   Grab a cheapie multimeter and probe around... and tell us what you find!  It's very likely that a few PCI-6509s sitting in a computer (or alternatively, some USB-6509s) will do the trick.  Even if the voltage isn't within the range of the 6509 there are many many solutions to your app, but none of them cheaper 😉 

Hugs,

memoryleak 

[Wayne.C]

Big Ben,

It sounds like you are testing just mother boards and that the LED's won't be connected and you want to monitor/measure the voltage pressent at the connectors for the LED's.  Is that correct?  This is important because it will affect the voltage level you will be measuring with the DAQ device.  The other question is about the circuit driving the LED's.  Sinking or sourcing?