LED Pin on 6001 not lighting up

[Sid05]

I have a USB 6001 that I connect to a USB port on my Windows laptop. Please see pin configuration below. Pin 18 on USB 6001 OEM points to the LED. But when I connect an actual LED to that pin relative to a ground [Pin 19] - the LED does not light up. What could be causing this?

The same LED does light up when I connect it to +5V [Pin 34] and Ground [Pin 32] - thus proving that the LED is fine and the DAQ is connected to the laptop. FYI - my intent is to have the LED mounted on a panel on my enclosure to serve as an indication of successful DAQ connection. Appreciate any help/guidance. Thank you. 

[Henrik_Volkers]

Don't know where your pinout is comming from, the USB 6001 spec tell me another pinout....

however: The mentioned LED output could be configured as an open collector output, so you should try to connect the LED (in series with a current limiting resistor , say 470 Ohm!)  between +5V and <LED>pin .  (with Anode to to +5V 😉 )

[AnalogKid2DigitalMan]

Henrik is spot on, see Fig 6 of the attached.

Henrik- this is the OEM version of the 6xxx series.

-AK2DM

[Sid05]

Henrik and AK2DM - The LED does light up when I connect the +5V PIN [#34] relative to LED Status PIN, even w/o a pull up resistor. 

But my understanding was that the LED Status pin with reference to a GND PIN [like # 19] can light up a external LED. In fact, that is how I was using the USB 6009 DAQ and it worked just fine, i.e. the external LED would start blinking just like the 6009 DAQ built-in LED blinks when connected to a PC. I wanted to do the same with the 6001, since the 6009 is no longer a supported DAQ and is also very expensive now! 

The +5V from the DAQ was being used to power a relay board so I don't want to deploy that just for an LED. 

The 6001 has a small built-in LED that lights up (w/o blinking) when connected to the PC.So, what else could be going on with the 6001 LED status pin that makes it different from the 6009? 

Thanks. Sid

[BertMcMahan]

It's not a 0 or 5V signal, it's an open collector signal. Read AK2DM's linked PDF and it shows you how to wire an LED into it.

Basically, that port can either block current from flowing, or pull a signal to ground. It cannot output any power. You need to connect one leg of the LED to 5V, and the other leg to the signal output- BUT you need a current limiting resistor inline, otherwise you'll burn out the LED (and maybe the card). Your LED may have one built in, but you should check that before you blow stuff up.

Are you CERTAIN your 6009 had an LED connected between the LED pin and Ground, and not LED and 5V? Or maybe you used a different digital IO rather than the LED pin? The 6009 lists the LED pin as an open collector as well, so it has to be getting its power from somewhere other than itself.

[Sid05]

Have been using the 6009 with an external LED connected to LED Status pin and D GND for over a year w/o problem!

I have both OEM DAQ cards with me. See pic from today showing the blinking LED with 6009 connected on those 2 PINS. But I get no response from the 6001 on those same 2 pins [and the same LED and laptop]. So, the process of elimination just points to something different with the 6001! 

[santo_13]

May be it is different between 6009 and 6001, as long as it matches the datasheet/user manual description, all is good.

[AnalogKid2DigitalMan]

Indeed, the USB-6009 OEM status LED output is different- it is referenced to ground.

https://download.ni.com/support/manuals/371728b.pdf

-AK2DM

[BertMcMahan]

---

@AnalogKid2DigitalMan wrote:

Indeed, the USB-6009 OEM status LED output is different- it is referenced to ground.

https://download.ni.com/support/manuals/371728b.pdf

-AK2DM

---

Maybe I'm reading the datasheet wrong, here's the section I'm looking at (for 6001)

And for the 6009:

Both say "An open collector drives the LED signal" and gives a very similar electrical specs table. I'm no EE, so I fully admit I could be wrong, but that's how the sheets read to me. The only difference I could find is that the 6009 says it's pulled up when the system isn't configured, which confuses me since it also says to add a 4.7 kOhm pullup for applications that use the signal.

[Sid05]

@BertMcMahan - You may be right. I see that both the 6009 and 6001 userguide say that they are referenced to the ground. 

I am no EE either, but I clearly was using the status LED driver in the 6009 in an off-label way, but it served me well! I did check that the pre-wired 3-6V LEDs I used did have a built in resistor! 

See below - the guide advises to connect the LED to a +5V via a pull-up resistor, but what I was doing was simply powering up the LED from that pin with reference to the ground! So, when the LED was functionining fine [i.e. DAQ was enumerated, configured and not suspended] the LED would keep blinking [@2Hz], and when it was otherwise, I would simply get a steady LED light [when suspended but DAQ connected to the PC]. And of course when disconnected from the PC, the LED would turn off too. 

I thought I could get to use the 6001 in a similar way - but clearly I could not. But why?? I still do not know. Need someone to advise on that. 

So, if I need to track the DAQ status via the LED, I need to use the +5V and the LED status? Is there no other way to check the DAQ status? If there is none, I would have to forgo that functionality and use that 5VDC from the DAQ to power the relay board! 

Thanks for your input.