U3 put gnd on a pin | LabJack
 

U3 put gnd on a pin

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lucian_v
lucian_v's picture
U3 put gnd on a pin

Hi all,

I have a simple circuit with a led and a rezistor. What i managed was to put the circuit on ground and put labjack pin to 5v and the led is ligh

What i want is actually to put circuit on 5v and labjack pin to ground to light the led. 

Any ideea of how can achieve that?

LabJack Support
labjack support's picture
I am not exactly following. 

I am not exactly following.  See if the following LED app note helps:

https://labjack.com/support/app-notes/driving-leds

lucian_v
lucian_v's picture
What you suggested me is

What you suggested me is exactly how i do it now, but i don t want like this.

I draw a little schematic to be more clear. In the draw we have a led, a +5v (same as labjack is powered - from usb), a GND (from labjack).

In my draw if i put pin 1 to GND led will light. This is what i want to achieve. To have nothing on pin 1 and led is off or to have GND on pin1 and led will be on.

lucian_v
lucian_v's picture
I actually ground it that pin

I actually ground it that pin

LabJack Support
labjack support's picture
Are you saying you want to

I do not see an attachment or link to a drawing.

Are you saying you want to connect:

VS to LED-Anode
LED-Cathode to Resistor+
Resistor- to FIO0

That is what is described in #2 in the Driving LEDs app note:

https://labjack.com/support/app-notes/driving-leds

The digital I/O on the U3 have 3 states:

Input (high impedance input, weak 100k pull-up to 3.3V)
Output-High (connected to 3.3V)
Output-Low (connected to GND)

So if you want to change FIO0 between high-impedance and ground, which is also called open-collector operation, you change FIO0 between input and output-low.

The following might also be useful:

http://forums.labjack.com/index.php?showtopic=596

http://forums.labjack.com/index.php?showtopic=6334

lucian_v
lucian_v's picture
Thank you very much

Thank you very much