NI6723 +5 V output is supplying much less current than 1 A!! (not even 30 mA)

[marles]

Hi there! I am using a NI-PCI-6723 board and I want to use the +5 V output that it is supplying on two of his pins (pin 8 and 14 from one connector). In his manual, it says that these pins can output around 1 A maximum. But when I connect some rezistors, it can draw only few tens of mili amps, far less than 1 A!! (I only need 30-35 mA, but both outputs can't supply me with this current!). This isn't normal! What may be the problem??

[Henrik_Volkers]

Maybe the Card needs an internal additional connetion to the power supply??

Or this current is only rated for the PXI version??

The installation manual might tell more.

[Henrik_Volkers]

The manual stated:

The +5 V pins on the I/O connector supply +5 V power. You can use these
pins, referenced to D GND   !!   

Did you used DGND or AGND for the current return path?

The blockdiagram of the hardware didn't show the +5V Power for the 672X....   

http://sine.ni.com/ds/app/doc/p/id/ds-157/lang/en 

[marles]

Hi there! Yes, I know the 5 V output is referenced to D GND. But it seems that it isn't reaching the stated voltage for the stated current. It supplyes 4.75 V and when I connect the load that draws around 30 mA, the voltage goes down to around 3.88 V! This isn't normal.. The manual says that this output can supply maximum 1 A! Well, 1 A is a lot larger that 30 mA... I just don't know what seems to be the problem! :( Greetings from Romania, Paul

[Jonathan_S1]

Hi,

Each digital output on the 6723 is capable of supplying 24 mA.  If you need to supply more, you can do one of two things:

1.  Use the digital output to trigger a relay that is hooked up to a power supply that can provide enough current.  This is the recommended approach.

2.  Wire the outputs together in parallel, and make sure they are always used concurrently as outputs.  It would be wise to place a diode at the output of each terminal to prevent any transient currents from entering the card.

Jon S

[Henrik_Volkers]

Jonathan,

he wants to get some more mA out of the +5V terminal ...

[marles]

I found the "solution"... The fuse from the +5 V wasn't working properly (probably from a previous shortcircuit or so... )... The + 5 V should provide the specified current if the fuse (F3) is doing it's job. Thank you for you interest in helping me! Greetings from Romania, Paul

[Jonathan_S1]

Thanks for updating us, I'm glad you were able to get to the bottom of it.  Henrik, thanks for catching my error;  I misread the additional post.  At least you know the current limitations of the digital pins now as well

Jon S