Smart Camera Input reads low

[jblc]

  I have a 1722 Smart Camera.  I can't get the inputs to read a "high" value.  Other than this, my application works well.

  I'm using the NI cable and screw-terminal block.  If I jumper any of input 0 or 1 (pin 2 or 😎 to +24V (pin5), still the inputs always read low, so I can never get past the step that waits for a "high" input before proceeding.  I used the data monitor as well while applying the voltages, but they always read "0".

  Note: the outputs also don't work; they always are at 24V even when set low (they have pullups to +24).

  The LEDs though work fine when I turn them on and off.

  What am I missing conceptually to have inputs read?

[Chris_1890]

I've got several questions for you to try and narrow down the issue.  First, are you using the NI Vision I/O Terminal Block for 177x Smart Cameras?  Second, what kind of power supply are you using?  Is it a custom power cable?  If so, what are the connections?  Third, what utility are you using to read the I/O lines?  Are you doing this in MAX, LabVIEW or VBAI?  Finally, what do the LED indicators display when you power on the camera?  

[jblc]

1)  Yes, it's the NI Vision I/O Terminal Block.  The power supply is a high quality 24V, 5A MeanWell regulated supply going into the terminal block.

2)  The system itself works well (inspections are passed/failed correctly), so I don't think it's the power supply connection.  However, the power supply is connected to the +24V and ground terminals on the block (pin 5 and 15, I believe from memory)

3)  I tried reading a few different ways.  (a) the Test Panel, which comes up when I double click the I/O logic block in Vision Builder AI (2011). I both shows the state, and also can chart the real-time values in a plot if the values are double-clicked.  (b) the VBAI application itself, where an exit condition from the very first state is waiting for a pin to go high.  This state never leaves, unless I set the exit condition to Low (which is what the system always reads).  I connect the two isolated input pins 0 and 1 (terminal 8 and 11 on the screw terminal block, again from memory) to +24V (terminal 5), so both inputs should be able to read High.

4) The LED indicators cycle through their startup sequence, then the Power is lit as it should, and the status LED is on as well.  The Fail and Pass LEDs work as they should, as mentioned (they were programmed to show a pass/fail condition, and then reset at the start of the next inspection loop).

  The outputs also don't seem to work despite pullups to +24.  They always seem to be low even when commanded high. I think, though, that at one point they might have briefly worked, so I suspect I'm doing something fundamentally wrong...

[jblc]

Anyone have ideas?

[BruceAmmons]

Here's my two guesses:

1. You are wiring up the signal wrong.  Check the manual and look again to see how signals need to be wired to the IO connector.

2. The part of the camera that does the IO is defective.  That would need to be repaired by NI.

These are just guesses.  I haven't used the IO on a smart camera personally, so I don't know the answer.  It sounds like everything else is working fine, so it is just the IO.

Bruce

[jblc]

Thanks Bruce for the suggestion.  I'm relatively sure it's wired up correctly; the pinout in the manual is pretty clear.  I'd also have to be in error on all 4 I/O (2 input, 2 output), which is unlikely.  This camera is brand new, so I'm guessing the I/O module is still good, especially since everything else works great (including the pass/fail LEDs which are also IO).  Thanks for the suggestions!

[jblc]

Anyone have ideas?  I'm still unable to read the inputs.

[Chris_1890]

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@jblc wrote:

1)  Yes, it's the NI Vision I/O Terminal Block.  The power supply is a high quality 24V, 5A MeanWell regulated supply going into the terminal block. 

---

I'm really hoping that this is a typo, but you said you're using a 5A power supply.  If that is the case, that is vastly exceeding the power limits of the 1722.  The maximum current for the I/O lines is 100mA per channel.  The input current for the ON state of the input line is 5.4mA.  All of these specifications can be found in Appendix A of the 17xx user manual available online at 

http://www.ni.com/pdf/manuals/372429b.pdf

If you are trying to push more current than this, then it could definitely be causing the problems you are seeing and could potentially damage the camera.

[jblc]

  Thanks Chris.  I don't understand what you mean though, because current can't be "pushed".
  A high current rating of the power supply shouldn't damage inputs: the current the IO takes in is just dependent whatever the input resistance of the input line is.  Fig 2-1 shows the resistor built in to the IO input lines, which should limit the current appropriately.  If I have a 100A supply or 100mA supply, the input impedance determines the input current to the I/O.

 In outputs, yes, I'd agree on that.  However, I'm not driving any output loads (just reading with a DMM or scope), so that should be within spec.

[jblc]

I'm surprised it's taken about a week now to get the inputs working.  This is pretty strange from a high-end system.  Has anyone here actually used the inputs on a smart camera?