Help with AB Compact Logix

sparkytex

Lifetime Supporting Member
Join Date
Jun 2013
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Port Hardy B.C.
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354
Hey guys,

So after installing the 1769-ECR end cap on my compact logix system my I/O faults went away which is great. However, after going online with the program that I downloaded to the processor I cannot get any of the I/O to work at all. The processor is in run mode and no matter which bits I toggle I cannot get an output to turn on. Same goes for inputs, If I jump 120v straight to an input the PLC input card LED light does not light up and you cannot see it go true on the rungs.

I've looked through a bunch of stuff but I cannot figure out why this is happening. I'm sure its something stupid that I've overlooked but any help is appreciated.

- Tex
 
Tex
If I'm not mistaken, the processor has to be in remote ("rem") on the little switch under the little door on the processor. Run won't let you write anything, just "look" and read. We had a bunch of PLC 5's at a water utility I worked at, and they were wanting security to keep people from going on line and messing up programs, etc. We simply put the PLC in "run" and took out the keys from all the processors. Only electricians and other select few had a key.
 
The Processor key is in remote right now and selected to "remote run" on RSLogix 5000. I'm stumped as to why the IO isn't responding to anything.
 
Well, there's only a couple of things I can think of. One would be if the I/O is wired correctly for source/sink, the other would be a rookie thing--are the JSR's all in place? Hope this helps.
 
So I figured out the inputs, it was something simple, I forgot to install an AC common on the two 1769-IA16 input cards.

However, I still cannot figure out the 1769-OA16 output cards. I have an AC 120V going to the both "VAC" terminals on both cards and using my voltmeter to test it I get 120VAC on every output channel. Of course, if I disconnect the 120VAC to both cards and force on the outputs I get nothing either and on the rung logic the outputs never turn green.

But if I install 120VAC to only one of the two available "VAC" terminals on the output card 8 out of the available 16 outputs have full-time 120VAC on them. I don't understand why the 120VAC is making its way to the output channels when nothing on the logic is telling the output to become true.
 
This is normal for discrete AC output modules

120V AC solid-state output modules use "Triac" devices, which always allow some leakage current. With no load attached, you will always measure 120V AC at the output.

You can experiment by attaching a neon bulb to an unused output; you'll see it glow even when the output is off.

But install an incandescent bulb, or a contactor, or a valve solenoid, and you'll see the leakage current flow through and the measured output drop to zero unless the output point is commanded to turn on.
 
So this is what I have currently wired up:

(1769 OA-16) 120VAC wired to both VAC terminals on both output cards (Slot 3 and Slot 4)

I have a 120VAC relay wired up to output 5 on Output card in Slot 3 (Local:3:O.Data.5). AC Neutral to A2 of the Relay and OUT 5 to A1 of the relay. When I force the output on or even toggle a test bit to turn on the output nothing happens. The status LED doesn't even light up either.

The output modules aren't inhibited and the processor is in remote-run. The input cards are working fine, I don't understand why I cannot get the output's to change state.

Edit*** Even when I force the output to on, the output value still stays as a "1" in the data table
 
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If the status LED isn't lighting up when you turn on an output using logic or Forcing, then the Output module is mis-configured or defective.

Take a look at the actual status of the Output module in the I/O tree; when you select the module you should see at the very bottom of the controller organizer window a list of the associated tags and three status indicators for Description, Status, and Module Fault.

One more thing; Forcing an Output on or off does not change the logical state of the Output tag. Forcing inputs does; forcing Outputs doesn't.
 
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Well, I'm an idiot, I didn't have my boolean bit toggled to "1" for my JSR to my "waste" routine. That explains why the outputs weren't working and the inputs were lol.

I know I'm going to get in **** for having that XIC bit before my JSR but it is just the way I was taught to program.

Sorry to have everyone scratching their heads. But I did learn about the leakage voltage and current with these output cards so that's a plus for me. Thanks for the help guys.
 
Everybody raise your hands if you've been fooled by a non-executing subroutine.

Now raise you hands if it happened this this week.
 
In your post #5 you mentioned the outputs in your program were not turning green . If these outputs are in a subroutine , check if the subroutine is being called . Also check if there is a jump instruction bypassing the outputs . Unless you get a green on the output instruction , the card won't work .
 
lol, I feel a little foolish to have missed something so simple but I'm glad its solved as I'm scheduled to install and commission this PLC tomorrow morning!

I definitely won't forget this one hahahaha!
 
Yes, and raise my--oops--your hands if you've wondered why your values aren't changing and inputs aren't going on and off and why outputs are on that ought not to be and you look up and you're off line. Ha. Did that AGAIN a few weeks back.

Glad everybody learned something. We had those triac output cards at the water district and now I understand them a little better. Thanks, Ken.
 

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