Output activating inconsistently

Hey guys, hopefully someone can help me out with real weasel of a problem.

I'm working on making a mobile PLC unit for a project and have run into waht I think is a software issue. Here's a quick rundown of the situation: the user inputs (touch screen) an arbitrary number of cycles for a loading/testing mechanism to complete, and upon pressing start the PLC runs that number of cycles and then stops. The mechanism in question has two cylinders, one is used for dispensing and BOTH are activated for unloading whatever is left in the hopper of the tester. The unloading is, ideally, controlled by a momentary button on the touch screen, separate from the cycling control system.

As of right now the cycling system is working flawlessly, correctly controlling teh one cylinder necessary for dispensing. The issue I'm seeing shows up when the unload sequence is run. The cylinder for unloading (remember, both need to activate) extends correctly, but the output used for the dispensing mentioned above does NOT activate, even though it works just fine for the cycling. I've tested with several different outputs, and it looks like the output used for dispensing just will not activate outside of teh cycling section of code. I've tried tying both outputs to the same input, and the unloading output will work but the dispensing output will not.

It's bizarre, almost like there's a lock on what can and cannot activate the output. Any ideas on what could be causing this behavior?

Software used: DirectSoft5
PLC: DirectLogic205

based on what you've described, it sounds like you're using TWO "outputs" to control the same field device ... most people call that a "double coil" situation ...

SUGGESTION: temporarily delete the last "output" in the program and run another test ... if my guess is correct, then the first "output" will then work correctly ...

if this DOES turn out to be your problem, then you'll have to "consolidate/merge" your logic so that you only have ONE (single) "output" for each field device ...

if this GUESS doesn't point you to a solution, consider posting your program code ... someone here should be able to help spot your problem ...

If Ron's suggestions turn out to be correct, AD has an output instruction referred to as an OROUT, which does just what it sounds like. It allows multiple rungs in a program to drive a singe "output" bit. If ANY of the rungs test for true then the output will turn on. Just replace all the OUT occurrences for that output with OROUT instructions and you will be golden. Many users will string you up from the closest lightpole for doing that because only select processors support that function and it can be hard to troubleshoot if you aren't used to it. But to each his own.

If that isn't your issue the other possibility is you are using stage programming and the logic for that output is in a deactivated stage.

Keith