Log Deck Stepfeeders

I am having problems programming the logic for my stepfeeders and am looking for some help! This is PLC5 just to clear that up.

What I've got now is the bit for a log being on the top stepfeeder and the forward signal, this latches a bit that I call "Log in Trough"

In the next rung, I have a XIC of "Log in Trough" and a XIC of a photocell that it has to pass by and clear before it feeds another log. If these are true I latch a bit "Log in trough and eye has seen the log"

In the next rung I have a XIC of "Log in trough and eye has seen the log" and a XIO of the photocell, if this is true then I latch "Belt is clear and ready to feed"

Next rung is XIC of "Belt is clear and ready to feed" amd this unlatches all of the above.

My problem is that the stepfeeder keeps doublefeeding on me. I thought this was pretty fool proof logic, but apparently not. For some reason if the log doesn't make it to the eye before the next is ready to feed it double feeds.


SOR EQU N42:24 0 BST BST XIC B33/20 XIC O:105/4 NXB XIC B271/17 BND NXB BST XIC B33/16 XIC O:105/1 NXB XIC B271/18 BND BND OTL B3/583 EOR SOR XIC B3/583 XIC I:027/16 OTL B3/582 EOR SOR EQU N42:24 0 XIC B3/582 XIO I:027/16 OTL B3/581 EOR SOR XIC B3/581 BST OTU B3/583 NXB OTU B3/582 NXB OTU B3/581 BND EOR

Thanks for your help again guys!!

Do you have on and off delays on your photocell? After the "Log in Trough" is latched, any slight 'blip' at the photocell will reset the system. At a minimum, I would add an on-delay to the photocell so it has to be blocked for a short time before it is considered ON. You want to know that there is an actual log, and not some insect that happened to fly past the photocell...



-Eric

P.S. There is no such thing as 'fool proof logic'...

Try using step logic instead so you have step one "Log In Trough"

When photocell is seen go to next step.

And so on until you can return to step 0 or step 1 and repeat the process.

I don't have much time at the minute to write you a little step program but I'm sure someone will come along soon that has

Mark

Try searching for "sequencer". There are some example programs there.

A few comments...

On rung 28, your branch arragement is a bit funky. It will work, but it looks odd and uses a few extra instructions. Try right clicking on a branch and picking "extend branch down" instead of inserting a new branch.

I'l echo Eric's comment about the delay on the photoeyes. The photoeyes can have delays built in the hardware, but we can't tell.

But I think the real problem is in rung 30 & 31. "Belt is Clear and Ready to Feed" is turned on in rung 30, and right back off in rung 31. Any other logic that is watching for that signal will not see it. Maybe you should wait to execute rung 31 until after the feed has started or completed?

We changed the logic from just the photoeye clearing to the debounce timer. The only reason behind just using the photoeye only was to just get the next log loaded quicker! I'mm going to start a new thread on a project that I am working on to replace all of this, Thank you ALL for your help!!!