This is a series of ladder logic rungs from a RSLogix 500 program for a MicroLogix 1100 connected with a PanelView Plus 1000 to help understand the logic. The goal is to label the instructions.
The original post is here.
My interpretation is:
Rung 86: A value of 1 is sent to N7:11 and T4:21 starts and continues timing for 5 seconds when LS_001 is on or T4:21 is done and T4:22 is not done. (The 5 second timer is here to show a 'true' low level?)
Rung 87: T4:22 starts and continues timing for 5 seconds when LS_001 is not on and T4:21 has timed for 5 seconds. (Is this timer here for five seconds to see that the tank is at a high enough level to not be a nuisance trip?)

Hi Mark,


Same old project eh? Looks like you made some changes (added some comments, deleted some rungs so
what you refer to as rung 87 was really something like 108 or so in the old program etc.).

Few suggestions:

1. You started new topic, meaning the old one is closed, which is fine. But, you should provide all needed information since this is all new topic. How about that new program? I can't see what do you call LS_001 in the link to PLC file. Post the new file so those who may be interested in helping don't have to start from zero.

2. when posting screenshots of logic, try to make it readable. for example this poor quality screenshot is hardly readable, try sizing applicaiton window before taking screenshot then crop and save only essential part. I'm posting sample of what I get when trying to zoom in and read screenshot from above post and screenshot of what it could look like (although from older version of the program plus resampled to look smaller than what it is on my screen). Actually it would be better to not use JPG for this because JPEG compression leaves more artifacts (meant for images of nature, not computer graphic).

I modified the original post based on your reply. Thanks for the tips.
What do you recommend for graphics file type and where to upload them?

looks way better, i see that latest file shows much more comments, only rung numbers still don't match (only off by one is not too bad).

your interpretation of mentioned logic is very close to what i see:
- timers 21 and 22 create so called debounce logic with bit T4:21/DN acting as status.
- value of 1 is writen to N7:11 when that status bit is on or LS_001 is active

Below is just another representation of that logic (both timers are still TON) with additional bit serving as status (B3:20/0).

btw. this PLC supports online editing, you can always add another few rungs to test something while process is running
(just pick some unused valid addresses and ... try to avoid things that may fault CPU if the main process is still running).

I modified the post so the rungs match, it seems to be a matter of getting the hang of the forum conventions that I am learning and will help in future posts. Is there a forum primer somewhere?

Also, uploaded the latest version with some more work done. Turns out three other projects got in the way of this one so I lost some time working through the code. Feels like putting together an unfinished puzzle that may not look good in the end. fun stuff and thanks for the help.

Debounce is also what I had in mind. This is for a 300 gallon tank so I think the switch and timer logic should handle both. I am leaning toward your code as easier to read right off and would be interested in what others think.

Is it recommended I start a new post for the next exercise or continue with this thread? The way I see the forum working is pretty neat that the most recent is at the top of the list. Just trying to keep the posts out there as a reference for others looking for answers without duplication.