BobLfoot

PLC Law

158 posts in this topic

In the now classic commercial a group of men sit around a table and generate "Man-Law" usually related to beer. A Sample Man Law Ad on youtube It is my hope in an equally light hearted way we PLC guru's can sit around our keyboards and draw from our own personal histories those jewels of PLC-Law that should pass to the up and coming programmers. PLC LAW #1 - DON'T OVERCOMPLICATE THE SIMPLE. In other words use the simpliest easy to understand logic allowable. Using a sophisticated high level instruction just to look cool doesn't help anyone. NEXT?? 9/6/2008 - Just Published the Edited Downloadable 2008 Edition of the PLC Laws to the MRPLC Download Section. We are now at Law #51. Note: The Posting has the 2006 and 2007 versions in the ZIP file as well. Edited by BobLfoot
6 people like this

Share this post


Link to post
Share on other sites
PLC LAW #2 - MAKE SURE YOU PLUG THE CABLE IN BEFORE YOU TRY TO FIGURE OUT WHY YOU CAN'T GO ONLINE. Don't laugh, I don't know how many times this one has gotten me
6 people like this

Share this post


Link to post
Share on other sites
PLC LAW #3 DURING STARTUP, ALWAYS VERIFY I/O BEFORE TESTING THE PROGRAM I don't know how many times I have seen people troubleshooting their program and the I/O is still not wired or tested. Then they try to fix the problem by modifying their program. Edited by newpageboba
2 people like this

Share this post


Link to post
Share on other sites
PLC LAW #4 WHEN CONNECTING YOUR LAPTOP TO THE PLC, DON'T TIGHTEN THE SCREWS ON THE SERIAL CABLE AT THE LAPTOP SIDE. Any damage or confusion caused by an intermittent disconnect pales in comparison to the damage done when somebody walks by your laptop (which is sitting on a 55-gallon drum) and trips over the serial cable dragging your laptop to the floor. Edited by TWControls
5 people like this

Share this post


Link to post
Share on other sites
PLC LAW #5 Read the manual BEFORE trying to install/commission an unfamiliar piece of hardware.
4 people like this

Share this post


Link to post
Share on other sites
Man Law requires us to NEVER read the manual!
4 people like this

Share this post


Link to post
Share on other sites
PLC LAW #6 Allways have all possible backup files (plus read from PLC etc.) before starting any changes... Once you touch it, you own it. If you can't at least restore previous condition, you are sc***ed.
3 people like this

Share this post


Link to post
Share on other sites
PLC LAW #7 Allways double check you have the right cables for your CPU type and backup install software with you before you step on the plane. (especially when it involves special connectors/converters/adapters)
3 people like this

Share this post


Link to post
Share on other sites
Not sure this counts as a law, but what the heck... PLC LAW #8 - Each vendor has their own programming software, so plan accordingly. Believe it or not, I had a call one where someone asked me if they could use RSLogix to program a Square D Symax. 'Well they're both PLCs right?" Duh... PLC LAW 8.1 - Some vendors software may not play well with others... See RSLinx...
1 person likes this

Share this post


Link to post
Share on other sites
PLC Law 9 When powering up a PLC the first time, make sure that the power supply voltage switch is set to the right voltage. Once when settinp up a compact logix it was wired to 120 but the switch was set to 240. All the lights lit up but I couldn't establish communications. I swapped out the processor, still no good. Five frustrating hours later, I noticed the swtich position. Edited by Alaric
2 people like this

Share this post


Link to post
Share on other sites
PLC Law 9.1 When powering up a PLC the first time, make sure the PLC is in program mode or I/O is disconnected.
2 people like this

Share this post


Link to post
Share on other sites
PLC LAW #8.1 - Order the correct software from your vendor instead of asking for it on MrPLC
2 people like this

Share this post


Link to post
Share on other sites
Yes, I know... I'm the woman who has to find & keep copies of the manual that the men never read. <g, d & r!>
3 people like this

Share this post


Link to post
Share on other sites
PLC LAW #7.1 When working in a LAN or WAN environment always triple check processor ID's before erasing and downloading new code.
3 people like this

Share this post


Link to post
Share on other sites
PLC LAW #10 Try to stage and test as much as possible before making big changes. PLC LAW #11 Spares should not sit of the shelf. They should be used for training and tesing. PLC LAW #12 Programs should have many rungs of diagnostic ladder that can be enabled or disabled quickly. This includes timers for timeouts. These determine when input devices are not working properly. FIFOs are good for logging real time events. Counters that count errors are handy too. PLC LAW #13 The best PLC programs are able to recover from error conditions quickly. This can make a big difference to overall production. These are not specifically PLC LAWs. These are things I see customers continually over look.
3 people like this

Share this post


Link to post
Share on other sites
I was going to second LAW#11 but all of these are such good point I'll second the whole thing. But LAW#11 is one I have never understood. Why have all of those components sealed in boxes waiting for the next breakdown. One they are great for test simulation of changes but the greater reward is letting your programmers hone their skills. If work is low let them go in there and work with them. A little bit a day can make a tremendous difference
4 people like this

Share this post


Link to post
Share on other sites
If this keeps growing we'll have to issue a compilation for use as a training guide. LOL.
1 person likes this

Share this post


Link to post
Share on other sites
PLC LAW # 14 ALL PROGRAMS SHOULD BE WELL DOCUMENTED This is so that when you go back to a project say twelve months later you know and any one else knows what is actuallly happening in the program.
3 people like this

Share this post


Link to post
Share on other sites
Here, Here on Law #14! I've spent many, many hours redocumenting PLC programs that someone else wrote & lost the original file. But there's always one comment I have to include near the bottom of the program... "You realize that since you understand this, I'm going to have to kill you..." It always gets a smile from the electrician.
2 people like this

Share this post


Link to post
Share on other sites
Ok Susan, I'm probably going to get an answer like MAN can't understands but I have looked and looked at this and still can't figure it out. I give up, what is it?
2 people like this

Share this post


Link to post
Share on other sites
Grin Duck and Run www.acronymfinder.com
1 person likes this

Share this post


Link to post
Share on other sites
And here I thought Susan was strong enough to make a comment like that and stand her ground.
1 person likes this

Share this post


Link to post
Share on other sites
Oh boy, that comment might get the wrath of Susan. Bob said it, not me
1 person likes this

Share this post


Link to post
Share on other sites
PLC LAW #15 MAKE SURE YOU ACTUALLY UNDERSTAND THE QUESTION IN THE DIALOG BOX BEFORE HITTING "OK" For example "all changes will be lost, are you sure you wish to continue?"
4 people like this

Share this post


Link to post
Share on other sites
I am. I'm the only woman on the floor in this plant so I know how far I can push "man laws" and still get away with it. Ok, it's my turn... PLC Law #16: Remember to put a paper copy of the latest PLC ladder in the electrical cabinet. If all other PCs & backups fail, this one won't.
4 people like this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now