best plc programming tips:

[Puddle]

Or we could follow vehicle VIN regulations and prohibit the use of the letters 'O' and 'I' completely, then for sure they are 0's and 1's.

I always assumed that this is why Siemens use Q for outputs, as the German translation starts with A.
British number plates on cars used to follow an alphabetical pattern and they omitted some letters such as I, O and U from the prefix for this reason.

 

[JesperMP]

British number plates on cars used to follow an alphabetical pattern and they omitted some letters such as I, O and U from the prefix for this reason.

"I" and "O" I can understand. But what number can the letter "U" be mistaken for ?
What about ..
B=8
G=6
I=1
J=1
O=0
Q=0
S=5

U=??

 

[JBooth]

When an operator interface is used, set up a seperate routine/program for mapping PLC logic tags to the PLC HMI tags. Keep names/descriptors as similar as possible between the PLC and HMI.

Set up screens on HMI for I/O state.

Keep coding methodology the same throughout the entire program.

Rockwell specific: when upgrading a system from a Logix5/500 to Logix5K, you can rename all tags to what they are, but if you do so, plan to redo the entire electrical references, manuals, etc and retrain operation/maintenance. Or just name tags as they would be in a 500 Data File and use descriptors to give the real world interpretations. All existing documentation can be reused that way.

When a process change requires logic change, remove all obsoleted logic and tags from the program (an archive copy of the program can be saved for future reference to original code). Makes it far easier a couple years later when you don't have to try hunting through to find out what a bit it used for only to find out it is not used.

 

[Puddle]

"I" and "O" I can understand. But what number can the letter "U" be mistaken for ?

Looks too similar to V apparently.


https://en.wikipedia.org/wiki/Vehicle_registration_plates_of_the_United_Kingdom#1983_to_2001

In order to avoid any confusion, the letters I, O, Q, U and Z have never been issued as year identifiers: I because of its similarity to the numeral 1; O and Q because of similarity to a zero; U because of similarity to the letter V; and Z because of similarity to the numeral 2.

 

[I_Automation]

Looks too similar to V apparently.


https://en.wikipedia.org/wiki/Vehicle_registration_plates_of_the_United_Kingdom#1983_to_2001

I'll support the U=V. I have always written them so close I can't tell what I wrote, and before I started adding a slash to Z I had to make sure I put a predominant loop on the bottom of a 2.

 

[KB1GNI]

When laying out I/O for a machine that has a lot of cylinders with limit switches, plan ahead and group them so that all of the switches representing the starting position are grouped such that a glance at the indicators on the card can tell if you are ready to start without having to refer to any documentation.

Example: a project I did had multiple 16 point input cards, which had four rows of four indicators broken up into bank 1 and bank 2.

0 4 0 4
1 5 1 5
2 6 2 6
3 7 3 7

Home positions were 4,5,6,and 7 on banks 1 and 2.
You could group the home position as 0-7 on channel 2, as well.

Not sure if this is a common practice or not, but I had never seen it done that way before.