PLC programming style??

[Wilso]

just remember who is going to maintain the machine, maintenance. keep the programming straight forward so that they can understand the logic. ask them what they are used to and how they would do it.

REMEMBER!!!!!
if maintenance can't understand the logic, the machine won't get fixed, production suffers, your boss gets yelled at and you in turn not only get yelled at, but baby sit the machine 24/7 or until you rewrite the code so maintenance can fix the problems. by that time,,,, I think you get the picture.

regards,
james

From a maintenance person - GREAT ADVICE. Last year our department spent $50 000 getting one of our programs completely re-written, because it was such a disaster that even our own engineers couldn't follow it. Nothing worse than trying to fault find an incomprehensible program on a broken machine at 3 in the morning.

 

[JesperMP]

Like others have suggested, he probably meant state machine, not statement list. Who would demand a program to be written in statement list ?

I use state machines for some of my programs. All the work is to define the state diagram. Pen and paper is used to make the 1st sketch, and then you continue to work on it until you have all situations covered.
When you think you have the state diagram nailed down, scan it and store the electronic copy together with the PLC program (!).

As to troubleshooting a PLC program based on state machine, then the printed state diagram is absolutely necessary. A PLC program based on state machine is very strucured, but may be confusing to look into by just looking at the code. This because the logic is split into states and transitions.

The HMI should indicate to the operator what state the sequence is in, and what conditions are required to transition to the next state (there may be several possible next states). This part may take a bit of work but is worth it. It may help to that the operator himself can figure out what is wrong without the need for a programmer to come.

 

[shooter]

is there any PLC program to make state programs?

 

[dwoodlock]

After reading all of these posts, does anyone have any examples they can share of a state diagram and corresponding plc logic?

 

[Lancie1]

This thread by member "Alyelhefni" has some state diagrams. I don't think that he actually ever used the state diagram to write his program, simply because it was shorter to write without the states.

http://www.plctalk.net/qanda/showthread.php?t=79204

 

[JesperMP]

Did you try the link in post # 10 ?