project help

hello everyone i am a student and i have a project to make using plc from siemens....the code isnt the problem,what i lack is experience in real projects for example i wanna run the plc in a transporting tape which categorize the products by height and sends them left or right...its pretty simple but since i lack the experience of the real think i dont know what parameters should i use...for what should i use alarm...what should i make sure not to happen...that kind of stuff...i dont know if i managed to get you the picture..i hope i did and u guys should help a bit understanding those things...thx in advance

Start with I/O

Even if you don't know what does what, think of what do I need to do this or check this.

Inputs take a physical movement and turn it to an electrical signal.
Outputs take an electrical signal and do something with it.

Photoeyes look for something. Input
Buttons do a operator comand stop, start or select. Input
Limit switches tell something is there. Input

Contactors start a motor. Output
Solenoids control movement. Output
Pilot lights tell you something. Output

The above should get you started, remember ask yourself.
How can I do this and what does it need to do.
What happens if I do that, what can go wrong, and how can I prevent it.

Good luck

Wow,

Takes me back to the day I stared into my first black hole of PLC.

On occasion I still have flash backs.

Start from the beginning, Identify your process and list your task. List your I's and O's

By this time you should have started putting rungs together in your head, what your going to do with the photo eye, the limit switch, the motor contactor, buttons...

The process will start to take shape. After a thousand emulations go to rung 2.

Believe it or not the secret to programming is in the "DO". You begin to find all the nifty things Siemens didn't tell you about. Like why it had to be so difficult to set a delay-on timer.

One day you sit back after four hours of coding and you realize you made three lefts just to make one right. ( epiphany ) That's when the real programmer in you will come out. You begin to eat, sleep, and breath code. You write little notes to your kids in their school lunches. They bring them back all confused cause you wrote "love you" in binary.

The hardest part is putting that first open contact on the rung and figuring out what to call it.

On a serious note, operators are never the brightest bunch, it is your solemn responsibility to make sure they can never get hurt on your machines.

Have fun, don't go crazy, and remember to look up occasionally when your walking down the side walk.

project so far

S1 : sensor that tell us that cargo is on the thansporting tape and starts it

S2: when its 1 tells us that cargo is short
S3: when both s2-s3 1 tells us that cargo is high

S4 : when its 1 tells us that cargo is near the peristrofic transporting tape and so it starts it.

S5 : its the peristrofic transporting tape. it has a little button in the end of it i dont know if u see it but when its 1 depending on the 1 of S2 or S2-S3 moves the cargo to the right or left and starts moving the other way pushing cargo of it.
S6 : when its 1 means that cargo went through so peristrofic transporting tape goes back to its 0 position
S7 : same as S6 (remember cargos can go depending on high left or right)

Q1 : when something goes wrong (which is what i need help for in the 1st place) this motor runs so it can shut down the tapes while it can

The theoritic part or else the "problem" is this :
lets say we have a factory that produces cigarette's and we put them in boxes so we can transport them. we split the categorize of boxes in high and shorts ones depending on how many packet of cigarettes we wanna put it for shipping. we have already secure that boxes go in the transporting tape (near S1) every 15 sec. if the box is high (S2+S3) put the box left (towards S6) if the box is short put it right (towards S7). if 15sec pass and S1 activates but S6 or S7 havent been activated yet means that cargo stuck somewhere so activate Q1.

thats all i though so far and what i want from you is just give me idea of what might go wrong....so that i could cover almost all the things that would happen....i have some more thought for example if the cargo isn shorter that S2's reach...or it isnt heavy enough to activate S5.... but i havent figure out how to use the 1 and 0 on the other yet so i can work those occasions. so thats what i really wanna ask from you guys...ideas of what could go wrong in a transporting tape. thx




















picture uploading

make a state diagram so start with S1
it will go to a state to check S2 and S3
on these positions you will go to another state like running left or running right.
start a timer and when timer is done and package not in end or past end stop process.

John Morris said:

One day you sit back after four hours of coding and you realize you made three lefts just to make one right. ( epiphany ) That's when the real programmer in you will come out. You begin to eat, sleep, and breath code. You write little notes to your kids in their school lunches. They bring them back all confused cause you wrote "love you" in binary.

Click to expand...

Isn't that the truth....I write my best code (or should I say rewrite), when I'm just waking up and I'm dreaming about what I need to do that day.

I remember bolting out of bed one morning realizing that I didn't interlock the steam heat with the low level indicators. (rookie mistake)

300 lines of main program and 5 subroutines and the seventh line of the of the third subroutine woke me out of a sound sleep

Course by this time the machine is squarely seated in north west CANADA in a plant with no Ethernet/wifi. My Happy a** was on a plane two days later. Needless to say the owner was p***sed. with good reason. I double check five ways from Sunday now.

It routine now to sit at the computer in the morning with a coffee and a hunny bun reading my code like it was the Sunday OPED.

But I digress.

What's also bad is when you reuse code from earlier projects and on the new project discover a bug in the original code....by now you've propagated that bug through several installs....now you have to send out a "patch" for something that's probably never affected them and likely never will but you can't stand knowing it's not perfect.