my first project

Hi, i have just been given my first work based plc project. I have to set up a system that counts pallets entering a heat run on a conveyor line. Each loaded pallet must remain in the heat run for 30min. Once the time is complete then they are allowed to move on to the next process. My problem is that i have limited knowledge of shift registers. Am i looking in the right direction or should i be looking at another way to control the pallets through the heat run?

PLC?
How many pallets in the heat run at same time?
Does the conveyor stop or does it stay running?

Bob O

There are between 10-15 pallets passing through the heat run at any one time. The pallets will contiue to enter the heat run but a stopper at the end of the run will prevent the pallets from leaving until the 30 min time period is complete.

First thought is to adjust the conveyor speed to keep the pallets in the heat run for 30 min. This assumes that the conveyor stays running.

Bob O

i am afraid the line speed is set for different tests further on down the line .

i would use a FILO array as such.

If pallet 1 arrives at 10:00, then store 10:30 in the array.
If pallet 2 arrives at 10:15, then store 10:45 in the array.
If pallet 3 arrives at 10:35, then store 11:05 in the array.
If pallet 4 arrives at 11:00, then store 11:30 in the array.

in this array you now have
[1] 10:30
[2] 10:45
[3] 11:05
[4] 11:30

Look at this array, when the first register [1] equals the time, open the exit gate for 1 pallet then shift the array up one, removing the first piece of data, so the array is now

[1] 10:45
[2] 11:05
[3] 11:30

Look at this array again, when the first register [1] equals the time, open the exit gate for 1 pallet then shift the array up one, removing the first piece of data, so the array is now

[1] 11:05
[2] 11:30

Just repeat these 2 seperate processes ad-infinitum.

Of course, there are more complications to take into consideration. I would not recommend using the time but perhaps a relative time measurement. I hope this helps somewhat...

So the conveyor is always running and while the pallets are held in the heat run and the conveyor is allowed to slip/slide under the pallets?

THANKS XION, i will look into your idea.
Bob, yes the conveyor is continually running.

Hi i am doing somting simpilar to this and also using a array to keep track of my pallets.
I have a conveyor with 4 different entries for the pallets and I have to keep track of them, because the 4 entries represent 4 differet types of pallets that have have to be strapped in the same strapper. I think i have solved that problem, but my question is:

which way is the easiest to shift the array up?
[1] pallet type 1 (interger value 1)
[2] pallet type 3 (interger value 3)
[3] pallet type 2 (interger value 2)
[4] pallet type 3 (interger value 3)
[5] no pallet (interger value 0)
and so on

1 pallet done move array move 1 up->
[1] pallet type 3 (interger value 3)
[2] pallet type 2 (interger value 2)
[3] pallet type 3 (interger value 3)
[4] no pallet (interger value 0)
[5] no pallet (interger value 0)

I know i can do it with the MOVE block, but then i have to do it with every value. Just wanted to know if there is a block were you can define which addresses that have to be moved one up.

hope you can help me

Thanks

edit: sorry I forgot to say i am using Siemens S7

What separates the pallets once the first one has hit the stopper and the following pallets bump into each other? Asssuming each pallet arrives at a random time, you need to be able to separate them (to get the stopper in between them) once each one has had it's 30min of heat.

Which plc will you be using ?

Edit: Didn't read the date on the original thread...ignore.

Hi Simon
I think the 30 min heat question is overdue. I just used this thread to make a new similar question. Hope you can help me with my question instead. pls read the item i posted on top of yours

Thread hijacking?

PLC Pupil said:

Hi Simon
I think the 30 min heat question is overdue. I just used this thread to make a new similar question. Hope you can help me with my question instead. pls read the item i posted on top of yours

Click to expand...

Probably better to start your own thread in the future, than to hijack someone else's that seems close to yours. Just a simple comment, not a bash!

Randy

I already did that. Realised the mistake too late. I just didnt want to create many of the same threads. I made a search first, but couldnt find any that answered my question