Simultaneous start.

[parky]

Here is a version that assumes the following:
All local start/stops are inputs to the PLC, there is a Hand/OFF/Auto switch.
So, assume in Hand mode then the conveyors can be started/Stopped locally.
In Auto then pressing the Auto start button activates the sounder for x seconds, then starts conveyors in sequence with 3 second delay, if the Auto stop button is pressed, then the conveyors stop in reverse sequence.
If the local start/stop circuits do not go into the PLC then you could use some PLC outputs to disable the feed to the local stop/start wiring something like the output logic in the PLC i.e. put an output feeding power to the stop/start locals for local control, so when the Auto or Off position is active then the output is turned off disabling the feed to the contactor.
Caveats:
Not tested fully but cannot see any problems, assumes there are e-stop systems in place, conveyors in this case are numbered 1 to xx i.e. conveyor 1 is the first to start & last to stop (depends on how your conveyors are numbered perhaps infeed is Conv1 & outfeed is conveyor 1 +xx then just reverse the numbers.

 

[drbitboy]

Where is the STOP all conveyors but I like the idea.

Thanks.

OP did not ask for that; it's left as an exercise:

XIC STOP_ALL_CONVEYORS AND B3:0 -3841 B3:0
​

or

XIC STOP_ALL_CONVEYORS AND B3:0 F0FFh B3:0
​

 

[drbitboy]

Reading your post again, some questions come to mind....

+1. There is a lot more involved here than ladder logic.

Here is a version that assumes the following:...

Nice!

 

[parky]

Yes, with no idea how the existing one is controlled it's guesswork.
I liked the idea of the bit OR you did, perhaps for sequence control use a bit shift but shift ones in for startup & back out again for stop & just zero them for manual control.

 

[jolton]

From installation of conveyor systems over the years you do sequential stat up last conveyor first , to prevent jamming and shutdown is a reverse of the process . 1 to 2 second lag will be good starting point unless you are moving long objects or high speed application like bottling .

 

[Manglemender]

One more thing to considder and, forgive me if someone already mentioned this and I missed it but you need to considder if it is safe to start all the conveyors from one place? Normally you would want line of sight from the start button to see that nobody has they arm in something. This may be covered in adequate guarding but something to considder.

Under EU/UK legislation you are changing the function of a machine beyond its original design and that would require you to take on the resposibility of the machine designer. under EU/UK legislation that would require a complete risk assesment and re-certification of the equipment. Does the same apply under NEC/NFPA?

Nick

 

[JesperMP]

A few more hints:

When stopping, are the conveyors supposed to be enmptied before coming to a complete stop, or can they stop with material on ?
In the first case, you may program a sequental stopping of the conveyors one by one, Beginning with the conveyor that is most up-stream.

Definitely investigate if a risk assessment has been done.
If not, it has to be done.
If yes, consider if you are changing an existing system in a way that affects safety, and if so the risk assessment has to be updated.
Whoever is tasked with doing the risk assessment must be proficient ! If there is a serious accident, and you made an unsafe system you might face litigation.
(I wont give advice on safeguarding a conveyor system. It is a huge topic and posting hints could lead you to wrong conclusions or underestimating the task).