FIFO dilemma

[blueyedpeter]

The point i was trying to make was that having executed each of or any sequence , timer control or staging , a delay timer on each stage could stop the rung from completing totally and allows for a 3 or 4 second change over to the next room to start . A single control rung could prevent the pump from being used on any more than one room at a time .
But stacking would allow the order to be maintained , on the other hand the timers would be random and would allow shorter program timers to come to the front and obvious longer timers to start last .
If total control over spray length and order of operation if required , then your fifo stack would allow for a greater level of predictability . otherwise creating or organizing maximum through put of the rooms would be difficult .Indicators indicating rooms in waiting would do just that but no more , and not give you an idea to an up coming event or process order .The fifo answer is probably your best but i haven't worked here yet .
Timers would be random but would lack a level of predictable and complete control but you cant shorten a distance between two points any shorter than a straight line . on any given day process time will need to be organised to help with the through put of the rooms . I suggested a small model of the fifo action not for counting but to bring up an output in an orderly fashion any how good luck.

 

[Paullys50]

Another thread on FIFO's that was fairly recent.

http://www.plctalk.net/qanda/showthread.php?t=80736

I chimed in on posts #4, #6 along with Lancie1 and a few others.

Probably doesn't contain a direct answer, but gives you more to consdier.

 

[jakeemon]

Yes I did thanks james, I will adapt that I think.

 

[jakeemon]

Thanks for all the help guys. I got it to work with a counter that increments with every spray request. Each room then checks to see if its number is called. At the bottom of program I have a reset counter if it equals 6.

Counter keeps cycling until it matches the correct number eg if room four wants to spray but current count is one the program will scan another three times until the count equals four and then sprays room four.

If current count is four and room two wants to spray, program will scan another three times until it equals two etc.

 

[jakeemon]

By the way in case you wanted to know, its for six meat chillers. we spray water to minimise weight loss as the meat chills. Both spray on and spray off times are variable from an HMI touchscreen.

my next project is to send a data packet from the spray PLC to the PLC that controls the refrigeration. I need to disable the evaporator fans during a spray cycle.

 

[blueyedpeter]

I used to work in small goods , and there chiller rooms were just that , but they used a separate chilling machine that sprayed super cold brine on the carcasses and the meat to reduce shrinkage as you say . As you are aware that with in the first few minuets after cooking the moisture loses is considerable .

 

[Lancie1]

I got it to work with a counter that increments with every spray request.

Ah-Hah! There is a spray request from each room. In which case you do not even need the counter. You only need a "Start Spray is Possible" relay.

Counter keeps cycling until it matches the correct number...

So your "Current Room Spray Request" is in the form of a room integer number from 1 to 6? How long does this number stay active or ON? The attached program print-out assumes that the "Current Room Spray Request" is in Integer memory location N7:0. If you really have 6 Spray Request memory locations (one for each room), then simply edit Rungs 2 through 7 and insert the proper memory word for each room in the "Source A" EQU comparison blocks. In cases where there are more than one request, they will be done in numerical order. If you want multiple requests done in First In, First Out order, then you should change over to using FIFO instructions.