Messaging between compacts and micro's, large scale

We are working on upgrading our communications to some remote sites to increase data rates back to our plant. We are basically doing a complete network overhaul and i'm looking to find out what is the most efficient way of doing the messaging.

The planned network layout (rough drawing attached) consists of our plant PLC reading from 7 repeater sites. The 7 repeater sites each have up to 20 remote sites that they will be reading from. The data from each remote site will be minimal, reading 5 DINT's.

The 5 DINT's are read into an array at the repeater sites then the plant PLC reads the array which is then read by the OPC server.

The current plan is explicit read from the repeater to the remote site. Then explicit read from the plant to repeater site. Does anyone know of more efficient ways to move this data to keep overhead and network traffic down?

As a side note the network is through wireless radios which is why this is of concern.

The most obvious question is how frequently you need to update the data from the remote PLCs.

The next question is do you need to continuously read the data, perhaps the remote PLCs can write the data if and when it changes..

That would be the fun part. It needs top update every 5 seconds. We have a third party system going in that requires this update rate.

The data will need to update continuously. I won't have the remote sites writing through this network, it has too much of a possibility of getting messy with this many sites.

You do not mention what media you are using, so I assume ethernet.
Have the remote sites write to the repeater sites whenever the data changes or every 5 seconds, whichever happens first.
You will then be able to have logic in the repeater to detect a com failure / bad data.

Then from the repeater sites to the plant plc use produced / consumed tags and include health data from the remote sites.

How is the reliability of the produced/consumed tags? Will there be and indication of communication fails between the plant and the repeaters?

Mike_RH said:

You do not mention what media you are using, so I assume ethernet.

Click to expand...

Oh and yes this is all over ethernet.

From micrologix to compactlogix or viceversa you have to use messaging, between compactlogix you can use produced/consumed scheme but wireless...you can try it, in theory it should work. you use a kind of watchdog.

Produced / Consumed may be set up to include communication / processor mode status by packing the data into a UDT.
The first member of the element of the UDT should be data type ConnectionStatus. The name & structure of the UDT must be the same at the producer and consumer.

However as widelto indicated, not sure about doing it over wireless.
I did not see that in your first post.

Ok Just for clarification

Between remote sites and repeater sites there is a 900 MHz radio with a data rate of 1,024 kb/s

Between repeater sites and the plant there is a 2.4 GHz radio with a data rate of 50 Mb/s

I think i will have to start doing some testing in the shop playing around with produce/consume. I've never used it before so it will take some time ot get used to.

One last thing though. I work with a tech who ran into an issue 4 years ago working on a job using p/c. There was an array of 100 DINT being p/c and somehow there was a tag in the middle of the array that stopped updating. everything else in the array was changing except for this one value. To get the value to update again they put the plc into program then back to run and it started working. I believe it only happened once but that's all it takes to lose confidence in it. Has anyone had any experience with this sort of issue? This was using V18 possibly 16.