DH+ Network with Low Overhead

Hi there,

I have a customer (Water Treatment) that has a DH+ network with 9 Nodes that are very busy. Each node is a Phoenix DH+ to Fibre Card and then from DH+ locally into ControlLogix DHRIO cards and then onto 9 individual Ethernet Networks. A total of around 42 seperate AB PLC's on site.

(PLC-DH+FibreCard-FibreRing-DH+FibreCard-PLC)

The Control Room PLC (SLC500) pulls data via MSG instructions (30 individual messages in total) from each of the main nodes.

There has been some reports that the network is running slowly of late and as the site is having most of its large treatment plants upgraded and more data brought to the Control Room, I feel this might be the root cause.

So what I was hoping to find out from this post is, how can I arrange the cascading message instructions so that there are less message connections occuring all at once? I have attached a PDF of the message sequencing method currently used.

Instead I would like to keep active connections to a limit to create more overhead on the DH+.

Any help greatly appreciated.

Cheers.

Hi Chris,

I have done something similar on a different brand PLC... I think your logic looks good, but can you lower the time value? 5 sec is a lot of time so I think you could save some time if you cut it down.

Is there some logic that you could write that once the message is complete then go to the next, that way you only have one message out and no wasted time... if it only takes 1 sec then you are not waiting for 4

You could use the active node table and use the en,er and dn bits of the msg instruction etc ?

Been a long time since i did dh+ messaging but there are plenty of control bits and status bits to aid in clean messaging etc

Thanks guys - will try your suggestions!