AB dh485 Comms setup

iamthelad

Member
Join Date
Jan 2004
Location
Wigan, Greater Manchester
Posts
9
Hello eveyone!

I wonder if any one could offer any advice on a pooject I'm about to setup.

I currently have 5 separate plc systems all using 5/03 processors. I wish to use a common LOI to display plant status and for paramater setting. The problem is I only have a Siemens OP270 10" for this purpose. I know I can connect the OP270 directly to one of the 5/03's and network all PLC's then use mesaging from each of the PLC's to the "master" or sit the OP270 directly on the DH485 network and monitor each PLC individually. However I know the limitations of DH485 and am unsure if either of these solutions is possible in the real world, what do you think?

Also how would you physically connect 5 SLC 5/03's together and still have a spare RJ45 socket left to connect my laptop to?

Or am I miles off with what I'm thinking and should I try a differnt approach?

Any help would be much appreciated.

Cheers, kris
 
how many values are you looking at?

what update time?

you can run an extra 1746-AIC which will give you an extra rj socket for your laptop.

Ive done a job like this recently. I started off with dh485 with 4 slc503's to a PC (rsview). about 300 tags... Was sluggish to say the least on 2s update time.

Ive now put each processor on a seperate short haul modem to a multiport serial card in the PC. Speed problem fixed and now the DH485 is useful for proram mods, msging etc.

cheers
Andrew
 
Cheers for that Andrew, unfortunately I have to use the Siemens panel so the multiport serial option isn't viable. I would imagine there would be around 300 tags needed in total. I'm thinking that using the existing 503's is gonna cause me to many problems so I may swap them for 504's. Does anyone know if I use a DH+ to RS232 converter such as the KF2 would I be able to see all nodes on the DH+ network? If so I could point the OP270 to each node on the network and eliminate any need for messaging?

Thanks in advance. Kris
 
you need a 1761-NET-AIC

converts DH485 network to RS232.
then you can browse to to a DH node. (I think)


does the siemens screen support ethernet?
you can get serial to ethernet adaptors which would be a way better option.
 
Last edited:
MSGing to one PLC and serial to that would be prob the fastest option (excluding ethernet) as you can schedule the messages so they dont all try to fire at once, say have a bit shift moving once every 3 seconds controlling the message commands.

Slow data update, but at least you will be able to do online viewing/programming still.

Just with the serial data to the screen, make one datatable ie N100:0-400 and use that for all of your ints/bits to be used on the screen. Keep the data all close together across the datatables and it will go faster.
 
Cheers for the advise Andrew.

The OP270 doesn't have an Ethernet port but a card is available.

In the end I've decided to swap the 5/03's for 5/04's and network them all via DH+. Then with the pass through enabled on one of the 5/04's connect the OP270 to the DF1 port using a standard 1747 CP3 cable. The OP270 will then be able to see all nodes on the DH+ network. This isn't ideal I know because If the 5/04 the OP270 is connected to fails I'll lose comms to all but it's better than using message commands.

Cheers, Kris
 
I know but I'm limited to what I can spend on this project so I can only use components that we already have. Hance the OP270. Still this is for a job in the water industry, as long as it isn't to slow the customer will be more than happy.
 

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