Devicenet subnet implementation

[EOFFJM]

I have a problem where the total drop length of a devicenet network is too long (39m). To prevent that, I am thinking of moving 3 flowmeters from the main devicenet network to a subnet. There is already a subnet on the network that uses 1734-ADNX with a lot of DIOs and AIOs.

If I were to move the 3 flowmeters from the main devicenet to subnet, that means I will have to change the wiring from devicenet to normal 4-20mA wiring for analog current input right? Or is there a way to keep the devicenet wiring and still use a subnet somehow?

Thanks.

 

[AlfredoQuintero]

Hi there. I do not fully understand your problem. if you have too much bus length a relatively inexpensive solution is to use a CAN repeater.
I am not sure what you mean by subnet, so I cannot figure out a correct answer.
What baud rate is your network using? if you are using 500 K you may be able to get your network to work with your current length if it is possible to use a slower baud rate if this does not affect your data throughput.

 

[EOFFJM]

Thanks. I actually don't know about CAN repeaters so I will have to research about that.

A subnet is a distributed network that is connected to a main network by using a devicenet scanner.

The baud rate is the highest one which is 500k. So yes, maybe I can lower that to 250k and see if there is no problem.

 

[AlfredoQuintero]

Ok, so you mean you would like to add additional DeviceNet scanners to the PLC's backplane module.
I think a CAN repeater is much cheaper and you need not change the PLC program. There are many makers of CAN repeater. In Japan Phoneix Contact and Turk have good support. Here are some of these products.
https://files.valinonline.com/userfiles/documents/turck-devicenet-repeaters.pdf


https://www.phoenixcontact.com/onli...08-12-03/19652d31-21ec-49ba-9495-528c944ceb0c

 

[Ken Roach]

DeviceNet data mapping can be complicated to explain and follow in simple systems.

POINT I/O by itself is fairly complex on DeviceNet, with the 1734-PDN and the 1734-ADN.

And 1734-ADNX sub-scanners are even more complex.

If your flowmeters have DeviceNet interfaces, you can move them to the subnet side of a 1734-ADNX.

But you have to re-configure the main PLC scanner and the -ADNX sub-scanner.

If you can provide more information about the main PLC and the software tools you are using, that would be excellent.