G_DeMark

Ethernet IP Nodes

5 posts in this topic

I have  a simple question that I think I know the answer to, but I want to confirm with you more veteran members.

When I am selecting a compact logix controller, the different models provide various numbers of Ethernet IP nodes.  For example, the 1769-L18ERM-BB1B is specified with 8 nodes.  What specifically is meant by nodes.  I have been assuming that the number of nodes is the number of Ethernet IP devices I can connect to the PLC.  So if I had the following Ethernet capable devices; HMI, Dataman, Atlas Power focus, then I would be using 3 of the 8 available nodes.  Therefore, with an 8 node PLC I would need at most an 8 port switch.

Do I have this thinking correct?  I am not sure.  Please correct me if I am wrong.  Thanks

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Number of nodes is the number of devices you can add to the I/O configuration:

https://rockwellautomation.custhelp.com/app/answers/detail/a_id/474754 (Access level: Everyone, will need a free login)

HMIs and PCs are not counted as nodes and don't count against this limit.  Your switch should be sized according to your needs and then increased at least one size to allow for future growth.  I think you will be fine with an 8-port switch but should allow panel space to go to 16 in case of future need.  For an unmanaged switch, we've had VERY good service and pricing on the N-Tron 108TX.

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I ditto the N-Tron 108TX unmanaged switch. Very good and reliable. 

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Posted (edited)

MOXA makes good switches too. Din rail mount, fiber / copper mixed, just copper, or just fiber. I know of one panel where the electrician stuck a UPS... a big UPS... like 10" wide x 24" tall x 18" deep inside a stainless steel panel, with the PLC (think heat, sucked back into the cooling fan, which increases the heat). The panel was in full sun for most of the day. It was in south TX, near the border with Mexico, summer so ambient temp was over 100° F. I drove out to check why the PLC was faulted (which is a full day drive round trip) and when I touched the panel face with the back of my hand (to make sure there wasn't an AC short that might make me dead) it burned the back of my fingers. The ML1100 inside was unhappy about that and it had faulted. The MOXA switch was happily blinking away. The electrician that put the UPS inside an enclosed panel was not happy with me on that day.

Edited by Michael Lloyd
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Posted (edited)

I second the use of Moxa switches. They have Ethernet/IP certified switches as well which is what we use.

Edited by Wild

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