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kku

Ethernet IP Integration

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I have been slowly converting to ethernet IP. There are so many devices on the market that it's hard to ignore. So far I have been only adding one or two devices to existing machinery. Using EIP has saved me quite a bit of time because there is so much less to wire! The existing machines we currently use have discrete I/O's so wiring something new, updating schematics, etc. will take me forever. Also taken the machines down for extended periods of time is not ideal since they are already in production. Anyway, my question is how many devices can I add to the EIP network before traffic becomes a problem? I currently have two Keyence (SR-652) barcode scanners on the EIP network and haven't had any problems. I plan to add one or two Cognex Insight Micro vision cameras and also one additional I/O interface for new sensors. With the new additions I will have 5 devices on the EIP network. I want to find out if this is still OK or should I invest in a managed switch? Edited by kku

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I am not familiar with Omron as much as I am with AB or GE PLCs. But in Allen Bradley Software, we have a tool called the TASK Monitor. And if we want to monitor the Ethernet/IP performance, max connections, how much CPU is being used for communications rather than user tasks, we go here to look. Does Omron have something similar? This tool is not normally installed with the software package, it's an addon that comes with the installer CD-ROM but you have to go in and install it like a custom setup.

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I wonder, what the cameras are supposed to transmit over Ethernet-IP?

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Managed Switches on EtherNet/IP provide several benefits, but are not necessary in most systems. The most useful function of a managed switch is something called IGMP Snooping, which stands for Internet Group Multicast Protocol Snooping. This function is used when a device is set to Multicast data, which is similar in concept to a broadcast. When using Multicasting on an Unmanaged Switch, all devices attached to the switch recieve all multicast packets, which increases the network traffic on each node. When using Multicasting on an Managed Swtich with IGMP Snooping, the switch has a subscriber table for each physical port on the switch, and which Multicast packets each device subscribes to. So, only the devices that request specific multicast data will recieve it. In most applications, multicasting is not necessary, so unmanaged switches will work just fine, as long as you remember to configure each connection as 'Point to Point', not multicast. The feature that I use most often on managed switches is Port Mirroring. Port Mirroring allows Wireshark running on my PC to monitor all traffic between a PLC and another device (IO Block for example). The Managed Swtich is configured to mirror all the traffic on one particular port (the PLC port for example) out another port to which my laptop is attached. The other key to understanding EtherNet/IP communications is the concept of RPI, which is Requested Packet Interval. Each connection to a device is made at a specified RPI, which the user can set. The RPI is set in ms, and is the interval that the data should be transmitted from the device. So, a Congnex camera can be set to transmit data every 50ms, which is a relatively low network load. IO blocks, which may need faster response, can be set to a 10 ms RPI for faster response. By setting the RPI for each connection at an appropriate value, it is easy to control the amount of network traffic on EtherNet/IP, and setup a very viable network, using an unmanaged switch.
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From what I understand you can configure the camera to send whatever you want over the Ethernet IP connection (using the format string and write EIP functions). Right now we use discrete I/O to transmit job numbers to the camera and inspection OK/NG from the camera. To do this we use the CIO-Micro I/O breakout box which is OK but this box only has 8 inputs and 8 outputs which really limit the system's flexibility. With the EIP connection I can expand on the number of inputs and outputs to and from the camera.

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I checked the Omron EIP configuration software and found a place where I can monitor the usage of the device bandwidth usage. I think this is similar to what you describe for the AB PLCs. The only problem is it's 'greyed' out and not accessible. I don't know how to enable this button. I am using a USB connection to connect to the PLC so this may be a problem(?). I attached a screen shot of my system configuration.

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PMCR, thanks very much for your detailed response. It's very helpful. I feel better now going into ethernet IP. Although not being able to monitor the network usage using the Omron EIP configurator is still bothering me. I will set all the network connections in the EIP configurator to point to point connections. I will keep in mind the port mirroring. I realized I have to get a swtich that will support power over ethernet anyway to power the cameras. So I will see if I can get a managed switch that support port mirroring, IGMP snooping, and also power over ethernet. I have used Phoenix contact switches in the past (unmanaged) so hopefully they have something that offers these features.

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Though an older post - I just wanted to add that Mencom has unmanaged switches as well. www.mencom.com

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