Legacy network connections

Consider these points when blending network upgrades and connecting to legacy networks.

Mark T. Hoske

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When connecting a legacy network, plan it out. Most networks can be connected, and multiple networks can be integrated. It is possible to keep existing network investments and move information to a higher-level network, such as an Ethernet protocol, according to Jeremy Bryant, industrial communications marketing manager with Siemens Industry Inc.

Look at the whole picture and consider the overall objective and the network design, he suggested, taking into account what the system needs to look like today and for the foreseeable future. Here are some additional considerations from Bryant for making legacy network connections:

• For new projects, put everything on the new network, Ethernet when possible. Ethernet provides “a future proof concept, the potential of having just one network, and the ability to easily share data with higher level systems.”
• Consider the cost and time involved in a full upgrade. Upgrades in pieces might be more practical. Updating the controller first then adding a gateway module to communicate with existing I/O connections allows flexibility to upgrade at a more practical pace.
• An Ethernet backbone installation can use gateways to keep existing I/O connections with serial networks connected to long-used devices. 
• PLC modules can serve as gateways to translate information.
• Ethernet can add reliability by serving the backplane outside the control panel. Inside, use the network that makes sense.
• For network selections (legacy serial networks or existing fieldbus networks), consider how many devices can be connected.

www.usa.siemens.com/automation 

www.controleng.com/new-products/industrial-networks.html

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new-products/industrial-networks.html- Mark T. Hoske, CFE Media, Control Engineering, www.controleng.com