Repeating I/O across a network without a PLC

Hi All,

I am involved in a project where around 300 I/O points (analog and discrete inputs and outputs) are connected to a local panel and we need to repeat these signals across to a remote panel (without any logic or process control) that is located approximately 5000 feet away (by way of the cable).

I could create a PLC system that has PLC w/ I/O in the local panel and a remote I/O setup in the remote panel and connect them via a fiber ethernet network. Then in the PLC, I would map the local I/O points to the remote I/O points. This seems like overkill because we aren't doing anything with the data other than just mapping from a remote I/O point to a local I/O point.

We have looked into using the Acromag 900EN series and EtherStax series and it looks to be a viable option using their i2o protocol (which sounds like modbus with fancy configuration).

Any other thoughts on good methods of doing this? Are there any other remote I/O systems that support "peer-to-peer" I/O mapping?

"Repeat" ?
You mean "duplicate", so that you have parallel inputs and outputs ? What if there is a discrepancy, that one input is ON and the other is OFF, what do you do then ?
Or do you mean "exchange", so that the inputs in one panel are outputs in the other panel, and vice-versa ?
Or do you want to create some kind of redundant system ?
Or what ?

Yeah... my use of "repeat" wasn't so good.

Based on your definitions, exchange. Inputs on 1 panel are outputs on the other panel.

Maybe you can find a dedicated I/O system for this kind of application.

If not, a small PLC with I/O and a bus connection to an I/O expansion block could be an OK solution. Even if the code merely copies the data back and forth. It wont be "overkill", since 300 i/o in both ends will be not so cheap after all.

I would use a Siemens IM151-8 CPU with ET200S i/o modules. In the far end I would place an IM151-3 Profinet (ethernet) adapter. You would have to go to fiber to reach 5000 feet (~1500m).
What is neat is that the IM151-8 uses the same kind of i/o modules as the ET200S, so you wont have to have different types of i/o in the two ends. I dont think that you can have that with AB for example (*). The IM151-8 CPU is not expensive (~700 USD).
*: AB 1756 (ControlLogix) can do it, but will be quite expensive.

If you want to go copper wire instead of fiber, then I suggest you look at Westermo:
http://www.westermo.net/Resource.phx/content/products/short-haul-modems/linesharingmodems/ld-02.htx

You would have to settle on a protocol that supports 9600 baud (for example profibus). The update rate will not be great, but could be OK for your application.

Thanks for the feedback, JesperMP.

I have not looked at the siemens offerings yet on the PLC side, so thanks for pointing to some part numbers to start with.

There is an existing cable that was used with the obsolete system we are replacing, so copper would be great. Although, I don't yet have the spec on what the cable is so who knows if it would be acceptable for a serial network. It is a proprietary network, so it will be interesting to see what they used.

Required update rate is another good question... still need to work that out with the customer. i am guessing that a response time of greater than a second would be deemed unacceptable.

Take a look om Beckhoff bus terminal controlers.
http://beckhoff.com/english/bus_terminal/buscontr.htm?id=23623607

Similar to the Beckhoff is the Turck Bl20, or you can mount the BL67 outside of cabinets and make everything connectorized.
http://turck-usa.com/Products/Networks/Industrial_Ethernet/IO_Products.htm
These are available with programmable gateways so you can easily map the io