Replacing Leased Line Modems with Ethernet Convertors

Hi,

Allen Bradley SLC 500 coms question.
We currently use a 4wire multi drop leased line system for plc coms, 1 master and 4 slaves using the A/B DF1 Protocol.
Master polling the slaves etc.
Is there a unit out there that i can replace the modems with and use our ethernet WAN to replicate the modem function across the WAN.

Cheers Andy.

Protocol converter?

You might want to look into a protocol converter. Digi makes one called the Digi One IAP. It is not cheap but it works great. I recommend a protocol converter rather than a simple virtual com port device. In my experience, ethernet can introduce lag that can cause problems with serial protocols. Using a protocol converter, the Digi actually talks AB Ethernet/IP across the network, and then converts that to DF1 on the serial side of the device.

http://www.digi.com/products/serialservers/digioneiap.jsp

This assumes your polling is done from a computer or device that supports ethernet. If you polling is done via serial then you have limited options..

That function is exactly what the A-B 1761-NET-ENI is meant to do.

You may have to do some MSG logic program changes when you change from Half Duplex to Full Duplex, and you will have to put some Routing Tables into the Net-ENI with the configuration tool (or write them into logic). Otherwise it's almost a drop-in replacement.

I have not used the Digi One IAP extensively and cannot comment on its comparison in configuration or performance compared to the Net-ENI.

In my experience, the Digi is superior to the AB Net ENI in many areas.

1. The Net ENI can only support a small number of open connections (4 IIRC), where the Digi can support many more (64 IIRC).

2. The Digi has a built in web server for configuration and diagnostics, the Net ENI has to be configured via a serial cable using a proprietary software (Different versions are needed depending on the series of the NET ENI) This is a major drawback for installations with remote locations. All you need is a web browser.

3. The Digi allows you to monitor the serial port stream (live) to help diagnose problems, the Net ENI program is very limited in this area. Digi T/S is free and very helpful.

4. The Digi is about half the cost of the Net ENI.

5. The Digi can be configured for many other industrial protocols (Modbus ASCII / RTU etc), where the AB only does DF1. I can stock 1 Digi and cover many customers.

6. The Digi has 2 serial ports that can be configured for 2 PLC's.

Oh, I agree, the Digi One and Digi One IAP are much more versatile devices. Cheaper, more fun, more powerful.

The guy who designed the Digi One also designed the original Lantronix serial server and the 1761-NET-ENI !

So why would you select the A-B device instead ?

1. It can be powered from the serial port from a MicroLogix 1000, 1200, or 1500 controller.

2. It includes DF1 to EtherNet/IP conversion, so a controller or operator interface terminal with EtherNet/IP capabilities that cannot be loaded with a Port Redirector can communicate to a DF1 serial device over Ethernet.

3. It does perform DF1 Auto-detect.

4. It has an e-mail feature that can be triggered from the DF1 side.

5. It has a DF1 -> IP node translation table for sending messages initiated by the DF1 device.

6. It cannot be reconfigured over Ethernet, which is in part intentional because it would require a security feature.

All of these functions are very A-B controller specific, and the general-purpose interfaces don't do them, which is why the 1761-NET-ENI was developed in the first place.

I've had my issues with the devices; some of the old firmware was infuriating, and the change in capabilities as the different hardware caught up with providing services to both Logix and SLC/PLC can be confusing.

I'm just saying that the 1761-NET-ENI is different, and for some good reasons, from general-purpose Ethernet->RS232 converters.

I always ask what the application is. If it's straight PC -> Controller and can work with a Port Redirector, and I think the customer can support the device themselves, I always recommend Digi or Lantronix. If I'm going to have to teach the user how to use it, or if they need the protocol-specific features, I go with the 1761-NET-ENI.

the lantronix

http://www.lantronix.com/device-networking/external-device-servers/xpress-dr-plus.htmlXPress-DR-IAP

admittingly I havent used the lantronix with df1