I just completed converting a mill at one of our facilities from an ancient Siemens S5 to AB Compact Logix. The rest of the facility used a DH+ network that we are going to upgrade as a separate project to ethernet/IP. But for the present time, in order to get the upgraded mill on the HMI and collect data, I was wondering if anyone has experience with a reliable gateway for Ethernet/IP to DH+ ?

I believe what you are looking for is a ControlLogix Gateway and they have been around since before there where ControlLogix Processors. It consists mainly of a 1756 rack, 1756 power supply, a 1756-DHRIO card and a 1756 ethernet card.

I am aware of AB Controllogix Gateway but was looking for a more economical third party unit since this is only a short term install till we upgrade the DH+ network to eithernet.

I've never used one of these, nor do I know the cost.
Take a look here: http://www.protocolconverter.com/products/dl3500dhIAP.html

I realize that the ControlLogix Gateway may look like an expensive solution for a short term problem, but you need to look thru a wider angle lens. You mentioned changing your DH+ Network to Ethernet. This means you have PLC 5 hardware and are planning on adding 1785ENBT cards or similiar. A CLGX Gateway could be upgraded to a CLGX CPU and using ControlNet you could upgrade the PLC 5 to Controllogix rather than just add ENET to a PLC 5.

Also be advised that DH+ gaurantees a comm window to each PLC while ENET is first come first serve.

Things to consider.

About $1200-$1500 if I recall correctly. Not cheap.

At the PLC level, you can always do block transfers. I ran for about a year over the existing DH+ network with block transfers on all the PLC-5's sending the data to a single "aggregator" PLC which was accessed via Ethernet.

At the HMI/PC level, you could use either network since Ethernet/IP works fine over Ethernet.

The basic problem is that DH+ absolutely, positively has poor support overall. So here's a couple approaches:
1. Use a ControlLogix and route across the backbone. As suggested. Roughly <$5K if you do nothing else with it, but it doesn't stop you from using the backplane for a regular ControlLogix that just happens to be a gateway, too.
2. Use the above device or one of the competitors. I believe I tracked down at least one or two others when facing the same sort of problem.
3. Use RS-Linx at the PLC level. RS-Linx OEM can support OPC communication for local-only OPC aware HMI's. Straight RS-Linx lite won't do it.
4. Use RS-Linx Gateway. Load the PC with nothing but the minimum software and this. Put a PCMK card in it so that it acts as a gateway server for everything or some things.
5. Get a KF2 box. This converts DH+ to serial. Then use a Digi One IAP to make it a multiple-connection aware setup. Or alternatively plug the serial port into a single PC and use RS-Linx Gateway. Or else use the KF2 box as-is but realize that it's a single-PC solution at a time no matter what you do. Or alternatively connect it to the serial port of your ControlLogix and use DF-1 protocol. You'll then have a ControlLogix that is speaking DH+ as a DH+ node. You lose all the Ethernet/IP features but my impression is that you were trying to get back to DH+ and not migrating everything early via some sort of interface onto Ethernet.

Note that there's no way to use Ethernet/IP directly via protocol conversion especially to route onto DH+ since Ethernet/IP doesn't have an easy way to do multiple gateway routing.

The last solution is what I actually implemented. It's kind of kludgy but it works. It was relatively inexpensive because we actually happened to have a KF2 already and I was only paying for the Digi One IAP.

I'd highly recommend buying an outright serial/Ethernet gateway such as a Digi One SP or a competitor's product if you want to simply connect the HMI. This gives you Ethernet TODAY on each processor for under $150. The limitation is it's a one-one protocol mapping. The more expensive Digi One IAP gives you 2 PLC's for each card and you can do many-many including mapping Ethernet devices to the serial ports and vice versa, but it's a little more expensive ($650).

I like the IAP approach because it's a true protocol bridge. A lot of stuff out there such as the Prosoft solutions do outright translation and you set up a "map". So from one side, it appears as an AB PLC and you have to know that N7:0 on the "phantom" processor actually corresponds to N10:15 on another processor on the other port. The protocol bridge is simply issuing reads and writes and buffering the data in the middle to allow processors on either side to independently access it. With the IAP, I can literally boot up RS-Logix 5 and program a non-Ethernet PLC-5 as if it IS an Ethernet processor.

There's one other hassle with this approach. You set the "Station address" (the "optional" number in your Ethernet settings in RS-Linx) to the DH+ port address. However, RS-Linx gets very upset if you have multiple stations with the SAME IP address. This is simple to fix. Simply define extra drivers. Each driver contains the same repeated IP address and since they are on different drivers, RS-Linx does NOT complain. So your RS-Linx "tree" looks kind of funky, but it is fully functional.

Thanks for all that posted. We do, in fact have a KF2 onsite. I will take this approach to keep the cost down since we will be upgrading shortly. Thanks again