How to add Ethernet communications to a non-Ethernet PLC-5

PLC-5 Today you’ll find Ethernet in almost every manufacturing facility, and on most all modern automation systems. But many facilities also have an installed base of legacy PLC-5 systems, and often clients call asking how they can add Ethernet connectivity to their legacy PLC-5′s.

Before we answer that question, lets first review the communication options available on the PLC-5 processor.

The original processors (5/10, 5/12, 5/15, & 5/25) which were released beginning in 1985, came with two connectivity options built into every model:

  1. Data Highway Plus (DH+, also known as Peer Communication Interface or PCI)
  2. Remote I/O (RIO.)

The second generation of PLC-5 processors (5/11, 5/20, 5/30, 5/40, 5/60, 5/80,) known as the “New Platform” (NP) PLC-5,  had an additional 25 pin RS-232 port, and could also be ordered with an optional Ethernet or ControlNet port.

So for all those PLC-5 processors without the built-in Ethernet port I list five options below which allow you to add Ethernet communications to your non-Ethernet PLC-5:

AN-X2-AB-DHRIOOption 1: EtherNet/IP to Allen Bradley Remote I/O or DH+ Gateway (works with all DH+ devices)

From Prosoft: “The EtherNet/IP to Remote I/O or DH+ (AN-X2-AB-DHRIO) Gateway is designed to help customers initiate a phased migration approach to replacing or upgrading legacy Remote I/O, HMI’s or Drives. The AN-X2-AB-DHRIO gateway has multiple operating modes that are selected during initial configuration and are described below..”

Pros:

Works with any DH+ device

Cons:

It’s not free?

PNs and Prices

AN-X2-AB-DHRIO  EtherNet/IP to Allen Bradley Remote I/O or DH+ Gateway $1,895.

1761-NET-ENIOption 2: DF1 to Ethernet/IP converter: (New Platform PLC-5 models only)

If your New Platform PLC-5’s serial port is available, you can easily add a DF1 to Ethernet/IP converter (1761-NET-ENI.)

Pro’s:

Least expensive option

Direct access to PLC-5 Data Table

Has built in email capability (converts PLC MSG to an email)

ENI configuration is done with a free utility

Con’s:

Only three simultaneous bi-directional connections to PLC-5 at any given time

The PLC-5 serial port is limited to 19.2K (low bandwidth)

Requires PLC-5 NP processor with available serial port

If you have an HMI on the serial port you can use the A-B Serial DF1 port splitter (1747-DPS1) but you’ll be splitting the bandwidth with the HMI.

PNs and Prices

1761-NET-ENI

$893.00 list price from A-B

1761-CBL-PM02

$74.10 list price from A-B

$25.00 from Amazon

9 Pin to 25 Pin Adaptor

$10 from Amazon

1756-DHRIOOption 3: 1756 DH+ to Ethernet Gateway (works with all DH+ devices)

A very common option to bridge from Ethernet to DH+, CNET, and DNET, a 1756 chassis with an Ethernet module and a single DHRIO module provides for the bridging from Ethernet to two DH+ networks at 57.6K or 115K, or one DH+ at 230K.

Pros:

One Ethernet gateway to many networks

Direct access to PLC-5 Data Tables

No programming needed to bridge Ethernet to DH+

Add additional modules for additional networks: ControlNet, Devicenet, DH+, DH-485, or 3rd party modules from Prosoft

Cons:

Expensive solution for a single PLC

PNs and Prices

1756-A7: 7 SLOT CONTROLLOGIX CHASSIS   $504.00 list price from A-B

1756-ENBT: CLX ETHERNET/IP BRIDGE $2150.00 list price from A-B

1756-PA75: 85-265V AC POWER SUPPLY   $911.00 list price from A-B

1756-DHRIO: DH+/RIO BRIDGE $1,910.00 list price from A-B

PLC-5 ENETOption 4: ENET Sidecar: (New Platform PLC-5 models only, firmware upgrade may be needed, )

If your New Platform PLC-5 has the correct firmware, or if you’re willing to purchase the firmware upgrade, and you have the ability to move whatever module you have in the first I/O slot (directly to the right of the processor,) the 1785-ENET Ethernet sidecar is an option you can consider.

Pros:

High Speed connection to PLC-5

Direct access to PLC-5 Data Table

Channel 3a configuration is simple

Cons:

Need to move and readdress I/O module in slot 1

Will likely need to update PLC-5 firmware chip which can be expensive

PNs and Prices

1785-ENET

$3720.00 list price from A-B

5/80 Firmware

~$685.00 from A-B (most expensive version, price circa 2005)

MVI71Option 5: Prosoft Ethernet Module for 1771 Chassis and all PLC-5 Processors: (works will all PLC-5 models)

From Prosoft: “Support for the storage and transfer of up to 4000 registers to/from the PLC processor using the block transfer. The module can send read or write commands to remote devices on the Ethernet/IP network. The MVI71-DFNT also has 20 servers that allows the module to receive commands from remote devices. The MVI71-DFNT Pass-Through server allows the user to edit, download, and upload the PLC ladder logic using an Ethernet connection. Up to 100 commands can be configured by the user.”

Pros:

Works with any PLC-5 in any SLOT

Cons:

Requires programming (Prosoft tech support historically has been good)

- Block Transfers needed in PLC-5 Program

PNs and Prices

MVI71-DFNT EhterNet /IP Communication Module ~$2,159 (circa 2005)

 

I hope you’ve found this article about how to add Ethernet to non-Ethernet versions of the Allen-Bradley PLC-5 helpful. If you have a question or would like to offer your own option please use the “Leave a reply” form below to comment on this article.

By Shawn Tierney

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