There is one potential pitfall: the default baud rate for DH485 is 19200, and this is what you will find most of the time. Make sure you also set the selector switch to RS232 or RS 485. In addition, you will need the female-to-female null modem crossover DB9 serial cable or a straight-through RJ45 ethernet cable, depending on which port you want to connect to. This protocol requires a special USB converter, the 1747-UIC, which you can order from A-B or find a number of 3rd party versions online. You'll notice the 5/05 also has an RJ45 port, but this is for Ethernet, NOT DH-485.Īll you need is a regular female-to-female null modem crossover DB9 serial cable, and a USB to RS232 adapter if your computer does not have a serial port. The SLC 5/01, 5/02, and 5/03 use DH-485 via their RS485 8-pin RJ45 jack (which is the same physical connector as Ethernet, but it won't work if you plug it directly into your computer!).Īdditionally, the 5/03, 5/04, and 5/05 have an RS232 DB9 port that MAY be configured for DH-485, but it will be set to DF1 by default and can also be configured for ASCII and Modbus RTU. The two most common ways to connect are DH-485 and DF1. Finding the Right CablesĪs you can see, each model features a slightly different set of physical ports and protocols.
However, as is often the case with legacy systems, if you don't have the program handy, you can usually figure out how to connect by method of elimination and a bit of luck. RSS file) and a copy of the RSLogix 500 programming software (contact your A-B distributor if you need one), you can open the project and check the communication settings by double-clicking on Channel Configuration under the controller section of the project tree:
If you have access to the original PLC program (typically a. This blog post summarizes the different ways that you can connect to these PLCs and some of the pitfalls to look out for. One of the most popular series of PLCs from the 1990s to mid-2000s is the Allen-Bradly SLC 500 series: SLC 5/01, SLC 5/02, SLC 5/03, SLC 5/04, and SLC 5/05.
With a large number of legacy systems, the original programming cables and software are often long lost by the time you want to make updates or need to troubleshoot an issue. Older PLCs, however, tend to use a myriad of different cables and protocols. With most modern PLCs, all you need to start programming or troubleshooting is to plug in your laptop with a plain old ethernet cable.
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