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How to Connect to an Allen Bradley Micrologix 1500 using RS-232 (DF1)

If at the end of this article you still need a little more help, there is a link at the bottom to a video that shows this entire process explained in this article.

For some reason, Allen Bradley requires two software packages to communicate with its family of PLCs. You'll need a communication software package which is called RS Linx, and the programming package called RS Logix 500 if you are programming a SLC or Micrologix PLC. This tutorial will cover connecting to a Micrologix 1500 configured as DF1.

Out of the box the Micrologix 1500 is configured as DF1 or RS-232. Of course you can change the protocol if you need to, but first we will connect to the PLC with the default parameters. Most engineers I have talked to leave the programming port as default configured as DF1. If you are unsure, hopefully you have a copy of the latest program that is running in the PLC and then you can check the channel configuration by opening the program in RS Logix 500 and make sure it's configured as DF1 before you try and connect.

Let's first start by launching RS Linx communication software. RS Linx comes with the RS Logix 500 installation cd-rom. If you did not install RS Linx, please do so now. RS Linx is a free application and does not need to be activated or a master key to be installed to run. Once the software is started, try and not click on any of the "+" signs. This starts the last configured driver and activates this driver. A driver can not be deleted in the configuration portion once it's running. Most generally, you have to close RS Linx and re-start if you want to delete a driver that is active or running already.

Alright let's assume that you don't have any drivers configured yet, click on Communications, then Configure Drivers. You'll see this popup window.

Click on Add New and find RS-232 DF1 devices in the pull down menu, and leave the default driver name as AB_DF1-1. Click OK, then you'll see the driver configuration screen.

The DF1 driver configuration screen is pretty nice because at this point you should have your programming cable connected and you can click on Auto-Configure. RS Linx will run through all the baud rate settings and try and auto detect the PLC settings. Most of the time this works pretty good. If it did a good job you'll see an Auto Configuration Successful message appear in the box to the right of the button you just pressed. If you get an error, try restarting RS Linx at least once and try Auto Configure one more time. Once you have your driver configured you can go back to the RSWho window and now click on the "+" sign. This will start the driver. If all is well you should see your computer and the PLC you are trying to communicate with in the menu tree list.

If everything is equal or matches in the PLC, RS Logix will display the green power rungs on the left and right. If it's not a match, generally you'll probably want to do an upload at this point. Go ahead and click upload and then once the program is uploaded RS Logix should go online.

If the last driver was the not that same as the driver you just used, you might get a warning from RS Logix if it's ok to change the last driver used. Just read the warning prompt and you'll start to understand what RS Logix is trying to tell you.

I'll offer a couple of tips. If you plan on connecting to another PLC or protocol, I always suggest that you close RS Logix and RS Linx. Then restart RS Linx, do not click on the "+" signs and go to configure drivers. Highlight the DF1 driver and click DELETE. Now you can configure a new driver or different protocol. If the driver is giving you problems, close and restart RS Linx. Sometimes RS Linx will try and take over the computer com port while it is running. If you notice this has happened, shutting RS Linx down will release the com port back to the windows system.

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