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streaker69

Compatibility Question

8 posts in this topic

Gentleman, I currently have a project going on where a Contractor is to configure a Allen-Bradley CompactLogix 1769-L32E to use a DataLink DLM-4000 dialout to a remote station. Basically it's an RTU panel. Problem is, contractor is saying they've talked to both AB and Datalink and they're both claiming that it cannot be done with the Spec'ed equipment. My question to you, is this true? I did not write the spec, a third party did, and they're claiming that everything should work. Has anyone had any experience with this hardware in this type of configuration? Thanks alot.

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Tell us more about the system. On your end, there's a 1769-L32E and a DLM-4000 modem. On the other end, there's "basically an RTU station". Is this correct ? What kind of modem and controller is at the RTU station ? I've used Data-Linc equipment with almost every kind of A-B controller and not found any insoluble problems. Is there ordinary "POTS" telephone service between the two stations ? I presume you have to dial out to the other station.

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I believe that the same PLC and Modem is on the far side as well. These are standard POTS lines. This panel is supposed to dial out to a pumpstation, poll for information from the remote PLC and return the information to the local HMI. The contractor is claiming that they can get the modem to dial out, but once it's connected, it won't switch modes to transfer data. I can't recall the term they used at the moment about 'switching modes'.

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I think I get it. They have the serial port in ASCII mode to dial the modem, and are trying to get it to switch to System Mode with DF1 protocol to transmit Message instructions. This isn't an easy thing to do automatically with any A-B controller. Usually the controllers are meant to run the serial port for an ASCII application or a DF1 application, but seldom to switch back and forth between. You can transmit ASCII strings out of the serial port using the AWT instruction on most controllers. That's often enough to dial a modem using AT commands. It is *possible* to switch back and forth between System and User modes on a Logix serial port, but it's not a normal supported function and you would have to do a lot of your own testing.

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The DLM-4000 modems also have a dial-on-power-up feature and a Auto-Alarm Dial Back feature that could be used in place of sending ASCII commands to dial the modem.

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That is what I was thinking would be a work around for switching between modes. Problem is, this RTU panel is eventually going to be polling 42 different stations. So, unless the modem is able to store 42 different numbers and have them triggered to be dialed by the PLC, I don't think that solution is going to work either. Is there another device that should be used in conjunction with the PLC that would make this type of task easier to get running? Ugh, and now just thinking about this, I think I just found yet another problem with what has been supplied to us.

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Let's try it the simple way first. Set the "Master" controller's serial port for System Mode with DF1 Full Duplex protocol. Use the AWT instruction to dial the modem, send your MSG reads and writes, and use another AWT to hang up the modem. Use a serial analyzer to measure the connection time between dial and connection, and just wait that time plus a little extra between dialling and sending the MSG. I know the staff at Data-Linc very well and we can help put together a strategy that works for your application.

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Now if the contractor that I'm working with would only figure it out. The point of my asking was I wanted to see if what they're telling me is the truth. We're having a big sitdown next week to discuss their lack of progress and this is a large issue at hand. I've heard that Data-Linc has very good tech support as well, but these guys don't seem to be interested in contacting tech support for any issues that we've run across for the entire project. They implemented Iconics (my choice) without ever sending any of their people to the Iconics classes, and they wonder why much of the stuff they did, didn't work. I appreciate the replies, Ken, I figured it was possible, and it's just their failure to do research and ask for help when needed.

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