Remote Modem Access to SLC

[navillusi 2]

I need to connect to an SLC on a remote site via a modem. I know that AB market a dedicated modem for connection between the DF1 port and a standard telephone line, the "RADKIT" I believe it is called. My problem is that there is no PSTN line in the vacinity of the PLC, and as such, I would imagine that using a GSM (mobile) modem would be my only option. Does anyone have any experiences or suggestions of what equipment would be required for this solution? The PLC is an SLC 5/03 with the DF1 port free to use and a connection to the DH485 network available Regards

[Ken Roach 194]

I recently helped troubleshoot a setup with an AirLink "Raven" GPRS modem. The modem uses serial input, then packetizes the data using UDP protocol and transmits it across AT&T Wireless's data network. The data comes out the other side serially. Although the serial ports were running at 19200 baud, it took about 1.3 seconds for the modems and GPRS network to encapsulate and transmit each packet of DF1 protocol data. Yuck ! Even ordinary RSWho wouldn't work because the default DF1 acknowledge timeout in the controller was 1 second and it took RSLinx about 2.7 seconds to acknowledge the controller's response because it had to get the response (1.3) seconds, and send an ACK (another 1.3 seconds). We ended up getting acceptable performance for telemetry (Kepware OPC into an RSViewSE application, polling every 5 seconds) but going online or program download would be painfully slow over this kind of modem. I'm still trying to get information from AirLink about whether or not this is typical performance.

[finfin 0]

Hey Ken! Any updates on this question? We need to upload programs with a wireless connection. Wireless being cellular here. these would be fore remote machines that must be setup on site via PanelView but at least the data entered would need to be archived at our site if not the entire program (prefered). Edited 10 Oct 2008 by finfin

[paulengr 44]

Whatever you do, there are two basic things to keep in mind with cellular. The basic protocol is CDPD which operates at the high speed of 1.2 kbps. Newer protocols go faster. Second, although the voice side is highly optimized for latency, the data side is just the opposite. And you can't expect anything like a "continuous" connection which is why even on an analog cellular connection (not sure if you can even get those anymore), ordinary telephone data modems would always hang up/give up on a regular basis. With that in mind, GPRS is about what you are limited to in terms of nonproprietary hardware. These are really intended for remote telemetry applications, not bulk data transfers. Data rates are a bit faster than CDPD (roughly 10 times), but still very slow. If anything, you might be best off if you could somehow use the cheapest/smallest PC you can get your hands on married to the cellular company's current "internet tether" card. Speeds will be much better than GPRS in most areas. In reality, probably your best bet is to simply use flash cards and forget about the troubles with the cellular stuff. Just Fed Ex preprogrammed cards whenever changes are needed.

[BobLfoot 301]

This may be more money than you have available but have you considered parking a cheap PC (some dells are in the $400 U.S. - 200 pound range) next to the PLC with Linx Lite and Logix on it. Most cellular phones can be connected to PC's as modems. This means your Programming PC only has to remote access the PC. This technology is a lot more forgiving of latency issues and works fairly well, just for for thought.

[finfin 0]

How would I get the program from a MicroLogix 1100 to the flash card? Do they make a module for that?

[paulengr 44]

It's a 1763-MM1. It's clearly documented in the manual. To upload the program, you have to initiate that from RS-Logix 500. Downloading of the program is automatic on power up, or again you can initiate this from Logix 500. It doesn't appear that you can plug the MM1 into a PC. I believe you will have to use another ML1100 as the reader/writer. So you can simply send over a new memory module and when it gets plugged in/powered up, the ML1100 will load the new program. Using data file protection, you can purposely "write protect" certain memory files so that during a download, those areas will not be overwritten by the download. You can also save settings (recipes) into the battery backed memory of a ML1100 using the RCP command. With a SLC/PLC5/CLX, using PLC memory would generally be a bad idea because of the chance that someone forgets to change the battery. But with the ML1100, battery life is several years so this shouldn't really be a problem. If you are truly concerned about "recipe" type data, I'd suggest doing it the "old fashioned way". Buy an HMI (Panelview+ and Panelview standard supports this) which will store/load recipe data. Then you don't have to depend on the capabilities of the Micrologix for this. And both of those HMI's do have the capability of taking and reading/writing a flash card (PCMCIA for the Panelview Standard, and CompactFlash for the Panelview+). With both of them battery life is so good that I've never changed batteries. That being said at the price of several thousand dollars for a PV+ or PV, you can easily buy an entire cheap PC to store everything and run a "real" HMI. For example, check out these guys: http://www.bb-elec.com/product_multi_famil...p;TrailType=Top About $1100 gets you a fanless PC with industrial temperature ranges, a low end Celeron processor, plenty of ports, and a solid state (2 GB CF card) "drive" running Windows XP in a case that you easily bolt inside a panel somewhere. It's not an "engineering workstation" but it's enough to run a standalone HMI and even be able to run Logix 500 if you really have to. If I didn't already have a gigabit fiber backbone and multiple servers running thin clients, this was my second alternative to eliminating industrial PC's and their poor plant longevity.

[finfin 0]

Yeah... There are problems with the 1763-MM1. Number one is that someone has to be on site with RSLogix-500 in order to burn the 1763-MM1 with the setup data. Since the machine is setup without a computer being connected to it by mechanical techs makes it impossible to get the setup data stored. Plus as the machine runs it may automatically update some of the data as it re adjusts itself. Second is that the 1763-MM1 will not write a new address to the processor; so if a processor fails, you can't just re-flash the program into a new (out of the box) processor. This forces us to have the processor in our hands so we can put in the address. At that point we may as well put in the program. The only thing we would be missing is the setup data from the original processor. Recipe data wouldn't work as the original processor has failed. The unit already has a PanelView + 400 on it. I will look into the "recipe" function. I was not aware that there was one. We have found that we could create a data log and store the critical data to a cf card. The customer could send us the card (overnight) and we could program a new processor and overnight it back. So they could be up and running in 2-3 days. If the customer has enough knowledge to e-mail the file to us we could cut it down to one day. I knew Ken did a lot of work on the wireless modem side of communications. I was just hoping that there was a simple cellular data connection that had made some ground breaking steps in the last 4 years. Edited 20 Oct 2008 by finfin

[finfin 0]

I read about the PanelView Recipe function, and it sounds great! Thanks Paul! If I could just get the MM1 to write the communication info into the processor all of my hunkies would be dorrie. I have an MM1 here but no manual. Could you give me the publication number or link for the manual that Defines this usage, Paul? Maybe I'm doing something wrong. Edited 20 Oct 2008 by finfin

[paulengr 44]

http://literature.rockwellautomation.com/ Then simply drill down through the menus and you'll get a "manual". Note that it is somewhat buried. The installation manual simply tells you how to pull the little cover on the left off and plug it in (useless). The real goodies are actually in the regular ML1100 user manual where it tells you how to save, load, etc.

[finfin 0]

Yeah, I did all that and read both manuals you described, although I would offer that both are "useless", when using the MM1. It must be a firmware issue that doesn't allow writing to the communications regardless of checking the communications protection box.

[finfin 0]

The recipe functions in the PanelView+ is working well, but I have a few wish lists. 1) It would be nice if I could Attach the buttons to tags in the processor so I could trigger the functions with the processor instead of just the PanelView. 2) I would like to have a recipe file viewer or conversion program so I could view the file on my computer.

[Noely 0]

I have used a Westermo GDW11 GSM modem with a SLC 5/03 and it works very well. I connected it through the DF1 port. Please see the attatched pdf. www.westermo.co.uk GDW_11_6615_2201_REVA.pdf

[jeyaprakash 0]

pdf file not show on this web site