PLC5

[simon Ong SK 0]

Hi Guys: I'm new with AB. Can anyone help me to configure this? A PLC 5 communicate to a MicroLogix (Model???) which the Micro is going to read a external device with RS232 com protocol. 1) which Model of Micro and what PLC5 card should Add? 2) What command Do I need to use at PLC5 and Micro? 3) What is the differences between DH+ and DH485. 4) Someone suggested to add 1771-DB (Ascii card?) to PLC5. But the proble does AB Pbase (Basic Software) supported with XP? Please help to get the optimum solution. Thx and regards Simon

[Ken Moore 23]

What model of PLC-5 are you using? Different models have different capibilities. Do you already have an existing control communication network? If so, which one?

[gravitar 3]

Hmmm.. Let me break this down and see if I follow.. The micrologix needs to use its RS232 port to talk to some other device. The PLC-5 needs to talk to the micrologix. I'm asusming you can't just get by with passing a few discrete signals back and forth from the PLC-5 to the micro.. Like Ken said, we'll need to know which PLC-5 because some have RS232 ports built-in and some don't. Also we'll need to know what model micrologix (1000/1200/1500) and what the other device is that you're trying to talk to.

[gravitar 3]

Oh, and as long as we're at it.. DH485 is a communication system used on the SLC-500 and micrologix controllers. The terminology gets confusing because there's two separate things you need to consider.. the DH485 physical media, and the DH485 communication protocol. DH485 hardware is based on the RS-485 standard, and uses twisted-pair media and differential line drivers to allow communications over LONG (up to 4000') distances. It also allows for a daisy-chained multi-drop network of up to 32 nodes. BUT.. Here's the catch, the DH485 communication protocol can also be implemented over an ordinary RS232 link! The nodes "see" the same data but you lose the long-distance and multi-drop capability. I mention this because that is how DH485 is implemented on the Micrologix.. If you want "full" DH485 capability, you need the add-on 1761-NET-AIC module. DH+ is a little simpler to understand, in that it is only implemented one way, using only one type of cable, etc. Like DH485, it allows for long-distances and multi-node communication. DH+ is more or less reserved for the "higher end" of PLCs. It is faster, longer, and gives you more nodes than DH485. All PLC-5s have it built-in, also the SLC 5/04. It can also be used with PLC-2,3, and ControlLogix with optional interface cards. There is NO WAY I can think of offhand to do it on a Micrologix. The 1771-DB is the "BASIC" module. It is named that because the card contains an 8-bit microprocessor with a BASIC language interpreter built-in. It can communicate over the backplane to the PLC-5 and also be programmed to communicate through the serial port. I believe it has DH485 messaging capabilities built-in, so this might be useful to you. One thing to watch out for is the series of 1771-DB module you're using.. the Series A and B modules are VERY different. (I only know this because the series A modules are highly coveted by the GM Truck & Bus group, and when I worked for Mac & Mac I had to find and hoard them for when GM came a-calling.. :) Anyway.. you also mention PBASE. PBASE is a nice luxury, but not necessary for programming a BASIC module. You can just connect to it with a "dumb terminal" program like Hyperterminal and you'll do just fine. As for PBASE I'm not sure if it would work in XP, I seem to recall a thread on this very subject recently so search this forum and see if you find it. In general though, I try to run DOS programs that use the serial port in a real DOS environment.. In other words booting up in DOS-mode on a W9X platform. You also mentioned the ASCII card, that is the 1771-DA but I don't think it would do what you want for this application. One other possibility you might be able to use is DF1 protocol directly from the PLC-5 to the Micrologix, but we'll need to know what model of processors you're using. Edited 21 Dec 2005 by gravitar

[Guest]

first things first ... EXCELLENT write-up, gravitar ... I’m putting this one on my “Favorites” list ... now on to Simon’s problem ... somehow I can’t help thinking that there might be an easier solution to this lurking somewhere just beneath the surface ... Simon, I suggest that you take a few minutes to outline just exactly what you need this system to do - and then let us see if we can suggest some alternate ways of doing things ... specifically, what type of control does the MicroLogix provide? ... and what type of data has to be transferred? ... and how much data? ... and how fast? ... basic idea: over the years, I have had several customers bring me “I-need-this-processor-to-talk-to-that-processor” problems ... in MOST (but not all) of those cases the cheapest/easiest/most reliable/best solution was to just let the main PLC-5 processor control the whole system (through a Remote I/O link, etc.) ... this approach eliminated having to keep up with a separate MicroLogix program ... and an additional software package (RSLogix500) ... and the convoluted communications between two dissimilar platforms (PLC-5 and MicroLogix) ... naturally I don’t know enough about your system to say for sure whether this “one-processor” approach would work for you or not ... but I’d suggest that you at least think about this idea before you dive into the deep end of the communication pool ... ask yourself this: if it’s THIS hard just to set the darned thing up, how hard is it going to be to troubleshoot and maintain it? ...

[gravitar 3]

Thank you!! My bread-and-butter back in my Mac & Mac years was setting up PCMK cards on obscure platforms and explaining DH+/DH485 networks. Oh, and I had the entire A-B price book memorized (kinda like the movie "Rain Man"). To this day I'm not good for much else :) Back to the original question though.. I think you bring up a good point. Is the Micrologix really "needed"? Perhaps he MUST have the local control at the remote end, even if the cable gets severed or the PLC-5 otherwise fails. Maybe he's using a radio link, but I can't imagine him forgetting to mention that!

[simon Ong SK 0]

Hi guys: Thanks for all the advices! I could not reply as I’m waiting for the correct PLC information! The Only Information till now I got: PLC5/40. (will post the latest info if I got one) Here is the actual scenario: Existing equipment is using PLC 5 to perform measurement by means of multiple analog signals from external measuring controller. There are numerous probes connected to this controller, so this controller will distribute the analog signals to individual analog input Card on the PLC 5. Then the PLC5 will performed calculation and determined the status of the measured specimen, the data then will be captured and displayed at Panel View. End user decided to find alternative (without discarding the PLC 5!) after a lot of rejects found a long the process line. There are multiple standalone measuring station at the production line using PLC5. Note: The same PLC5 also perform other tasks. So, the measuring equipment agent proposed to change the current equipment to digital measuring equipment with RS232 capability (No RS485/DeviceNet/Profibus model available). So at that point of time 1771-DB seems to be the answer. I did some reading, that why the Micrologix came to mind (1200 or 1500). The Idea is to use Micro to perform the measurement and in real time (peer to peer?) data will pass to the PLC5. Besides the end user using some controller which they could performed online diagnostic. Micro will have to perform send and receive tasks. Like send a string to the controller and read the result from the controller, then perform calculation and summation. Then the calculation result will be posted back to PLC5. ------------------------------------------------------------------------------------------- Today, I got a Micrologix 1500 LRP (2 RS232 Com), I used Channel 1 to read a Weighing Scale (Just to test the Serial Com Port). I can perform Ascii Read, But the LED of the Channel 1 Com did not Blink (should it be like the Channel 0? Just Like Online?) I had to performed Ascii Buffer Clear when the Ascii Read is done (R6:0/DN) otherwise the string will not be updated. Am I correct?? Thanks for Help Again….Merry Christmas and Happy New Year.