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  • looking for a good communications PLC

    Howdy all, soooo, i have a need for an inexpensive but robust PLC to handle RS485 communications with multiple blocks and would be only used to display data on a screen.
    Ive been looking at the productivity 2000. any other suggestions? some I/O may be needed at some point. does the 2000 have a good track record for this type of communications?


  • #2
    Don't know the PxK line, but inexpensive/robust/485 sounds like a BRX or other Do-More to me. If you're only doing data display, do you need a PLC to aggregate? You might be OK with a HMI that polls all your data sources, either one with a built-in screen or Weintek type that has video output so you can use a generic monitor if you want large screen. Or a PC-based HMI might be another alternative.

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    • #3
      Either a BRX or many HMI's will also add data-logging, which might be of some value to you. Also, some HMI's (Idec for one) will allow you to add some I/O, and some will allow the I/O to be used for logic as well as data collection.

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      • #4
        Thanks Control Guy

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        • #5
          The P2k is a good RS-485 platform, but so is the BRX.

          How many RS-485 ports do you need? The BRX has 1 built in, and you can add one:

          https://www.automationdirect.com/adc...-dm1e-10ed13-d
          https://www.automationdirect.com/adc...-10e)/bx-rtb10
          https://www.automationdirect.com/adc...bx-p-ser4-term

          $388 for BRX with 2 ports, and 2 ports is the max



          The P2k has 1 built in, and you can add a dozen more if need be, but it would be expensive. RS-485 is for multidrop so I doubt you need more than 1-2 but figured Id mention the P2k can add a dozen of them if you need to connect to a bunch of different networks. Having more than 2 ports could be handy if you have some drives or other devices running 9600baud, some 19.2baud, some 33.6kbaud, and/or some 115.2kbaud. Useful for connecting a bunch of different networks in 1 PLC. You could use all the extra RS-232 ports to control a crap ton of stepper drives if you need to also. lol

          https://www.automationdirect.com/adc...)/bases/p2-04b
          https://www.automationdirect.com/adc...pplies/p2-01ac
          https://www.automationdirect.com/adc...remotes/p2-550
          https://www.automationdirect.com/adc...working/p2-scm

          $558 for P2k with 2 ports, additional ports are possible



          Or the P1k also has a single built in RS-485 port and the same overall functionality as the other Productivity lines with code that can be moved between each series. The 1000 can not add any additional ports at this time though, you only get the 1.

          https://www.automationdirect.com/adc...c)/cpus/p1-540

          $169 for P1k with 1 port, and 1 port is the max.
          Last edited by MikeN; 10-29-2018, 05:41 PM.

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          • #6
            The Productivity's make array usage very easy. So if you need to store logged data from network communications in arrays you can do that. It also has a minimally good actual logging feature that you can use to store data on a MicroSD card you can take to a PC later. Getting data off of the Productivity and onto a PC is difficult and/or costly outside of the very basic logging features.

            BRX has pretty good logging features where you can save all sorts of data to different files on a MicroSD card. You can then either take the MicroSD card to a PC in the same way as Productivity, or email those logs to you any time you want. They are also building a very nice web feature to view data and is supposed to offer easy manual downloading of data logs from PLC to your PC via a web browser. If you need to keep a log and get those logs to a PC, then BRX is the one I would use.

            If you do not need to keep extensive logs or get the logs to a PC, then the P1k is the one I would use. It is the cheapest by far and extremely small, yet offers powerful features and speed for its price.


            Both lines of PLCs have memory buffers for RS-485 and allow easy automatic polling with minimal to no interlocking nonsense needed. The only time you have to manually block out communications sections of the code is if you have so many devices you start filling the buffer and then you have to sequence groups of devices a bit more. I dont know the exact amount of buffer memory in either the P1k, P2k, or BRX. However I would suspect the productivity has the most as all of them have 50MB basic program storage space and I notice they tend to just have higher capacity in every way that a BRX. So depending on how many devices you have, a Productivity may offer more ease of use as you probably wont fill the buffer as fast, allowing more devices.

            EDIT: The P3-SCM seems to have 1 megabit of memory on the module. Could BobO chime in on how much buffer memory the RS-485 POM has as well as the main units buffer memory? I would look but I only have USB and Ethernet POMs here.


            This is what the instruction blocks of the Productivity and BRX look like for the ladder logic:


            Productivity:
            Click image for larger version  Name:	P2k.png Views:	1 Size:	66.9 KB ID:	118757




            BRX/Do-More:
            Click image for larger version  Name:	BRX.png Views:	1 Size:	29.2 KB ID:	118758
            Last edited by MikeN; 10-29-2018, 05:50 PM.

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            • #7
              Not sure the buffering comparison is apples to apples. All of our comms are fully buffered. Deep buffers are only required if running as a co-processor and there is delay between the CPUs (like an I/O scan).

              Won't help the OP now, but the BRX SERIO module is late in development, and will add 4 additional RS232/485 ports per module. Supports all CPU protocols, plus the addition of DMX512 master and slave.

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              • #8
                Thanks Mike, I did notice the scan time on the P1 was 1300mS. I dont like having to use the panel real estate for the P2 or 3. Im looking at the Do-More now. downloaded the software to see how it ticks. Im used to..... big drum roll.... allen bradley and rockwell. i suspect the capabilities are limited by comparison but dont need anything fancy on this one. just need to get some data from proprietary controller and display on a screen. might be a whopping 25 words max. may need to add some I/O to help with some testing functions but mostly just basic communications. I have used the P2 in the past and the program is a bit weird but once I got used to it i realized i could do quite a bit with less code than rockwell but was limited in ways rockwell is not.
                There is limited need for local datalogging but planned on doing that in the HMI.
                jb
                monkey C monkey D

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                • #9
                  Originally posted by BobO View Post
                  Not sure the buffering comparison is apples to apples. All of our comms are fully buffered. Deep buffers are only required if running as a co-processor and there is delay between the CPUs (like an I/O scan).

                  Won't help the OP now, but the BRX SERIO module is late in development, and will add 4 additional RS232/485 ports per module. Supports all CPU protocols, plus the addition of DMX512 master and slave.
                  DMX512!?!? Thats awesome. I have a fun use for that I bet I can sell someone on...

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                  • #10
                    Originally posted by MikeN View Post

                    DMX512!?!? Thats awesome. I have a fun use for that I bet I can sell someone on...
                    We've had multiple requests, I'm a musician familiar with its use, and it was virtually free to add.

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                    • #11
                      Originally posted by jboothby View Post
                      Thanks Mike, I did notice the scan time on the P1 was 1300mS. I dont like having to use the panel real estate for the P2 or 3. Im looking at the Do-More now. downloaded the software to see how it ticks. Im used to..... big drum roll.... allen bradley and rockwell. i suspect the capabilities are limited by comparison but dont need anything fancy on this one. just need to get some data from proprietary controller and display on a screen. might be a whopping 25 words max. may need to add some I/O to help with some testing functions but mostly just basic communications. I have used the P2 in the past and the program is a bit weird but once I got used to it i realized i could do quite a bit with less code than rockwell but was limited in ways rockwell is not.
                      There is limited need for local datalogging but planned on doing that in the HMI.
                      jb
                      monkey C monkey D
                      There are definitely areas that Do-more/BRX could improve on, but I've never heard anyone say it was limited compared to AB.

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                      • #12
                        I am a huge fan of the productivity series for the easy learning curve but there are some ares where the BRX has some nice features that might make some of my projects have a bit more polish to them (E-mails that you can attach log files to for one) but am sure the AD Productivity team is hard at work adding some of the nicer features

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                        • #13
                          Originally posted by BobO View Post

                          There are definitely areas that Do-more/BRX could improve on, but I've never heard anyone say it was limited compared to AB.
                          I can't speak for the OP, but one has to think a workaround in Do-more when coming from AB like myself. For example, the inability to perform a typical array. I know you've explained the use of Pointers on the Host forum is the solution. The Do-more is a fine platform, as I've used it on five machines without problem, but it did involve thinking differently. And there is the rub, not knowing "how" to implement in Do-more what one has done in RSLogix.
                          Why worry? If you've done the best you can, worrying won't make it any better

                          - Walt Disney

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                          • #14
                            Originally posted by Todd Dice View Post
                            I can't speak for the OP, but one has to think a workaround in Do-more when coming from AB like myself. For example, the inability to perform a typical array. I know you've explained the use of Pointers on the Host forum is the solution. The Do-more is a fine platform, as I've used it on five machines without problem, but it did involve thinking differently. And there is the rub, not knowing "how" to implement in Do-more what one has done in RSLogix.
                            What do you mean by a 'typical' array? Every Do-more memory block is a single dimension array addressable directly as Block0 or indirectly as Block[X].

                            If you are referring to 2 or more dimensions, then yes, it requires a little bit of knowledge. It's the difference between Block[Y][X] vs Block[Y*RowSize+X].

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                            • #15
                              Originally posted by BobO View Post

                              What do you mean by a 'typical' array? Every Do-more memory block is a single dimension array addressable directly as Block0 or indirectly as Block[X].

                              If you are referring to 2 or more dimensions, then yes, it requires a little bit of knowledge. It's the difference between Block[Y][X] vs Block[Y*RowSize+X].
                              Typical meaning formatted like an Excel spreadsheet. It is how it is done in RSLogix/Studio 5000.
                              Why worry? If you've done the best you can, worrying won't make it any better

                              - Walt Disney

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