Ausman

Hi all, thanks very much to everyone for their input. I love your comment, Joe, about wire vendors being "proud". Also, about "getting familiar" with modbus, I am doing lots of workbench mockups for my knowledge increase, before committing it's use to the project. If I decide to go the bus way I'll bite the bullet and invest in some proper cable for the final install as it looks to be the only surefire thing. Cheers from Aus,

Thanks Paul, I realise now I should have been more specific, sorry. It's Modbus RTU on 485 with the 130 as a master getting info from various modules by other makers. Call me cheap!, but it's just that I've been a bit amazed at the prices of 'proper' 485 STP 1.5 cabling and was wondering if I really needed it for the runs I might be doing, or might be able to get away with a cheaper alternative. I've read of lots of people using some of the twisted pairs on ethernet cables quite successfully. thanks for the help, Aus

Hi all, I know this is a dumb question, but I am considering using Modbus on a job. I have never had to use it before, with components normally fairly close together and direct IO being perfectly adequate. I have read far and wide about cable requirements and need some advice from those who regularly use it. To do a run of 40m max, am I going to get away with Cat5 in a fairly noise-free environment? Using one pair as signals and another commoned as the ground, with the other two pairs perhaps being used as 24dc digital IOs or as spares. I guess I am really asking what types of cables have people used for what distances? V130 as controller, speed isn't that important but it has to be reliable. Cheers from Mr Modbus-Know-Nothing-but-Learning-Fast!

Thanks Emil, and everyone else for their input. I think that I'll go down the 2 x 230 on ethernet path as it looks to be the easiest. I'm sorry I didn't think to ask about snap-ins in the first place...brain stuck on a misconception. This solution is a bit like that elegant bit of programming you've done. You work on the issue and eventually arrive at something far simpler and better than what you started with, then look at it and wonder why you didn't think of that in the first place! Learn something new every day, so thanks to all. Cheers from Aus.

Thanks for your very helpful suggestions Simon, I know this is a dumb question, but is it ok to operate a 230 without a snap-in and just be connected to IOs via the expansion port? It has just occurred to me that this would give me simple ethernet only connections using the two 230s I have, instead of one 230 and one 120, but I have always thought they needed to have the snap-in attached. From what Emil and Joe say it appears that ethernet is easier to set up and this way I would only need to get one 19-ET1. Call me chicken, but I don't want to try running the 230 without the snap-in without someone telling me it's ok! I can't find anything about this in anything I've seen so far, but it's probably in a manual somewhere. Visilogic doesn't seem to mind it as a build config. cheers from Aus.

Additional relevant info is that I only have one snap-in for the 230, though, hence not able to use both 230s that I have. I know, I know!!! I shouldn't be so cheap, and just go and spend some more $! cheers, Aus

Thanks Joe and Emil, I agree a 130 would make it far simpler, but the issue is that I already have the 120 and 230. I had a job a few years ago that got changed, leaving me holding a fair few items....grr grr. This install is actually on my own property so I am just trying to save some $ as I have two of each controller along with a heap of IOs. cheers from Aus,

Hi all, A new forum member but have used small Unitronics gear on and off over the years. Question is a bit involved but please bear with me. I normally only work with standalone controllers, but I have a situation where I am going to be using two controllers and IOs that I already possess and may as well use…a V230 and a 120. I have an Ethernet card for the 230. Both PLCs are going to be using analogue IOs as well as digital. Having two controllers is best from a redundancy aspect in that the two main plant rooms will have a controller in each. The setup is controlling a small but complex pump, valve and power system. The issue I have is that I have to work around existing cable limitations tying in to the lack of Ethernet port for the 120. Both plcs have to be able to be accessed via remote. I have looked up programming examples a bit, but perhaps the easiest solution is if I pose my situation to the forum where hopefully someone can give me quick answers that won’t take too much of their time. The cable problem is that I only have 2 free cat5 runs between where the 2 controllers have to go. 1 end is near the router that will provide remote access. The other end is 80m away, which tests fine on Ethernet and also using the cat5 as 485. Owing to very full and awkwardly placed conduits, I simply cannot run any new cable between the endpoints, so Canbus on dedicated cabling is not possible although it would have saved me having to post this!! I only need to be transferring around 6 words of data b/n the two controllers in both directions, and speed isn’t essential. It is just so that some info can be seen and perhaps acted on at either end. So what will be the best layout? It’s a bit of a conundrum! I have the following ideas: 1). The 230 or 120 at either end, with the 230 on Ethernet and the 120 connecting by a serial to Ethernet/wifi adapter, but can communication between the two happen over this style of link? As in Ethernet talking to an essentially much slower serial conversion that is still ethernet? I could possibly use some spare pairs in the unused cat5 line to do digital signals b/n the two controllers to say a particular communication was happening/should happen etc. 2). The 120 at the far end, linked to the 230 by 485 with the 230 on Ethernet for remote access. However, my understanding is that I cannot remote access via Ethernet any controller linked by 485, although I can set up transfer of data b/n the two on 485. 3). Perhaps a variation of no. 1 where the controllers are linked by 485 for intercommunication, and I also have the serial to Ethernet adapter on the 120 to let me get into it remotely as well as the 230 by its native port. This one seems the most likely to me. 4). Somehow run canbus on the cat5, although everything I’ve read says this is not possible. 5). Put your suggestion here!! Trusting that you can see my puzzle! But don’t let me take too much of your time! This is not an urgent job and I will likely only check the forum/post once a day, so please don't be offended if I don't answer immediately. Cheers,