Data communication 1 mile away


#1

I plan on replacing a network of three old modicon quantum PLCs with SNAP-PAC-EB1 and Opto IO units. The existing data communications between the old modicon units use RG-11 coax. When I replace the modicon PLCs with the SNAP-PAC-EB1s, I will need to communicate with them via ethernet but the third modicon unit is quite a distance away - close to a mile. I am considering different options to communicate with the EB-1 that will replace the third modicon quantum unit. One option is to utilize the existing RG-11 coax and a converter. Which brings up my first question: Are there any recommended RG-11 to ethernet converters that would work for this situation? Or does anyone have any other ideas that I can use to establish data communications at such a distance?

Otherwise, my other thought is just replace the RG-11 with a Cat 7 cable.

Thank you.


#2

Too far for CAT7. An RG-11 bridge device is probably worth a try. I have no recommendations other than what comes up in a google search. If you have line of site, you could do wireless - I’d look at the Ubiquiti Nanostation models. We use their normal wifi access points, and they work quite well.

Either of those options should be more cost effective than running new cable/fiber. (Or do both and have some redundancy.)


#3

Have you looked at our serial SNAP brains?
http://www.opto22.com/site/pr_details.aspx?cid=1&item=SNAP-PAC-SB1

They will hang off the back of a 1 mile serial drop.
(Not sure if lighting is an issue, if so, I can only recommend fiber optic or wireless).


#4

Thank you. One option that I have seen may be an ethernet over coax converter:

http://www.veracityglobal.com/products/ethernet-over-coax-devices/highwire.aspx


#5

Thank you. What are your thoughts if I use EB-1s to replace the first two Modicon Quantum units and SB-1s to replace the third Modicon Quantum unit. I can run Cat 6 or 7 cables for data communications for the first two locations (the new EB-1s will be in the same spots as the first and second Modicon Quantums). Then run RS-485 from the last EB-1 to the SB-1 unit to replace the third Modicon Quantum. Will this work?


#6

Looking at it, I would go with your coax to ethernet adapter and just run all three locations as EB’s.

What controller (in what location) are you planing on using?
In other words, three EB’s and no controller is very unusual.


#7

That one doesn’t look to meet your distance requirements.

Here are a couple I found that state they can do the distance.

Startech EOC1110K

Antaira EVC-3010
http://www.antaira.com/core/media/media.nl?id=266575&c=685553&h=2b7e747d8b80e95ab7bd&_xt=.pdf


#8

I will be using a DCS controller by Control Systems International, Inc (CSI). I have been using CSI controllers to communicate directly to our Opto 22 EB1 units via ethernet. The older Quantum PLC is actually just for IO and I am replacing it in favor of the Opto 22 units. Later I will have to upgrade the DCS controller to it’s current version.


#9

thank you philip. i appreciate the information.


#10

You’re welcome.

Please note, I haven’t used either of those, it’s just what I found doing a google search. Of those two I found, I would probably try the Antaira unit. I like the datasheet better, and they are local and build equipment for industrial applications. Startech is more towards the IT/consumer side. Ignore the gigabit of the Startech, you won’t get anywhere close to that, it appears to be a marketing feature.


#11

Hi,
We upgraded a WWTP from quantum to R1’s and tried to reuse the old coax with Ethernet converters. It was very unreliable (slow and crashed a lot).
We wound up using ubiquit radios and it has been working great for 5 years.


#12

Remember, long runs of communication conductors unless run in metal conduit and supplied with a ground wire (not the drain) that connects the ground of both sides will be guaranteed to fail regularly. The foil shield on instrument cables is not sufficient for shielding low frequencies <1 mhz. The freq component of lightning strikes are 100-200 khz. The resonance of long cables 50’+ is essentially a tuned antenna for VLF frequencies. Just a nearby lighting strike maybe as much as 300 feet away is enough to blow quality surge arresters off both ends of a long run like that.

Depending on how this coax was run, you might be way better off with fiber. You can have these cable outfits provide you with a fiber run as long as you need with ends attached and pull eyes ready to go. With single mode 20 km is common. You can buy 2 - Mikrotik routers with fiber ports for <$300 including the GBICs. The pre-made cable will probably cost you about $2600 for a full mile but you would have a bullet proof connection for the extended future.

A less expensive and only slightly less reliable would be a Mikrotik PTP wifi link at 5.8 gig. If installed and implemented correctly, it would provide you 100meg duplex + if there are no obstructions to the LOS. With this method depending on units used and LOS, you can do 10+ miles. Two SXT’s will give AC connection at 1 mile and they only cost $109 each. The key here is grounding the SXT with a copper conductor directly to a real ground on each end and powering the SXT and DC injector from a UPS.


#13

+1 on the ubiquiti wireless bridge setup. We use one for some cameras about 1/2mi away. It has been really reliable. I have not messed with it since we set it up. Other than re-aligning the antennas due to birds perching on it. It actually still worked with them way out of alignment.


#14

You might peek at https://www.digi.com to see if there is anything there that will work for you. I’ve used the 2.4 GHz stuff, but the 900 MHz stuff claims up to 28 mile range. Then they have a
Digi XLR PRO® Long-Range 900 MHz Industrial Radio.


#15

Nowadays, the 900 spectrum is soooooo messed up that you are luck to get anything to work reliably other than real short distances with few obstructions. It used to be a pretty good band, but unless you are doing something like this where it is only 1000 feet of relatively unobstructed LOS, it may have problems. I have a wisp for my neighborhood and a client that was only 1000’ away and it worked but barely. Now to be fair, there was a fair number of trees in the way, but 900 normally can do this with no problem.