Wireless Ethernet/IP recommendations

Hi all,

I'm throwing together a broad design outline for a customer which will likely require some sort of wireless Ethernet/IP link, and I'm looking for some recommendations for equipment that you can vouch for

Basically, customer wants a mobile counting/weighing station that they can wheel into position at 4 or 5 different places and run. They want to control this via the central ControlLogix PLC and interface it with the existing FTView SE SCADA system.

So my plan is:
- A 3 phase outlet at every location they want to use it
- An onboard point I/O rack with ethernet adaptor
- Some sort of wireless uplink to the main panel

I'm not sure whether I'd be best to set up a dedicated point-to-point wireless link, or utilise the existing factory wireless network. I figure a dedicated point-to-point setup would be the most reliable, but I'm cautious because of the area range they want to use this thing over.

If I use the existing wireless, I know that all of the WAP's are on a different subnet to the PLC's. There is a layer 3 router in place, so I don't think there'd be any issues, but I've still got some more reading to do on that

Can anyone share any success stories (or miserable failure stories!) with an arrangement like this?

Thanks!

Oh, yeah, I've got stories. But they are not pleasant and have no heroes and I will not tell them here.

In general I very strongly recommend dedicated wireless networks for I/O and automation. Accept that you *will* lose packets and *will* get disconnections and plan accordingly. Don't even think about installing equipment before doing a spectrum analysis of the area.

If you're sticking with Industrial Line...

http://ab.rockwellautomation.com/Networks-and-Communications/Stratix-5100-Wireless-Router

I would recommend a stand alone controller for the weighing station, probably a compactlogix, and use messaging over wifi back to the HMI and main controller.

Also, we have used Ubiquity stuff with very good success.

If you're going to have a 3ph outlet at each station, why not add an industrial plug for hard wired Ethernet? We had a similar setup in the last place I worked, an auger on wheels was moved between 4 stations. Two sockets, one for power, one for IO feedback such as analog level sensor. With frequent moving, be prepared to replace plugs and cabling on a regular basis.

I wouldn't do remote/IO via wireless. Put a PLC on the rack then do message to it.

what the_msp said! save yourself the hassle and plug in an ethernet along with the power.

There are several ways to skin that cat.
First off you do want a dedicated network. This eliminates any issues you might not have control over I.E. the IT department making changes that all of the sudden makes your application not work anymore.
Second, if at all possible you want to do messaging when doing wireless. As Ken mentioned you will lose packets and with message instructions the process will sort it all out. That does eliminate anything related to EtherNet/IP UDP (Produce/Consume) but if the application doesn’t need “real time” data then that’s not a problem. To be clear, “real time” data is defined as literally that, real time. If you can tolerate 50mS+ (depending on the radios) then you should be OK with EtherNet/IP TCP (message instructions).
Next, pick your medium. You can go with slower but MUCH more reliable and robust Frequency Hopping Spread Spectrum in the 900MHz range (something along the lines of Data-Linc’s SRM6230’s). They will go a very long distance and in shorter ranges line of sight is (probably) not an issue. They are also very capable of dealing with any noise source. The drawback is the maximum data throughput is up to 100Kbps. With that said, with message instructions that typically isn’t an issue. The other way to go is a 900MHz OFDM type modem (Ubiquity sells some as does Data-Linc (FLC910E)). This is basically an 802.11g modem but at 900MHz instead of 2.4GHz. This gives you much higher speed but less range and more dependence on line of sight.
One thing you want to do is stay out of the 2.4GHz range. It’s very crowded and IT generally has control over it. 2.4GHz is also much more dependent on line of sight, has a much shorter range and is much easier to interfere with.
What you’re looking to do is actually pretty easily accomplished as long as you plan accordingly and design the system with wireless in mind.

Thanks for the input everyone! At this stage I'm inclined to agree that I should use a little CompactLogix rather than just a Point I/O rack.

Speed wise, there's no really critical data that needs to get back to the main plant urgently - just a few status tags, production data, and a call for product/don't call for product type arrangement. So no issues with a slower, more reliable link.

I've seen one of our clients have good results with a Prosoft unit, has anyone tried them? They have some units that use frequency hopping around the 900MHz band. They also have 2.4GHz and 5GHz units, but as somebody mentioned above, the 2.4 & 5GHz bands are pretty well used by the existing wireless network.

Ken/Firejo, when you suggest that I should use messaging rather than produced/consumed tags for my comms back to the main plant, why is that? I would have thought that either way I'm going to have occasionaly issues with dropouts, and I would have thought produced/consumed tags would recover faster than messaging?

Oh, and I'm not sure if it's relevant - but the plant wireless network is solely dedicated to control, and I have pretty more control over it than the IT guys. It has internet access via a gateway/firewall/etc but it's not for checking emails and browsing the web with in general - it's for the wireless barcode scanners and programming laptops etc. There's not a whole lot of traffic. That being the case, is there a possibility that I could use this network? I imagine it's still far less than ideal, but I'm just not sure yet how big their budget is for this project and it'd be good to know if it's at least plausible

Thanks!

Oh - and firejo - which ubiquiti units are you referring to? Their existing plant wireless is ubiquiti gear so they'd probably like the idea of staying within the brand...

While I do have a single wireless Point IO drop here, and it is working fine, it was only installed because there literally was no other option aside from digging up a road. I used a Prosoft frequency hopping pair, with directional antenna's pointed at each other. It is also not on any network in the plant, but lives in its own isolated little world.

I can't ever imagine deploying WiFi generally for controls. Especially if you have (or will in the future have) a corporate IT group... Shudder.

Thanks rdrast. From what's been posted here and reading elsewhere, I have to agree that using the wifi is asking for trouble. I think I'll just leave it out and only bring it out as a last resort (and with a big asterisk beside it) if cost turns out to be a really big issue.

So just to try and get my head around the one other issue -

When it's suggested that I should use messaging rather than produced/consumed tags for my comms back to the main plant, why is that? I would have thought that either way I'm going to have occasional issues with dropouts, and I would have thought produced/consumed tags would recover faster than messaging?

I message rather than use produced/consumed because:
A) I am writing specific messages to multiple, or may be looking for replies that depend on the message.
B) Produced tags permanently take a connection for each consumer, messages don't need to.
C) It is much easier to know when a message fails, and retry it (or take other action), then see the P/C link go down.
D) Messages can be created/modified and deleted online and on the fly.

I'm sure there are compelling reasons to use P/C tags, but as of yet, I haven't actually found any.

Have a look at Schneider's Trio J series 900MHz radios. Great diagnostics, I mainly use their M series licensed serial radios but have used a couple of Js before as well. You haven't mentioned what range these need to work over but they should be fine for a factory floor arrangement, mine are always for outdoor applications and i get several km out of them easily.

ASF said:

... They want to control this via the central ControlLogix PLC and interface it with the existing FTView SE SCADA system...

Click to expand...

Never ceases to amaze me how many end consumers dry hump Rockwell. I understand that's probably 95% of their controls they already have in place, but geez.

Anyway, I would try to stay hard wired as much as possible. Dealing with IT and wifi and SOP just sounds like a bad time.