Wireless Monitoring

[Bob O 8]

I am going to be installing a number of flow switch through out the plant and my boss asked what is would take to go wireless instead of pulling network cables to each machine. I am using the ML1100, RSLinxGateway, and RSView32 and we are going to monitoring water flow, and the number of time an alarm has been set. Any ideas or recommendation is appreciated. Thanks, Bob

[TimWilborne 108]

PLC to PLC does not work on store bought wireless. You need something like Prosoft or Datalinc PC to PLC is possible on store bought wireless but it depends on a few things 1. What is the line of sight like 2. What is the distance 3. What is the environment like? 4. How often do you need to communicate with the device? 5. Can you deal with an occasional missed packet?

[Guest low on the pole]

Just a comment, Don't ever download wireless, from a laptop to plc. You will regret it. I had laptop on a cart right under wireless transmitter and reciever. Thought it was safe to do. It wasn't. And I regreted it.

[TimWilborne 108]

Did it just lose communications during the middle of a download and you had to start again or was it worse?

[Bob O 8]

TWControls, I have “stuff” going on outside of work so I will look into your questions next week. Thanks Bob

[TimWilborne 108]

Hope it's not bad "stuff" Take your time, no hurry

[Guest low on the pole]

TW, It actually set the presets to about 100 different timers in different file numbers i.e. t;100,t;140 to zero. It was on a large juice processing line with about 70 a/b 1305 drives over remote i/o.It played havoc, it was at the end of a cip. All the toetappers were out and about, and made my day a real pleasant experience. The things you learn by doing, it's amazing.

[TimWilborne 108]

Wow that is bad. I haven't experienced any problems like that but the one thing I will say about wireless, for now, consider it a convenience and not a necessity. Wireless is great for troubleshooting but make sure you have a wired hookup near by too. Especially store bought equipment, it is very fragile in an industrial environment. And this includes the wireless card in you laptop. I have lost one of them too

[autocontrolit 0]

Actually I have a wireless set-up in my facility using off of the shelf Netgear WAPs and 5-port ethernet hubs. The wireless allows a SLC 5/05 on a transfer car to communicate with another WAP that links 3 other 5/05's as well as a PanelView 550 & a PanelView 1000. The set-up works well and is reliable, only issue as far as the network is the 550 on the transfer car constantly looses connection and the error will not go away until you tell it to. We also have another wireless network running Parallel with Linksys WAP's more for monitoring/troubleshooting. I did learn the same lesson online edits are ok, but downloading over a wireless is not recommended.

[DanW 41]

If your situation is inside a factory plant, you'll have to encounter fairly high hard wiring costs to justify going wireless. Industrial I/O wireless costs are on the order of $700 - $1400 per point, at least an order of magnitude greater than PC 802.11x wireless (at less than $50/point). My experience shows that wireless wins when wiring involves trenching, getting across a road or pond, hazardous areas, really remote locations, like outside storage tanks, cooling ponds, water towers; or across a really large plant (steel mills and refineries that cover square miles). For a manufacturing plant inside a 20,000 square foot industrial building, it probably costs less to wire it, unless wiring encounters extreme obstacles, which could be physical or political, depending. When you mention "pulling network cable to each machine", I suspect you're not a wireless candidate. If you have to read a discrete switch, then you're talking industrial I/O wireless, rather than wireless data communications, say rack to rack, PLC to PLC or HMI to PLC. So that leaves out 802.11x stuff, which, by the way, does NOT have the noise immunity of industrial wireless in the same band. "Industrial wireless" is "industrial" for a reason. For an example of wireless flow switches, I worked on an installation of wireless transmitters at a refinery where standard mechanical flow switches monitored safety showers. Hardwiring was estimated to cost in excess of $100/foot, for the Class 1 Div 1 hazardous areas the safety showers are in. At that cost, given the widely spread apart locations of showers, wireless made a lot of sense (saving hundreds of thousands of $) The devices used are transmitters that take a dry contact, transmit the status of the contact to a central receiver. The receiver uses Modbus RTU to get data to the installed control system, by plant choice. The alternative could have been to recreate the switch outputs as DOs at the central receiver. The Honeywell transmitters are battery powered so they don't need power wiring, have IS (intrinsic safety) rating for hazardous area and are NEMA 4 for outdoor weather protection. The Honeywell model was close to ideal for that environment. However, each switch transmitter costs about $1300 (some with high gain antennas, even more) and the central receiver is about $2k. The layout was such that only one DI could be used per transmitter, due to the extreme costs of hard wiring a second DI to a transmitter. If it had been a safe area, not a hazardous area, where a couple switch contacts could be consolidated at one transmitter, transmitter costs could have dropped significantly. I've also used Phoenix Contact wireless, which is not battery powered (needs 24Vdc). It has standalone tranmitter-receiver sets that simply replace wire - put a discrete contact in at one end, get a discrete out at the other, at about the same cost: $1300 for a combo transmitter/receiver, which can handle 2 discretes. Other models can handle large number of discretes, but then one has to wire the field switches to a central point. Being a powered system, Phoenix Contact has much greater power and can handle longer distances. To see if wireless makes sense at all, get a number of your cost of wiring/foot (or meter, depending on where you are) from someone who's done a project recently, make a sketch of the area, pace off the distances, don't forget that indoor wiring typically goes up, across, and then down, so add in the ups and downs; total your distances and calculate where you come to for wiring costs. Dan