Connecting a PLC to an existing wireless network

[markymark31]

Can it be done ?

I've seen suggestions with routers etc. but surely this would be if I wanted to create my own wireless network ?

How do I go about this if there is already a wireless network in the building that I want to put my PLC & HMI on to ?

As always, any suggestions will be greatly received !

Mark

 

[Johnster]

I'm going to assume that you've given security some kinda thought here - if the existing wireless is on the internet (even behind a firewall) you are exposing your plc/hmi network to Viruses/Malware/DOS attacks from the outside - I would never do that in my plant (electric generation infrastructure), but yours may be different. Remember that wireless also opens up our threat surface - anyone sitting outside the fence with a good antenna can get onto your network or at least try (highly recommend WPA2 encryption - WEP can be hacked too easily)

Wireless also introduces more latency (delay) in the I/O transfer process - usually 10ms or 50ms but up to 2 or 3 seconds of your network is congested - keep this in mind.

That being said...
It should just be as easy as buying a wireless router (any off-the-shelf model will to), setting it up on the existing network (make it a 'repeater' or range extender), then plugging the PLC into the new wireless router.
some PLC manuf's make wireless cards for thier machines, but I'm not very familiar.

I'd be very wary of security with a PLC/HMI on wireless.

 

[JesperMP]

How do I go about this if there is already a wireless network in the building that I want to put my PLC & HMI on to ?

There must be a router.
Simplest is if the router can have a fixed IP on the port that is connected to your PLC, or network to several PLCs/HMIs.
On the other side of the router, it typically is set up to DHCP to easily connect to the companys LAN.

If the companys own router cannot be setup with one port with fixed IP, you simply add your own router in between:
PLC (fix IP) --(LAN1)-- (fix IP) Router (DHCP) --LAN2-- (DHCP) Router

The PLCs/HMIs should have fixed IPs, and must have the routers fixed IP as "gateway".

From then on you can connect to all PLCs and HMIs from the company LAN side.
If the company LAN has wireless or not is irrelevant to you.

 

[Paullys50]

If wireless exists, chances are it's only setup for the "Business" network. Hopefully you won't ever see a controls network and business network mixed...but you never know. So chances of you getting online with an existing wireless is slim without IT intervention...dun DUN DUNNNN!!!!

With the right IT involvement you can isolate business and control networks using routers/gateways/DMZ/VLANS....but the time vested to do this would mean you are planning for a permanent wireless implementation.

If you are looking for a temporary solution, configuring a router as an "Access Point" works great, I do this all the time when I am onsite (if the company has no objections). Bring my own router and configure it with a static control network IP address, give my laptop a static IP as well and I'm off to the races. Works extremely well for IO checking, or when you are looking for a more comfortable spot to program.

I typically setup the router for non-broadcasting with WEP security. At the end of the day everything gets unplugged, and with only 1 access point within a plant chances of that wireless getting outside of the facility are very slim.

 

[Dravik]

You can use a Workgroup Bridge to accomplish this pretty easily.

Talk to your network admins, Cisco APs can transmit multiple SSIDs using the 2 radios. Likely you could put one channel to the standard wireless and have them setup a separate VLAN and SSID for your process management stuff.

 

[shawn_75]

If the existing wireless network is already yours, go ahead and connect into it.

For the same reasons one wouldn't connect a PLC to the 'front office' network, I would never connect a PLC to a wireless network that falls into the same category.

You'll need a wireless bridge on the PLC side and a compatible access point on the network side. In theory, any wireless bridge will do but it is best to have the bridge and access point made by the same mfg. I am using these:

http://www.engeniustech.com/index.p...nts-client-bridges&id=3381:eoa3630&Itemid=123

This is an outdoor AP/bridge/router etc... I like that it is outdoor rated (keeps the dust and dirt out). You can setup multiple SSIDs on different VLANs with these APs. I use WPA2 security along with MAC address filtering. These would also work with a radius server.

 

[arunsinha]

I think it has been covered, but you can set up a WiFi network separate from any IT network by using a Wireless Access Point (like the N-TRON702-W). If you haven't selected your PLC yet, there are PLCs & PACs out there that support 802.11 (a,b,g), i.e. wifi, natively.