Dear Friend & Subscriber:
It's almost impossible to believe that just 10 years ago a lot of people thought industrial networks were risky, unreliable and extravagant. Now people are doing I/O over wireless Ethernet.
Let's not forget that back then installing a modem in your Windows 95 computer often required eleven attempts at jumper switch configurations, device driver re-installs and machine reboots. Compared to all that, 75 feet of wire running from PLC to prox switch was a lot easier and a lot less expensive.
Still, I say: If Jane Q. Public can get her SMTP right and send emails to her tea-tasting friends, then wireless is surely practical too. Even in a world where your electricians distrust anything their voltmeter can't understand.
So we're full steam ahead with a whole suite of wireless solutions. Wires are a big pain in the butt anyway. I'm happy to report they're mostly unnecessary. If you're gonna replace wires with air, I've got some things you'll want to know.
First, there's always a series of tradeoffs - between speed, redundancy, power consumption, complexity, distance. On this page you'll find a chart that helps you quickly determine which networks fit your requirements:
http://www.bb-elec.com/industrial_wireless_communications.asp
You see here that Wireless USB and Bluetooth are great for short distance, high speed communication but would never work for a long distance app at a wastewater treatment plant. And there are very few industrial USB / Bluetooth products.
802.11 is the reliable standby these days. But if you're doing simple I/O it's got a lot of overhead and isn't going to be nearly as fast as it sounds. Not to mention, 802.11 will catch the interest of your IT department, I'll let you be the judge of whether that's good or bad…
ZigBee (more correctly, 802.15.4, but that's not nearly as fun to say) is great for sending short packets of data at low speed, but you wouldn't use it to transmit video. If you're using ZigBee here's what our Zlinx approach looks like:
http://www.bb-elec.com/product_multi_family.asp?MultiFamilyId=67
1. First, you decide whether you're doing simple Wire Replacement, or Modbus data communication between sensor and controller.
2. You choose a wireless base module. Based on your distance and I/O needs, you pick. Transmission range is 300 feet to 14 miles (20km). Hang our "Wireless Base Module" on a DIN rail next to your PLC.
3. You pick the wireless I/O modules you want. Various combinations of 2, 4 or 8 inputs / outputs available. Analog / digital. Snap them together with the base module.
4. If you're using a Modbus system, choose a Radio Modem. There's a table that tells you which base module works with which radio modem. Communicates to your PLC or HMI via Modbus protocol. Connects to Wonderware, Labview or any other Modbus compatible software. Or, if you're just doing wire replacement (like remote sensors into PLC inputs), buy a pair of systems and set them to peer-to-peer mode.
5. Configuration software is free download. No registration fees.
This is laid out in detail online, here:
http://www.bb-elec.com/product_multi_family.asp?MultiFamilyId=67
Next week I'll cover serial ports and how to make them transparently accessible to your Wireless World.
Meanwhile you can get all the help you need from our tech support crew at (815)433-5100.
Happy Wireless,
Mike Fahrion
support@bb-elec.com
(815)433-5100
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