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or years, MRCs had a strange, illogical fascination with PC-based controls, and annually predicted the coming demise of PLCs. PCs will drive PLCs out of the market, the MRCs would say. All this was much to the amusement of machine builders, process equipment skid builders, end users and system integrators, who were buying PLCs as fast as they could. If PCs were being used for automation and machine controls, it was mostly for HMIs and certain motion control tasks.
PC-based controls barely put a dent in the huge PLC market, and everybody seemed to know it except the market analysts.
Finally, one of the chief proponents of PC-correctness, ARC Advisory Group (www.arcweb.com), appears to have given up. As is its wont, it created another three-letter acronym (TLA) called Programmable Automation Controller (PAC), said PLCs are now PACs, and it is now happy to predict that the sales of PLCs â¦ er, PACs will remain as strong as they always have, at about 4.6% annual growth, reaching $7.5 billion by 2008.
As for industrial computers, Venture Development Corp.(www.vdc-corp.com), predicts that they will continue to grow at 4.4% annually, reaching $537 million in the industrial automation, control and instrumentation market by 2006.
In other words, there is nothing new in the machine control marketing research universe except another TLA.
Some commodity pico and nano-PLCs now cost less than relays, commodity micro PLCs have the capability of the full-size PLCs of 10 years ago, and larger PLCs have become hybrid controllers with PC architectures, networking and web servers. You can buy commodity PLCs in the $100 range, especially with OEM quantity discounts. And if you pay $1,000 for a PLC, you get an outrageously powerful device. Going the other way, you can get a PLC on a chip and embed it in your machine.
No matter what you call them, PLCs are still the most reliable devices on the planet. That, plus their low cost, is why machine builders cling to them with such tenacity.
As you can see in the product round-up that follows, PLC vendors are keeping their products extremely competitive and up-to-date by using the latest hardware, software, and communications technology. This month’s round-up has PLCs and PACs with web servers, fieldbus networks, Linux operating systems, motion control functions and firewalls.
Although some may consider PLCs to be 40-year-old devices, they are as up to date as Kansas City. And, as we all know, “Everything’s up to date in Kansas City” (from the musical, Oklahoma!, which was revived last year on Broadway, with PLCs moving the scenery).
The APC680 industrial PC has Windows XP with real-time expansion, Soft PLC software, slots for PCI and ISA cards, and fastened plug connectors, making it suitable for industrial applications. It is available with a Intel Celeron or Pentium III Tualatin CPU up to 1.26 GHz, and comes with two 100 Mbps Ethernet ports, four USB slots, and four serial interfaces. Flat screen displays can be mounted up to 16.4 ft away.
B&R Industrial Automation: www.br-automation.com
PLC Software Runs Under Linux
Version 4 of SoftPLC control is built on an embedded, real-time version of Linux. Other enhancements include integrated firewall support, encrypted secure communications with the FTP Server, and remote command shell access to run programs, perform diagnostics, and restart the controller. Remote file access lets the software read/write production data to a remote disk.
SoftPLCL: 512/264-8390; www.softplc.com
Redundant Controller Runs Reliably
The PACSystems High Availability controller has two physically independent controllers with an automatic switchover system for redundancy. The controllers have dedicated and redundant links to one another, operate synchronously, and transfer all of the application’s variables, status, and I/O data with each data sweep. Each controller has a Pentium 300 MHz CPU, Cimplicity Machine Edition software, and support for Ethernet, Profibus, DeviceNet and Genius networks.
GE Fanuc: 410/242-0300; www.gefanuc.com
The QTERM-G55 lightweight, handheld terminal has a 320 x 240 pixel, grayscale, graphic LCD display that is viewable in most lighting conditions. Suitable for use in NEMA 4 industrial environments, it has an overmolded rubber boot for shock protection, an ABS polycarbonate plastic case, and a 24 or 40-key membrane steel snap dome keypad. It comes with two serial ports, Ethernet 10Base-T, or a Power-over-Ethernet (IEEE 802.3af) interface.
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