When powerful computers sporting brilliant graphics and multiple screens hit the factory floor in the 1990s, it seemed like curtains for their lower-priced, lower-featured sister. Then the fairy godmother of technology worked her magic, and full feature sets began to appear in smaller, less expensive form factors.
Operator interface for machinery traces its lineage to banks of green, amber and red pilot lights with little identification tags mounted in a control enclosure or operator console. An experienced operator could glance at the array of lights and determine an approximate status of the machine. But information available was sketchy, at best. Small displays manufactured from light-emitting diodes (LEDs) and liquid crystal displays (LCDs) evolving from the emerging laptop computer market enabled suppliers to replace large banks of lights with a smaller display that often either just replicated the lights or was solely text-based.
The higher-end large personal computer and software solutions that came along were fine for control rooms but were often too expensive for original equipment manufacturers (OEMs) or smaller installations.
Competition and technology has solved that problem. With the price of quality graphical flat-panel displays dropping and increased competition, Cinderella has now been fitted for her gown suitable for dancing with a prince.
Communication concentration
Red Lion Controls (www.redlion.net) is widely known in manufacturing circles for its large catalog of temperature, speed and other controllers and peripherals. The York, Pa., company has also jumped into the operator interface fray. President Mike Granby says, “The key thing is connectivity—building multiple serial ports plus an Ethernet port in the operator interface device. Given an appropriate protocol library, this type of operator interface device can connect to many devices in the field. In fact, adding this communication capability turns it into a sort of communications concentrator. The operator interface gets everything on the control network talking together, then serves it up to other applications using Modbus/TCP (transmission control protocol).”
Although HMI packages provide for large databases to store manufacturing data for later analysis, adding memory such as compact flash to operator interface devices enables local data logging. The data can then be downloaded in comma-separated-variable format via a Web server function into a spreadsheet application.
To put this into perspective, Granby adds, “From the point of view of a traditional machine builder, there is an advantage where there are several different types of devices to talk to, yet an inexpensive solution is required. These devices go beyond the usual programmable logic controllers and drives to fingerprint readers, vision systems, bar code and RFID (radio frequency identification) readers and even GPS (global positioning satellite) receivers in mobile devices. Local data storage comes in handy for OEMs in food and beverage and pharmaceutical industries where data logging is a must.”
It is usually dangerous to lump everyone in the same category, but David Crump, spokesperson for Opto 22 (www.opto22.com), the Temecula, Calif., automation component and system supplier, differentiates a couple of groups. “Customers in general like built-in Ethernet support and low cost,” relates Crump, “and they are also looking for larger, brighter screens, better screen resolution and more onboard memory.”
While many users seem to prefer operator interfaces that will connect to many controllers and input/output systems, Crump notes that some customers like devices that are tightly integrated with their hardware of choice. “These customers like to directly reference control program data tags.”
Gary Mintchell, [email protected]
