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YOU WOULDN'T use a sledgehammer to drive a nail, and you may not need an expensive, general-purpose, full-featured HMI package for your remote monitoring and control applications. Instead, you may be able to use HMI software optimized to run on limited-resource targets, such as a personal digital assistant (PDA), pocket PC or a smart phone. These HMI software packages combine low cost with enough features for most remote monitoring and control tasks.
Many of the big players in HMI software have trouble competing because of software bloat caused by the proliferation of features in operating systems and applications. Software bloat drives system resource requirements such as dynamic memory, static memory and processor speed to levels unthinkable just a few years ago.
These added features, most requested by one end user or another, cause software bloat, and require many HMI applications to run on fully loaded desktop and industrial PCs. This is fine when the HMI target is a PC, but causes problems for limited-resource PDAs. If an HMI application is optimized for a PC target, then downloading that same application to a PDA can be difficult.
In the best case, the database or some other software component must be manually manipulated, and cut down to size by the end user, so the HMI application can run on the PDA. Another approach is to make the PDA part of a client server network, usually as a thin client. The database is then stored on the server, but this approach requires a network and a server PC with consequent hardware and software licensing expenses.
Now riding to the rescue are HMIs designed to run efficiently on PDAs and other limited-resource devices. These HMIs don’t contain all the features of their bigger brethren, but most have more than enough functionality for remote monitoring and control applications. They’re configured on a PC, just like their more full-figured siblings, but they can be easily downloaded to most any platform, including PDAs.
Money is saved because the PDA can stand alone, and run the downloaded HMI application without needing a server host and a network. More savings accrue because a PDA can be used instead of a much larger and more expensive tablet PC.
Development system and runtime licensing costs are also cheaper for this new breed of HMI, primarily due to its more limited feature set.
For instance, a typical process control application could use a PDA as a wireless, handheld remote in a batch process. The PDA could be set up to communicate directly with the controller via wireless Ethernet. An operator would be prompted to execute local manual operations such as ingredient additions. The operator could check off steps as executed, satisfying electronic signature requirements.
One leading supplier of this new breed of HMIs is Software Horizons. Its InstantHMI software claims write-once run-anywhere capability for targets ranging from a PC to a Windows CE platform to a PDA.
Software Horizons’ president, Ramal Murali, says InstantHMI’s run-anywhere capability comes with minimal target customization. “While the end user must be concerned with physical target limits such as screen size and memory size, no special software configuration or manipulation is required no matter what the target.”
Screen size limitations can be handled either by developing screens optimized for the PDA display, or by only displaying designated portions of screens developed for larger PC displays.
Memory size limits also are becoming less of an issue. “Users can get PDAs with 128 MB of RAM, which is quite a lot for HMI applications developed with our software,” observes Murali. Low-cost, gigabyte memory cards for non-dynamic data storage and transfer also are supported by many PDAs.
Another proponent of compact HMIs is InduSoft. Its Web Studio product runs on Windows CE, and takes advantage of that platform’s features. “Windows CE has a smaller footprint, and requires less dynamic memory, static memory and disk space than Windows XP,” says Marcia Gadbois, InduSoft’s business development VP.
What might the future hold for portable HMI applications? The next horizon may be the cell phone, which is cheap, ubiquitous, and produced in larger annual quantities than any consumer electronics device in history. So, the day may soon come when your cell has enough processing power, memory and display area to effectively run your remote monitoring and control HMI applications.
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