The right HMI tool for the job

HMI software packages designed to run efficiently on PDAs don’t have all the features of their big brothers, but most of them have more than enough functionality for remote monitoring and control.

Dan Hebert, PEBy Dan Hebert, PE, Senior Technical Editor

YOU WOULDN'T use a sledgehammer to drive a nail, and you might not need an expensive, general-purpose, full-featured HMI software package for your remote monitoring and control applications. You might be able to use HMI software optimized to run on limited-resource targets, such as a personal digital assistant (PDA), pocket PC, or even a smart cell 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 because of software bloat caused by a proliferation of features in operating systems and applications. Software bloat has driven system resource requirements such as dynamic memory, static memory, and processor speed to levels unthinkable just a few years ago.

These added features, most probably requested by one user or another, require many HMI applications to run on fully loaded desktop and industrial PCs. This is fine when the HMI target is a PC, but it causes problems for limited-resource PDAs.

In the best case, the database or some other software component must be manually manipulated and cut down to size by the 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 then is stored on the server, but this approach requires a network and a server PC with consequent hardware and software licensing expenses.

Riding to the rescue now are HMIs designed to run efficiently on PDAs and other limited-resource devices. These HMIs don’t contain all the features of their big brothers, but most have more than enough functionality for remote monitoring and control applications. They’re configured on a PC, just like their more well-endowed siblings, but they can be downloaded easily to most any platform, including PDAs.

You and your customer will save money 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 also are cheaper for these new HMIs, primarily due to their limited feature sets.

For instance, a typical control application could use a PDA as a wireless, handheld remote in a regulated packaging 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 they’re done, satisfying electronic signature requirements.

One supplier of this new breed of HMI 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 his 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 HMI 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 vice president.

What might the future hold for portable HMI applications? The next horizon could be the cell phone, which is cheap, ubiquitous, and produced in larger annual quantities than any consumer electronics device in history. The day probably will come when your cell has enough processing power, memory, and display area to effectively run remote monitoring and control HMI applications.