A Reader Writes:
I guess we're way behind the curve here, but we've gotten along with building dedicated operator interfaces for our machines. Lately, the demands of open standards technology are catching up. It looks like we'll be using more configurable Windows-based software, but I'd like to know if any readers have had any buyer's remorse and find that rolling your own, for a panel that just needs a few hard-wired buttons and switches, is still not a terrible idea.
--from March Control Design
Answers
Buying Is Too Good to Pass Up
With the cost of programmable operator interfaces now below $1,000, the cost of materials and installation for a pushbutton/alarm light panel is pretty close. The programmable interface allows you to modify the display at any time, and if you have any analog data to present, it is a slam-dunk decision. I would do it every time, just to avoid having to calibrate and maintain the old-school analog and standalone digital display units. When I was working for a major oil company, our policy was to install the programmable interfaces. Any new control panels are now fabricated to a standard, which includes a programmable operator interface touch screen.
Jonathan Pollet, President
PlantData Technologies, Houston
Consider Using Visual Basic, Too
For a few pushbuttons and switches, we like to use an inexpensive operator interface from a number of manufacturers. These generally plug and play with many industrial networks and Ethernet. They are reasonable in cost, and programming is relatively simple. Most vendors will supply the programming software for their devices at a very nominal cost. You can also match the brand to fit the customer request.
...If you need to go to an open Windows-based product you have a couple of options. Some operator interface vendors have a Windows CE environment, which is Windows-like. CE is an embedded operating system and is popular in the display area. Technically it is not really open, but it has Windows in its name and might be open enough for the customer base. Programming is generally done by the vendor's software packages. These products are more costly than the above-mentioned operator interfaces. Connectivity is generally via Ethernet.
...A full-blown Windows NT or above will require a computer. The software can be purchased and is generally licensed per installation. This drives cost up. You also need to be operating system-fluent to some degree. Not all software you will use on these devices will load seamlessly. We use these applications on high-end machines or machine cells where there are a lot of recipes, data collection, and third-party applications required.
...If the machine is a repeat and the operator interface can be designed so as to not require a lot of changes, Visual Basic is an alternative to the license costs. VB applications take a little longer to make screens look professional, but you don't need to keep paying license fees for each machine. But maintaining this type of application requires programming capabilities. Machine OEMs sometimes prefer this method on medium machine control applications where cost is a frequent issue and changes are minimal. This can be done in-house or via a cost-effective relationship with an integrator.
Kelly Trumpour, Sales Manager, System Integration
Automation Intelligence, Duluth, Ga.
September's Problem:
Help With Cabinet Cooling
As we pack more controller power, drives, I/O, even operator displays in our cabinet designs, we're getting reliability questions from potential customers. The ambient temperatures at some customer installations can be as much as 90[deg] F. Fan/filter vendors tell us we're still OK with what we have. Vendors offering various types of heat-exchange tell us differently. We even hear that just changing to a stainless steel enclosure from plastic would make a big difference in heat dissipation. Any suggestions?
Send us your comments, suggestions, or solutions for these problems. We'll include them in the September issue. Send visuals, too,a sketch is fine. Have a problem you'd like to pose to the readers? E-mail us at [email protected] or mail to The Answer to Your Problems, CONTROL DESIGN, 555 W. Pierce Rd., Suite 301, Itasca, IL 60143. You can also fax to 630/467-1124. Please include your company, location, and title in the response.
