Priorty Interrupt by Steve Ciarcia Design98—A Marketer's PICnic

If you hang around me long enough, you learn that I tend to use a lot of metaphors when I'm trying to make a point. Invariably, when I'm talking about the evolution of embedded control, I eventually get to a comment that, someday, even toasters will contain microprocessors. Of course, I've been saying this to emphasize how far embedded processors have come both in application and cost effectiveness. In truth, it's just a metaphor and I've never really looked to see if any toasters use them.

Well, I guess I have to coin a new metaphor. I've finally seen a design for a microprocessor-controlled toaster oven. Mind you, this is no schlock control scheme. It's a serious demonstration of surface-mount technology, with a platinum RTD temperature sensor, 2 x 8 LCD display, rotary-encoded input dial, and RS-232 interface!

No, I didn't whip this up in the cellar. It was one of the designs submitted among the tremendous volume of entries we received for Design98, the Circuit Cellar/Microchip PIC design contest. Probably the best part about these contests is the richness of design ideas that are presented. Here was a group of people who had solved engineering problems and they wanted to tell the world about it.

And tell about it they did. We received projects on RF remote control, video digitizing, motor controls, image scanning, security keys, energy management, electronic games, a single-chip Internet server, smart switches, I/O expanders, data loggers, rocket telemetry, fuzzy-logic buck conversion, a taxi meter, and assorted transmitters, receivers, programmers, interpreters, etc., etc., etc. And, oh yes, there was a toaster-oven controller.

While everyone could not be a winner, they all were worthy of winning. And no doubt, they'll be rewarded in the marketplace. Of course, certain projects really caught my eye. In the necessity is the mother of invention category, there was the Great Highland Bagpipe Chanter. Apparently, learning to play the bagpipe is a demanding physical task. It's equally demanding on anyone who's around you when you're practicing. The only volume control on a bagpipe is distance! With the addition of a few buttons and a 12" PVC pipe, this ingenious entrant made a PIC-based electronic bagpipe simulator so his students could practice without creating a riot.

In the proverbial 10 pounds in a 5-pound bag category, we had a couple graphing data loggers. The first was a weather monitor with a built-in 128 x 240 LCD. It monitored, stored, and displayed pressure and temperature as a continuously updated scrolling graph showing the present conditions as well as the previous 48 hours of weather data. The second project was an x-y graphing data logger with eight 12-bit ADC inputs, 20 KB of data space, and a 200-hour battery life. Using a Casio graphing calculator as the display (64 x 128 LCD), the combined system performed sophisticated analytical and statistical math processing on the analog data.

In the it's better to see you category, I loved the electronic automobile sun-visor project. This one answers the question, what do you do (besides swear a lot) when the sun isn't blocked by the usual flip-down sun visors? This circuit uses two CCD linear arrays to continuously track the sun's x-y position. With that information and some neat calculations, it automatically blocks the blinding sun from reaching the driver's eyes by darkening the appropriate pixels on a 24 x 64 pixel (0.4" x 0.6" each) optically clear automotive LCD sun visor. When can I get one?

Finally, in the why didn't I think of that category, there was an X-10 Remote Temperature Sensor. The circuit used a Dallas digital thermometer and 2 x 16 LCD (as a local display) combined with a TW523 X-10 transceiver as you might typically expect. Without using X-10 extended data, however, designers tend to resort to using a whole bunch of house and unit codes to represent the wide range of potential temperatures. This circuit relied instead on the host controller and a single house code. The sensor decodes two consecutive On commands to ask a specific comparison temperature value. The sensor responds with an On command if the comparison temperature is greater than or equal to actual temperature or an Off if it's less. It takes a few commands to zero in on the measured temperature, but this technique allows many sensors.

Some of the Design98 entries were elaborate; others ingeniously simple. For Microchip, it only confirmed their assertion that cost-effective 8-bit processing ultimately expands all the potential applications. As for us, we've got a boatload of great designs and a whole new group of potential authors. Our task will be turning many of these entries into published projects on our Web site and in the magazine. Congratulations to all the entrants for a job well done.

steve.ciarcia@circuitcellar.com

Published: May-1998