Designing Ideas

Medieval theologians may have argued about how many angels could dance on a pinhead, but contributors to Design Ideas seem focused on driving more LEDs with fewer microprocessor I/O ports. Here we go again, with the latest and possibly last (for a while) entry in the category. This time, authors Nedjeljko Lekic and Zoran Mijanovic show us that “Three microcontroller ports drive 12 LEDs “—in this application, the LEDs form a bar graph that’s part of an engine tachometer. Previous entries included: “Single-port pin drives dual LED,” by Tom Gay ofDornstadt, Germany; Noureddine Benabadji of the University of Sciences and Technology, Oran, Algeria, showing how a “PIC microprocessor drives 20-LED dot- or bar-graph display,” and Abel Raynus of Malden, MA, demonstrating how to “Squeeze extra outputs from a pin-limited microcontroller.”

And if you’re faced with the holiday chore of debugging strings of recalcitrant incandescent Christmas tree lights, visit Design News (one of EDN’s sister publications) and peruse the Gadget Freak Elves' Workshop Edition for tips and techniques.

While we’re thinking in debug mode, chances are you’ve encountered a situation in which you needed to investigate a misbehaving magnetic field. While mag-field meters are commercially available, they’re not yet in the same price class as garden-variety digital multimeters, and justifying the purchase of an infrequently used instrument to your boss may prove difficult. Authors Sandeep M. Satav and V.V. Rama Sarma of Hyderabad, India, offer a low-cost alternative. In “Magnetic-field sensor requires few components,” they show how an AllegroMicroSystems Hall-effect sensor and a DMM equipped with a "Relative Difference from Reference Reading" (RELD) function can do the job.

If you’ve noticed the proliferation of PC add-ons, instruments, signal processors, and whatnot that exploit a PC’s USB port as a power source, chances are you’ve looked on with envy and wondered “How much juice could MY project get away with stealing from a USB port”? Donald Schelle of Sunnyvale, CA, shows how to do so safely when a “Dynamic siphon steals current from USB port.” And while we’re on the subject of USB ports, are you finding that the absence of conventional parallel and serial ports on newer-model PCs constitutes a pain in the neck, or merely a nuisance?

Should you find yourself with excess leisure time over the holidays (Hah! What a concept…read Anthony Lockwood’s column “Out not with a bang but a bawk” in Desktop Engineering magazine for November, 2006), find a book to read. Here’s the most-recent addition to my to-be-read pile: “AC/DC: The savage tale of the first standards war,” by Tom McNichol. Although short on chewy technical details, the book explores the nasty conflict between Thomas Edison’s advocacy of DC power distribution and the AC system proposed by George Westinghouse and Nikola Tesla.

And finally, here are a couple of additions to your information toolbox: Educypedia bills itself as an “educational encyclopedia” (I thought they all were), but it’s actually a multilingual compendium of topics that link to many, many Web sites. Take a look at the “Electronics” category and see what I mean.

Here’s an RF engineering-related site that offers a number of downloadable tools, tips on RF breadboarding, and much more. Although similar to Educypedia, 101Science provides a portal to a claimed 20,000 scientific and technological sites. From the home page, select “Electronics” and then “RF Design”, or else go here. Don’t stray from your quest, or you’ll find your attention wandering into other topics.

Best wishes for a joyous and peaceful holiday season, and a peaceful and prosperous New Year.

—Brad AA1IP