We tend to think of extreme low-power, long-life designs as relatively recent phenomena, made possible by the combination of advances in IC processes and battery chemistry. Yet somewhere out there are designers who conquered the low-power/long-life world years ago using "ancient" tools and techniques.

Certainly, with today's ultralow-power technology and small, yet powerful batteries, it's easy to do a simple energy-usage calculation and get a theoretical 20-year life for a product and its original battery cell. Some devices, such as smart power meters for home installation, are promoted with such long lifetimes - a real benefit since battery replacement is a maintenance nuisance with high labor cost.
Still, I wondered: even if a calculation shows such long potential life, can a battery really function for that long? Its basic mA-hr rating may imply so many years of energy reserve, but won't the cell's internal chemistry just deteriorate before then? What about the cell's physical package: wouldn't that corrode first, as well?

Recently, though, I saw first-hand proof that such very-long run times are possible; and then I realized that the corresponding power-miser circuitry is not just a recent development. I was using my low-cost kitchen scale (see photo) and realized that it has been using the same battery for over 25 years. Of course, the duty cycle is quite low, only a few minutes per day.

Obviously, this device is full-power on all the time, with no sleep mode and no quiescent current operation. I have changed its pair of "357" button-cell batteries only three times since I received it. (Being perhaps a little obsessive here, I mark those dates on the back.) That's impressive, for sure.

Certainly, today's extreme low-power design is a consequence of the improvements in process technology and shrinking IC geometry. Yet is seems that even 25 years ago, there were engineers who were able to create designs which used relatively power-hungry process technology, yet could manage on microamps. Were these engineers the elite of the IC design world? Or were they considered design eccentrics working off in the corner, focused on pushing the envelope for some specialty uses? We'll never really know, of course.

Whatever they were, they did some amazing work with technology they had available. Doing that is the mark of truly inspired engineering, and has always impressed me. It's like the scientists and engineers in the early 1950s who determined critical magnetic-spin parameters of the electron to six significant figures, using clumsy vacuum-tube instrumentation that is laughably crude by our standards. They figured out how to achieve this accuracy not only by using the "best" technology they had, but also by assessing all potential sources of measurement error and devising ways to have these cancel out.

Have you used any products that have worked long after you thought they should have? Was this due to skillful design and execution, or just plain luck?

Tags:

Original Hyperlink: http://www.edn.com/electronics-blogs/power-points/4429542/There-s-nothing-new-ab..

For more information from this magazine/website? Please click here http://www.edn.com/

Note: The copyright and the ownship of the brand, product names, product numbers, and content mentioned belongs to their repective companies.