SAN FRANCISCO--With the International Electron Devices Meeting
(IEDM) hopping this week, a key focus is low-power electronics, either advances in improving circuit
design or the impact of other design considerations on low power.
Toshiba researchers, for example, will describe how they
lowered power consumption in a mobile CPU by replacing from
high-performance (HP)- SRAMs to spin transfer torque (STT)-MRAMs
using perpendicular (p)-magnetic tunnel junctions.
Japan's Low-power Electronics Association & Project will
describe a new low-power phase change memory.
(You get the idea, and we've previewed some of the conference here
and will cover the proceedings daily during the week).
But it seems as scaling continues in conjunction with the battle to
stop leakage current, we're running on an endless hamster wheel:
small circuits and thinner gate oxides create more problems that we
later confront with new processes or materials.
This notion occured to me when I read Steve
Leibson's post on Low-Power Design a few weeks
ago. He marvels at the battery life of some devices in the old
HP Voyager calculator series. Some participants on an HP board
report their calculators still run, 20-30 years later, on the same
Granted, the materials were different, linewidths more generous and
performance demands not nearly as rigorous as today's handheld
devices. But one would think we'd be staying one step ahead of the leakage
gremlins during the technological march of progress. Wireless sensor
networks today are really smart but in some instances the best-case
scenario for battery life is 10 years (I know, I know: a radio
device, like Zigbee etc. are not calulators, but humor mefor a second).
So, with that said, here are two questions for you:
What's the longest continuously running piece of
battery-powered electronics you own?
Do you think, given the sophistication of "modern" electronics
that we, normalizing for application, can radically improve battery
life in the near future? (Keep in mind, as Leibson points out,
the Voyager series--which drew 0.25 milliwatts and had a
standby leakage of 5 – 10 nanoamperes--was intended to last a
user for one year on one set of batteries).
In 1981 I got a Casio hand calculator: LCD display, running on one AA battery. I never turned the power switch off. I used it daily for a decade and after 25 years found it, and it was still functioning. Under a quarter century of grime. I recall over 30 years ago when the first chip was released for flashing an LED with a very short duty cycle. It was postulated that the batteries (way before Lithium-ion and when NiCad was the Gold Standard) would last longer with a very slight current drain. It seems they were right.
Not sure about longest lasting battery but it always makes me smile when I see a single AA battery quartz clock on a wall struggling to overcome gravity with the big hand stuck at about 20 minutes to the hour still ticking away.
When a quartz clock can no longer keep the arms moving its time to finally retire the battery.
When I have a remote control or other device with an (allegedly) dead battery, I save it for use in the wall clock. I can usually get another couple months of power using the battery in the clock before it finally 'gives up the ghost'
Across the hall from me, my colleague has an hp-15C calculator that he has had since college 25+ years ago that is still going on the original button batteries. He does only use it a few times a month on average, but still, that is a long time.
Separate application, but my father bought a Sony transistor radio in the 1960s... one of the earliest. We still have it. It still works like a charm. We listened to some historic events on that thing...
I have a HP-15C calculator and a HP-12C. I haven't used them much in the last 7 years but when I pulled them out they still work. I didn't buy either one new so I can't tell you how old the batteries are except they are both more than 7 years. Some SOB stole my HP-15C about 12 years ago so I had to buy one on eBay. Why would an EE use any other calculator?
I'm afraid to leave common, alkaline batteries in anything nowadays for very long without regularly checking them. I have had so many things destroyed when they leak and/or grow the white chemical "fuzz". It's really frustrating. Do modern-day batteries do this more than they used to?
Join our online Radio Show on Friday 11th July starting at 2:00pm Eastern, when EETimes editor of all things fun and interesting, Max Maxfield, and embedded systems expert, Jack Ganssle, will debate as to just what is, and is not, and embedded system.