Thermocouples use the Seebeck effect to generate a small current based on temperature differences. Humans, warm-blooded as we are, conveniently generate heat and dissipate it through our skin. The stage is set.
The hot side of our thermocouple watch contacts our skin, toasty warm at 37 degrees C. The cold side, from which our relative temperature difference is derived, is suspended from a small helium balloon tethered to the watch.
Unless you're suffering through Arizona's dry heat, the temperature difference should be sufficient to power a simple digital watch.
Your new battery-less watch not only shows that you're technosavvy and up on sustainability, but the balloon offers limitless possibilities as an additional graphic accessory for the fashionable.-- Turbofrog, Jun 12 2006 Patent on voltage step up circuit powered from Thermocouples http://www.freepate...ne.com/6340787.htmlI was originally searching on selenium, which has a very high Seebeck coefficient (0.9mV per degrees C). There is some mention of using in a watch. [Ling, Jun 12 2006] Even under a watch, skin temperature will normally be less than 37°C. I also have a problem with the balloon; it seems unnecessarily complex, since the face of a watch is cooler than the back anyway. Good idea though. (+)-- spidermother, Jun 12 2006 What is the helium balloon for?
Maybe it can work in the opposite way in the summer, where I live (Las Vegas).-- BJS, Jun 12 2006 How about a "Thermocouple underarm watch".-- BJS, Jun 12 2006 Helium balloon? Apparently to put the cold junction high up enough to where the air is sufficiently cold - a few km up.
This sort of watch is going to seriously restrict your mobility, son, as well as attracting any lightning that comes anywhere near.-- neelandan, Jun 12 2006 It also attracts a fishbone from me.-- baconbrain, Jun 12 2006 Since the heat from your arm rises, the helium balloon will hold the cold junction at a lower temperature gradient than if it just hung over the side.
Therefore, if you weighted it with a small fishing lure, you could dip the lure in water on a hot day, as fishing is the surest way to keep time passing.-- lurch, Jun 12 2006 // Helium balloon? Apparently to put the cold junction high up enough to where the air is sufficiently cold - a few km up. //
The helium balloon probably wouldn't be further than a foot away, and is indeed probably quite unnecessary from the technology's standpoint. It's more a peripheral fashion accessory that happens to be vaguely related to the concept.
I just think a balloon dangling off your watch would be a great conversation piece.-- Turbofrog, Jun 12 2006 random, halfbakery