I’m getting many questions about what kind of technologies we’re using in haytag. In order to stuff so much functionality into such a small enclosure, we need to be very creative with our mechanical design, as well as the electronic components themselves. For example, there is just no way that haytag would function with a normal battery — not even a small coin-cell would be suitable. To make it smaller, lighter, and smarter than any wireless tag/mote/etc designed to date, we are using the very latest electronic components in haytag.
The Power System
The most interesting piece of haytag is the power system. We’re using an amorphous-silicon solar cell — the component is familiar to the wristwatch market — in combination with a bleeding-edge 0.35mAh lithium thin-film battery that is familiar to … space probes. Yes, you read that correctly: 0.35mAh, and space probes. The combination of the film battery and film solar cell is 0.4mm thick and weighs almost nothing. Plus, the little battery here is basically “the little battery that could” — it can pulse up to 15mA, which is enough for DASH7 (but basically no other wireless standard), and it has a rated lifetime of up to 1 million charge cycles. With haytag, that’s roughly 2.5 million days. Humans might not exist on Earth in 2.5 million days, but haytag will live on!
The solar powering unit is also over-engineered as if we were thinking about sending haytag to Mars. 12 hours a day of low indoor lighting is enough to power the device indefinitely. The actual figure here is 200lux, which is about what you get in a fancy restaurant. About 20 minutes of outdoor light will do the same job, or 10 minutes if you live in a sunny place like California.
The Computing System
The other part of haytag is the computer and the radio. By computer, I am of course referring to a microcontroller. We are still evaluating a handful of different parts to find the very best performers, but all of them already work with OpenTag (which just went to version 0.4, BTW). So far I can’t tell you exactly which combination will win, but either way the device will have encrypted, over-the-air firmware upgradeability and the ability to load-on Wiring programs (Wiring is what’s used in Arduino, Maple, Energia, and that sort of thing). In the end, haytag will also be a pretty cool computing platform if you want to use it for something other than locating pets.