Hi all (I hope this is in a suitable section),
I've had a good read around the forum for this, but not yet come up with an answer. I was looking to power nodes from 1 or 2 alkaline AA cells. I have already used nodes powered by 3 or 4 cells, feeding that into the MCP1703 regulator to get a well-regulated 3.3 V, and generally reliable results. The end result, though, is either a bit awkward (AAs are generally sold in 2s or 4s, not in 3s) or a bit bulky (4 AAs take up a fair amount of space).
I'd really like to run nodes off 2 AAs, as that seems like a good capacity / size compromise, but would also like to ensure a well-regulated and low-noise 3.3 V for the processor, radio and any attached sensors. I read that using an LDO regulator is the best way to get that (and also a very low quiescent current), and that a boost circuit is not a good way, as the output would be noisy, which may affect the radio parts. But it seems that boosting the 2 x AA voltage to 5 V (or thereabouts), just to regulate it down to a smooth 3.3 V again would waste about 40% (or more) of the power in the cells.
So I was wondering if anyone had run Moteinos (or similar hardware) off a boost circuit, providing it directly with 3.3 V (not regulating the voltage back down again through an LDO)? Some of the boost ICs seem to have quite low quiescent currents, and some appear to claim low ripple/noise, though "low" is a relative term, and I don't know how low that needs to be to not interfere with the radio parts. Does anyone out there have any experience of trying this?
I'd rather stick with inexpensive, long-lasting alkaline AAs than use AAAs (seem to be a worse size-to-capacity ratio), "exotic" AAs (expensive, less available) or LiPos and all of the extra (charging/safety/transport) issues those bring.