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I'm working on a project that includes an ESP8266 (requires 3.3v input (250 mA peak)) and a HC-SR04 (requires 5v 20 mA peak). I'm making it battery/solar powered.

I'm trying to keep costs down as well as make a system that works reliably and has good longevity.

I'll be waking the device every 15 minutes and keeping it in deep sleep at the other times.

Originally I was going to use a battery source over 6v, like a 6 cell AA rechargeable battery pack, a 10v or so solar panel, and a breadboard type voltage regulator that conveniently provides 3.3v and 5v on the same board. This seems to waste a decent amount of power though.

Right now I'm looking into using a 2 AA rechargeable NiMH batteries, a 5v solar panel, a 3.3v step up voltage booster, and a 5v step up voltage booster. 5v step up voltage boosters are everywhere and cheap because of their uses for portable cell phone chargers. 3.3v step up voltage boosters on the other hand are more expensive and harder to find.

Looking for any advice or affirmation that I'm on the right path. Thanks!

  • You can probably reconfigure a boost converter for 3.3v, and definitely find one intended more for the sort of thing you are trying to do, though perhaps not as a discount module. You may however need to put some thought into the enable input for the boost converter, what it may draw when inactive, what you are going to cause the timed wakeup, and what that is going to run on. – Chris Stratton Nov 8 '15 at 5:25
  • You could use a 5v boost converter, and then use a voltage regulator to bring it down to 3.3v. I'd probably use a higher voltage battery and go with a buck converter. I think those are a bit more efficient. Also take a good look at the quiescent current of those voltage converters. As the quiescent alone can drain your battery pretty fast with nothing attached. – Gerben Nov 8 '15 at 17:17
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A time a go when searching for some circuit to provide power to ESP and also being capable of charging batteries I came across this reply here. Is intended for usb charger/Li-Ion batteries but maybe it could suit your needs too and be adapted. In the output the circuit presented there, you could use some LDO like MCP1825S (or even the MCP1825 with extra information possibilities). Never test the circuit yet, so can not provide any good answer about how long it provides juice to ESP.

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