I'm starting to do more on a raspberry pi I've got in the house, and I wanted it to survive short power outages. I looked at buying an off the shelf Uninteruptable Power Supply (UPS), but it just struck me as silly that I'd be using my house's 120V AC to power to fill a 12V DC battery to be run through an inverter into 120V AC again to be run through a transformer into DC yet again. When the house is out of power that seemed like a lot of waste.
A little searching turned up the PicoUPS-100 UPS controller. It seems like it's mostly used in car applications, but it has two DC inputs and one DC output and handles the charging and fast switching. The non-battery input needs to be greater than the desired 12 volts, so I ebayed a 15v power supply from an old laptop. I added a voltage regulator and buck converter to get solid 12v (router) and 5v (rpi) outputs. Then it caught on fire:
But I re-bought the charred parts, and the second time it worked just fine:
The rpi and router draw 0.69 amps when running from the battery, so the 12Ah sealed lead acid battery I have in place should get me a good 17 hours or so.
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