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13 Responses to “Solar powered Sheeva Plug”
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When I talked with the person who build it, he told me that it was a solar kit from a while back. I did a quick search and found that sundancesolar.com have 5w solar kit that charges a 12v battery. I suppose you can get something like that and then rig a 12v to 5v converter to get the output to 5v.
I have a 12v solar power system that charges a bank of batteries. Right now I run a Linksys NSLU2 and all my networking equipment off of it. I built a 5v power supply with a very high efficiency switching regulator. I used the Murata Power Solutions 78SR 2 Amp Series - I bought mine from mouser.com. I takes the voltage from the battery (10-15v) and provides a stable 5v supply. I plan on using the same power supply for my Sheeva Plug. For more information see “How to make a battery powered slug” (http://www.nslu2-linux.org/wiki/HowTo/MakeABatteryPoweredSlug) and scroll down to the section titled “Powering a NSLU2 from a 12 Volt Battery.” The same concepts apply to powering a Sheeva Plug from a 12v battery system.
Wouldn’t there be a significant power loss in the 12V > 5V transfer? Would that still be more efficient than AC>DC transfer? I run our entire house on DC, with AC through an inverter, and being able to run this 24/7 on DC would be great, if it actually took less power.
I suspect the reason he had to use a 12v regulator is because the output of the solar panel he had around the house outputs 12v. If you can find a panel or battery/charging unit that outputs 5v then you can plug it directly into the sheevaplug mainboard.
The power loss depends on the type of 12 to 5 volt regulator / converter used. The 78SR series switching devices have high efficiency. Small DC-DC converters are typically quite efficient too. Ordinary 7805 style devices use an internal series pass transistor, with excess energy being dissipated as heat.