dj-party
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5V Regulator (battery powered)

Wed Jul 11, 2012 3:03 am

What do you guys think about this thing (http://www.ebay.co.uk/itm/DC-DC-Convert ... 599705500?) to power my raspberry pi, a usb hub and a la fonera wireless access point? wold it work? Do i need any extra protection? I wanted to use a sealed lead battery at 12V as power source.

thanks for your help :D

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Super-Nathan
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Re: 5V Regulator (battery powered)

Wed Jul 11, 2012 6:58 am

I don't see why that wouldn’t work, might be a bit expensive though.

I'm just a hobbyist and i might be wrong, but the lm340 here.
http://www.futurlec.com/ICLinearRegulators.shtml

Might serve you well for a fraction of the cost. If you build it with a cap in line to filter out high spots in the current i think it would be fine.
echo "Something Useful" > /dev/null

kaos
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Re: 5V Regulator (battery powered)

Wed Jul 11, 2012 9:31 am

@ dj-party: Yes, if it does what it says on the label, it should work. I assume the access-point takes 5V and non-ridiculous amount of current? Though, with 10A to play with, current really shouldn't be an issue.

@ Super-Nathan: I wouldn't recommend the LM340, or any other linear regulator for that matter, in this case. Sure, it will work ... for a certain value of "work". Assuming a nominally 12V lead-acid battery, that means ca. 14V during float charging, meaning a voltage drop of 9V across the regulator. If it is delivering the maximum 5A current, that means it has to burn off 45W in heat, while delivering 25W of usable power, i.e. ca. 36% efficiency! Compare with the claimed 90% efficiency of the switch-mode regulator (which I confess I have some doubts about, but not enough to really affect the argument). Also remember that you have to get rid of the waste heat, which for these kind of numbers means a big-ass heatsink and forced ventilation.

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fireraisr
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Re: 5V Regulator (battery powered)

Thu Jul 12, 2012 11:57 pm

You"ll have plenty of power to spare. Just be sure your battery can supply 10A of power.

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mahjongg
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Re: 5V Regulator (battery powered)

Fri Jul 13, 2012 12:08 am

Look out that at the very small load (in comparison to 10A) the PI form's the output of this converter isn't too high, which sometimes happens with such heavy power supplies, it might damage your pi if at 500mA load it outputs something like say 6 Volt instead of 5 Volt.

I would never use such a supply above say 3A with a PI.

JustFun
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Re: 5V Regulator (battery powered)

Fri Jul 13, 2012 8:48 am

well if you want to fell "safe" use a fuse (don't remeber the english word for those fuses that are "quick responding"... but that what i should use)

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