Power supply for raspberry pi setup

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spacedoggy
 
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Joined: Fri Apr 22, 2011 3:45 pm

Power supply for raspberry pi setup

Post by spacedoggy »

hi, I want to build/buy a powersupply/lipo charger for a raspberry pi + screen + populated powered USB hub

screen draws 400mA at range 6V-12V
pi 250 - 500mA at 5V
hub and peripherals draw another 500mA at 5V

i tested with bench supply 6.5V connecting LCD and 2 linear 5V regulators in parallel
(I figure having 2 regulators will share the load as they get a little hot)
1 regulator runs the PI
the other runs the hub usb connected serial lines and common ground seems to bench test nicely

I want to power all of this using a rechargeable battery with the option of wall power operation and charging.
I was thinking along the lines of of a 7.4V model battery like this...

http://www.hobbyking.com/hobbyking/stor ... duct=32213

but need a charging board capable of this functionality.
any ideas for this would be appreciated.

any suggestions comments on my dual 5V regulators, suggested filtering and safety features/components would also be appreciated.

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adafruit_support_bill
 
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Re: Power supply for raspberry pi setup

Post by adafruit_support_bill »

any suggestions comments on my dual 5V regulators
Connecting them in parallel pin-for-pin is not recommended. One of them will end up doing most of the work.
Here's one solution:
http://www.electro-tech-online.com/gene ... allel.html

spacedoggy
 
Posts: 46
Joined: Fri Apr 22, 2011 3:45 pm

Re: Power supply for raspberry pi setup

Post by spacedoggy »

Many thanks for the link/info, I'm going to go with a switching regulator circuit.

have you any ideas for the battery and charging circuit that can handle this load?
safety is of primary concern as the end product is for a toy laptop for kids.

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adafruit_support_bill
 
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Re: Power supply for raspberry pi setup

Post by adafruit_support_bill »

If safety is a major concern (as it should be for this application), I'd consider using NiMH batteries. LiPo packs can fail catastrophically (i.e. explode) if mishandled or improperly charged/discharged. DIY LiPo chargers are tricky to design and LiPo packs designed for hobby/RC use generally omit some of the protection circuitry (for a model airplane, it is better to risk battery damage and keep flying than to simply cut power).

NiMH doesn't have quite the same power density as LiPo, but it is pretty safe and NiMH packs and chargers are readily available from hobby stores and electronics suppliers.

spacedoggy
 
Posts: 46
Joined: Fri Apr 22, 2011 3:45 pm

Re: Power supply for raspberry pi setup

Post by spacedoggy »

sweet as a biscuit, thanks for the info :D

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