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abishur
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Re: Power supply

Fri Aug 05, 2011 8:22 pm

actually, that was just an early working prototype. Both models at this point are planned to be around the size of a credit card. Though a battery would still add some slight size, there are many applications that would benefit greatly from even a AA battery backup.
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AmyS3
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Re: Power supply

Fri Aug 05, 2011 9:13 pm

its true that the lipo im going to use is way bigger than the raspi but im not going to use the raspi as a portable device in common sense.
it will be acting as the cpu in a uav which is 59" long and 35" wide... (i had to use a ruler to convert the size from metric into imperial)
so for my use the size does not realy matter...
and the solar module is now a bit bigger too.. ->http://www.ebay.co.uk/itm/230652892330
which delivers around 50W.. so i would say im safe :-)
maybe i should buy some more of the lipos...

maybe i should put that in the new projects section..

kyrol
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Re: Power supply

Sat Aug 06, 2011 12:28 am

How about using something what actually exists? It could be i.e. Nokia recharger (this with thin connector). I do not know it is permitted by law, but using something what most of people owns, seems to be good idea.

Moreover Nokia released rechargers with usb connector too, so in case you need to use two computers at once, there isn't needed any additional power supply:)

AmyS3
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Re: Power supply

Sat Aug 06, 2011 1:29 am

the problem with the nokia charger is if you use a nokia battery as well the voltage.
since those mobile phone batteries normaly have 3.7V you could not run the usb or hdmi port which need 5V. but i bet you could still get it working with a booster of some sort...
the board itself can run on the 3.7V but since it wants 3.3V you would have to use a regulator.

ShiftPlusOne
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Re: Power supply

Sat Aug 06, 2011 1:30 am

[embed][/embed]

AmyS3
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Re: Power supply

Sat Aug 06, 2011 1:58 am

Fantastic!! :-)
cheers to that. that helps a lot. i can stop searching vast amounts of forums now
i may going to use this chip here: MCP73844 ->http://www.microchip.com/wwwpr.....e=en010555

oh and it seems that nokia batteries have 3.6V and not 3.7V which i was stating...

edit: im going to use this charging controller: L6924D -> http://www.st.com/internet/com.....079821.pdf
reason for that: i have 3 of them at home ^^

ShiftPlusOne
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Re: Power supply

Sat Aug 06, 2011 2:40 am

Sounds like you'd be interested in his other videos too. He covers things like pcb design for mass production, parts selection advice, thermal calculations, power supplies, DIY LED home lighting, beginner tutorials (through-hole & smd soldering and such), honest equipment reviews, job search and interview advice for students, FPGAs and the list goes on and on. He's got a tour of a typical Chinese PCB fab house as well which is pretty interesting. Well worth subscribing to if you're into any kind of electrical/electronic engineering.

AmyS3
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Re: Power supply

Sat Aug 06, 2011 2:54 am

i updated my previous post.
i think im actually going to subscribe.. need to reactivate my account first.
when he showed the st website i had the feeling "wait.. i have that" :-)
ahh i im such an airhead.. shame on me to forget what i have in stock...
well i maybe even use a totally different chip... since if i have 40+W i need a chip which can handle a higher current....

danielu
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Re: Power supply

Sun Aug 07, 2011 4:24 am

you should check hobbyking if you're looking for lipo battery chargers.

AmyS3
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Re: Power supply

Sun Aug 07, 2011 5:29 am

checked that website already but i need a custom charging design since i cant monitor the charging process.
but all this does not belong to this forum topic which should only cover aspects to power the raspi :-)
you can check my project topic for more infos about my special power needs ^^ ->http://www.raspberrypi.org/?pa.....&t=82

AmyS3
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Re: Power supply

Mon Aug 08, 2011 9:17 pm

ok here it comes..
when could we get an official statement about the power input possibilities?
since if you would make a 5V input aviable then i could provide a cheap solution to power the cake and peripheral usb devices (monitor) from a single li-po battery including a charging circuit.
output would be 5V at ~1Ah (~2Ah with 2 cells).
but i could make a 6V version as well.
the shematic is in work and aviable tomorrow when im home from work (~5:30 GMT)

the price for a singe cell version is ~ 4.5 GBP dual cell is twice the price :-)

ShiftPlusOne
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Re: Power supply

Mon Aug 08, 2011 9:24 pm

It's pretty safe to plan around a 5v input voltage, isn't it? Seems like you'd have the know-how to hack the board to fit your needs.

AmyS3
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Re: Power supply

Mon Aug 08, 2011 9:36 pm

yeah somehow.. did quite some resarch for the right parts..
and if i remember correctly, than there was a statement from eben that we maybe could slave in the 5V over the usb port when we do some modding on a few resistors/diodes...
but it would be nice if it would work without killing the warranty ;-)

eben
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Re: Power supply

Mon Aug 08, 2011 9:43 pm

Well that's the nice thing about a $25 computer - it's *cheaper* than a Curry's extended warranty on most of the stuff they sell....

AmyS3
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Re: Power supply

Mon Aug 08, 2011 9:46 pm

so true..!
but can you tell us about the 5V thingy? it would be realy very conveniant if it would be possible.
i could make a 5v+6v version of the carging/powering circuit but it would add another 1.5GBP to it

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Lob0426
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Re: Power supply

Mon Aug 08, 2011 9:46 pm

The radio control airplane market has numerous slow and fast chargers for all flavors of lithium batteries. Hacking one of these may speed you along in your project.
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AmyS3
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Re: Power supply

Mon Aug 08, 2011 9:47 pm

but they dont use 5V in they´re planes.. they just use 5v for the charging..

AmyS3
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Re: Power supply

Mon Aug 08, 2011 9:52 pm

to give a little insight to the circuit:

as a charger would be used: MCP73871-2CCI/ML -> http://ww1.microchip.com/downl.....22090a.pdf £1.25 at mouser

and for the power conversion: TPS61252DSGT -> http://focus.ti.com/lit/ds/sym.....s61252.pdf £3.07 at mouser as well.

add some resistors diodes and done. maybe a powerswitch too.

AmyS3
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Re: Power supply

Mon Aug 08, 2011 10:16 pm

here is a shematic for the chargin circuit with the calculated values to charge a single li-po with a supply voltage of 4.4-6V at ~ 1.7-A.
suitable for li-po´s which can be charged at a maximum current of 1A !!

the charging state pins are obsolete or can be used with a led´s connected to "IN"
this shematic is drawn for my own usage.
i add a full circuit with the power conversion if i know if the 5V powering of the raspi is definitely possible.

AmyS3
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Re: Power supply

Tue Aug 09, 2011 4:50 pm

ok im done with the circuit.
i hope i´ve done it correct.
would be nice if someone with more knowledge could take a look and check it for errors.

short description:
this circiut can charge an singel li-po cell with 1A, and should be able to power a system at 5V with a current of ~1-1.3Ah from that cell, even while the li-po gets charged..
the li-po which will be used need to be able getting charged at 1A and also need to be able to deliver a constant current of up to ~1.5Ah. so take a big one ;-)
a suitable power adapter would be one with a rating of 5V and 2Ah.
this circuit is designed to power the raspi and leaves around 800-1100mAh for peripheral devices.
here is the shematic.

AmyS3
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Re: Power supply

Wed Aug 10, 2011 12:02 am

due an inoffical statement from a official source, it is now most likely that the pi will be able to be powerd from the hdmi/usb ports directly.
if the circuit above is correct (currently undergoing error checking) than would that be a little powerhouse for the raspi ^^

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Gert van Loo
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Re: Power supply

Wed Aug 10, 2011 8:20 am

You can not power it from HDMI. I have seen that wrong statement several times now.
The HDMI standard says you can draw max 50mA from the HDMI connector. See HDMI spec section 4.2.7. That is not enough to run the board from. USB is max 500mA, so that is doable but a lot of USB ports can not provide that amount of current (e.g. Laptops) I have a diagram available how to do it but have not figured out how to upload the picture.

AmyS3
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Re: Power supply

Wed Aug 10, 2011 6:01 pm

oh i made a mistake in my prior post.. (was already half asleep..)

to not make an error again i post the original text:
We’re still reviewing the power supply elements of the board, as they’ve turned out to be surprisingly expensive in their current (no pun intended) form. Right now I believe we may well end up requiring an input voltage of exactly 5V, and feeding this through to the HDMI and USB outputs. I assume this would suit?

so if you would take that charging/powering circiut i made you can power the raspi and would still have lots of current left which you can use to slave in some power into additional usb devices or anything else which uses 5V.

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abishur
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Re: Power supply

Wed Aug 10, 2011 8:21 pm

Quote from AmyS3 on August 10, 2011, 19:01
oh i made a mistake in my prior post.. (was already half asleep..)

to not make an error again i post the original text:
We’re still reviewing the power supply elements of the board, as they’ve turned out to be surprisingly expensive in their current (no pun intended) form. Right now I believe we may well end up requiring an input voltage of exactly 5V, and feeding this through to the HDMI and USB outputs. I assume this would suit?

so if you would take that charging/powering circiut i made you can power the raspi and would still have lots of current left which you can use to slave in some power into additional usb devices or anything else which uses 5V.

Just to make sure we're on the same page here, the quote referenced is stating that they hope to be able to use a 5V to power the r-pi as well as provide power out to the HDMI and USB (rather than the opposite of bringing 5V in from the HDMI and USB to power the r-pi), right?
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AmyS3
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Re: Power supply

Wed Aug 10, 2011 10:26 pm

yes absolutely.
i almost passed out in front of the monitor when i wrote the wrong statement.. must have been dreaming already ;-)

but yes its rather powering the raspi over the "normal" power jack and not via usb.

still, this power option is not to be rated as a fact. sadly..

but im going to use the circuit i´m provided here anyway i a slightly different form since i have 4 cells to charge and not only one.
and im going to power the raspi with 3.3V cos i dont need the hdmi.. usb maybe but this would be powered by the 5V from the charger circuit...

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