maccboy
Posts: 10
Joined: Tue Mar 13, 2012 5:22 pm

Re: Wind-up charger

Thu Mar 15, 2012 11:01 am

Hi

Been watching this forum for a while - and ordered my RPi (haven't we all!). I must say that I've learnt a lot from this place.

I was wondering if anyone had thought about using a wind-up charger for powering their RPi. I'm not sure what current rating they have - or voltage output for that matter - but wondered about one for a mobile solution.

Kernel
Posts: 395
Joined: Sat Mar 03, 2012 12:53 pm

Re: Wind-up charger

Thu Mar 15, 2012 2:11 pm

well a quick google search shows this and I am sure others are available:

http://www.maplin.co.uk/usb-wi.....ger-225747

Model B needs 700mA but A is ok with 500mA :




Output Voltage:
DC 5.5V (±0.2)
 
 
 
 
 
 
 
 
 
 


Output Current:
0.5A (500mA)
 
 
 
 
 
 
 
 
 
 


Output Power (Max):
2.75W
 
 
 
 
 
 
 
 
 
 


Regulated Output:
Yes
 
 
 
 
 
 
 
 
 
 


Output Tips/Socket Type:
USB A Socket
 
 
 
 
 
 
 
 
 
 


Number of USB Sockets:
1



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Burngate
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Re: Wind-up charger

Thu Mar 15, 2012 3:41 pm

Looking at that one: charger in one hand, winding with the other, how do I use the mouse or keyboard?

It really needs to be fed into a battery, with proper regulation to feed the Pi.

Also, I've found, at least with wind-up torches and the like, that they're remarkably inefficient - most of the work put in goes into the gearing, not the electrical output.

I'm vaguely thinking of getting the bike out and using its dynamo.

Ravenous
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Re: Wind-up charger

Thu Mar 15, 2012 4:08 pm

Burngate said:


It really needs to be fed into a battery, with proper regulation to feed the Pi.

Also, I've found, at least with wind-up torches and the like, that they're remarkably inefficient - most of the work put in goes into the gearing, not the electrical output.


I have a cheap brand wind up radio - simple plastic gears and a standard toy motor.  Tops up two small (half-AA size?) rechargeables of some sort, so we're talking about 2-3 volts.

Yes it'll need over-voltage protection too, and I suppose some proper charge circuit to prevent the batteries getting overcharged.

Also it puts out a huge amount of RF interference - so ironically the radio is unlistenable while you're winding it.  By the way this even interferes with my digital (DAB) radio so might upset other things in the area like wireless networks?

So I suppose it could be done with a decent generator, or a bike and 6V dynamo sounds good (or large solar panel), but we'd need a big battery...

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alexeames
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Re: Wind-up charger

Thu Mar 15, 2012 4:11 pm

I'll be using a 2.4 watt solar panel (that was sitting in its box doing nothing) and a 10 Ah Gel cell that came out of a golf trolley - along with a switching regulator to bring it down to 5v [£4 the only bit I've bought for it].
Alex Eames RasPi.TV, RasP.iO

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Chromatix
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Re: Wind-up charger

Thu Mar 15, 2012 5:43 pm

You should be able to sustain several tens of watts on a bicycle quite easily, provided the dynamo you're using is efficient.  Experienced cyclists are able to sustain 100W.  With a battery to store excess energy, it would be quite a good solution to powering an R-Pi.

If, that is, you're not very fond of overall energy efficiency.  The human body isn't very good at that part.  This same argument applies to wind-up systems as well.
The key to knowledge is not to rely on people to teach you it.

trikidiki
Posts: 12
Joined: Thu Mar 15, 2012 9:00 pm

Re: Wind-up charger

Thu Mar 15, 2012 9:04 pm

All very well winding up for the Pi.

Have to get the motorbike out to power the telly.

gimliflea
Posts: 76
Joined: Fri Nov 18, 2011 4:14 pm

Re: Wind-up charger

Thu Mar 15, 2012 9:34 pm

Hitch up an exercise bike to a generator and take some exercise every so often. Come to think of it lets build a human powered Gym!

gritz
Posts: 449
Joined: Sat Jan 28, 2012 2:33 am

Re: Wind-up charger

Thu Mar 15, 2012 9:53 pm

I could (just) sustain 500W on one of the exercise bikes at the gym, but there'd be no energy left for surfing the net or even watching telly!

I expect the web is laden with projects utilising motors as generators and high efficiency switch-mode converters. As always the hard part is not the electronics, but the mechanical stuff that converts effort into rotation.

S0litaire
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Re: Wind-up charger

Fri Mar 16, 2012 12:41 pm

Hm...

Is it me of can i imaging a clockwork wind-up charger for the R-Pi??

simple mechanism (ok... "relatively" simple) to store energy in a spring, attach that to a dynamo and rechargeable battery

Clockwork-Pi ^_^
--
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Bill "Solitaire" C

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