maemo.org - Talk - my modified n900 - "normal" usb port and solar panel

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- Nokia N900 (https://talk.maemo.org/forumdisplay.php?f=44)

- - my modified n900 - "normal" usb port and solar panel (https://talk.maemo.org/showthread.php?t=90460)

Re: my modified n900 - "normal" usb port and solar panel

Quote:

Originally Posted by ryu1 (Post 1352151)

Yes exactly, it's not a usb hub, its the same port. I wanted to no longer carry usb adapters or Y cable with me.
As for the solar panel, you are right, it's kind of useless, but it doesen't bother me (i barely notice its presence on the back). And about diodes, i simply couldn't find anymore space for them :) but i sticked a tape on the contacts (you can see it in the last picture), so in everyday use the panel does not make contact with the battery. However that was a proof of concept only :) to show that it is possible. Back in the days of symbian, i was out on a trip for one week, and my nokia n70 depleeted its battery in the first day, and there was no place to charge :) so i could not power the phone on at all, and i really nedded to check email, but that was not possible.

As a side note - let's keep the discution more on-topic. The reason i did not hold the phone with my hand was becase the phone i used to take the pictures (nokia e72) was with problems, so i had to keep one button pressed to focus and another button to take the photo. I always thought maemo.org is a respecable site where we discuss ideas, not social networking crap.

It was an Joke, a Joke FFS :D Back to the topic, like in previous posts, I as well think that the solar panel isn't much needed due to it's lack to be suffictient. There is pleanty good quality and bigger (i.e. more effective) solar pannels we can use for charging while outdoors.
Them all can be used with N900, only not when on the move I suppose (because need to watch out for mUSB port). But now You don't have to think about it.

I always wanted to use solar panel attached to back pack, charging N900, and be able to walk forward thru hard and bumpy terrain.

Remember to smile from time to time, smile is good for You :D

Re: my modified n900 - "normal" usb port and solar panel

Quote:

Originally Posted by Garrett_PL (Post 1352169)

I remember i read somewhere on TMO that a user blow up a usb fuse while using one of those bigger solar chargers. Even i, destroyed :D my first n900 messing with a broken charger that directed current via the data pins of the usb port and fried the usb chip. The phone was still functional, but no usb connection could ever be make via the usb, no charging, pc did not recognize it and i have nothig else left to do then sell it for parts :(

Re: my modified n900 - "normal" usb port and solar panel

found the post here is it (it is not on TMO) :
http://dmidv.de/articles/11/thanks-f...-fix-your-n900

Re: my modified n900 - "normal" usb port and solar panel

Unregulated solar panel can ideed fry your charging cirquitry by overvolting. You need one with USB out.

The biggets theoretical output one can expect from a solar panel small enough to fit on the back of the N900 is about 0.4W, i.e. about 108mA @ 3.7V (our battery's nominal voltage). That's assuming a rather optimistic 20% efficiency of the solar panel and maximum exposure to the sunlight (with constant tracking etc). You can see here how much the N900 consumes in various conditions.

Re: my modified n900 - "normal" usb port and solar panel

What i tryed to do, was to make the n900 as standalone as posible. So i don't have to carry any extra solar charger, or usb cable, or adapter. Simply put the phone alone in the pocket and that's it :)

Re: my modified n900 - "normal" usb port and solar panel

Quote:

Originally Posted by pichlo (Post 1352224)

Unregulated solar panel can ideed fry your charging cirquitry by overvolting. You need one with USB out.

It is not the case here, as he connects it to battery itself, (not USB) when need arises.Which, of course, mean even more risk in case of over-voltage - battery circuicity should just cut it off, but you will still have overvolt on N900's battery terminals, which may fry everything (even more, due to 0 load from battery, when it cuts-off in emergency mode).

Of course, there is risk only, if that panel is ever capable of providing more than 4.25V (even for s hort while). Everything below should be safe.

OP said, that normally, this panel isn't connected to battery (isolated via tape), and he mean to use it only in emergency situations. Even then, over-voltage could be catastrophical, so I would check that panel's output in different conditions, extensively.

/Estel

Re: my modified n900 - "normal" usb port and solar panel

Quote:

Originally Posted by Estel (Post 1352357)

It is not the case here, as he connects it to battery itself, (not USB)

My post was meant as a follow-up to post #12 about the blown fuse. Absolutely agree with the rest of course.

Re: my modified n900 - "normal" usb port and solar panel

Quote:

Originally Posted by Estel (Post 1352357)

Well, i don't think that small panel i used can overvoltage since it's barely charging the battery. But my voltmeter is broken :( so i can't measure the output of the pannel.

Re: my modified n900 - "normal" usb port and solar panel

Here is a question: What other hardware modification should i do?
That solar panel cover was not my idea, althought i thought abut it long ago.
However, i was thinking of making the card slot hot-swappable :D .
I will use a card slot from a nokia n97, solder its terminals to the terminals of the n900 slot, make a nice cut in the battery cover, and that's it!
What do you think about this? And if you have any othe idea of hardware mod post it here, and i'll do my best :D

Re: my modified n900 - "normal" usb port and solar panel

Quote:

Originally Posted by ryu1 (Post 1352435)

Well, i don't think that small panel i used can overvoltage since it's barely charging the battery. But my voltmeter is broken :( so i can't measure the output of the pannel.

You'd be surprised what even a small PV-cell can do when no load (device shut off, battery full and cut out due to protective circuit kicked in) and you give it a flash from a photography electron flasher.

Estel is absolutely right with his concerns. I'd like to add concerns about USB2.0 electrical properties getting messed up by your rework, resulting in data errors or even complete failure to establish connections at highspeed (480Mb/s). Even some cheap USB cables can fail for highspeed when the building quality and cable are poor.

[edit] re your 2nd post: all that's reasonably hot-swappable in N900 is already made to support hotswap. uSD slot gets powered down when you remove the battery cover, so you don't destroy the uSD by removing it while powered. SIM is useless to hotswap anyway. So what's the rationale of your hotswap plans? I failed to get the point.

[edit2] With sufficient electronical expertise you could create a convenient way to hotswap the battery, but the needed know-how is not trivial. To give you a starter: you MUST NOT parallel-connect two LiIon cells with differing charging level.

/j