Redeyez

Hey guys. I was just surfin' the web looking for something fun to do the other day, and I came across a charger that some guy made for his ipod. I looked around, and there was actually quite a lot of different designs. However, the basic idea is that you pack some batteries in an altoids tin and wire them to a firewire or usb plug to power your external hardware.

Intreging, I know. The only problem I have is that my mp3 player, the Samsung YH-920, is charged off a wall socket, not a usb or firewire plug. Luckily, I realized that my phone, an Lg VX2600 (I think), uses the same type of plug!

Now I have to make on of these.

Obviously, the two devices don't have the same power requirements. The mp3 player requires 5Vdc @ 1amp.

Here's my plan:
hack a power chord for my phone off;
wire a few 9V batteries together in a series circuit, along with a 7805 regulator to keep the batteries from frying my player;
connect the phone charger to the batteries and;
mount the whole setup in an altoids or similar tin box.

Here're my questions:
does the 'ground' or 'common' pin on the regulator connect to the case or the negitive terminal on the battery or what?

I'm pretty sure the middle pin goes to the case, but I just wanted to make sure (don't want to fry my player).

Is the regulator going to get really hot in there, or will it be ok in the metal box? I know it will get warm, but will either mounting next to holes or outside the box be necessary?
What are the other options for dumping off that extra voltage? How do they compare in price to the $1.50 regulator?
I'm sorry if I'm asking stupid questions.

Here are a few (kinda) similar chargers:
http://www.retechnologies.org/news.php?extend.30
http://www.chrisdiclerico.com/mt/archives/001572.php
http://www.math.columbia.edu/~bayer/iPod/
http://www.hackaday.com/entry/1234000520028239/
http://www.hackaday.com/entry/1234000270029372/

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Redeyez

anybody have any input on this? questions? comments? en- dis- couragement?

rubicon

The 7805 has three pins: "IN", "OUT", and "GROUND".

The "IN" should be connected to the input voltage (7-35VDC, IIRC, but don't quote me on that), "OUT" should be connected to the +5V line of what you're hooking it up to, and "GROUND" should be hooked to the common ground.

BTW, the 7805 is a linear regulator, and generates quite a bit of heat. Make sure you connect a heat sink of some sort to it.

Zac

yeah - stop before you blow something up









(serious answer: gnd on the 7805 connects to the negative on the 2x9 volt bats)

Redeyez

so, it should look like this, right?

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rubicon

I assumed he knew *something* about electronic circuits...

BTW, Redeyez: if the 7805's going to be in a metal case, you could theoretically use the case itself as a heat sink. Keep in mind, though, that I think the heat sink of the 7805 is connected to the 7805's ground, so make sure everything's propery insulated - i.e., metal bits aren't touching other metal bits that they're not supposed to touch.

rubicon

It's really a pretty simple circuit, though I know electronics can seem really bizarre to someone who hasn't had instruction.

What you have seems ok, so long as you have all the connections done right (+ to +, - to -/ground) and are sure of the necessary voltage requirements/limits.

BTW, your graphic skills humble me.

PS - Good job wiring the 9-volts in parallel (vs series) - are you sure that'll supply the 1 amp that you need? If so, I don't think it'll last for very long.

PPS - I spent 6 weeks in San Antonio for USAF basic training. I feel for you, man.

Redeyez

yes, i have taken all my time learning the complexities of ms paint rather than electronics.



actually im not THAT stupid, i just tend to overlook stuff that somepeople's 'common sense' fills in for them. I'm not stupid, i just lake common sense

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Redeyez

what base?

rubicon

Lackland - that's where USAF does all of its BMT. Then on to technical training - 4 glorious months at Keesler, in Biloxi Mississippi!

It was all quite a bit to take in for a boy from New Jersey.

Redeyez

i just tested the battery, and i can pull 5 amps off it, but it drops fast. I hope that with two wired up, 1 amp could go for a bit of time. maybe i would have to go with three? I'm considering getting a switching transformer (i think that's what it's called), so it would be more efficent. (please advise as i'm surly WAY off track here).

rubicon

Well, as long as you wire them in parallel (as you have been), adding more batteries will decrease the load on each individual battery, and the circuit will last longer while still providing 9V. For example, 2x9V in parallel (assuming 1000mAH [milliamp/hours] per batt) = 2000mAH at 9V - that's 2000 miliamps (2 amps) for a period of one hour. (My numbers are just pulled out of the air, so don't follow my instructions verbatim.)

A linear regulator is more wasteful (of energy, in the form of heat) than a switching one would be - but is cheaper, and generally smaller. See what kind of life you get out of the 2x9V setup, and if that doesn't work for you, put another 9V in the circuit.

Redeyez

Thanks for all the help rubicon. I apologize for all the stupid questions and appreciate your replies. Thanks for not flaming me, too!

__________________
Current status:
wtf is a carputer??

Fatigue

I was born at Lackland :d

My Ipod ( the "amazing" shuffle..) has a male usb, and just plugs into the computer to recharge. Pretty much the only neat thing about it. Got it for free so..

Redeyez

how did you get a free shuffle?
don't really want one, though. dosen't even have a screen!

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