Mp3 Player charger (help please)

**Redeyez** · 03-12-2005, 10:04 PM

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/

**Redeyez** · 03-12-2005, 10:51 PM

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

**rubicon** · 03-12-2005, 11:03 PM

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** · 03-12-2005, 11:09 PM

yeah - stop before you blow something up

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

**Redeyez** · 03-12-2005, 11:16 PM

so, it should look like this, right?

**rubicon** · 03-12-2005, 11:17 PM

Originally Posted by ksmyarse

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

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** · 03-12-2005, 11:21 PM

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** · 03-12-2005, 11:26 PM

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

**Redeyez** · 03-12-2005, 11:41 PM

Originally Posted by rubicon

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

what base?

**rubicon** · 03-12-2005, 11:47 PM

Originally Posted by Redeyez

what base?

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.