Build an iPod Charger with Declining Balance
Obligatory Disclaimer
I did this and it worked. However, I generally know what I'm doing. Even if you know what you're doing, you might break your iPod, computer, or other stuff by trying this project. If you haven't done any electronics before, you might want to think twice about attempting to build a charger for an expensive piece of electrioncs. It's a pretty simple project, but there are still ways to make a mistake and break something. Before you plug your iPod into your charger, make sure that the output voltage is correct and that you've done everything right.
I cannot be responsible for any damage you do to your computer, your iPod, your furniture, your cat, yourself, or any of your other possessions by attempting this project.
[top] Side note
This page gets a lot of hits from people who are looking for something else. If you're looking for how to fix your iPod, I don't know; keep looking. If you're looking for how to break your iPod, well, there are lots of ways. Be creative. Send me pictures.
If you're looking for how to tell which wire on your AC adapter is positive and which is negative, try here.
If you have a cable with wires of a certain color, and you want to figure out what the green wire does, beware! There are some conventions: black is often ground; red is often a power supply of some sort. But these are not standards, and if you try to guess which wire is which without using any kind of test equipment, you're probably going to break something sooner or later.
[top] What is it?
It's a USB charger similar to the one described here, with a bit of inspiration from Minty. The nice thing about it is that you can buy the case, typically one of the more expensive parts of an electronics project, for $2.50 of declining balance!
When I built this, I had almost all of the parts lying around my room. I ended up paying only $1.12 of real money.
I call it an iPod charger, but you can use it for any device that charges through the USB port. I actually built it for my iPod Shuffle.
My instructions here aren't terribly detailed, and that's partly on purpose. If you don't know how to do something that I'm telling you to do, you might want to think twice about attempting an electronics project that connects to something as expensive and un-fixable as an iPod. But you can find more detailed instructions for doing basically the same thing here. Also, feel free to comment if something is unclear.
[top] Instructions
First, acquire the following things. You may have to pay actual money for some of them:
- Female type A USB connector
- ~9V AC to DC adapter. Anything from 5V to 15V or more will probably work.
- Connector that fits the AC/DC adapter (optional)
- 7805, LM340T-5 or equivalent +5V regulator rated for 500 mA or more
- Soldering iron and solder
- Dremel tool (better) or wire cutters
- Voltmeter
You can get the regulator and possibly the power connector at the EE Stockroom (029 Moore). You might be able to get the USB connector there too, or you might have to cut a USB extension cable in half. If you have to buy a USB extension cable, this will be the most expensive part of the charger, so try to find one lying around. A type A connector is the kind that the iPod plugs into.
The AC to DC adapter will likely be the biggest part of the project. I used a very small one from a RadioShack wireless remote control range extender. You should try to use an adapter rated for 500 mA (0.5 A) or more. Mine isn't, and it seems to work fine, but it might overheat and die.
You can also use a 9V battery connector instead of an AC adapter, but I'm not sure how many charges you can get out of a 9V battery. With the LM340T, you can actually use any battery that gives you 7.5V or more. With a significant amount of ingenuity you might be able to cram the batteries inside the case.
Note that I'm assuming you're using an LM340 or compatible regulator. If you're not, you should look at the datasheet for your regulator to make sure that the pinout is the same.
Now for the declining balance part. Go to Broad Cafe and buy a tin of Broad Cafe mints. They're against the wall on the right in a jar and cost $2.50.
If you're not at Caltech, of course, you can use whatever sort of mints you prefer.
Put the mints somewhere and clean out the tin.
Cut a notch in the side of the tin for the USB connector. A Dremel tool would be nice for this, but I used a wire cutter.
Cut another notch for the power connector (if you have one) or the power cable (if you don't).
Using the voltmeter, figure out which wire from the power adapter is positive and which is negative. If you're using a power connector, connect a wire from the appropriate terminal on the connector to the middle terminal of the voltage regulator. If you're not, cut the plug off of the end of the cord from the power adapter and tie a knot in it (for strain relief), then solder the negative wire to the middle terminal of the regulator.
If you're using a USB connector from an extension cable, like I did, it should have a black wire, a red wire, a white wire, and a green wire. (The white and green could conceivably be two different colors.) Solder the black, white, and green wires to the middle terminal of the regulator. If you're not sure which wire is which, plug the USB connector into a USB port and use a multimeter. The "black" wire is ground, the "red" wire is +5V, and the other two are data. If you're using an actual USB connector instead of a cable cut in half, "black" is pin 4 and "red" is pin 1.
Connect the red wire from the USB connector to the output terminal of the voltage regulator. When you hold the regulator with the leads pointing down and the part number facing you, the output terminal is on the right.
Connect the remaining terminal of the regulator to the positive side of your power supply
Mount the components in the tin. The inside of the tin should be covered in white paint that makes it not conductive, so don't worry about things shorting out by touching the tin. However, you may want to cover all of the exposed connections with hot glue.
Plug in the power, but don't plug in the iPod yet. Make sure that the voltage between the red wire from the USB connector and any of the other wires from the USB connector is close to five volts. (Mine was around 5.13.)
If your iPod loses power after it's been charging for a while, it probably means that the regulator is overheating. If this happens, you should figure out how to attach the metal tab on top of the regulator to the tin. The best way is to drill a hole and use a screw. Scrape off some of the paint so there is metal-to-metal contact between the tab and the tin.
The problem with simply bolting the regulator to the tin is that it's not very aesthetically pleasing. You might also try soldering the tab to the tin. You'll need a really hot soldering iron or a lot of patience, and the thermal conductivity won't be quite as good, but it'll probably dissipate enough heat to keep the regulator from shutting off. You might kill the regulator by doing this, but they're pretty much indestructible, so don't worry too much. Another problem you might have is that the paint will heat up and rub off of the tin, leaving an ugly metal spot on top, so be careful.
