( http://www.instructables.com/ex/i/C2303A881DE510299AD7001143E7E506/ )
"????-- a project that uses another project as a stepping stone for further refinement, improvement, or application to a totally different problem. The community of DIYers that we're all a part of can really do some amazing things working together as a community. Innovation rarely happens in a vacuum. The obvious next step is to let the community help refine and evolve ideas that aren't yet ready to be finished projects."
We submit this now so that other iPod enthusiasts could pickup where we left off.
There are (at least) two reasons this charger _does not_ work:
1. The transistor doesn't let enough current flow to fully charge the inductor. The other option is a FET, but a FET needs a minimum of 5 volts to switch fully on. This is discussed in the SMPS section.
2. The inductor is simply not big enough. The charger doesn't produce nearly enough current for the iPod. We didn't have an accurate way to measure the iPod charging current (save cutting apart the origional charging cable) until our parts arrived from Mouser. The inductors recommended are nowhere near large enough for this project. A suitable substitution might be the coil Nick de Smith uses on his MAX1771 SMPS. Its a 2 or 3 amp coil from digikey:
( http://www.desmith.net/NMdS/Electronics/NixiePSU.html#bom )
This device can provide a small amount of power to a USB or firewire device, but not enough to charge an (3G) iPod. It WILL power, but not charge, a totally dead 3G iPod.
Step 1: Switch Mode Altoids iPOD Charger using 3 'AA' batteries
Standard disclaimers apply. High voltage....deadly...etc. Think about how much your iPod is worth to you before connecting it to this little stun gun in a tin can.
For all the math and dirty details of SMPS, read the nixie tube boost converter instructable:
Read on to see how the nixie tube SMPS design was adapted to be an iPod charger....
A ton of previous work inspired this project. One of the first DIY chargers used a combination of 9 volt and AA batteries to charge an iPod through the firewire port (works for all iPods, mandatory for 3G iPods):
This design has the problem of uneven discharge among the batteries. An updated version used only 9 volt batteries:
The design below appeared on Make and Hackaday while this instructable was written. It is a simple design for a 5 volt USB charger (this type will not charge earlier iPods, such as the 3G). It uses a 9 volt battery with a 7805 5 volt regulator. A stable 5 volts is provided, but the extra 4 volts from the battery is burned off as heat in the regulator.
All of these designs have one item in common: 9 volt batteries. I think 9 volters are wimpy and expensive. While researching for this instructable I noted that an 'Energizer' NiMH 9 volt is only rated 150 mAh. 'Duracell' doesn't make rechargeable 9 volters.
A 'Duracell' or 'Energizer' NiMH 'AA' has a healthy 2300 mAh of power, or more (up to 2700 mAh ratings on newer rechargeables). In a pinch, disposable alkaline AA batteries are available everywhere at a reasonable price. Using 3 'AA' batteries nets us 2700mAh at ~ 4 volts, compared to 150mAh at 9 or 18 (2x9 volts) volts. With this much power we can live with switching losses and extra energy eaten up by the SMPS microcontroller.