Just a small information up front: I tried the following modification myself and it worked for me. When you decide to do this modification also, you can loose warranty or even break your devices. Which means: Everyone who is doing this modification is solely responsible for the consequences!!
USB charger for iPod and other devices
Recently I got an iPod nano 2nd generation for free. I like it very much. The only thing I do not like: Charging is only possible through the data cable and a running computer. But I didn't want to spend 40,- € for an original Apple power supply.
Therefore I bought a cheap USB power supply set through ebay, which contained of a power supply for home, one for the car , and a data cable. I favoured USB power supplies as there are lateron usable for otehr devices, too. In this case for my mobile phone and an external image tank.
Those cheap power supplies only have on problem: The iPod nano is not being charged. After some searchign I found a reason for this which lead me to this modification as described here. Generally speaking this modification can also be done using a short USB cable typa A-A male/female which you cut into two pieces.
The reason for the power supplies not charging was simply that only the both outer pins of the USB connector are used (GND and +5V). Both middle data pins were not connected and therefore the signal voltage levels were not defined. It looks like the iPod is doing some kind of checking. (I guess that this checking is done by the charging circuit, because this behaviour can be found with various other devices, too.) To allow charging the data pins have simply to be set to a defined voltage level. The folowing circuit is totally sufficient:
As you can see two simple voltage dividers are enough to set the data pins to a defined (middle) voltage level. Resistor value can be 22kΩ od 47kΩ. Basically the resistor value is not that important. It only should not get too small, because otherwise there is too much load on the power supply. By using the power divider you also make sure that there is no short and the drivers of the Ipod are not damaged.
I did this modification in the powersupplies itself. Of course you then have to be very careful to not create a short and isolate everything properly. Make also sure that no part of the circuit extends to teh 230V parts of the power supply. (Otherwise the iPod might get damaged!)
Small hint when integrating the above circuit into a cable: The power wires are usually a bit thicker than the other ones.
BTW: Such a changed power supply can be also used with an iPhone 4!
Comments:
leider will Apple das anders als Android-Geräte. Bei denen sollten die Datenleitungen kurzgeschlossen sein (bzw. max. 100 Ohm dazwischen). Außerdem verlangen manche Apple angeblich 2,5 und 2,8V, also zwei unterschiedliche Spannungsteiler. Habe ich zumindest bei einigen Universal-Ladegeräten gefunden, die dann bei Android nicht den vollen Strom liefern. Gerät zeigt USB statt AC an
Sorry Vlad, but chargers that work for blackberry do not work for iphone. I tested several...
For Blackberry simply the powerlines have to be connected. I know it, I had one before.
When shorting 2 and 3 you are shorting data lines. As far as I know the data transmission is a but and uses diferential voltages. If for some reason the iphone switches the datalines to output mode you are shorting e.g GND with +5 volt which leads to high current and might damage the iphone. Normally you can expect the used circuits to have a current limiter, but on the other hand, why risk a expensive repair?
Nevertheless shorting 2 and 3 might work, I never tested it.
Why not just short 2 and 3?
I found that just shorting 2 and 3 works for most devices (Blackberry, for example). Also, four resistors seem redundant. A simpler, 1-resistor-2+3-resistor-4 circuit should be sufficient (+ is a short between 2 and 3).
ergänzung: zur Steckdosenversion kommen ebenfalls 3 DC-DC-Wandler zum einsatz! :-)
Bei meinem USB-Adapter mit 2A habe ich 2,7 Volt am Daten+ und 2 Volt am Daten- und damit wird die 2A-Ladestromstärke freigegeben. Meine Entwicklung wäre ein 3-Fach USB-Ladegerät für iPad, Samsung Galaxy Note 10.1, ... für die Steckdose (mit TDK-Lambda Schaltnetzteil Eingang 85-265V 47-63 Hz AC und 120-370V DC und 12V 12,5 A Ausgang mit zusätzlicher Zigarettenanzünderbuchse für andere Endverbraucher wie 12V-Kompressor,...) und einer KFZ-Version mit 3 DC-DC-Wandlern (Traco Power THN-2411 Eingang 9-36V Ausgang 5V 3A), das mit 12-24V (14-30V) betrieben wird! Grüße aus Wien ;-))
@Vlad: This is necessary to get some "mid" voltage. If you would just connect to +5V or ground the data lines would be also have +5V i.e. Ground level. I tried it and it did not work!
Diagrem is a bit confusing
Great idea and a thorough explanation that makes sense, thanks. I just find the diagram a bit confusing. Why connect both positive and negative power supply pins (1 and 4) to each data pin? Shouldn't it be sufficient to just short pins 2 and 3 and connect them to the positive pin with a single resistor?
I also found that just connecting pins 2 and 3 together works for many (if not all) devices. Did anyone try that with iAnything?
Hatte auch eins dieser nicht-apple-geräte. funktioniert super! vielen dank dafür!!
