I did run into some snags that the guy above covered but i found a way to do better.
I did do this instructable after building it becuse I wasnt planning on making a instructable.
I used an old Memorex boom box that I had lying around that the cd player didn't work in.
And this will be for moderate modders probably not for beginners. What i wanted to do was make a ipod dock that would charge and play music though the built in speakers, all within the boom box with no other wires besides the power.
I have an addon that i have yet to do: Add blue led's to the inside of the boom box.
Mine only fits the ipod touch!
Step 1: Docking Station
After i had gotten the insert to fit into the slot in the boom box I needed to make holes for the headphone cable and the charging cable. Below is the final product! Hot glued into the boom box.
Step 2: How to Make the Ipod Charge?
To achieve this we must use pull up resistors, a pull up resistor is a resistor that takes the hot and pulls it to the other pins. Below the resistors are the zig zag lines going to the G and the W those are the data lines Green and White. For both of those I used 470 Ohm resistors.
I had 12v supply coming out of the transformer from the power supply. It took about 300mA to run the boom box by itself. I also found out that the iphone and ipod touch pull about 1amp when in quick charge. I looked at the power supply and I decided that it could handle 1A.
I pulled off that 12v source and inputed it into my 5v regulator, I used a 7805 , ask radio shack for a 5v regulator and it will most likely be a 7805. In most cases the regulator doesn't need a heat sink but if you are pulling 1A or more then a heat sink will be desirable and extend the life of the chip. A simple binder clip will do.
I ran into a snag because the boom box wasn't grounded I had to filter the output, the regulator does some of this but i wanted to make sure it was smooth. A Cap - Coil - Cap does a good job. You can see it in my schematic below.
Step 3: Audio
A simple T-pad solves this problem, A t-pad is a relationship and below is a calculator to determine the resistors you should use.
A common output for an ipod headphone jack is 33 Ohms and the common output of the built in cd player is about 1kohm, a big defiance in impedance so i had to go from low to high impedance. The problem with this is that i get some volume loss in the prossess.
I lose about 21db and the resistors I used in the schematic below are:
R1 = 1ohm
R2 = 987ohm
R3 = 33ohm
Once i had gone from headphone jack - t-pad - amp i was good to go and it charged and played music!
Step 4: Enjoy!