Introduction: Boom Box Ipod Dock / Homemade IHome

This was my first mod, I took the idea from another instructable: https://www.instructables.com/id/PLAY-AND-RECHARGE-IPOD-USING-OLD-BOOMBOX---Hints-a/

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.

Backround:

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

Well first I needed a place to hold my ipod while it played music and charged so I decided to dremal the insert that came with the ipod. But I ran into a problem, i didn't want to remove my case when I plugged it in so i did more dremeling to make the slot bigger. Also i had to dremal out a spot in the boom box for the insert to insert into.

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?

The new ipods have a thing that makes it so they don't charge with universal chargers. That is because the ipod looks for a handshake with a computer on the 2 data pins, green and white, and if they don't find a handshake then they look for those pins to have a voltage between 2.5v and 5v.

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

Next we need it to play music. I took the headphone cable and wired it into the amplifier but i found static when i played it. Later i found out that the cd input into the amp has a high impedance and the ipod had a low impedance so i had to match impedances.

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.

http://www.nu9n.com/tpad-calculator.html

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!

Enjoy! I hope this gave you some tips on how to build your own!

Happy Modding!
-GamingRobot

Comments

author
eli2k made it! (author)2010-01-10

Hey, how did you determine the impedence values for the ipod and cd player? If you use other mp3 players, wouldn't they have differing impedence values (though I guess they would be low, instead of high like the cd player)...

author
FrostEnergy made it! (author)2009-08-23

haha yea! i did the same thing before i saw this instructable! but wouldnt it be great to get your hands on one of those cables that have everything in just the usb plug with the stupid apple "verification chip"

author
FrostEnergy made it! (author)2009-08-23

a much simpler way to do this, is to simply bridge the data connections with a 10k ohm resistor, that acts as the "hand shake" i have a touch 2g, and it also works with everything ive tried =)

author
Phil B made it! (author)2009-02-04

I am impressed with your knowledge of electronics at age 17. I had never heard of T-pads. How do you know how many decibels to drop the iPods output to match the signal insertion point on the boombox?

author
GamingRobot made it! (author)GamingRobot2009-02-04

I looked up online for the ohms of the cd input and the ipod output<br/><br/>I used this url to calculate the t-pad resistor values<br/><a rel="nofollow" href="http://www.nu9n.com/tpad-calculator.html">http://www.nu9n.com/tpad-calculator.html</a><br/>

author
The magical duct tape kid made it! (author)2008-12-22

Very Nifty

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