Hi Stefan,
1) Is it possible to use a stepper motor (I think that would be most convenient to use) without a microcontroller? It just has to turn in one
way at the same speed all the time.
If you dont want to control the motor using microcontroller, the DC motor is the best option. Easy to connect, more torque and cheap.
2) I found a project (you can google “simple SD audio player” it’s the first link to elm-chan .com
This project can play only .wav files and not mp3. mp3 requires a decoding algorithm whereas the .wav is the raw form of musical data which can be played directly.
3) Where can I find a chargable battery that will support the need of the system?
There is a mouser catalog button at the upper right hand corner of this page, you can find it from there.
4) More on the battery: how do I make it possible to be charged through a mini sd input (Like one of those simple SD card mp3 players)
Find out the SUPPLYVOLTAGE and SUPPLYVOLTAGE_GROUND pins and connect the battery charging circuit there.
5) Where do I find an on/off switch (like on a mp3 player) and how do I impliment this in my schematic
There is a mouser catalog button at the upper right hand corner of this page, you can find it from there.
6) Could I make this one a double sided PCB (one side mp3 and one side stepper motor) and still make it run with one battery?
Yes, If you are using a 9V battery.