In this instructable I'll show you how to build a boombox for your bike. It's a cheap and useful project even for beginners. The device has a build in mp3 player chip with navigation buttons and with an LED screen. The power supply is a rechargeable 3.7v phone battery with 1000mAh of capacity. This is enough for about 10 hours of usage time.

We no need to connect our phone to this device because the mp3 player plays easily anything.

The speaker's imdependense is 8 ohms that would ensure a very cool music experience while cycling.

I really like to ride a bike and I go almost everywhere with my bike, but I like to listen to music too. So I just combined these two things together and created this DIY portable mp3 player. Now let see what you'll need for this!

Step 1: Parts and Tools

Tools:

• Soldering iron
• Rotary tool
• Glue Gun
• Cutting and Crafting tools

Materials:

1. a plastic box
2. USB cable
3. 8 ohm Speaker
4. wires
5. a mp3 player-You can buy fake iPods like this here. You'll need to take out the mp3 player circuit. Follow the images and remove the battery because we no need this low capacity.
6. 1000mAh phone battery
7. LM386 audio amplfier chip
8. 470uF capacitor

That's all. This is a mono speaker device but you can add one more speaker if you make two amplifier circuits. Put the small battery away for another project.

Step 2: Heat Up Your Soldering Iron!

You need to know that I changed the speakers three times until I get the best quality and sound. I know in the diagram is an error with the USB cable mark, sorry!

1. Follow the circuit diagramm and build the circuit. First make the audio amplifier circuit with the LM386 chip and with the 470uF capacitor.
2. Then add the battery wtih a switch.
3. Now you'll need to search the audio output pins on the mp3 player. Solder these to the ampifier chip's input pins, just like on the diagramm.
4. Add the speaker
5. Clean the USB cable's end.
6. And finally solder the USB cable to the battery.

This battery can't be overcharged, but please use a charging circuit. I used some heat shrink tube,but this isn't so important.

Step 3: Prepare the Plastic Box

This step is pretty easy but you'll need to have forbearance. Cut a big hole for the navigation buttons, and some smaller holes abowe the speaker. One more hole will be needed for the power switch.