Pocket-Sized Stereo With Built-In MP3 Player and Power Supply

I'm always trying to make a better, smaller mini stereo that fits comfortably in your pocket, but also puts out at least a half decent level of sound. This is my latest creation...

It's a small tin that has not only a built-in amplifier and speakers, but also a 600mAh LiPo battery and USB 5v boost converter for charging your USB devices on the go. The battery powers both the boost converter and the amplifier. The amplifier and speakers consume very little power, so the 600mAh battery is plenty for charging a small MP3 player (my Shuffle has a 250mAh battery) and playing some tunes at the same time. On top of all of this, it is also designed specifically to fit my iPod Shuffle inside. Having the MP3 player inside the tin is great because you don't have to worry about cords or anything either. It doesn't sound great, but what do you want for half a watt?

I used my first generation iPod Shuffle in my design, but obviously this project can be modified to fit any small MP3 player. My Shuffle has a whopping 512mb of storage (don't laugh, it was a big deal in 2005 for it's size lol), but these days you can get an mp3 player half the size with ten times the storage for about 20 bucks at Walmart. 

Note: You'll probably notice by some of the pictures that the order of the steps in this Instructable are not the same order in which I did them. I just ordered the steps in the way I thought would make the most sense based on the trial and error of making this project.

Here's what you'll need:

-Small metal tin (I used one that had multi-vitamins in it, but an Altoids or similar tin should work fine)
-A small MP3 player (I used a 1st gen iPod Shuffle simply because I had it lying around, but if you don't have a cheap small one, just  hit up Target or Walmart and you can get one for under $20)
-USB boost converter (You can get these on eBay for about a buck with free shipping from China)
-Small amplifier (Again, like a buck on eBay)
-Small speakers (I used some small 8ohm 0.5 watt ones because they had a very shallow physical depth, which is what I needed for  this  project)
-Male 3.5mm jack (This can be salvaged from an old set of headphones or aux cable)
-On/Off switch (I used a small dual dip switch)
-LiPo charger
-LiPo battery (Whatever size/capacity will fit in your tin)
-Some thin gauge wire
-Heat shrink tubing

Tools:

-Drill and various bits
-Soldering iron and solder
-Several metal files and/or a Dremel with cutting discs
-Hot glue or epoxy glue
-Sharpie
-Awl

The best thing to do first is get all of your parts together and try and decide on a good place for each piece in the tin. Also, if you're using an old MP3 player like me, make sure the battery is still good. I actually ended up needing to replace the battery in my iPod Shuffle before I began this project.

My design is fairly simple, the hard part was making everything fit in the tin and still have it able to close. I based my entire design around my iPod. The original Shuffles are somewhat unique in that they have a built-in male USB connector, so you don't need a cable to plug them in to charge or sync. Still one of my favourite designs Apple ever came up with. I would say designing around your MP3 player is the best approach, since all of the other internal parts are fairly generic when it comes to size and shape.

I decided to mount my boost converter at the bottom of the tin off to one side and then cut a slot out on the opposite side to make it easy to put the iPod in and remove it when needed. I found there was enough space leftover on either side of the iPod for the battery to fit.

Everything else goes on the lid. I chose to mount my speakers on the outside of the lid and just drilled two small holes to feed the wires into the tin. This saves valuable space inside the tin for your other parts. The amplifier board and LiPo charging board both get mounted on the inside of the lid. Just make sure you place the LiPo charger in an area that you can access it's charge port without any obstructions when you have a cable plugged into it to charge the battery (I sort of jury-rigged mine...more in depth on step 6).

I recommend making a scale sketch on graph paper. It's just easier to plan everything that way in my opinion. There's a picture of my basic schematic in this step as well.

Once you've figured out where everything is going to go, mark those areas with a Sharpie.

Now that you've decided on placement of your parts, you'll need to make some holes. First, mark the areas to be drilled with a Sharpie, and then use an awl to mark where you want to drill so the bit doesn't skate when you are drilling.

Next, make some small pilot holes. I find the best way to drill into thin metal tins like this is to gradually increase the diameter of the hole, rather than trying to use a large bit right away.

Then, file or Dremel out any areas that you need to. I just needed to file out the one end of my tin in the shape of my iPod and a small circular slot for my aux cable to fit through.

I drilled holes for the following:

-LED indicator from boost converter
-One hole on top for each speaker to feed the wires into the tin (2 holes total)
-Hole in the bottom to be able to push battery status button on my iPod
-Hole in the bottom to be able to view battery status light on my iPod (this probably won't be necessary with other MP3 players)

I filed slots for the following:

-One large slot on the right side for my iPod Shuffle to protrude from
-A small square hole for my dip switch
-One circular slot next to the iPod slot for my aux cable to feed out through to enable it to plug into my iPod without having to leave the  tin open

I used some self-adhesive cork to both insulate the boost converter from the metal tin and as a cushion for my iPod so it fits snugly inside the tin.

I also wrapped electrical tape around the USB port of the boost converter. This is just in case it comes in contact with any other metal parts when the tin is closed.

Solder two wires to the positive and negative inputs of the converter before you secure it. Then, use either glue or silicone to secure the boost converter to the cork or whatever insulation you decide to use.

I used two headphone jack dust plugs for my battery status holes. One black one to basically use as a button extension so I can actually press the battery status button on the back of the iPod without removing it from the tin, and one clear one directly underneath the status LED on the back of the iPod so I can view the colour of the status LED.

Now, mount the switch in the previously drilled/filed hole. I used epoxy glue.

At this point, I also cut the LED terminals off of the boost converter and extended them with small wires so I could see the LED on the outside of the tin. After extending the terminals, I fed the LED through the hole I drilled and secured it with epoxy glue.

Make sure you have your wires soldered to your speakers before you mount them. Get out your hot glue gun or epoxy glue and secure your speakers to the outside of the tin after feeding the wires through the holes drilled in the previous step. I sealed mine off with some plumbing washers that I had lying around.

Solder your speaker wires to the L and R positive and negative output terminals of the amplifier. Then, grab your old headphone jack and strip the ends off of the wires. I used a male to male 3.5mm cable I had which was actually a bit difficult to prepare for soldering to the amp. There was some sort of nylon or cotton interwoven with each of the three wires and I had to used tweezers to separate it from the actual copper wire. Solder them to the L, R and GND terminals of your amplifier.

*Note: If you are separating an old aux cable, pay close attention to which wires are left, right and ground. I used an ohm meter to be certain. After you strip the ends off of the 3 wires, simply check which wires have continuity with which sections of the male connector end. I've included a picture in this step labelled with which parts of the male connector are which channels (6th photo).

Next, solder two wires to the power input terminals of the amplifier.

Now you can insulate and mount your amp with either silicone, cork or electrical tape.

Now, solder three sets of wires to the battery positive and negative terminals. Take one set of wires from the battery and solder them to the output positive and negative terminals of the charger.

In order to mount the charger in the tin and still have it clear everything, I had to sort of jury rig it. I cut a piece of plastic out of an egg carton twice the area of the charger, folded it in half and glued the charger to it. Then I glued it down inside the top of the tin. The purpose of this is that the plastic acts like a spring. When the tin is closed, it compresses. When the tin is open, it pops up so you can plug a cable into the charger to power it and recharge the battery.

Now, take both of the remaining positive battery wires and solder them to the two switch 'Off' position terminals. Then, solder the positive input power wire from the amplifier to one of the 'On' terminals of the switch, and the positive input wire from the boost converter to the other 'On' terminal.

Then, solder the other two negative battery wires: one to the negative input of the amp and one to the negative input of the boost converter.

Now, just slide your MP3 player into the tin and test it out. If everything works, great! If not, check all of your connections.

You now have a pocket-sized MP3 stereo/charger that can both charge and amplify your MP3 player, either independently or simultaneously! Or use it as a 5v power supply/charger for any other device too!

Hope you enjoyed this little instructable :)