Getting That Hack On Pt. 1 — A cheap, no frills MP3 shield for Arduino

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This post is long overdue. Prior to midterm and CHI craziness, we had originally planned to do a wizard-of-oz prototype which didn’t really use (or minimally used) the arduino, but rather relied on some clever trickery to mimic the Story Sash experience using an mp3 player, some simple buttons/switches, and an LED light show. As part of that experience–and because I wanted an excuse to take stuff apart–I found an instructable detailing how to make a very cheap mp3 shield for the arduino. For only $2 direct from China, or, as I’ve been told, $20 from a local Walgreens, you can easily include sound into any electronics project. Yep, sure makes prototyping a heck of a lot easier!

In all the colors of the rainbow! I personally like blue :)

In all the colors of the rainbow! I personally like blue =)

Honestly, with my limited electronics experience and hardware programming knowledge, I found the instructable a little hard to understand since it used an analog dip-like switch and some cryptic arduino code. I’ve learned from past projects with my car and various electronics that it’s important to fully understand how a system works. Ignorance can result in some costly mistakes and I didn’t want to destroy my $5 investment! Plus, I’m a dork and love learning 🙂 So then I delved deeper here and here and here. Oh and here and here and here…you can see where this is going…

mp3 close up

Sorry for the blurry image–another late night hack.

mp3 player guts.

mp3 player guts.

After taking the mp3 player apart and playing around with my multimeter, I realized that a button press is just completing the circuit between the outer ring and bulls-eye of the contact. So we could either control the mp3 player via two methods:

METHOD 1: Manually complete the circuit by using a homemade switch/button to force physical contact.

Quick and dirty cardboard switch made out of aluminum foil and speaker wire. Amazing how conductive the foil is!

Quick and dirty cardboard switch made out of aluminum foil and speaker wire. Amazing how conductive the foil is!

METHOD 2: Write code and have the arduino trigger another component, like a DIP switch, transistor, or optocoupler, to complete the circuit.

Lots of wires to keep track of. I should probably make a schematic at some point...

Lots of wires to keep track of. I should probably make a schematic at some point…

Late night hack=no open stores. So why not harvest parts from old electronics! Desoldered an optocoupler and two transistors from this cheaply made battery charger ; )

Late night hack=no open stores. So why not harvest parts from old electronics! Desoldered an optocoupler and two transistors from this cheaply made battery charger ; )

One word of caution I will give is to make sure to look up the data sheets of your optocoupler or transistors. The pins are different for each manufacturer and you don’t want to make a mistake and cross wires. That could be bad =(

You can see that the prototyping possibilities are endless! Glad to say everything worked fine, except for a momentary scare when my mp3 player decided to stay stuck on fast forward. Desoldered the battery and left it alone for a few days to fix that! (Which is one reason why I hate the movement toward non-removable batteries in computers and phones…but that’s a rant for another time)

Stay tuned for part 2 where I add an RFID reader to tell the arduino to tell the optocoupler/transistor to change tracks. And also introduce…the zipper potentiometer!

 

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