My Daughter wanted music to play when she opens her locker at school. This sounded simple enough. A blue-tooth speaker would start playing anytime she was in range. She has a phone that can pair with the speaker and play her own music. The more I thought about it and the power constraints, I decided that the battery on a speaker that can turn on/off with the locker door would last longer between charges. So I came up with this plan: start with a small music player, add a toggle switch that can be triggered by the locker door, use a non-destructive mount, make it simple to "plug-and-play" and voila; a refrigerator-light type music box!
Step 1: ILive Portable Color Changing Wireless Speaker (ISB07B)
I chose this speaker since it was inexpensive, had the desired features (SD card), and it is easy to hack. After removing the stickum from the bottom, there are only two screws holding the speaker/cover on the base. Removing those screws reveal two more screws that remove the circuit board. Under the circuit board is the battery. I decided to splice a wire clip in the negative side of the battery leads. I also took out the switch slider and routed the wire clip through the switch slider gap. By turning the switch on and using the wire clip to connect/disconnect the negative battery lead, I can add a mechanical switch that can be triggered by the locker door.
Step 2: Music
I put my personal music on the SD card and was disappointed when it didn't play. After a little research I discovered that the files need to be in MP3 audio format. I found "Switch by NCH Software" that would convert my music files for free with a Non-commercial home use only version. I experimented with files in sub-folders or all in one folder and determined that the folder structure doesn't matter. I also determined that the speaker would start playing at the beginning of the song that was playing when it powered down.
Step 3: Non-Destructive Mount
Locker space is scarce and the School District frowns on modifications to the locker. I needed to come up with a secure mount that my Daughter could install without power tools. Using scraps of metal brackets and a magnet that I had from other projects, I came up with a mount that fit the bill. The metal bracket also provided a place to mount the mechanical switch and allow for adjusting the switch contact. The magnet is really strong so we practiced how to install without pinching fingers.
Step 4: Mechanical Switch
The switch is simple enough using a spring, lever and contacts. This switch can be done many ways so it may just depend on the materials that are available.