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You’re halfway through listening to “Layla” when it happens: Your MP3 player’s battery dies. Normally you’d have to wait until you were at your computer to finish rocking out, but there is an easy and eco-friendly way to do it on the go. First, slip a piezoelectric transducer—a device that generates a tiny charge when touched—into your shoe. A connected module collects the voltage created every time you take a step and continuously powers up a rechargeable AA battery. (It takes a lot of walking to get a full charge, but it’s perfect for reviving or topping off a gadget.) Once the battery is charged, put it into a DIY 5-volt converter and plug in your dead MP3 player. Now you can listen to the guitar solo while you walk some more juice into another battery.

Walk your way to a charged-up gadget

A man in a red jacket, a white collared shirt, and jeans, putting a battery into a shoe-mounted device charger.
The next time your MP3 player dies, you’ll have a fresh AA battery in your shoe charger. Peter Pachoumis
A man in a red jacket putting a battery into a converter box and attaching it to an MP3 player to charge on the go.
Pop it into the converter box, plug that into your MP3 player… Peter Pachoumis
A man in a red jacket and jeans walking happily into the sunset along a path between large hedges while listening to music on an MP3 player.
…and enjoy your tunes as you walk off into the sunset. Peter Pachoumis

Stats

  • Time: 6 hours
  • Cost: $73.12
  • Difficulty: medium

Parts

Instructions

Clockwise starting in top left: a piezoelectric device, an AA battery charger, a converter, and an AA battery.
These letters refer to items in the steps below. Luis Bruno

1. Download the wiring diagrams. Build the AA battery charger [A]. Connect the piezoelectric device [B] to the energy-harvesting-module input.

2. Mount the battery holder on the project box. Connect the battery holder’s terminals to the energy-harvesting-module output, and install the module in the box.

3. Test the battery charger by tapping on the piezoelectric device and measuring the voltage output. Then measure the energy-harvesting module’s voltage output.

4. Adapt the converter [C] for USB output. Snip off its plastic connector. Solder the wires from the circuit board to the USB receptacle’s pins. Install the converter inside the USB enclosure. Test the converter with a fully charged AA battery.

5. Put a rechargeable nickel-cadmium battery [D] into the charger, and get a move on.

Projects
batteries
evergreen