Power Walking

Build a device that lets you charge batteries for your cellphone or music player just by taking a stroll

By Dave Prochnow Posted 05.18.2009 at 10:36 am 8 Comments

Nooooo!!!! You’re out walking, and your mp3 player dies! Peter Pachoumis

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 five-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

Luckily, you have a fresh AA battery in your shoe charger: Peter Pachoumis

Pop it into the converter box, plug into the MP3 player...: Peter Pachoumis

... and enjoy your tunes as you walk off into the sunset: Peter Pachoumis

Time: 6 hours
Cost: $73.12
Difficulty: Medium

PARTS

(1) Energy Harvesting Module (Mouser #585-EH300; $49.83)
(1) 1.25mm 2-position receptacle (Mouser #798-DF13-2S-1.25C; $0.29)
(1) 1.25mm 4-position receptacle (Mouser #798-DF13-4S-1.25C; $0.28)
(6) 1.25mm female contacts (Mouser #798-DF132630SCF; $0.78)
(1) Piezoelectric buzzer element (DigiKey #102-1170-ND; $1.62)
(1) 5V DC-DC step up (SparkFun Electronics #PRT-08248; $10.95)
(1) USB type-A receptacle (DigiKey #ED90065-ND; $1.34)
(1) AA battery holder (Mouser #12BH311-R; $0.69)
(1) AA NiCd 900mAh battery (DigiKey #SY116-ND; $2.33)
(1) USB enclosure (Mouser #789-P3A-210603; $2.10)
(1) Project box (Mouser #546-1551HTBU; $1.91)
(1) Plastic pocket clip (Mouser #546-1599CLIPGY; $1.00)

Let Your Feet Do the Charging: Luis Bruno

STEPS

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.

Previous Article: Stop! Who Goes There?

Next Article: 25 MPH on a Propeller-Powered Skateboard

8 Comments

Link to this comment

unitedelectric

05/21/09 at 12:11 am

An intermitant 30mw of power will not even wake up your MP3 player. Peizo scavenging schemes are for sensors and not much else.

Link to this comment

jonniboif_16

from Pleasent Hill, CA

05/26/09 at 6:15 pm

Is the energy harvesting device the right one? It has an input voltage of 500v and output of 1.8-3.6v.

Link to this comment

1174

06/08/09 at 4:18 pm

To be fair- while it accepts up to 500v, the minimum input is 0.0V at 1nA- so it will make use of the periodic spikes and sustained sources or even inductor loads. Sensitive and versatile- and while yes most piezoelectric power generators are for powering sensors- those sensors typically demand constant consumption, this idea uses what could be hours of input to give you enough power for another song, or maybe a cell phone call

Link to this comment

tedwool

09/05/09 at 1:23 pm

Man, this article is a life saver. I cannot recall how many times my phones ran out of power when I need to make a call. The process looks complicated though. Anybody tried it yet

http://www.woolarearugsguide.com

Link to this comment

paolosan888

09/08/09 at 4:51 am

For long distance hikers who want to listen music or watch a movie in the tent on the pda at night, or make a quick call home, this could be wonderful. I’d love to test one. Just keep the weight down.

http://www.giocogiochi.com

Link to this comment

big_turk

09/11/09 at 2:56 pm

Test the battery charger by tapping on the piezoelectric device and measuring the voltage output. Then measure the energy-harvesting module's voltage output.
-----------------------
Ali Eren - http://www.playstationturk.net

Link to this comment

pfollers

08/03/10 at 2:35 pm

well, To be fair- while it accepts up to 500v, the minimum input is 0.0V at 1nA- so it will make use of the periodic spikes and sustained sources or even inductor loads. Sensitive and versatile- and while yes most piezoelectric power generators are for powering sensors- those sensors typically demand constant consumption, this idea uses what could be hours of input to give you enough power for another song, or maybe a cell phone call

www.lipoescultura.net/lipoaspiracao/ | www.lipoaspiracaoweb.com.br | www.lipoaspiracaohidrolipo.com | www.protesesilicone.org