Breath powered USB charger

Step 3 Build the generator

Now you need to make the generator. You should play around with the gears and motors until you get a satisfactory arrangement. You will want to use a multimeter on the motor while turning the gears to see how much voltage you are getting. You want to get in the 2-3 volt range while moving the linear gear slowly about an inch in travel. When setting up the gears, you want to use the ones that have a large gear molded with a smaller gear. Stacked in series these will give you a good gear ratio as shown in the drawing. (ignore the fact that the teeth are the wrong size in the drawing, I was too lazy to redraw with matching tooth pitch) You should shoot for somewhere in the 25-50:1 range. More is better but eventually the losses in the gear train pile up and it get too hard to turn the motor and the gears will strip.

One of the keys is to find a way to use the linear gears on the CD tray or other piece to turn your breathing motion into rotation of the DC motor. I included a pic of another prototype version of the CD drive generator where you can see the linear tray gear clearly. Also visible are the cut marks in the plastic. This prototype was also capable of lighting the LED array pictured. Don't be afraid to chop this thing up to suit your needs.

In the other pic the DC motor is mounted in place in the plastic of the drive I cannibalized. Near this was a linear slider that I used to couple the breathing motion to the gear train. I also added another gear (see pic) to the drive train in order to increase the ratio and to allow mounting another motor in the future to increase output. The main challenge is to effectively get the breathing effort translated into rotation of the motor efficiently. Also pictured

Comments

[Asmodeo]

Excellent! Nice weekend project. I have a bunch of old CD drives hanging around.......time to put some of them to work. Thanks