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I'm searching into ways of generating very small amounts of electricity, by small I mean enough to light a couple of leds, nothing more

The main idea is to have toys that my daughters (2 and 4) can play with.

I started with a pet project that, installed on the steps of the stairs, would light a led when step on it (using a piezo; does pavegen uses the same piezo principle?), and then went on investigating other means of generating electricity.

know of any?

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    \$\begingroup\$ Electricity can be generated(at various efficiency levels) from virtually any other type of energy. Possibly it would help if you limited your scope to the type of force or chemistry you have available (water wheel, wind farm, nickles pennies and saltwater...etc) and then ask how to generate electrical power from that. \$\endgroup\$ – Matt May 6 '13 at 14:11
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    \$\begingroup\$ "Energy harvesting" is the general term for this - searching from that should help. \$\endgroup\$ – pjc50 May 6 '13 at 20:14
  • \$\begingroup\$ Yes, Pavegen is a piezoelectrical device. But, honestly, it is Schneider's green company image project. Piezocrystals are expensive, generates high voltages at very low currents and doing its best at impact grade pressures. Simply inefficient. \$\endgroup\$ – user539484 May 28 '13 at 17:32
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A DC motor with some kind of asymmetric weight attached to the shaft would probably output a bit of useful current when shaken. You could even light two different colored LEDs this way, since depending on the direction the motor starts moving in, you'd get a different polarity on the output.

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  • \$\begingroup\$ For the kids who love to shake things, I'd suggest simplier and better linear generator, readily available design can be found in El Cheapo shake flashlights. \$\endgroup\$ – user539484 May 28 '13 at 17:24
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If all you want to do is light LEDs, set yourself up a piece of sheet metal at so many feet off the ground. Run it to a capacitor with a diode in series and ground it. You'll charge the cap from a couple of energy sources: 1) whatever happens to be the dominate frequencies in the local environment and 2) PLUS the "electron leak" energy available in the dipole between earth and sky -- basically like electron leakage across capacitor plates. The higher you raise the metal from the earth, the higher your rate of charge should increase.

If most of the energy comes from the local frequencies, then you can put two caps in parallel each with an opposite facing diode, and you'll be able to get twice as much energy since you're pulling energy from both sides of whatever the dominant frequencies are in the environment. If the dominate energy is coming from the dipole between earth and sky, then only one diode direction should be dominant (at least theoretically. It's been a few years since I ran these kind of experiments).

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Make a battery out of lemons. you will probably need about 4 cells (lemons connected in series) to power an LED. here is a link on how to make them. http://www.how-things-work-science-projects.com/lemon-battery.html

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  • \$\begingroup\$ Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. \$\endgroup\$ – user17592 May 6 '13 at 16:55

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