Energy harvesting

google "shake light"

The problem you will have is you *still* need storage of some sort (lest the light blink).

Il 06/03/2010 18.54, D Yuniskis ha scritto:

Yes, that's true. A supercap for example.

But at the end the energy provided must be enough to power the load even with the storage unit. Otherwise the led will turn off after some time.

Marco

New devices use a small Li cell. And, when *that* dies (refuses to accept charge) you throw the thing away!

Il 07/03/2010 19.58, D Yuniskis ha scritto:

So, what's the advantage of the Li cell instead of the supercap?

Any rough values for sizes of magnet and coil to obtain some hundreds mW? Just to know how big should be the "torch".

Thanks! Marco

Marketing! Pick up one of the Li cell shake lights, shake it for a few seconds, turn it on: "WOW! LOOK HOW BRIGHT THAT IS!!!" (Li cell undoubtedly still has a charge from the last person who shook it or from the factory, etc.)

Let it sit, unused, on a shelf for a year (after all, it is just for EMERGENCY USE, right?) and wait for The Big Disappointment when you shake the sh*t out of it and find *nothing*! :>

The same is true of the "crankable" flashlights now en vogue.

I've debated whether replacing their Li cells with supercaps would be a step in the right direction or just a different sort of failure waiting down the road.

(I have a "squeeze" light that works well -- all the energy is stored mechanically -- but it gets tiring to use)

No idea. I was pointing you at the shake lights thinking you could get an idea from them (physical size, etc.). I have seen them in sizes similar to a "2 D-cell" flashlight and a "2 C cell" flashlight. Both used Li cells and both had LED emitters. (seeing one with an incandescent lamp would be more telling)

Il 08/03/2010 19.08, D Yuniskis ha scritto:

Ok, I got it.

No problem, thank you.

Marco