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shake light


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A flashlight that you shake, which makes a magnet move inside a coil and generate a little amount of power?
Do they actually work? Guys have found ordinary batteries hidden inside!
I tried shaking one in the store for a long time and I thought my arm was going to fall off. Then its LED was bright for a moment but quickly got dimmer and dimmer until it couldn't be seen after a few seconds. It was useless.

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i;m form macedonia here sell a shake light in tv they workin fine but they are expensive for our standard but here sell and copies they not working fine they have batteries but they on tv also have batteries but when its shaked they are charge batteries

SORRY FOR MY BAD ENGLISH

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i agree with audioguru., these shake lights are all gimicks. i got one and when i took it apart i found 2 3V coin cells in it that powered the LED. even if they used a rechargable type battery as the power source they would need atleast a 3.6V battery to power a white led. to charge the battery u need more than 3.6V DC. remember when u shake the torch u generated electricity but its AC (as the magnet moves in and out of the coil, thats faradays principle) so u need a rectifier to convert it to DC. but u also need to keep in mind the drop across a rectifier diode (nom. 0.6V for Si and 0.3V for Ge or Schottky) so u need an AC source of min 5V considering which the coil size will be quite large. if u use thinnner guage for the coil, u lose on the current side as the coil will give u voltage but the current will be too low to charge the battery. also since the voltage generated is directly proportional to rate of change of flux, i don't think that just by moving ur arm u can get sucha  high voltage. i've heard of some using very high capacity capacitors (more than 1 Farad) which are also known as gold caps, but they are just dc to dc converter circuits which steps up the voltage from small 3V cell to charge the cap and the use it to illuminate a led. ;)

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Hi,

If you need a battery less torch it’s much better to use an old stepper motor and a few diodes or rectifiers and some bright LEDs. It’s possible to charge some Ni-Cads with the stepper or if you need some backup and don’t want rechargeable cells you can use a Gold-cap or two! Almost any old stepper will work fine for this!

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Hi AG,

There are many ways you can turn the stepper. If it has a belt wheel it’s enough to turn it between your thumb and index finger. A small crank will work fine too, windmill, gears or rack and pinion with a spring! There are endless possibilities!
Even a small stepper generates a fair amount of power, if you got one in your junkbox try turning it with your fingers and then short all the wires together and try to turn it! ;D

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Hi Ante!


I did it with a bipolar one but the motor spined as easily as before.




Then you have a faulty stepper motor or some other kind of motor! Stepper motors will even whiteout shorting the wires have clearly noticeable steps, and when shorting the leads it will be very sluggish! Unless of curse the magnets or the windings are gone, then it will spin easy!
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Then you have a faulty stepper motor or some other kind of motor! Stepper motors will even whiteout shorting the wires have clearly noticeable steps, and when shorting the leads it will be very sluggish! Unless of curse the magnets or the windings are gone, then it will spin easy!


Yes my stepper motor whiteout shorting the wires have clearly noticeable steps. I have experienced difficulty in spinning the motor while on. But just shortning the wires has no effect. Ante have you experienced it yourself?
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