What would a bleeding-edge Shakelight be like?

Brlux

Brlux

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If you are trying to make a gear driven generator on a budget then the quality and reliability will be terable. But a quality gear driven motor generator can be made out of metal gears and other high quality parts which should be very reliable. Remember you said you wanted a good quality light, so you are expecting a little higher cost.
 
Sub_Umbra

Sub_Umbra

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...The only advantage I can see to the shaking method is the case of the light can be made compleatly sealed.
IMO that is a huge advantage. If you want a light you may stow in your sailboat with the intention of never thinking of it again until nothing else works, the seal advantage is a big deal. If you live in the tropics or sub-tropics and want a light in your storm kit expressly for when nothing else works, the seal is also a big deal. There are many other situations where the seal may be a primary consideration for an emergency light. Even aside from locations where salt in the air and water are a problem desert environs also come to mind as being very hostile to crank/squeeze lights because of the lack of a good seal against sand/dust.

The seal is one of the shakelight's strongest design points that draw people to it.
 
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tron3

tron3

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Shake lights are a novelty, and will be next years trash and stocking stuffers.

To mod one, and why bother, I would put more capacitors in parallel to hold a charge longer. Could mean a few more shakes to get it started.

The only "non-use" standby light worth while would be a gyro-wind light, and/or the solar charged ones. Shake lights are throw away merchandise.
 
Sub_Umbra

Sub_Umbra

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Airplanes, autos, computers, flashlights and all manner of other things you use everyday were once novelties that many said would never go anywhere. The people who dissagreed with those points of view ended up making them a part of your life.
 
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Brlux

Brlux

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If we are stuck on the idea of having a shake light then the best thing I can think of to improve it would be to use several sets of paralel coils so that each pass of the magnent will produce 3-4X the power. O and of course use a good led like a Nichia CS.
 
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greg_in_canada

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I think there is an optimal coil inductance that depends on the magnet strength, shake frequency, and maybe capacitor size. Unfortunately I don't know how to calculate it. But imagine such long and effective coils that the magnet moved like it was going through molasses. That would indicate the magnets are too strong or the coils too inductive, so there must be a lower value that would let the magnets move quickly and produce lots of electrical energy.

Greg
 
Sub_Umbra

Sub_Umbra

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Greg,

That makes sense -- but it makes my brain hurt. There must be someone around here who could answer that.

I was also thinking of the coils themselves and the materials that they are made of. In particular, I was wondering how far along research has come with 'room temperature superconductors.'

So many of the successful high tech products of today don't really rely on one big breakthrough for their successful design. Rather, they often take an old design and improve it by incorporating any number of breakthroughs in diverse fields into the final product. They boost efficiency (for example) by 4% on this part and then by 2.5% by using this material somewhere and by another 5% by using this new part, etc.
 
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greg_in_canada

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I don't know if the resistive losses in the coils are significant. I suspect the shake light has a diode to only pass the positive pulse to the capacitor. If that's the case then you lose 0.25 or 0.3 volts across it which is likely much bigger than the resistive drop in the coils.

They could use a bridge rectifier (4 diodes) to allow the negative part of the pulse to charge the cap also, but then you have 2 diode drops to contend with (.5 or .6 volts).

A really fancy shake light could use synchronous rectification (I think that's what it's called) where you use a low resistance FET and turn it on when the voltage pulse is the way you want it to be. You could probably get 0.1V or less drop that way, at the cost of a lot of complexity.

The (RMS) current times the rectifier voltage drop is the power lost. I'm not sure what percentage that works out to be.

Greg
 
Brlux

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I agree that adding to many coils would cause the magnent to not pass through them at a decent speed but I have not yet seen a shake light that seems to aproach that point. All the ones I have played with have the magnent pass through with little precieved resistance. I have a lame shake light that someone gave me because quit working. The capacitor had gone bad. I replaced it with a new one and not long afterwards the new one also went bad.
This thread has interested me enough to do some testing on the piece of junk. My particular version uses a full bridge rectifier. The DC resistance of the coil is 36 ohms. I shortrd the coil and noticed a little noticabe resistance in the movement of the magnent, But it still would have needed to be many times more resistance to keep the magnent form sliding through the tube when shaken. I soldered a 1 ohm resistor across the coil and shaking it as violently as posable created a curent of about 500ma peak lasting about 25ms. This was determined by reading the voltage across the resistor with my O scope. I next conected the scope to the coil under no load and measured peak voltages over 25V. I believe that this is what damaged the caps which are rated at 5.5V and are easily damaged by any higher voltage. While under load the coil will never reach this voltage but it could definantly go over 5.5V.
I have seen other versions of this light that use 3 small n cell looking NiMh cells.
 
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greg_in_canada

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Interesting. I guess the resistive loss is bigger than I thought. So perhaps a design with stronger (rare earth) magnets and larger diameter wire would be more efficient. To protect the cap you might need a zener diode across it.

This is a cool topic. I might have to visit the dollar store to see what I can find to play with.

Greg
 

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