Battery-free flash light

[YT2095]

Hmmm... here`s a thought for you then, using such an engine, and giving it a greater heat diferential (a few 100c) it might be possible to power several LEDs from the wasted heat of an ordinary candle, since much of power given off by a candle is lost as heat and the amount of light given off is fairly small, such a device would boost the candles efficiency several fold

[The Thing]

Thanks calbiterol. And YT, your idea might just work.

Anyways, for the flashlight: I'm struggling to create a plan for a stirling engine that is cylindrical. The only types I've seen are the disc ones with a giant wheel on top or in other funky shapes, none cylindrical though. Any help please?

One more thing: what decides the temperature difference required to make a Stirling engine move? I don't want to build an engine and find out that it requires 200 degrees temperature difference to move .

 

EDIT: After some thinking, I think a beta stirling is the way to go . The tube containing the piston and displacer, the lower portion can be grasped by the hand. The upper portion, the cooling part, the user must NOT touch with the hand. Is that plausible? I'll have to think of a way to make sure that the heat from the hand doesn't travel to the cooling part of the flashlight. I HAVEN'T workout ANY details for it though .

 

Oh yea, please answer my questions above too . Thanks.

[calbiterol]

I don't quite understand what you're asking when you say cylindrical, Thing. As far as the temp difference, it depends on the size of the chamber and the quality of construction, IIRC. Perhaps the surface area as well, but I'm stepping into the realm of speculation. The materials used (their heat conductance, for one) would also make a difference, I would think.

 

If you can think of a way to make the bottom end of the flashlight the cooling portion, you'd be fine - I don't know how you even could hold the flashlight by the bottom, much less anyone who does.

[The Thing]

Okay, I'll have a go at trying to explain the cylindrical stirling engine.

A flashlight that you clutch normally is cylindrical, right? With a bulb at the front.

I'm trying to think of a design that would be the same shape, with the heating portion being in contact with the hand, thus it has to be at the very outside of the flashlight. Anyhelp with this design?

 

And I'll try to explain the beta stirling engine design that I had in mind.

Take a normal beta stirling engine, the tube containing the air, the displacer and the piston would be cylindrical already. At the top of the engine, attached to the piston and the displacer, is a mechanical wheel that's used to crank the displacer as well as to generate electricity (is that plausible?).

I got the idea from the picture attached of the beta stirling engine. The wavy red lines are of course heat, and the hand will grasp the entire cylinder there. I need to make sure that the radiator part, the cooling portion, does not get any heat from the hand. Well, should this work?

Also, I could switch the cooling & heating portions around so that the cooling's at the bottom, but then I need longer sticks for the cranking wheel or I have to place the wheel at the bottom.

Well, that's it for my thoughts today. Any help is greatly appreciated!

Incidentally, how long do you think this thing will take me to build if I work for 6 hours a day but with only small hand tools such as drills?

[calbiterol]

Quick link before I go to bed that might be of some use: HowStuffWorks: Stirling Engines

 

Page 3 might be especially useful.

[YT2095]

another type (and I don`t know the name of it) is the sort explained here: http://www.scienceforums.net/forums/showpost.php?p=152015&postcount=23

it works on a similar principal but has no moving parts per se.

perhaps a modification of this would be possible?

 

another type (again I don`t know it`s name) is the sort used in certain "Active" heatsinks. basicly it`s a heatsink with a tube of refrigerant liquid in it, the item to be kept cool is placed at an ofset on this heatsink, this causes local heating and the refrigerant to expand a little, as it does some is forced past the cooling fins and then reaturns on it`s loop back to where it started and so it continues...

 

btw, this is getting a little off topic, and I`m just as guilty, if the OP wants, I`ll split this thread and make a new one with the latest material presented here, it would be a shame to waste any of it.

it`s your call Lance

[The Thing]

Okay, thanks calbiterol and YT. Yeah, I think we should split the thread.

The problem now is that I know how the stirling engine works and I have a design, but I DON'T know what temperature difference it will run on and whether it is powerful enough to generate enough electricity (Will I have to use weak magnets?). Also, I have no heads or tails on how to even BEGIN building this thing. Well, that's the problem.

[The Thing]

Woa, I just had another idea .

Can I use an array of thermocouples instead of a stirling engine to generate electricity? Obviously the thermocouple will generate miniscule amounts of electricity, but is there a way to maximize that?? To get enough electricity for a LED from about 17 degrees of temperature difference?

[joema]

There are many different commercial human-powered flashlights. Shake lights and "crank" lights are two common types. They use rechargeable batteries or capacitors to store the energy. Newer ones generally use LEDs since they're more efficient than incandescent bulbs. For extensive info on these and other flashlights, see http://www.flashlightreviews.com/

[Mjs11211]

Could one apply a voltage to the coils, and make a cylinoid that pushes the magnet out?

yes, it is possible, I believe that is called a rail gun and are not that hard to make. I have built a variation on the rail gun that fires aluminum disks, by using a coil on the bottom of the barrel. Check out http://www.amazing1.com it has a kit to make one. they call it a mass launcher

 

for the original shake flashlight, like alchemist said couldn't you use a transistor to amplify what current you get from shaking?

[YT2095]

for the original shake flashlight, like alchemist said couldn't you use a transistor to amplify what current you get from shaking?

 

and what supplies the transistor with this current?

[Mjs11211]

i meant transformer, not transistor,(oops) but i realized that wouldn't work either

[cchea]

I am attempting to build a working Battery-free flashlight flash light. It would be powered by coils around a pen tube with a rod magnet inside. When you shake the tube the magnet goes up and down reversing polarity inducing a charge in the coils. The only problem is I can’t seem to get more than 0.9 volts out of the thing. I need at LEAST 3 volts. Not to mention that the current output is pitiful. The coils I wound are PERFECT. The layers are on top of each other with no overlaps. There are somewhere between 500 and 1500 turns. I can’t even begin to guess how many.

 

So does anybody have any ideas? I have attached a schematic.

I am sorry. i think i response too late here. But why there is a need of full-wave brigde rectifier? why not just use a large capacity to charge more V drop from magnet? anyone pls enlighten me!