See Note at bottom. Years ago I bought a shake flashlight and it was nearly worthless. I shook it for quite awhile, and as soon as I stopped, the LED went dim. So how am I supposed to shake the light and try to aim it as something that needs light? And if it wasn’t being shaken, it was dim? No way!
Later I bought a crank flashlight and it used a motor that was identical to the ones in a DVD drive to open the drive door. I believe it used a super capacitor about 1 Farad, but I’m not sure – it has been several years ago. In any case, the flashlight took too much effort and was difficult to charge and it didn’t put out very much light.
Last year I contributed to a “crowd funding” website for the Gravity Light, which uses a bag of sand, dirt or rocks to drive the LED for 20 minutes or so. They have been going through the process of getting the manufacturing prototypes and testing for durability, and they should be shipping one to me sometime soon before February. My thinking is that I can increase the time it will run by two or more times, by using a pulley on the weight and anchoring the rope to the ceiling. The rope path will be changed from an upside down U to an N shape. As the weight is lifted the rope will have to travel twice as far, but the weight will have to be twice as heavy. But sand, dirt or rocks are free or “dirt cheap.”
The technology is somewhat the same but I’m hoping that the Gravity Light will be a lot more successful than the previous mechanically rechargeable lights I’ve had.
Note: I see two distinct kinds of mechanically operated flashlights, but I’m trying to name them appropriately so that the name indicates the type. There is the mechanically operated flashlight, where the light is produced by mechanical motion. This could be a light that operated by the squeezing of the hand, or it could have a spring that is wound up and slowly unwinds generating the light. But the other type is different in that the mechanical action generates electricity that is stored in either a battery or a capacitor, and then this is used to make the light. In other words, the energy is not held in mechanical device but is held in an electrical device. Another part of this distinction is that the stored electric energy may be generated by other means such as a solar photovoltaic cell.
A friend of mine has a shake flashlight that he has been using for over 2 years and loves it. It cost him $30.00 and has a large neo magnet and 2 large coils, 2 bridge rectifiers and a battery (ni-mh 3.6v 40mah) 3 diodes and 3 leds. He brought it to me to repair the switch. Other than the switch failing it works very well.
It was several years ago that I bought mine. Since then, the makers probably had to do something to get customer satisfaction up to a level that was better than unacceptable, so they probably have had to make improvements. You said there were bridge rectifiers in there. They are a big waste of power, since each diode drops up to nearly 1 volt, and there are two diodes in series for every bridge. The best thing to do is use four 1N5817 Schottky diodes instead, which give half as much drop. Better yet, use FETs in an active rectifier. What you’re doing is not only saving wasted power, you’re saving your arm muscles as well, and also it gets terribly boring to have to mindlessly shake one of these for so long.
The gravity light sounds like a good idea, just need an opposite set of pullys and a crank handel to reset it easly.
I just got to thinking about the pulley situation. If I put a pulley on the heavy weight end to extend the run time, then the light weight end will also have to have a pulley. If it doesn’t, then the rope will be too long and end up lying on the floor. I’ll have to think about that.
Maybe the best solution is to hang the Gravity Light outside from a higher place, like the limb of a tree.
Thats what I was thinking too, just give a longer run. A shaft that runs from the attic to the basement.Could get over an hour of fall.
Problem is I don’t have a basement, and my attic isn’t much bigger than 3 feet (1 meter). See my blog for more brainstorms.
http://rustybolt.info/wordpress/?p=9063
I guess your stuck to out side, adding more reduction pullys would requier more weight, or have 2 when 1 comes down the other is going up ?
Merry Chistmas and happy new year.
http://rustybolt.info/wordpress/?p=9063
Oh, by the way, Kirk. I got a bit of sunburn on my arms while I was pulling a few weeds out of my garden today, here a few miles from Disneyland. The weatherman forecast that the high was going to be 82 deg F (28 deg C) tomorrow and Thursday, maybe the mid to high 70’s the rest of the week. We’ll probably set a new record high for this time of the year, and the high temps for the whole USA. I’ll be out sweating during my morning walk. It’s going to be a white hot Christmas!