- Joined Jan 17, 2007
A series regulator to switch off the voltage when it exceeded some preset value would work well and not dissipate a lot of power. So there would be less stress on components and they would run cooler and last longer. And probably the series elements could be cheaper as well.Definitely worth looking into it... mind sharing any clues as to how I should be looking for it? i.e. what would the right search keywords be for me to use?
Thanks, I'm currently looking at some energy harvesting ic's out there, that feature a polarity rectifier, such as this one. Right now I'm not sure exactly how this thing is going to end up working, but I'm beginning to get the idea. An important requirement is low cost....A series regulator to switch off the voltage when it exceeded some preset value would work well and not dissipate a lot of power. So there would be less stress on components and they would run cooler and last longer. And probably the series elements could be cheaper as well.
And the generators that use a rotating permanent magnet are usually called alternators because they produce AC and need an external rectifier. The more efficient systems use all of the output voltage to power an inverter circuit that serves as a regulator. A lot more complex, but about as efficient as can be.
A small stepper motor would also work as a variable reluctance generator and they are often available quite cheap as surplus, as well as in scrapped printers. And most of them come with a gear already attached.
Thanks for the suggestion. But it's a requirement that the device itself be gearless.A small stepper motor would also work as a variable reluctance generator and they are often available quite cheap as surplus, as well as in scrapped printers. And most of them come with a gear already attached.
Yeah, I had thought as much... it's probably easier to use FEA to simulate it than trying to calculate this thing. And easier than FEA would be to build several prototypes and test them, which is what I intend to do.With difficulty I suspect. Rate of change of magnetic flux through a coil determines the generated current, but will be highly dependent on magnet strength, pole geometry and rotor position. Rather too many unknowns.
Been thinking about this. They may be a little bigger than you are wanting but would be cheap to get to experiment with. go to an auto wrecking yard and get some relays from a car. Then take them apart to get the coils from them. You then should have a cheap coil on a bobbin ready made that can then be used to size the stator core from. If they work out, then using new PCB mount relays in the same way will get you a smaller version, at a higher price. But the car relays would be good and cheap for experimenting.Question, where can I find said coils already wound?
Ok, so I want to build one of these things so I can test it. What I'd like to do is simply select a commercially available coil, and attach six of them to a structure similar to the one shown in the image...
Alright, here's my plan.
I stripped naked an inductor that I had laying around, and after careful consideration, I think that it could be used as a coil element in a semicircular arrangement...
Shortbus, I think your idea is definitely worth considering. All of the literature I've found out there deals with the kind of design that places two magnets between two halves of a toothed stator. But also these designs consider much larger dimensions than I'm contemplating. Using coils wrapped around individual magnets like a guitar pickup makes a lot of sense to me... (and I also happen to play the guitar... well duh! ... why didn't I think of that before?)Without either a central magnet or other metal in the core of that coil(inductor) I don't think it will give very much output if any. Personally I'd go with a magnet for the core, then your rotor only needs to be iron/steel. Doing it that way makes each coil like a guitar pickup, with the rotor teeth being like a string.
IIRC, your looking for a low loss DC from this. Is using three phases(6 coils) the right approach? Doesn't that increase the voltage lost to rectification?
The reluctance pickups used as cam and crank sensors, that I've replaced and then took apart to see what was in them, don't have any magnetic "return path". By this I mean they don't use a ring or surround to give a path for the magnetic field. So don't think that is needed. So aluminum would probably work, since they just use plastic in the cam/crank sensors. Again think about a guitar pickup, they, other than Humbuckers don't use a ferrous plate to connect the magnetic field.What would the outer ring's best material be? Magnetic, or non-magnetic? ... for instance, steel or aluminum? I'm guessing the best choice would be to use magnetic, to better focus the magnetic fields inwards... but it's just a guess.
I'd say it depends on what you're wanting voltage wise, AC or DC. Alternating the magnetic poles would give AC, Like a car alternator. Having them all the same pole should give DC, like a older cars generator.Instinct tells me that the magnets' poles should be oriented alternatively. That is, pointing inwards one magnet's north, and the next one's south, and so on. But I'm not sure as to why that should be.
From years ago here on the forum one member, Praonevou was his name but the spelling may be off, was using a free "magnetics circuit simulator" but I don't recall the name of it. This may be it but I don't really remember.If I were to use 1/4" diam x 1/4" long magnets, would it be ok if the coils consisted of 150 to 200 turns of ga #28 magnet wire? ... this is just an estimate (read: wild guess) on my part, and I'm not sure if there's a "rule of thumb" out there that I should follow.
Oh, your going about the gear thing different than I would have. Since you were having to re use the gears from the first and third reduction, they would already be correct. Then by having the center to center distance of the second and third reduction, you would just pick what ever gears that make up that distance. And by picking those gears they would be the correct pitch for that pair. Almost any seller of gears gives the pitch diameter of the different pitches and tooth sizes. Over the years I've made many things work by doing this without having to buy or make special gears.As for the drill thread, that project's still very much alive. Right now I'm having a couple of plastic/aluminum samples of the actual gears generated, since they seem to be of special design and do not comply with standard tooth dimensions. When I finally get it right, then I'll work on the modified versions.
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by Jake Hertz
by Jake Hertz
by Jake Hertz