iYo: Would a yo-yo phone charger actually work?
There's no reason Peter Thuvander's "iYo" yo-yo-powered charger wouldn't work — except perhaps physics. He hasn't actually built one, but suspects that the motion of a yo-yo with a magnet inside would generate enough power to charge his iPhone or anything else that can sip power from a USB port.
Help me out: would this actually work at a rate that would be practical? I haven't the first idea of how to do the math.
iYo project page [PeterThuvander.se via Core77]
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A downward stroke should produce more torque than required, so the axle should have a centripetal "clutch", to release, allowing the disc to spin at the bottom of the string until it has slowed to a point that the clutch would then close, reengaging the axle to rewind the string.
This way, the harder you throw the iYo downward, the longer is will spin at the bottom of the string before returning.
I've seen alot of yoyo charger concepts but nothing come to fruition. I remember one where it was an mp3 player and the yoyo halves came off into headphones; but like I said only a concept.
Now that I think about it how would you link the thing to charge without off setting the balance with a port?
man I'm such a yoyo dork
Problem in this would be with the string/cord.
A frequently used Yo-yo cuts through a string fairly often, even if this cord is tougher then a string, it will break at some frequency or it will be so string it cuts your finger off.
I don't think it would work. The design of a yo-yo requires that it preserve its angular momentum, so that it can wind its way back up the string after hitting the bottom. Attaching a generator would suck up that energy to convert it into electric current, so the yo-yo would hit the bottom and then fail to bounce up, requiring you to look like a nøøb and wind the string up by hand before giving it another try.
Anyway, we already have perfectly good hand-cranks that can power radios and flashlights, so besides cuteness, what does a yo-yo add?
This thing already exists in a sense. It's the Potenco pull-cord generator. The only notable difference is that you pull the cord instead of dropping the device like a yo-yo. I suppose the device itself would have to be heavier for that to succeed. Here's their website:
http://www.potenco.com/
Doesn't appear this person knows much about yo-yos or motor/generators. The outer shell is spinning when you release it, what stops it from rotating?
To make this work, if at all possible, the outer shells must have a hollow shaft and spin freely, the inner part should be weighted to prevent it spinning. The inner stationary parts would be joined through the outer shell's hollow shaft. The yo-yo would then be thrown, allowed to sleep, and returned as any other yo-yo. Diodes would allow power generation in either direction.
according with #4
don't work
ok, basic order of magnitude calcs. the weight of the thing is going to be like 0.1 kg. figure the energy you give it is equivalent to a good throw, which would, if you threw it upwards with no string attached, send it 5 meters into the air. so that means the energy you give it per throw is m*g*z = 0.1 kg * 9.8 m/s^2 * 5 m = 5 joules. figure it takes 10 seconds for your yo-yo to extract the energy out of each throw gives it a net power of 0.5 W. that's assuming the thing works under fairly ideal conditions. might take a while to charge at that rate
Sure, why can't it work. Here's what you have to overcome:
1) You have the initial problem of the limp yo yo wielder who puts in just enough energy to get the yo yo to come all the way back up. Normal yo yos used in this way would generate no electricity.
2) Your typical hand-crank flashlight generators actually provides two forces... the force to spin the coils and the force to hold the body in place. It's these two forces acting against each other that generates the electricity. The Yo Yo wouldn't actually be pushing against anything. think of the pull rope on a lawn mower that isn't attached to anything. In this yo yo design, there is no force that pushes the outer shell against the inner shell except the inertia of the outer shell. You could try putting in an off-center mass so the outershell doesn't spin, but by generating elecricity, you will be pushing that outer shell to spin with the inner shell.
A better design may be to generate electricity by making the thing spin fast, then when the user grabs the yo yo and stops the outer shell the thing generates electricity as the outershell slows the inner core.
3) Obviously, the yo yo would feel different from a normal yo yo because you would not be able to get it all the way back up if the user didn't throw it with enough force to both have it return all the way up as well as generate the right amount of energy.
4) To keep the string from over-winding/unwinding itself, each throw would rotate in the opposite direction as the previous throw, so you would have to do all your power collection in one cycle of the yo yo.
#3 has the dealbreaker on this thing. It's not the charging power, it's that the cord would have to be made of some god plastic or alloy so it wouldn't break.
Also, you have to remember that every strong yo-yo throw (palm face up with the yo-you in it as you throw down) causes the yo-yo string to turn 180 degrees when your hand flips over, twisting the cord and putting additional stress on it. Yo-you strings are spiraled loops which allows them to be retwisted when the spiral gets too loose, but I don't know how that would work with charging wires.
Ok, I might have been a bit hasty in my previous post. It looks like you yo-you normally, and then plug your device into the side to charge. As in the yo-yo string is really just a string.
His string looks like a wire garrot that he stole off of some mafioso, I'm not sure if that's good or bad.
A yo-yo could work...but I've been thinking how well a "Powerball" (http://www.thinkgeek.com/gadgets/electronic/6a4b/?cpg=ab) would work if it had a usb port in it. That thing can generate some power (13,000 rpm's), and it stays in your hand instead of going all over the place like a yo-yo does. It would be simple too, they already have an attachment that tells you your speed, get rid of the screen and add a usb port.
No no no, for goodness sakes. This product would not work at all. Forget the silly limitations of string quality.
#4 got the basics right; since the yo-yo must return to your hand, any energy in the yo-yo obtained during the fall MUST be used to get the yo-yo back up. In the real world there is string friction in the center of the yo-yo, so you have to throw the yo-yo down harder than simply letting it fall. So in one cycle of the yo-yo going down and up, the only energy you'd have left to use to charge a device is Extra_Energy_In_Throw minus Energy_Lost_Due_To_Friction.
That's a trivial amount of energy. Think of how hard the yo-yo hits your hand when it returns. A hand crank is much more efficient use of your time.
Dear energy-based naysayers:
Don't discount the magnitude of Extra_Energy_In_Throw. I don't know about you guys, but I had one of those cheater yo-yos that were popular back in the late 90s. They have a catch, assorted mechanical stuff that makes it a lot easier. The reason this makes a difference is that you can put some serious oomph on the thing, and it will still catch and come back after a not-unreasonable period of time. There was a significant smack when it hit your hand, and you could feel the hard throw. Even with a classic yo-yo, you can get it to catch before it's slowed down too much, and it comes ripping back up toward you. Most people don't, but you can put a lot of energy into a yo-yo.
With a good, solid yo-yo (thanks to battery weight), and a good mechanical design that doesn't rely solely on string/roller friction (I believe there was a rotational inertia trip when it dropped below a certain speed), it could work.
So, math: Figure you put three times as much energy into the throw as it gets from the drop (thinking an around-the-world, this is entirely reasonable). Starts at 4x, ends at 1x, say, if you want it coming back fast. So, twice the energy equivalent to the drop energy is available, after losing 1x drop energy to regaining altitude. Lose a third to friction, say, and get 20% generator/storage efficiency out of the rest of it. All very conservative. Call it four throws in ten seconds (just sitting here and pretending to throw a yo-yo, that's what I get). 2/5 throw energy per second. Drop is probably three-fourths of a meter. Looks like yo-yos are usually , but in this case, heavier is better, so we'll go with 100g (as Chdunk did), which is not unreasonable. 2*(.1kg)*(9.8m/s^2)*(.75m), multiply by .33*.2 for efficiency, multiply by 2/5 to convert from energy to power, and we're talking about 0.04 watts.
You can get those numbers higher. You could throw it harder, use a heavier yo-yo, and with a good catch lose less energy to friction, but we're still well under a watt no matter how you slice it.
So you could, but yeah, it wouldn't work well.
When converting mechanical energy into electrical energy one part of the generator must not move, this is where this falls apart. The mass of the stationary parts of this yo-yo generator will need to be large enough that the act of generating electricity does not start them rotating. The mass of the rotating parts must store enough energy to generate electricity and rewind to your hand.
It may be possible, but the amount of mechanical energy converted into electrical energy may not be worth the effort. If I could do the math, I would solve for the difference between the inertia of the stationary parts and the force of the magnetic field necessary to generate electricity, this would give a rough estimate of the amount of electrical energy the yo-yo would produce. The magnetic force must not overcome the inertia of the stationary parts.
And CHRS is right, throwing a yo-yo can hurt your hand.
As the Design Engineer for Potenco (the people who are creating REAL cord-based human power devices) I can tell you with certainty that this design will not work. This concept might generate electricity, though an order of magnitude less than it takes to reasonably charge the average portable electronics device, especially the iPhone that is pictured with it. While fun to think about, the yo-yo motion is just not suited for real electricity generation. Trust me. I know. I've tried. -Mitchell Heinrich, Design Engineer, Potenco Inc.
I think post six has a strong point. I would suggest that one would try and have the outside of the yoyo spin with the internal disk rotating slower, if it was made of lead it would have a much higher rotational inertia 1/2MR^2 and would spin slower than the outside cylinder 1/2M(R1^2-.R2^2) A relative velocity between the two is all that would be needed to generate some juice. I love juice.
What if you were to seperate the magnet and coil, with one in the yo-yo and one near the floor?
You'd have to raise the floor part slightly so that the yo-yo could spin next to it, and maybe the magnetic forces would upset the spin, but this solves the 'keeping one part stationary' problem.
I agree with the "not enough energy to be useful comments", but I the "not enough energy for the yo-yo to come back" comments are way off. Generally, when you use a yo-yo, you whip it down instead of simply dropping it(you can flick your wrist down like how you throw a frisbee); this is how you can get a yo-yo to "sleep" for almost up to a minute at the bottom of the string and still come back up. When you do things right, the yo-yo can come back up the string extremely fast and smack against your hand(this hurts a LOT with a Duncan Butterfly). This would be easily more than enough extra force to bring the yo-yo back up when some of the energy is "stolen" to generate a charge. However, there is that big problem of the entire yo-yo body rotating; maybe a "more" efficient way would be if a flywheel could spin freely in the yo-yo, but only one way(you have to throw it a specific way), then throwing the yo-yo hard and stopping it in your hand would allow the flywheel to continue spinning to generate charge. Of course, I could be totally, utterly wrong.
A pullcord generator(like Potenco's) would of course be way more efficient, but not as old school fun. To get that retro feel, maybe they could work the mechanism into a sparking raygun form for iPod charging spark gun awesomeness. Vrrrrr! Vrrrrr!
The idea of a Powerball hack is intriguing, considering they make models that light up a ring of LEDs brighter and brighter the faster you get the gyro to spin. Maybe you could connect the electrodes to a port or a rechargeable battery instead...
#16 is wrong, in that the yo-yo changes the direction of its rotation every time it pulls up. Thus a stationary core would be out of phase w/ the rotating part, and that phase differential is where the power comes from.
However. Ever played with a yo-yo? Most of the time you don't do anything: your hand doesn't move up and down by much. You just give it a sharp pull when it's down, and/or a twist when it goes over your hand. (People who don't know that twist will get sore hands rather quickly, with a 100g yo-yo.)
However²: The energy calculations are wrong. You don't drop a yo-yo down and wait for it to come back up, that's just the first time. Instead, you spin it. Masters can do that _really_ fast.
However³: The energy still has to come from _somewhere_, ie. your hand. Given that most of the power, at high speeds, is required just to apply centripetal force without imparting any actual energy onto the yo-yo, this is really inefficient.
Go with a hand crank, or a pull cord. It's unsexy as hell, but at least it works.