Ridiculous Exerciser Becomes Useful As A Charger

[Scott Nietfeld] built a charger from a Dyna-flex wrist exerciser. We hadn’t heard of a these gyroscopic devices before but once we saw the promo video (embedded after the break) we realized that this is the kind of thing that infomercials were made to sell. [Scott] knew the internals spun to fairly high RPM and figured that adding a few magnets on the inside and coils on the outside would turn this thing into a generator. Four rare-earth magnets fit the bill, with two external coils feeding a rectifier and linear regulator. Below you can see his demonstration video where he takes the orb apart, then spins it up, generating 250 mA at about 7.5 volts to drive the regulator and charge a cellphone. Not bad!

Dyna-flex promo video


[Scott’s] walkthrough video:


41 thoughts on “Ridiculous Exerciser Becomes Useful As A Charger

  1. Powerballs are great, and you really can’t understand how it works till you have tried one. By the time you get it up to operating RPM, it takes all the muscles in your forearm to keep it going. Do it for 5 minutes, and your entire arm aches. I bought one about 5 years ago, and always wondered why someone didn’t convert one into a charger. Great write up!

  2. Huh? you’ve never heard of a Powerball before?

    … and you claim to be a tech blog. Did you never read Slashdot or visit ThinkGeek when these things were popular?

    I’ve got one, it sits on the mantlepiece along with some buckyballs.

  3. The powerballs have a magnet inside them already and there is a little RPM counter you can snap into the top.

    They used to sell an ISA card and wired sensors that would plug into up to 4 powerballs and display the RPMs in realtime on the screen so you could have competitions. I have one somewhere; it was a lot of fun. It would be rather easy to duplicate the functionality of this system these days with a small microcontroller and a few hall effect sensors. Maybe I’ll dig it out and try it.

  4. Like many I also own a powerball. I find it impressive that TFA calls it a ridiculous device. One might look ridiculous (wanker) while exercising with it, however I promise that the results are serious. I use it regularly to complement push-ups.

    One thing that this little ball can do that no other exercising device can is shaping of wrist muscles, these muscles are really difficult to exercise.

    +1 for powerball

  5. i belive this balls are original made for astonouts to train in space pepole that use the ball no how hevy it can by to train whit it
    it looks of you have havy ball off steel that will fly out off your hand do to the g force generaat by the steel ring
    nice bild

  6. I thought of the generator aspect years ago when I first got my Powerball, so this is great. That said, “ridiculous”?!?!? Seriously? Those things are awesome. You can’t even begin to describe how well they work until you’ve used one.

  7. The powerball I’ve laying around even has a built-in generator, used to power a series of leds on the spinning ball that functions as a POV-display, showing your peak RPM. Using this power to charge a cellphone is quite a bit more useful of course!

  8. Yeah, the Powerball Techno would be the way to go for a project like this. No need to take the ball apart to mount more magnets. I would be putting any more magnets in the rotor of one of these anyway. Too much risk of unbalancing it and at 15krpm I’d hate to be holding it if it breaks.

  9. @Jehu,
    You are worrying for no reason. Even if it were to break, it has momentum in a spinning motion. The result would be like a billiards ball that spins in place, even at 15k RPM in your hand, the worst that happens is it falls out and rolls on the floor.

  10. @Fallen. Exactly. The outer shell of these things is pretty tough but the rotor is the bit I would be worried about. Even at 7krpm the rotor can bite your hand. I know, I have one. Having a few shards of Nickle plated NeFeBo flying around in there and a cracked rotor would not treat your hand very nicely.

  11. @Jehu. The rotors actually have an .25″ thick aluminum sleeve in them that spans the circumference, so I think there’s very little chance of the rotor cracking all the way through. I’ve had the magnets pop out of the spokes while the thing was running, but it didn’t do much more than make a terrible rattling sound and slow the rotor to a stop.

  12. It’s odd to see ferdi’s english, normally the dutch don’t have much trouble with it.

    And it’s also odd that he doesn’t use firefox with the english dictionary for spellcheck, but that’s not that uncommon as we all know ;)

    But it’s still clear enough and it makes his posts stand out. Actually.. come to think of it – maybe it’s all some trick to get noticed, that would be sort of clever.

  13. So we could take this idea and use the concept of producing electricity from gyroscopic rotational devices and use it on a larger scale. Where could this idea else be used you may ask, well after watching this idea I thought this project could be scaled up and used in gymnasiums everywhere. Potentially exploitable human produced energy is wasted at gyms where people could power theses generators! Am I brilliant or what? Of course this would require new designed equipment but if mass produced this could be very positive in the search for a greener future.

  14. +1 for the power-ball. It is really great for developing wrist strength which is critical for rock climbing. I had a friend who broke his arm as was prescribed one of these to regain his strength.

    1. Yep, they’re just coils of magnet wire I wound around a mandrel with the help of a power drill. It took some trial and error to get the number of winds right. The AC voltage out of the coils increases with the number of winds, and the linear regulator I was using needed ~6V or more to regulate down to 5V properly.

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