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Thread: Contactless dynamo light from today's BSNYC

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    Default Contactless dynamo light from today's BSNYC

    Magnic Light: Get New Energy! by Dirk Strothmann — Kickstarter

    Any engineering folks that can shine a light (bam) on this? Is it for real? Downsides? If it is so great then why hasn't anyone thought of it before?

    Also, who wants to go in on some lights with me? Heh.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    It's not obvious how it works, so it's not too surprising that it's never been done before. It also has limited power output, so the emergence of super bright leds are critical to its usefulness. It wouldn't have been workable less than 10 years ago.
    There is some speculation here and there that it's a scam. My physics isn't that great, I keep meaning to try to learn more about eddy currents to see if I can figure out how it might work.

    It would be interesting to know how it compares to a good dynohub. A dynohub doesn't have mechanical losses, the losses are all electromagnetic. A naive analysis leads me to believe that the losses of the magnic light would be similar to those of a dynohub, but the details make all the difference in this case.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    It basically works by Eddy currents and Lenz's Law, that is, moving a piece of conductive material(Al Rim...Carbon rims won't work) through a magnetic field. That induces a current and that current can be passed into a load. It probably has a battery and regulator to keep the light constant. It does have to be close to the rim and will result in some drag and heat. I don't know what the overall efficiency would be but it's a cool concept.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    Looks like it blinks with the spokes or does not have good current modulation or whatever the proper term would be (like when my dynamo blinks when just rolling the bicycle along before the battery/whatever it is gets a good charge in it). That's one possible downside a layman like me can spot. Assuming what he presented in the video is true, I'd be very interested in kicking in money and getting one.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    Quote Originally Posted by foo_fighter View Post
    It basically works by Eddy currents and Lenz's Law, that is, moving a piece of conductive material(Al Rim...Carbon rims won't work) through a magnetic field. That induces a current and that current can be passed into a load.
    I don't think it's quite that obvious. There are currents in the rim, but capturing those currents back into the light doesn't strike me as trivial. They would be extremely low frequency currents which can't be inductively coupled. This has led some people to speculate that there is a rotating device in the light.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    Quote Originally Posted by foo_fighter View Post
    It basically works by Eddy currents and Lenz's Law, that is, moving a piece of conductive material(Al Rim...Carbon rims won't work) through a magnetic field. That induces a current and that current can be passed into a load. It probably has a battery and regulator to keep the light constant. It does have to be close to the rim and will result in some drag and heat. I don't know what the overall efficiency would be but it's a cool concept.
    From experience designing drive circuits for eddy current motors, the efficiency will be of the order of 2%.

    That's why nobody's done it before, basically it's a stupid idea.

    It would be easier and far more efficient to switch a dynamo into and out of circuit when braking, thus achieveing a degree of regeneration. Wouldn't be hard to integrate a dynamo into a disc brake setup, although you'd have to watch the heat load if using NdFeB magnets, they have a low curie point.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    Quote Originally Posted by foo_fighter View Post
    It basically works by Eddy currents and Lenz's Law, that is, moving a piece of conductive material(Al Rim...Carbon rims won't work) through a magnetic field. That induces a current and that current can be passed into a load. It probably has a battery and regulator to keep the light constant. It does have to be close to the rim and will result in some drag and heat. I don't know what the overall efficiency would be but it's a cool concept.
    Also: carbon conducts electricity quite well - I once built a series of amplifiers with carbon fibre casework using the conductivity of the carbon for shielding.

    The device would be more likely to have a capacitor to store energy peaks and a constant current source to run the LEDs since that's the normal way to run them. It's still a dumb idea.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    I think it will be a fun question for my daughter's AP physics class.

    They probably have rotating magnet inside of a wire coil which gives you the faraday induction. It's a fun idea, whether it is really practical or not is another matter.

    In the write up, they aren't using capacitors to store energy so light goes off as soon as you stop.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    Battery lights are currently brighter than dynamo lights. I think it would be pretty neat if a dynamo could be used to keep a battery virtually permanently charged (like an alternator I guess) and allow for brighter lighting. I suppose it couldn't keep it permanently charged but would slow the rate of discharge to the point it pretty much wouldn't matter
     

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    Default Re: Contactless dynamo light from today's BSNYC

    i just stepped up to the big boy lights (designshine/stephen pethel). absolutely outrageous light-but pretty hefty batteries (by cycling ww-ism) will try genuine old-skool dynamo hubs soon enough-which, as i understand it are used with lights that stay ON when you stop (assume capacitors) i love lots of light!

    but to the OP, some light is better than none i reckon.

    oh-a brainfart for you designer/engineer types: make the dyno hub/big capacitor engagement upon-braking switch engage in the first tiny bit of brake lever travel-just like the engine brake on a diesel truck. (and make it sound like a jake brake too!) gives the "feather" of braking effect before/as pads make initial contact. of course the first step there is making the generator assembly such that engage/disengagement is possible. this is all for rolling resistance weenies. i'm over that.






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    Default Re: Contactless dynamo light from today's BSNYC

    Quote Originally Posted by WadePatton View Post
    i just stepped up to the big boy lights (designshine/stephen pethel). absolutely outrageous light-but pretty hefty batteries (by cycling ww-ism) will try genuine old-skool dynamo hubs soon enough-which, as i understand it are used with lights that stay ON when you stop (assume capacitors) i love lots of light!

    The ability of the light to stay on while stopped is only for being seen. You will not have the same amount of light as you have when riding. My Supernova E3 Triple has one LED lit when stopped and only enough to be seen from the other side of the street. Just a heads up. If I were to buy again I would go with the Schmidt Edelux light instead of the Supernova. And the Busch & Müller is good too. The Supernova is bright but has no beam pattern. It just throws a lot of light out there. My buddy with the B&M has more useful light 25-50 feet in front of the wheels and his light cost half what mine did. FYI.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    I think it works like this: strong magnet(s) in the unit induce a current in the conductive rim. Since the rim is rotating, this is going to produce an eddy current, which produces a varying magnetic field. Then they have a wire coil in the unit, which through faraday's law will produce a current, powering the LED.

    It could be more efficient than a dynamo hub if you exclude all the circuitry that make the light steady. Any rectifiers, diodes, or regulators are going to disspate heat (i.e. lose energy). That's why a 1 W eDelux takes more like 4 or 5 W of power input. He might not have any regulator because the process might be inefficient enough that you can't blow the LED at normal bike speeds.

    There's no such thing as a free lunch when it comes to energy, so chances are it has issues.
     

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    Default Re: Contactless dynamo light from today's BSNYC

    [replying to Saab]

    Stephen has the pattern/side lighting/intensity dialed atwo. my perfect solution would be a dyno driving these lights. i'm going to run that by him. i'll makes some pics and maybe even vids of these when i get a chance. but yeah, a topped off battery could be very much smaller and have heaps light at a stop.

    [end hijack]
     

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    Default Re: Contactless dynamo light from today's BSNYC

    How about a magnetic rim strip or "veloplug" magnets for a Faraday induction system? That would explain the pulsing at low speed, too.
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    Default Re: Contactless dynamo light from today's BSNYC

    Quote Originally Posted by Saab2000 View Post
    The ability of the light to stay on while stopped is only for being seen. You will not have the same amount of light as you have when riding. My Supernova E3 Triple has one LED lit when stopped and only enough to be seen from the other side of the street. Just a heads up. If I were to buy again I would go with the Schmidt Edelux light instead of the Supernova. And the Busch & Müller is good too. The Supernova is bright but has no beam pattern. It just throws a lot of light out there. My buddy with the B&M has more useful light 25-50 feet in front of the wheels and his light cost half what mine did. FYI.
    This is true of the triple, but there is a version of the supernova E3 has a shaped beam, which throws most of the light on to the road. I don't know if it's better or worse than the Edelux, I've only used the supernova.

    Chris
     

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    Default Re: Contactless dynamo light from today's BSNYC

    Quote Originally Posted by cp43 View Post
    This is true of the triple, but there is a version of the supernova E3 has a shaped beam, which throws most of the light on to the road. I don't know if it's better or worse than the Edelux, I've only used the supernova.

    Chris
    I have the E3 Pro asymmetric, and it is comparable to the edelux. The standlight is pretty good too. Supernova has been upgrading their leds, so an older model will not be as good as the newer ones. I haven't figured out which emitter my light has in it, but it's clearly one of the more recent ones

    Quote Originally Posted by Saab2000 View Post
    Battery lights are currently brighter than dynamo lights. I think it would be pretty neat if a dynamo could be used to keep a battery virtually permanently charged (like an alternator I guess) and allow for brighter lighting. I suppose it couldn't keep it permanently charged but would slow the rate of discharge to the point it pretty much wouldn't matter
    I already have problems with drivers thinking my light is too bright. I have never outrun the Supernova, so I see no reason to go to a battery light on the road. If I really did want more light, I have batteries that will last many hours. Don't really see any reason for a charger circuit. The charger circuits cost too much anyway, $150-200.
     

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