# Magnic Light contactless bicycle dynamo



## bwack (Oct 11, 2009)

I found this light prototype in a topic at AllAboutCircuits. It is presented as a contactless bicycle dynamo light. They claim to generate power from the spinning rim without contact. This method of generating power is all new to me so I'll try to explain and you can also read all about it in the links below.

The light housing is mounted close to the rims.
In the housing there is a stationary magnet and a pick-up coil.
The stationary magnet in the housing disturb electrons in the moving rim resulting in currents flowing in the rim (eddy currents), think of these currents as swirls around a paddle dragged on the water surface.
These "swirls" of currents have electromagnet fields of their own and they are picked up by the coil and sent to the LEDs..

So did I get it right, is this wishful thinking and at last, it does look pretty cool doesn't it if this is really feasable?  Whenever I see "get new energy" I get very sceptical, but they do have a very interesting video demonstration.

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


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## yetibetty (Dec 24, 2007)

I've just watched the video and think it's a cool idea. No light when stopped though so for the road you still need a pair of battery blinkies.


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## bwack (Oct 11, 2009)

Shouldn't be too hard to make a it atleast blink when stopped in these days of microcontrollers.

I wonder how they manage to generate this power. The designers are keeping the methods secret until it has been presented. This is what a guy at AllAboutCircuits got from them in email:

"We use a technique that works with *alternating magnetic fields* instead of a constant magnetic field. At the moment we think it is best not to publish everything because other companies that don't car for patents could copy the system before we are ready to start.
We present the technique *this weekend* at fair trade in Essen/Germany where everybody can check this is real (for exmaple exchange wheels and drag,...) . So we wouldn't have a chance with a fake there.
Best,
Dirk"

This weekend! :yesnod:
They have also sent an email reply about the high price, and they say they use some expencive components. 

Oh btw, heres an interesting demonstration of eddy currents braking effect by dropping a magnet down a alu rail. Neodymium Magnet against gravity - YouTube Neodymium magnet in copper pipe - YouTube


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## Vancbiker (May 25, 2005)

My youngest son, a mechanical engineering student, is working on a fly fishing reel that uses eddy current technology for the drag device as his senior design project. It is kind of cool.


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## ThinkBike (Jun 16, 2010)

Is this really enough light at 16 mph?



> And in november we tested the first carbon prototypes: A front light of 150 g emits 150 lumen at ~16 mph.


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## znomit (Dec 27, 2007)

ThinkBike said:


> Is this really enough light at 16 mph?


Not with those optics. I wonder how it scales with speed and how critical the gap is.
Also likely to get filthy in the rain.


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## brad72 (Jun 12, 2009)

I have seen lots of eddy current braking devices but still can't get my head around how they are harnessing the current produced to actually drive the led,s . There must be some coils in the housing somewhere harnessing the current but this is where the physics voodoo evades me. 

Might have to buy some rare earth magnets and have a play.. Your household power meter uses eddy currents via the spinning aluminium disc that you can see through the front glass so it might be fin to pull one apart and see what makes it tick so to speak 

I certainly love the idea and would love to contribute to their project but what happens if they cannot generate the $50,000 for the project to be viable?


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## manokaiser (Jun 30, 2008)

I am concerned about the currents in the aluminium rim. Could they cause electrolysis on the rim material?


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## El34 (Jan 11, 2009)

A cool idea I suppose, but you would have to have two of them on the front a fat tire bike.

Looks to me like a big fat tire would block some of the light

The tail light need to have a flashing function like the super bright blinky tail lights. 

I doubt it is enough light for us old guys going down the sides of mountains in the dark. My eyes need lots of light these days.


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## bwack (Oct 11, 2009)

Thanks brad72 I didn't know about the eddy current technique used with the alu disc in the household power meter.

On their webpage in their FAQ, they state: "Is there a battery inside?
No, the Magnic Light system contains a magnet driven dynamo which needs no batteries."
and the fact that I wrote above in a post above ""We use a technique that works with alternating magnetic fields instead of a constant magnetic field."
With that in mind I guess I was wrong about the coil in my original post above. I'm thinking there is a spinning magnet inside the dynamo, spinning motion caused by eddy current braking perhaps? and then that rotating magnetic field is spinning inside a coil.


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## brad72 (Jun 12, 2009)

There is quite an in depth discussion I have been following over on CPF Magnic Light: contactless bicycle dynamo light

If it truly does work it will be pretty good but in the end a dynamo hub with standlight circuit would probably better.For mountain biking I cannot see how a light beside the tyre, with a shadow on the opposite side will be any use for us. Commuting, maybe but we will have to wait and see.


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## No-Fork (Apr 5, 2012)

Interesting discussion there on CPF. Not much physicists there though. 
My guess is this ia a valuable solution to bike lighting. How much light it will gave, we'll have to see. But with all components in a closed box, no wiring, seems like a fail-save solution to me. Not sure about the moving parts, there has to be a change in mag. flux to induce a current. That almost implies movibg parts.


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## bikerjay (Sep 16, 2007)

Seems like it might just be a faraday disc generator or a Homopolar generator. Look it up on wikipedia. Its based on the lorentz force and some maths that scare me. I say just but every thing about how the contraption works seems like voodoo to me.


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## diveplane (Mar 26, 2012)

yetibetty said:


> I've just watched the video and think it's a cool idea. No light when stopped though so for the road you still need a pair of battery blinkies.


they are considering a capacitor type unit so when u stop the lights will remain on for some time

this is a fantastic concept of a light, could be a big hit.


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## minisystem (Sep 22, 2011)

I asked the inventor at what current his device drives the LEDs and he coyly implied that it was around 300mA, so about 60% what a standard 3W/6V hub dynamo puts out. My impression is that this device is really meant for commuting and not for providing illumination on dark country roads. It'd be neat if they could run a wire from the 'kernel' beside the wheel so the lamp mounted somewhere more useful.


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## encouragable (Dec 24, 2011)

If its 300ma EACH that's not terrible. Depending on the LEDs and optics the beam can penetrate a good distance. Looking at their KS site it looks like they're using XM-L T6 emitters, which seem a bad choice for this application. At that current it lags about 15 lumens behind the newly-released XT-Es (124 x 139), and only 4 lumens above an XP-G R5 (or 4 LESS for an S2 bin). Both the XT-E and the XP-G would have much better throw due to their smaller size. XM-Ls are also more expensive than either of their low-powered brethren.
Either way, since most people get a $15 Cat Eye as their main light, this is still brighter than 90% of the bikes I encounter on my commutes/night rides.


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## h79 (Jun 27, 2012)

Interesting technique … I'm looking forward to any new information. Let's see how bright it is in reality.


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