Rotellino - 3€ Battery Free Contactless Bike Light

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Introduction: Rotellino - 3€ Battery Free Contactless Bike Light

Rotellino is a cheap DIY bicycle light, simple to build and battery free.

Rotellino creates electricity almost frictionless because it uses the variation of the magnetic field generated by the wheel rim (Eddy current) to make a rotor rotate with 6 neodymium magnets and generate the current needed to power 2 LEDs.

For this project I was inspired by Magnic Light and Stonioni

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Step 1: Materials and Tools

Materials:

Tools:

  • Soldering iron
  • 3D printer
  • Cutter
  • Dremel (optional)

Step 2: Prepare the Relay

We need to extract the coil from inside the relay and remove all the plastic and metal parts that we don't need.
The process is simple and done with common tools as shown in the pictures.

Step 3: Add the Leds

Solder the LEDs to the relay as shown in the pictures to fit well into the light housing.

Remember to connect the LEDs with reverse polarity as shown in the circuit drawing.

Step 4: 3D Print!

Download files from thingiverse.

There are special considerations for printing.

I used .25 layers at 50mm/s speed. The printing takes less than an hour and a half.

Step 5: Put It All Together!

Assembly is simple.

Remember to insert the magnets into the rotor with alternating polarity as shown in the drawing and video.

Step 6: Installation

Mount the light to the fork with a cable tie. I used a piece of red rubber to make it stick better.

Use the 2 joints to ensure that the rotor is 2-3 mm from the rim. The rotor must not touch the rim.

To figure out if the distance and position of the rotor is good, try turning the wheel and see if the rotor turns and the LEDs light up.

Step 7: Working Test

If well regulated Rotellino powers up between 5 and 10 Km/h. It emits a good amount of light for urban use of the bicycle.

I have been using it on a daily basis for about three months without any problems.

Soon I will upload a video with the bike in motion!

Any suggestion and advice to improve the project is welcome.

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    25 Discussions

    3
    ajoyraman
    ajoyraman

    24 days ago

    Great project! There are two physical effects in action: the first is the eddy current rotating the magnet ring, and the second the magnetic flux cutting the coil to generate the emf.

    0
    lee78
    lee78

    Reply 21 days ago

    I think the eddy current that is by far the largest is the one thru the LEDs, induced in the coil by the changing magnetic flux cutting the coil to generate the emf. There will also be tiny eddy currents induced in the rim (steel or aluminum) like in any conductor near a changing magnetic field. Are those eddy currents in the rim generating enough of a magnetic field to rotate the magnet ring? I don't think so, the magnetic attraction to a steel rim is rotating the magnet ring. (Or is "magnetic attraction" also an Eddy current on the scale of electron spin?)

    I'm surprised if this works with aluminum rims.


    Eddy current
    Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. -- Wikipedia

    0
    kai.h
    kai.h

    Reply 21 days ago

    It looks like an aluminium rim in the picture - being more of a matte silver texture. Steel rims are usually chrome plated to prevent rust so are a shiny chromed silver texture instead. If it were magnetic attraction, then a magnet would be attracted to the rim, and stay there - whereas the eddy currents "drag" the magnets along in the direction of rotation, leading to the dynamo spinning.

    0
    lee78
    lee78

    Reply 17 days ago

    I think the core of the coil is ferromagnetic. Why isn't a magnet attracted to the core and stay there?
    I know eddy currents in the rim generate a field that opposes the movement of the magnet, tending to make the rotor spin. But eddy currents in the coil resist its spinning. Looks to me like the coil is closer, more conductive, and more efficiently configured.

    0
    gravityisweak
    gravityisweak

    Reply 20 days ago

    It definitely works with aluminum. Although its counterintuitive. Have you ever seen the videos of people dropping magnets down large copper pipes? Although copper is non ferrous and doesn't attract the magnet, it still has an effect on it's field. https://www.youtube.com/watch?v=uh0bbW6S3BY

    0
    BP7
    BP7

    19 days ago

    Nice, but NOT frictionless.

    0
    JimG50
    JimG50

    21 days ago

    Such a neat idea. Thanks. Just think, after some miles the wheel will become magnetized and if you let go of the handle bar the bike will turn due east! - Just kidding. 😜

    2
    dariocose
    dariocose

    Reply 21 days ago

    I have been using this dynamo every day for months so now I can move objects remotely :D

    0
    AmeliaE2
    AmeliaE2

    21 days ago on Introduction

    What a great idea! I've been thinking about adapting a bike light for my treadle sewing machine and this is even more suitable than the products I'd been looking at. :)

    0
    dariocose
    dariocose

    Reply 21 days ago

    brilliant! :D

    0
    technovative
    technovative

    24 days ago

    I like this design, it's very clever.

    0
    dariocose
    dariocose

    Reply 21 days ago

    Thanks :)

    0
    nikdo_nic
    nikdo_nic

    Tip 24 days ago

    you could make fully encapsulated body to prevent dirt and other parts to stuck on magnets

    0
    dariocose
    dariocose

    Reply 21 days ago

    you're right

    3
    nikdo_nic
    nikdo_nic

    24 days ago

    nice idea!
    I was thinking about to make a ring with magnets to make frictionless dinamo on my bike but there was always a problem with complexity
    this use of eddy current is genius for such small load as LED lights
    you can also add little voltage regulator, bridge rectifier and supercapacitor so it can stay light up for several minutes after you stopped or slowed down
    (I had the same circuit on my classic dynamo and it was working great until I bought new bycicle which unfortunatelly didn't had one)

    0
    dariocose
    dariocose

    Reply 21 days ago

    Thanks for the comment!
    Unfortunately the bridge rectifier has too much resistance, so I only used 2 LEDs with inverted polarity. In this way the amount of light is better.
    I think I will design another more powerful dynamo with a more optimized circuit!
    Sorry for my English

    0
    KVSBUNNY
    KVSBUNNY

    24 days ago

    This is so cool!

    0
    dariocose
    dariocose

    Reply 21 days ago

    Thanks!

    0
    perec3
    perec3

    21 days ago

    Just curious. If the rim is made of aluminum, will it still spin the magnets? Thanks for posting, really interesting project

    0
    RobertD235
    RobertD235

    Reply 21 days ago

    I'd speculate in the case of an aluminum wheel it would be getting magnetism from the Spoke eyelets in the wheel, nipples or spokes that could be different grades of steels...
    The efficiency to spin the magnets might be limited by their strength quality and distance to metal parts and bearing drag.....

    Nipples are sometimes chrome plated brass, or Different grades of stainless for nipples or spokes also have no or different low levels of magnetism so efficiency of magnets and ability to spin the mechanism to generate current might be limited relative to strength of the magnets and magnetism of the metals .. But most aluminum bike wheels still have some level of magnetic material in the rim area to be magnetic.. A limiting factor for the magnets to spin might be drag in the bearing or is a premium made wheel with no magnetic material in it...unless air flow at speed can make the bearing turn... .

    In order to get top $ for scrap aluminum bike wheels, have to drill out, remove all the spoke eyelets that had always been magnetic on any bike wheels I've had..
    And also get top scrap $ for non magnetic stainless steels... most don't know there is a difference in different grade stainless steels...