Introduction: Contactless Dynamo Bike Wheel Lights

On this instructable you will see how to power some LEDs spinning in a bike wheel without any battery. This project is very similar to another one previously presented ( ), with the difference that now the coils and the LEDs are spinning and the magnet holds still.

What you will need:
  - 3 relay coils (I had some with 200 and others with 600 windings);
  - 1 HD magnet;
  - 3 diodes (general purpose diodes are ok, I used 1n5818 schottky for the low voltage drop);
  - 18 blue LEDs (you may use how many you want or even other colors - white is also cool).

For the continuous mode just add:
  - 1 capacitor (4700uF seemed fine, you could test some other values);
  - 1 switch to be able to choose between modes.

Step 1: Circuit Diagram

Each coil is placed in series with a diode and three of these configurations in parallel. This way when one coil is providing energy, that power will not be consumed by the two other coils (simple half wave rectifier). The current flows directly to the LEDs where the voltage is the one generated by the coil with about 0.6V drop at the diode in case of a general purpose one. For a schottky it should drop only 0.3V or even less.

When the capacitor is connected to the circuit, it will be charged and will keep the LEDs on for some time when no coil is providing power.

Step 2: Rear Wheel Setup

I used pieces of aluminum to place the coils on the spokes. There is a gap of about 4mm between them and the HD magnet.

LEDs have their anodes wired to the circuit while cathodes are attached to the spokes, which are connected to the coils. This makes less wires around the wheel.

Step 3: Front Wheel

Here we the setup from the older instructable applied to the front wheel. The circuit is just all LEDs (1 blue + 5 white) in parallel with the one coil. The blue LED is located ate the coil and the white LEDs are on the front light.


giovarie2 made it! (author)2013-02-03

Hello i'm just wondering wouldnt it over load? or over heat?

Databanks made it! (author)Databanks2016-08-22

Doubtful, since it's going to be air cooled - the faster you go, the more it gets cooled. As for overloading, if in doubt you could always place a limiting resister or regulator, but those coils aren't really going to be too much of a risk

mkretman made it! (author)2014-03-07

Has anyone seen any instructions with getting something like this to work with revolights?

grumblecake made it! (author)2013-07-05

Just did this on my girlfriend's bike. She's so happy. Great instructable!!

wobbler made it! (author)2013-07-03


RyanWilliamTyler made it! (author)2012-08-30


About how many volts dose this produce?

RyanWilliamTyler made it! (author)RyanWilliamTyler2012-08-30

I am looking to get 12v or more, is that possible?

dremeldude made it! (author)2012-07-08

Would you get the same effect on continuous if you used 5 high brightness leds instead of 18 standard leds?

iaikin made it! (author)2011-11-30

Hey what LED's did you use? I'm trying to figure out the maximum forward voltage so they aren't blown

Databanks made it! (author)2011-10-12

I'm just wondering if changing the diodes into a bridge rectifier setup would help - at the moment to my thinking you're losing half the energy generated. Looks great, though. I'm seriously tempted to build one of these for my bike wheels. Just have to scrounge the parts.
At the moment I'm using battery powered blue wheel lights - big chunks of silicon that slide in between the spokes.

Databanks made it! (author)Databanks2011-10-12

never mind, I spotted the reason behind the half wave. My bad.

aroff made it! (author)2011-09-12

Thanks man for the great idea

abadfart made it! (author)2011-08-05

im looking at putting thison a sport bike but could you put another video up? youtube wont let me see it

ploomus made it! (author)2011-03-26

Ooh i totally love bicycles, theres so many things i want to add to it =P You got real good project. Thanks for giving inspiration to me.

f22archrer made it! (author)2010-12-04

hey friend, i failed to find a relay coil so i used a small 12v transformer. with normal magnets it produced around 6 mA. hhah is it because of the magnets or coil length
as i recon resistivity is propotional to length,area of crosssection

chouf made it! (author)2010-09-13

by the way, nce song - viva la mano negra ;-) !

chouf made it! (author)2010-09-13

wow this is great, I commue by bike everyday and I'm looking for a solution to be seen this winter. last winter i had blinking lights hanging from the bike, my bag and so on but this year i'd like to have it on the bike.

the other i saw the led blinking bicycle tyre ( which look amazing. Now I found your instructables which +/- does the same; unfortunately it looks a bit beyond my knowledge :( I have no eletronic knowledge at all

dannyo013 made it! (author)2010-08-26

Is it possible to use ordinary magnets in place of the HD magnets? I have some strong magnets I might be able to use if so.

abbakus made it! (author)2010-08-12

I don't know if HD magnets are proper, because they are half N and half S.And not on the opposite site (that's normal), but on the same side. To prove it, put 2 different magnet on contact. Too difficult to explain here, just think on what you expect by normal magnet and verify that it does _not_ happens. You can cut it in half, but i read that high temperatures generated by the cut may demagnetize them (if you use grinding machine). The efficiency is very low here i think. But you spent nothing for neodimium magnets, so i approve your choice and your project! :) Anyway is better to know this characteristic of HD magnets. Bye.

carpe_noctem made it! (author)carpe_noctem2010-08-24

perhaps i'm mistaken, but i think that cutting the magnet would just make two magnets similar to the original (provided they weren't demagnetized. Again, i'm not really sure.

abbakus made it! (author)abbakus2010-08-24

Read this: www[-]physicsforums[-]com/showthread[-]php?t=331609 Change [-] with . I've found this information about hd magnet reading information to construct an electricity wind generator. I have many broken hd, so... Bye.

deswong made it! (author)deswong2010-08-23

I think this method is quite good, but I would change the orientation of the coils. Faraday's law which this is based upon needs a moving magnetic field to induce current in the coils.

deswong made it! (author)2010-08-23

Is there any reason why you have used the diodes on the coils when you could use some LEDS in their place for better efficiency?

kikiclint made it! (author)2010-08-15

I think this is one of the first semi difficult projects I have done off an instructable I have seen. This is a great idea. I never thought to use a relay coil. I cut the coil half of the relay off, coated it in plastidip and used some silicone glue to mount them in one of the small triangles near the center of the wheel. I put the coils in series to get higher voltage with the magnets placed to pass each at the same time. Three coils total. I then put 6 magnets on a set of cds glued together for strength and that goes on with the bolt. Once again, great innovative idea. My lights start blinking at around 3 mph. I may have to do a reverse one to power a battery pack for my headlight now.

ham4fun made it! (author)2010-08-15

Moving the coil and magnets to the rim of the wheel, you may get more energy... But then balance would be more of an issue. Great Idea. 5 Stars

shooby made it! (author)2010-08-11

Excellent work. Why didn't you configure the front wheel to light up the same way as the rear wheel does?

Pedalit made it! (author)2010-08-11

Is it possible to use smaller more streamlined magnets here?

Pedalit made it! (author)2010-08-11

zizou361: I was thinking the same thing. My idea to waterproof is to put each finished piece in a resin mold. This would also allow you to paint it afterward. You will want to make sure the whole thing works and that you don't change any of the tolerances with the resin. The resin shouldn't affect the magnets. This beats the hell out of buying expensive battery operated wheel light systems.

zizou361 made it! (author)2010-08-05

This looks like a great idea, and one I would like to try, but it doesn't really seem like it would be waterproof. any ideas on how to make it so?

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