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.
Step 1: Materials and Tools
- 02x Plastic 623 bearings 3x10x4mm Aliexpress or Aliexpress
- 12x N52 Magnets 6x3mm Aliexpress or Banggood
- 02x M3 20mm screws + nuts Aliexpress
- 01x Cable tie
- 01x Relay 12V 20A Aliexpress or Banggood
- 02x Bright White LED 5mm Aliexpress or Banggood
- Soldering iron
- 3D printer
- 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 aren't 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.
First Prize in the