Intro: DIY Contactless Magnetic Induction Bike Dynamo
***WORK IN PROGRESS***
I'm in test phase of this project and i want to share with you the progresses!
First of all, inspiration:
...and its patent: https://www.google.com/patents/DE202011107060U1?cl=en
Then, principles involved in this project:
- Eddy current
- Magnetic induction
Step 1: TEST #1 Magnets Rotor, Rim and Eddy Currents!
Bike upside down, i assembled a magnetic rotor and fixed it to the frame.
The rotor is made up of six neodymium magnets applied on a bolt, settled in a HDD bearing.
Here it is the video, put subtitles on! ;)
Step 2: TEST #2: Adding a Little Coil
I added a very little coil disassembled from a relay for some tests in my last project, and i fixed it on the stirrup, really close to the magnetic rotor.
Here it is the video, put subtitles on! :)
Step 3: TEST #3: Selfmade Coil...
I winded up a very rough coil made up of more or less fivehundred turns of 0.1mm copper wire, and i soldered the terminals to a blu led...
Here it is the video, put subtitles on ;)
Step 4: Winding Up a New Coil...
Okay, first coil worked, but now it's time to draw the max current from that rotor...
I've collected some informations around:
"thinner is always better
go for a few layers; too many will take away from the conductance of the copper"
So the new coil have:
- more turns
- larger windings in order to have less layers
- more precise shape to get closer to the magnets rotor...
I took a little square-shaped ink container and winded on it one turn of paper tape with the sticky part outside; then started to wind up the 0.1mm insulated copper wire on it.
After more or less 700 turns i covered the exposed copper with other turns of paper tape, and slipped it out from the ink bottle.
Once removed the enamel on the two terminals, i soldered one to one led, and tested with 2x1,2 AAA batteries if led would be turned on.
In the end i soldered the second terminal and wrapped all with tape.
Note i blended and left out the led terminals in order to check voltage while working :)
Hope will be more efficient, tomorrow i'll know!
I decide to try something similar to that would be the final result.
I took the inside of a small roll of scotch, the classic for office, and I worked it with cutter and heat gun to get a square ring. Inside there I have stayed the magnetic rotor, and I proceeded with the winding of copper wire. About 400 windings, the thread is always 0.1mm.
After fixing it on the fork, I did the measurements that you can see in the video. The tester was connected after the diode bridge. Here are the results:
- Without the capacitor:
2.8V @ 25kph
2.6V @ 20kph
2.4V @ 15kph
2.0V @ 10kph
- With a 470uF capacitor:
3.1 @ 22kph
2.9 @ 15kph
2.2 @ 10kph
Objectives for the next tests:
Obtain higher voltages
- Probably using a magnetic rotor more often and with greater magnetic power you can get a good increase. For now I think I will keep this rotor, because I have no other magnets (these I am been given away).
- I understand what going to change in the coil to obtain an increase in voltage. if anyone has suggestions about it I would be very grateful!
- An alternative method would be to use a joule thief, I just found out and I can imagine influre positively.
increased stability at low speed:
- I'm waiting for a 1 Farad ultracapacitor to see if it can make up to voltage sags when the wheel turns slowly ...
Hints and collaboration are welcome!
- Ok, i winded up a new coil of quite 1300 turns and seems working better.
- Anyway i need more volts. For this i'm waiting to receive the components to test a joule thief. I'll also try a DC-DC boost to 5V... We'll see.
- I received the capacitor, the circuit i've done makes the capacitor charge while led is already fed by the primary alternate current. As soon the capacitor is full enough, it contributes to light up the led.
At this point voltage is really manageable, so i don't need resistor or voltage regulator for now.
Hints are welcome!
Step 7: Working on New Rotor...
Those are N52 Neodymium Magnets, 10*2mm... I suppose are stronger than the others i used before.
The bearing is from an HDD.
Waiting to have time to design a lego machine to wrap the copper wire..!