This is my design for a encapsulated mini axial flux alternator for tiny wind or water turbines. It's capable of producing >12V when turned by hand. A detailed power analysis has not been done yet, but the design is proven to work quite well. Smaller magnets were used at the beginning but they were not performing that well. The 20x10x2mm N52 ones are much better for that purpose.
A 3D-printable coil former for winding the 6 coils is also provided. It can be attached to a continous rotation servo or a power tool. Attach a mechanical or electrical counter. I've put together a quick and dirty arduino-based counter with a reflective distance sensor as you can see in the pictures. This project was a motivation to build a fully automatic winding machine as well which guides the the wire for you, which was quite a bunch of work. I'll post more details about all that on my blog in the future, I hope you find this alternator useful.
What you will need besides the printed parts:
- stainless steel M4 rod (about 80mm long) to be used as an axis.
- 4x 60mm M4 bolts an nuts to assemble the enclosure
- 2x M4 hex nuts for each magnetic rotor flywheel
- 2x M4 self-fixing nuts to fix the flywheels to the axis
- 2x MR 84 ZZ 4x8x3 mm Ball Bearings for stator shell front as well as back
- hot glue or silicone to be used for sealing the enclosure
- about 300m of 0.15mm enamelled copper wire for the coils
- 16 x N52 20x10x2mm neodymium magnets for the flywheels
- electrical tape for fixing the coil windings while making them
- 6x 1N5819 schottky rectifier diodes for the 3-pase rectifier
- 1x 470µF 25V or bigger electrolytic cap for smoothing the generated current
- epoxy resin to pot the stator as soon as the coils are wound and wiring is done.
For the coil winder:
- about 40mm long countersunk M3 bolt with some hex nuts and washers
- continous rotation servo with arm
- mechanical or digital counter to count the windings
Short instructions: I have to be more precise when it comes to the coil winding part, since I have built a dedicated machine for that. A post on my blog will come soon. I hope the concept is comprehensible enough though. What is most important about this generator is: the coils have 700 windings each and are wired in "star" configuration. The magnets on the flywheels have to be arranged in alternation N-S-sequence and fixed with a drop of super glue. Be sure to have them in the right order, the fit is quite tight and removing the magnets once they are in place is quite hard.
I've printed all the parts in black PLA. you have to file the coil former a little until it is smooth enough and in the desired shape because the wire is pretty thin and you will have trouble removing the coils once they are done. The slots on the coil former are there to run slim strips of electrical tape through them to hold the coil together. This technique turned out to be beter than using super glue. Use a small zip tie to wind the tape around the coil windings.