uwezi

even though he has not described it, but it appears that he has built a bridge rectifier from discrete diodes - you can see it among the images in Step 5. With this design you will have to use a bridge rectifier because you will have to use opposing magnetic poles on either side of the cubes otherwise...

If you have your own 3D printer you can create a relief of this kind without signing up using the free software OpenSCAD...

while being more flexible for the task at hand even the cheapest Arduino-clone is about 100x more expensive than a 4017...

I like your idea and project, I have done something similar some years ago - the wall wart is on the other side of the dry wall in a closet.I am not concerned about the electrical safety of your project, but rather concerned about a fire hazard, keeping the wallwart in a small hidden volume inside the wall. I see a risk of overheating and smoldering which could go quite some time unnoticed...

Thank you for this documentations, however it's not a L293D chip on these boards: the pinout does not match! But the manufacturer of these boards has been very careful to strip down the chip markings... but the L293D would not contain MOSFETs either... I found an image with complete chip code on Alibaba, it's either an MX130B or MX1308.

He will not be able to destroy (or charge) any lithium battery with this reverse fan. You might get a certain open-circuit voltage out of a "generator" like this, but there is no way it will deliver any significant amount of power (current times voltage).You have just to compare a high quality hub dynamo which delivers 2.4 W with this fan - you cannot turn a wheel attached to such a dynamo by just blowing, yet riding along you don't notice the extra resistance. What happens with the fan if you actually try to extract power is that it will simply not rotate anymore...

if - only if! - this wind turbine would be anywhere close to producing 2-3 W of electric power (which could charge a smartphone in a mere 3 hours) it would produce at least a comparable drag on the bicycle. Just imagine it dangling on one side of the handle as in the photos ;)