How does it work?
The wind catchers catch the wind and rotate, while rotating it turns a stepper motor which acts as our generator. The stepper motor outputs around .6 volts to maybe a full 1volt, depending on how windy it is. That energy is then rectified to dc and stored in a nickle based rechargeable battery(what is stored is what is outputed). The energy stored in the battery is then toggled on by a swtich and runs through a joule theif. The joule theif takes the low voltage and steps it up enough to power 5 white leds.
what are some factors to consider?
There can be a few. One factor to consider is the stepper motor, you want one that is easy to turn and that can output at least half a volt at a slow RPM rate. It is best to test your motor before building this. Since the wind (another factor) isn't as consistent as the power coming out of your wall it is also hard to give an accurate charge time. In my area winter kinda came early this year bringing some strong winds, which works out well for this build.
So in short there are two factors really, the wind and the specs of your motor. All stepper motors are different. Some are hard to turn and some are easy, some output a decent voltage and some don't.
Lets get things started by first watching a video of this in action! view the next step for the video.
Step 2: Making the wind catcher wheel
Follow these steps in order.
1- cut the tops off of four small pop bottles and put them to the side.
2- grab your four sticks and wrap some electrical tape around them. This helps them become more durable.
3- hot glue the four sticks wrapped in tape spaced out around your CD
4- mount the pop bottle tops on the sticks. This is easily done by making two notches in the top of the bottle and securing with hot glue. Be sure to cover up any space in the mouth of the bottle to prevent any air from pushing through and be sure to have them all facing in the same direction.
5- optional. Hot glue another CD over it to add a bit more strength.
6- attach the stepper motor. I used a bottle cap to do this step. I drilled a small hole through the cap that just fit over the stepper motors gear and used hot glue to bond it.
After this step is done blow into the wind catcher while holding the motor and watch how effortlessly it spins.
Step 3: The full bridge rectifier.
In this step you will need four standard diode, solder and helping hands.
First study the diagram and connect all the diodes together by twisting the leads together. Solder all the leads and trim them if needed. In a full bridge rectifier there are four connection points. two of those points are ac input and the other two are dc output with polarity. For the ac input connections it doesn't matter what wires from the motor are soldered to the connections. But it does matter for the DC output. The last picture has a circuit diagram again be sure to study it.
After the full bridge rectifier is made you can connect the two wires from the stepper motor to the AC inputs of the bridge rectifier. Again it doesn't matter what wire goes where for the AC input.
Step 4: The joule theif
For this step you will need a 1k ohm resistor, npn transistor (2n3904), hand wound toroid, soldering iron and helping hands.
First solder the 1k ohm to the middle leg (base) then solder the toroid. one wire will go to the resistor and the other will go to the collector. Then solder the led wires to the transistor. Since I am using 5 leds from a flash light I had to solder wires to the circuit board of the leds (nice circle PCB where the leds are mounted). Solder the positive wire or lead of the leds to the collector of the npn. Then solder the negative wire or lead of the leds to the emitter. Then take a 5 inch piece of wire and solder one end to the emitter as well. This will help us connect the battery in the other step.
I will not be showing you how to make the toroid. I had this one made a while ago and have no pictures of it being made so I am sorry for that.
Step 5: Adding the battery to the joule theif and wind generator
Step 7: Bring it all together! Mounting it.
Also be sure to insulate where needed!