Build a coffee cup model wind charger

Ever wanted to build a wind charger but not sure where to start ? Well now you can enter the world of wind power with this mini model wind charger that produces around 75milli watts of green recycled power. Easily constructed and made of lightweight materials so particularly suited to gusty locations. This little windmill would make a nice addition to a set of solar lights, boosting their power on overcast/rainy days, simply connect the output  to the batteries in the solar light.

Heres what you need:

10 X Paper Coffee cups
An old CD
Small scrap of plywood anything above 6mm thickness will do.
A stepper motor from an old printer/fax/scanner/till etc  (the older the machine the better usually)
8 X 1N4001 General purpose diodes.
General purpose glue, must adhere to metal.
Miscellaneous small wires
Battery holder to suit batteries
Electrical insulation tape

Note - Not all stepper motors will work well here you must experiment!

Solder
Soldering iron.
Scissors
Sharp knife.
Hole Saw
Pen

Multimeter or ammeter (optional)
Anemometer handy too but not at all necessary.

The video below shows the mini windmill producing some power, the full scale of the meter is 50ma so it's producing around 10 - 30ma typically at wind speed of around 6 - 13mph. It doesn't start charging until around 8.5mph. You can lower the cut-in speed (wind speed that it starts charging at) by just using one ni-cad (1.2v instead of 2.4v). The cut in speed also depends on the amount of cogging your stepper motor has.

There isn't much wind in my garden being surrounded by garden fences, houses and  the like, you will get much better performance if you raise the turbine up above everything, but it isn't really worth building such a tall tower for such a small turbine.

Step 1: Mark the cups mounting point

The cups are fitted onto the CD by cutting a slot into the sides of the cups. You need to cut a slot about 2" long at the half way point. To make all of the slots the same size, I used a piece of paper cut to size to mark them out. When you have cut the slots test them to make sure they all slide onto the CD.

Comments

[rapidprototyping]

I made vertical axis wind generator model using three cd's super glue and some 3/4 white pvc water piping cut in half. for the axel shaft a melat 3/8 rod and attaced the rod to the cd's using pan washers . the whole model was really really light weight it hung from a thread in my living room and slightest breeze could get it spenning. i painted mine silver and it really served the purpose of a model is to work through design issues proportions engineering and pick and choose your matereials. Make and madify models add to take away like it says rapid prototype and dont give up

[trialex]

Nice one!

I think you should explain how to identify which to wires from the stepper motor belong to each coil - it's easy to do. Or you could link to some of the other instructables that show how to do it.

Also I'm not sure about this, but would it be be better to have the two diode bridges in parallel rather than in series? In the current configuration, the output of one bridge has to pass through the other, and there the voltage is reduced by the voltage drop of two diodes in the other diode bridge. If they were in parallel this could be avoided. Happy to be corrected on this if that's not right.

[scraptopower]

I got some advice off someone more knowledgeable with electronics (thanks ghurd!) and yeas you are right the rectifiers work much better in parallel. I'm going to change the instructable now.

Thanks for pointing this out!

[scraptopower]

Thanks.

You reminded me, I actually took some photo's of how to identify the wires from the motor, but somehow forgot to put them in the 'ble, I'll go add them now.

I'm not really sure if there is a disadvantage to having the two bridge rectifiers in series, the reason I did this was to gain more voltage so it could charge two batteries instead of one. Hopefully someone with more electronics knowledge can answer your question.

[celalboz]

yes it will be nice to know how did you determine the coils of the step motor as I have about 10 of them and all have different colors and number of wires coming out of them, measuring impedance is not clear to me color are also not sure way we'll see your method..
thanks

[scraptopower]

The best way if you don't want to use an ohmmeter is to use an LED to see which wire have voltage across them when the motor is turned.

With the ohmmeter method you just measure across different wires until you find two that have a resistance, they should be roughly the same resistance.

If you finding different resistances across different wires it probably has a centre tap where all the coils meet at a central point. To figure out which wires are which you have to find the centre tap by measure from each wire to every other wire until you find a wire that has an equal resistance to every other wire.

[celalboz]

hello again,
I see in the diagram that you measure the miliamp output by connecting the AVO meter same way when you measure voltage, parallel to the motor?
yes/ no
thanks

[scraptopower]

No the ammeter is connected in series with batteries so I could measure the current flowing to the batteries .     Stepper ---> Rectifier output ---> Ammeter ---> Batteries --> Then back to rectifier negative lead.

Hope this helps.

[celalboz]

Thanks a lot, I was second guessing myself.. I am also building several of these combined to charge an SLA.  they will be 1m tall each..
thanks

[celalboz]

Thanks a lot, testing with a mini bulb is brilliant and that's just great idea...
thanks for rapid reply..
Al Boz