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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.

Step 2: Cut the "sails" Shape From the Cups

Next you need to cut the front off the cups so that they can catch the wind and make us some power.

You need to remove the front section of the cup as shown in the photos but leave the rim around the top of the cup.

Step 3: Make the Sail Extensions

With the rotor one cup high it doesn't have enough area to turn the stepper motor at a reasonable wind speed so you need to make the cups a little taller. Take three cups cut them in half and cut the rim off the top. Then cut small bevels in the corners where the rim was to help them fit  in better

Step 4: Cut the Mounting Slots for the Extensions.

Cut a slot parallel to the front of the bottom sails that is wide enough for the sail extensions. Test fit the extensions in place. The extensions are pushed down about 10mm, they should be reasonably tight.

Step 5: Cut the Adapter for the Stepper Motor

Now we need a way to connect the CD to the stepper motor. Cut a circle that is smaller than the base of the cups. I used 12mm plywood because I had some scraps lying around - you can use anything from about 6mm upwards.

You'll need to drill out the centre of the circle to match whatever cog or shaft your stepper motor has.
The adapter should be a tight fit but not so tight you need a hammer to fit it!

It doesn't have to be a circle though you could use a square piece of timber.

Step 6: Drill and Mount the CD.

Drill two holes either side of the CD then use these to drill pilot holes into the adapter. Then you can screw the CD down with pan head screws.


Step 7: Solder the Circuit Together

Stepper motors output an A.C voltage which is of little use for our battery charging application. So you need to build a rectifier to turn the A.C into DC.

Follow the diagram and solder all of the diodes together as well as the stepper motor and battery pack. I used a three AAA cell holder purely because I had it to hand you only need a two cell holder.

Identifying the motor output wires:

To identify the wires from the stepper motor you can use an ohmmeter to measure the resistance between the wire, the two wires that connect to a coil will have a resistance somewhere between 5 - 100 ohms (roughly). If you don't have an ohmmeter you can simply use an led, connect it to different wires until you find the ones that are producing power. When you have identified the coil pairs, twist them together so you don't lose them.

Ammeter Connection :

I left a break in the wires so I can measure the current flowing to the batteries easily  you can omit this if you don't want to measure the output.

If you have  connected a meter to the circuit you can spin the motor by hand and see how much current it pushes. I measured around 75ma spinning it by hand.

Make sure that you get all of the lines in the right places on the diodes, they indicate the polarity of the diode and must point the right way. As an alternative to soldering the diodes together you could buy ready fabricated bridge rectifiers (they are very cheap) and connect it all together with screw blocks.

There's no reason why you can't connect some LED's in place of the batteries to make a decorative LED wind spinner., if thats what you'd prefer.

Note: I changed the rectifiers to parallel on 26/04/2010 thanks ghurd and trialex

Rectifying other types of stepper motor:

There are 5 wire and 6wire stepper motors too, The Back Shed has some circuits for rectifying these see here : http://www.thebackshed.com/windmill/assemblyMini3.asp



Step 8: Attatch the Rectifiers to the Motor

I taped the rectifiers to the motor to keep them out of the way and to stop them shorting to the batteries.
First of all put a layer of tape on the back of the stepper motor then thread a piece of tape through the centre of the rectifiers to tape them down. Then tape over it all (gently!)



Step 9: Glue Everything Together

Now you can glue everything together. Glue the cups to the CD and glue the sail extensions to the lower cups

Step 10: Glue the Motor in Place

You'll need to cut a hole to suit your motor in the bottom of a cup, then glue it in place using the adhesive. You can also tape the wires in place underneath.

Step 11: Make Some Tent Pegs

I made some little pegs to hold the generator to the ground out of some copper wire. Simply bend a hook in the end and pierce them through the base cup. You can also use these to pierce two small holes for your meter wire if you intend to use those. If you intend to mount the wind mill on a pole, you can skip this step.

Step 12: Test It

It should be finished now and ready to be tested. You can typically expect there to be absolutely no wind for at least three days after you finish any wind mill, so be patient!

If you're using the tent pegs to hold your turbine down, can simply push them into the ground so that they hook into the holes you made in the side of the cups.

If you're mounting the turbine on a pole you'll need to fix the cup at both sides with two screws either side to prevent the cup from tipping, you'll also need to glue the battery holder to the inside of the base cup (unless you don't mind it hanging loose)

If you have an anemometer you can plot the windmills output versus the wind speed to get an idea of how it might perform in different locations

How much power you get depends on the stepper motor you chose and the wind speed. 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.
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
Nice one!<br /> <br /> 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.<br /> <br /> 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.<br />
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.<br /> <br /> Thanks for pointing this out!<br />
Thanks.<br /> <br /> 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.<br /> <br /> 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.<br /> <br /> <br />
yes it will be nice to know how did you determine the coils of the step motor as I&nbsp;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..<br /> thanks<br /> <br />
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.<br /> <br /> 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.<br /> <br /> 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.<br /> <br />
hello again,<br /> I&nbsp;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?<br /> yes/ no <br /> thanks<br /> <br />
No the ammeter is connected in series with batteries so I could measure the current flowing to the batteries .&nbsp;&nbsp;&nbsp;&nbsp; Stepper ---&gt; Rectifier output ---&gt; Ammeter ---&gt; Batteries --&gt; Then back to rectifier negative lead.<br /> <br /> Hope this helps.<br />
Thanks a lot, I&nbsp;was second guessing myself.. I&nbsp;am also building several of these combined to charge an SLA.&nbsp; they will be 1m tall each..<br /> thanks<br /> <br />
Thanks a lot, testing with a mini bulb is brilliant and that's just great idea...<br /> thanks for rapid reply..<br /> Al Boz<br /> <br />

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