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Forum Index : Windmills : Using HDD motor as generator
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| mygatt3 Newbie  Joined: 02/03/2010 Location: Posts: 13 |
there is no restriction for battery size or voltage limits. we just have to charge any type of battery or capacitor for five minutes and then disconnect the battery, connect it to a 3volt led and whose ever stays lit the longest wins. So i will be trying to find the most efficient combination. Matt |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I am wondering how they will test what charge is in a battery before charging begins for the 5 minutes. This sounds like an unknown advantage to be gained here. I would think a large cap with a very low internal leakage value would work best BUT the cap will store a much higher voltage than a battery and will more than likely let the magic smoke out of the 3v led. A resistor can be used if allowed but this will effect the low end charge in the cap ...so no easy solution. Looks like 2 nicad batteries might be the better option and depending on the output voltage of the mill, it might be best to charge them in parallel and run them in series for the led test. I would not use a resistor for charging the batteries as for a 5 minute charge you will be very unlikely to over charge them and the resistor will only reduce the amount of charge the batteries can receive. AAA might be better than AA batteries and again will depend on the output of the generator. I would charge them prior to the test and connect a led and allow them to discharge only to the point the led stopped working. This way you will not be starting with a battery any lower in charge than it needed to be or you will be charging them from a level that you will not get any benifits from. This will depend on how the rules are implemented. Pete. Sometimes it just works |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I just done a quick test here with a hhd motor and all i got was between 1-2 volts DC depending on how close i was to the fan. You will require at least 1.4 volts or above to get any reasonable charge into the nicad battery. If you are able to find or buy cheap 6 solar garden lights (the little ones on a short pole with a led in them) then you could remove the schottky diodes from these and use them for your rectifier as they have a very low forward voltage and they will give you around 0.5 volt or more output. Kinder cheating in a way but in a smart way. The solar lights would also give you 6 AA nicad batteries that you could use 2 of. If the solar lights are old then the batteries might be shot and give you a poor result. Pete. Sometimes it just works |
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KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
certainly go the AAA over the AA if you can, pinch the batts from the family cordless phone (N size). In 5 minutes very little charge is going to make it to the cell whatever you use, there will be no smoke getting out of the batt! Luck favours the well prepared |
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| mygatt3 Newbie Joined: 02/03/2010 Location: Posts: 13 |
alright well i tested it, and three of them read 5 ohms and one read 2.5ohms. I think i am going to try and find a stepper motor instead. it doesnt seem logical to try this when i know that it will not be very effective. What kind of stepper motor should i look for that will be the most efficient and powerful for my application? Matt |
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| mygatt3 Newbie Joined: 02/03/2010 Location: Posts: 13 |
Alright guys i also had this laying around what you think? its from a floppy drive i believe there are three terminals in the upper left corner in the pic with the cover off matt |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
The floppy drive will be about the same as the hdd drive in output and both 3 phase. AS for using a stepper it would be better but you are limited by you max. blades size allowable, You might have some trouble with getting the blades to start in front of a fan with a stepper due to the cogging effect they have. You will find it different out in clean open air with startup. To answer your question a small one, maybe a 3.2 deg step one, out of a bubble jet printer but you will find it hard to fix your blades to it as you will have a small shaft. Have you tested the hdd and blades infront of a fan. Pete. Sometimes it just works |
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| mygatt3 Newbie Joined: 02/03/2010 Location: Posts: 13 |
yes your are right they are both the same i just connected the original one to the bridge rectifiers i have and ended up taking it apart and saw that it was the same as the floppy drive i just posted but smaller. I put a fan in front of it once connected and got about .5 volts out of it i believe, which is small like we suspected. As far as blade size they do not matter they can be as large as you want as long as the rest of the structure is 2 feet or smaller and under 4 cubic feet. I should have mentioned that earlier. Im thinking that a stepper motor with larger blades would be the way to go Matt. |
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Bub73 Senior Member  Joined: 10/12/2009 Location: United StatesPosts: 116 |
My nephew just made these today for one of my little 6 wire steppers out of a old scanner. 10 to 12mph wind on a pole and I seen 40.4 volts no load about 12.3volts max with a 10 led brake light for a load. It did start much slower when loaded. Bob 
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Come on Bob its ok to say you made them  stop blaming the kids for the fun you have.
Give them a go in front of a fan and tell me how they preform. I think it might be a bit disapointing. Be interested to know the result. Nice work who ever made them. Pete. Sometimes it just works |
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| Bub73 Senior Member Joined: 10/12/2009 Location: United StatesPosts: 116 |
No, my nephew works in a machine shop and he had to recycle some aluminum paint cans yesterday, this is how he done it. I don't have a fan but I will see if I can barrow one from my brother. I have doubts that a fan will start them but we'll find out If I can find one. It was fun testing yesterday till our fingers got cold; still 25 to 30 degrees fahrenheit here, Bob |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Back to the original topic i was thinking for a short life mill like Matt needs to build a standard DC motor out of a toy or printer or something might work best as it wont need to be rectified but will need a blocking diode otherwise the mill will become a fan when connected to a battery. There should be a lot less drag/cogging at startup with a dc motor. And the output should be reasonable. Pete. Sometimes it just works |
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| Bub73 Senior Member Joined: 10/12/2009 Location: United StatesPosts: 116 |
Yes I think a stepper would be to hard to start with a fan; sorry couldn't barrow a fan today to be sure. Perhaps as you said a dc motor out of a toy or cordless screw driver, drill or shaver would be better for his project. It seems to me though that multi blade setups 3,5,6 etc work somewhat better in turbulent air; but then turbulent air is never good but always around it seems. Bob |
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| isaiah Guru Joined: 25/12/2009 Location: United StatesPosts: 303 |
Downwind' '
Bubs Nephew is 38 yrs old! But he has gotten bitten with this project,Has to have one of his own mini mills! The blades are cut out of spent spray cans with a cut off wheel in a die grinder. We will have more as time allows. We have 4 big mills in the air and several mini's started and a long ways to go to get 20 mills on the farm!! I may use a mini and a small solar for power in my chicken coop. last summer I used a battery a solar panel and a electric car radiator fan to cool it on hot days'  ' enjoy the project''URL=http://www.motherearthnews.com/Renewable-Energy/1973-11- 01/The-Plowboy-Interview.aspx>The Plowboy Interview[/URL> |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Yes you need to be careful about the bug, as it can bite. I am not a supporter of the metal blades and would not go that way. Rather dangerious i ihink and even worst on a small mill than a bigger one. As they are often higher speed and lower to the ground...or near head height. Your hen house is rather ritzy with lighting and airco. Mine is too its called the supermarket....lighting ,airco, and full of old hens. Pete. Sometimes it just works |
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| mygatt3 Newbie Joined: 02/03/2010 Location: Posts: 13 |
hey guys, so i finally got my hands on a stepper motor looks kind like this one 
I noticed this is harder to turn compared to the almost no friction 3 phase i had before. Will i even be able to get this thing to turn from a fan? Any pointers on size shape of blades? number of blades and maybe gearing? Thanks Matt |
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vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
An image with the label can help. Vasi Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
The motor looks to be out of a printer and would think it to be 3.2 deg steps (compared to 1.8 deg) Yes you will feel the "cogging" effect between the magnet and the coils. This will mean more power out if you can get it to start up with a fan. It will not be that the fan air flow is not fast enough but because the fan air is so turbulent. Try cutting the ends out of a box and holding it in front of the mill so the air travels through the box to the mill, this will knock some of the turbulencs out and give a better start (wind tunnel effect) It will be harder to mount the blades onto the shaft. You might try a disc of thick plastic with a tight hole in it to press over the cog and glue it in place then attach your blades to the disc. At least then you can try different blades on the mill without needing to remount to the cog each time. Pete. Sometimes it just works |
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| mygatt3 Newbie Joined: 02/03/2010 Location: Posts: 13 |
would more blades be beneficial in this application? matt |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
There is trade offs for more or less blades and a little testing on your behalf should find the best combination for your application. There is no magic answer to your question as it all comes down to startup torque and top end rpm needed to generate the amount of power required. For instance more blades should give more start up torque but will spin at a slower top end speed. Same sort of thing with blade length. It is all a balancing act to get the best design for the application. Then there is different blade styles that changes everything again. As i said make a few different designs and test them out you will soon see which gives the better preformance for your conditions. Pete. Sometimes it just works |
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