Eh WilliB,
I found an interesting site www.thebackshed.com thats the bloke that did the article for that Fisher/paykel steppermotor for a wind genny, anyway he's got another design using a simple steppermotor for charging nicads. I made one today based on the saviuonas design but as usual there isn't any wind :x . I reckon this is a top site for people to use those old steppers to good use to take a look mate I'm sure ya'll be impressed.

Cheers Bryan1

 

Bryan , you gotta post some pics of your savonius..
Last night i wound another armature with 22 gauge wire (0.025 " diameter) ,it had a resistance of 1ohm so i calculated that it was about 60 feet ..
anyway with a test fixture which is a motorcycle brake rotor 12" dia. spinning at 300 RPM , and two magnets , i just got 7 V p-p . no load..
the wave has a similar shape to the one a couple pages back .. just bigger..

 

i was thinking about the difference between the pull on the armature ,when i have the armature connected through a diode bridge , and when it isnt..
both tests were done with a 1ohm resistor as load..as you might guess the pull was considerably higher without the diodes in place..why you might ask? the answer is the forward Voltage drop on the diodes..so i googled ultra low forward voltage drop and this came up..
http://www.semiconductors.philips.co...EG1020EA_1.pdf
at 2 Amps these diodes have a forward voltage drop of only 460 mV !! wow..!! they have a 5 Amp version in the works
here
http://www.irf.com/product-info/data...ta/mbrs320.pdf
is another one.. with 0.36 forward voltage drop at 3 A .. wow..

 

Hiya peoples,
Well I finally got round to making a wind genny, my saviounis version needs a total rethink to the design but the one pictured looks promising. I used a bipolar stepper motor rated @ 5 volts and draws 1amp. Well the initial tests show a voltage of 12.6 volts with a current of about 250 milliamps using a 5watt 1 ohm resistor as the load. Now thats when the prop is doing approx 50 rpm. Murphy's law states when you make a wind genny you wont get any decent wind. Good ol' murphy woz right again ops:
Anyway the last pic is of the retifying circuit using 2 wo4 bridges and a 47uf cap, I shrunk some heatshrink over the board once it was wired up and shoved the lot in the back of the soupcan which is sealed using silastic. The prop was made from some scrap water pipe and I need to take it off and balance it.

Cheers Bryan1

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nice !!
i was thinking about the Fisher/Paykil site .. He used the same magnets that came with the machine ? ..i suppose that if he had used some of the new Neodium (sp) magnets , he could get more power out of it..
50 RPMs is plenty to work with , with some more work on the prop i bet you could get it to 200 RPMs !!

 

Hi WilliB,
Yea the next steps I'm workin on is a copper disk to pick up the voltage then I can let the genny spin round without any wire hookups. Currently I have a stop on it so it can't get twisted but with the wind coming from all different directions it sometimes gets stuck. When I noticed a strong wind blowing I rushed out to see the meters showing 13 volts and 260 milliamps. :shock:
I currently looking on the net for some hall effect circuits so I make an rpm readout for it as I picked up a few effect sensors today

Cheers Bryan1

 

cool ! if i find one i'll let ya know .. i was wondering what time and day it is in Austrailia ?

 

if anyone has HDPE foam (High Density Poly Ethalene) around , it makes a great tool for forming propellers..
it cuts fantasticly with a cerated knife , and can be sanded with rough sandpaper , and you can also melt the little sandings down with a lighter..
the one in the pics is 16 inches in diameter.. i just eyeballed it , and it didnt come out bad..last night i tested it from the car , it rocked !! but i couldent test the torque because it wasnt firmly connected to the shaft..it is now hopefully..http://www.artools.de/AVR/irl540n.pdf

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i made a new Prop last night , this one is 32 inches in diameter..
i used a 5 1/4 disk drive frame , bearing and the plattens too..
i used two pieces each 16 inches long for the blade..
i also mounted a handel on it..
well when i tested it today *sigh* i couldent test the torque because ( in pic one ) the screw in the center kept unscrewing when i put pressure on the back of the HDD spindle .. :roll:
On the positive side it spun very well , and the blades tend not to bend backward in a heavy wind , in fact their position relative to the hub stayed the same .. it was quite windy here today so they had a fairly good test..
getting the bolt pattern was easy , as i just drilled the bolt circle from a motorcycle brake disk rotor ..

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http://www.windstuffnow.com/main/dual_rotor_turbine.htm
Check out this Page .. wish i had a miller..

 

After wading through this thread I could do with a brewsky about now too :lol:
Anyways this thread has been very interesting and educational, thanks people. I'll have to give it a go soon, probably with a floppy drive motor.

Edit: Wow, I didn't realise I hadn't posted here before :shock:

 

i know , it is a long one :wink:

 

You're missing an important point. Schottkeys are good for forward voltage drop, but can suck for reverse leakage. Whereas a normal diode has a leakage in terms of microamps or less, the Schottkeys can be into the milliamp range. A fullwave bridge has double the leakage. Gets worse at elevated temps. Sometimes it doesn't matter, Schottkeys have a lot of uses. Depends on the app. In yours, if you're doing something like charging batteries, you may find the loss of a couple of milliamps the whole time the wind is not blowing may be more costly than the forward voltage of a normal diode.

There is another solution, the synchronous rectifier, which uses a driver to switch MOSFETs for extremely low losses. Vf could be just a few mV. But the circuit can be quite complicated, challenging to design, and may consume a few mA so it might as well be a few mA of Schottkey leakage loss.

 

I see nothing wrong with using another circuit to control the output , in fact i have had it in mind to use a PIC uController to eventually control the whole thing..
the pic would be connected to the anemometer to detect wind, and switch everything on..i could even have it switch on and off when the wind is blowing , say for example if my wind collector ( be it a savionous , a prop , or a cyclo turbine ) isnt big enough , then i could turn it off , for a short time , to let it build up speed , and turn it back on..
and maybe i could use the built in diode ( of a mosfet ) to my advantage..
ps i think kazakhan knew that i ment milling machine , right? :wink:

 

Yeah, I knew what you meant, just trying to be funny