First windmill

[41south]

Thought I would post this as a diary of my windmills. This experiment is based on a project from Glenn at www.thebackshed.com It uses an old scanner stepper motor. The motor had 2 sets of windings, each of which I took out to a bridge rectifier and then added the DC outputs together. Open circuit it generates a max of about 50 VDC, but short circuit current it delivers not much more that 125 mA. So its only really good for charging a couple of AA size nicads I think. I must admit I haven't put it accross a 12 V battery yet, I will do that soon and post the results.

To give you an idea of the scale the nacelle is about 2 1/2 inches across. The blades were mabe from a piece of plastice plumbing pipe I had in the shed and are about 18 inches diameter. I have no idea what the TSR is, but its certainly fun watching it go flat out in a good wind. The blade "hub" is a plastic cog off an old printer.

Cheers, Colin.

[Garry]

What a beautiful place.

[windstuffnow]

 Very Nice job there Colin!  Keep up the great work!

Windstuff Ed

[RP]

Colin,  A few thoughts:

1.  You have more voltage than you need and less current than you want.  Did you connect the two rectified outputs in series?  If so, switch them to parrallel.  Double the current, half the voltage.

Since the two coils are out of phase you may get some benefit by connecting some capacitance to the output.  If you keep the two outputs in series then each rectifier needs its own capacitor.  Only one is needed if they're in parrallel.  About 1000mfd should do it.

rp

[BrewFasher]

Hey RP, do the caps help with the reactive component of the signal?

[BrewFasher]

Nice job Colin.  I'm sure you get great wind off the coast at your location.

[gizmo]

Hi Colin

Looks good, these little stepper motor windmills are a great little weekend project and fun to fly. Does it make much of a whiring noise, I could always tell mine was working by the noise it made.

Keep a bit of grease on the drive shaft where it enters the motor, the bearings dont last more than a few months out in the weather without it. Thanks for the web site plug.

Glenn

www.thebackshed.com

[41south]

Hi Glenn, thanks for the tip on the grease. Yeah it makes a great little hum, a very satisfying noise indeed.

[41south]

Hi RP, I connected the rectifier outputs in parallel. I'll give that cap idea a whirl and see what happens. Thanks for the info.

[zubbly]

hi 41south.

your little unit looks almost identical to my first genny that i made. it was able to light up a 1157 tail light for a car. it has long been retired and may give it to some interested kid sometime.

small units are great for learning and i sometimes think they get overlooked to easily.

my #1 rule is never give up and the fun just keeps comming!

have fun

zubbly

[ghurd]

Hi Zubbly!

WHAT kind of stepper will light an #1156?

G-

[ghurd]

I am working on the same thing right now.

Have you tried just 4 diodes, 1 diode for each coil, commons to ground?

It lowers the voltage and raises the amps.

I bet you are very suprised what it will do into a 12V battery compared to a pair of Ni-Mh (3V).

Connected like yours...

One of mine at the same RPM, is 50V open also.

With 3V is 64ma.

With 6V is 64ma.

With 12.8V is 55ma.

No explaination for any of that.

High coil resistance maybe.

Another is 25.3V open.

With 6V is 100ma.

With 3V is 105ma.

With 12.8V is 63ma.

That makes a little more sense.

Definitely watch those bearings!

G-

[RP]

Its not so much the reactive component as the fact that the voltage and current from each winding are not in phase.  The sine wave from one phase reaches its peak and starts dropping and then a few degrees later the second one reaches its peak.

The capacitor holds the peak voltage from winding #1 even after its falling.  This voltage is then available to add to the peak voltage of winding #2 when it rises next.

This can make a lot of difference when two windings are in series when you're trying to "stack" the voltages from each winding.  If they don't peak at the same time then you need a way to store the peak of one winding until the other one hits its peak.

When in parallel, the capacitor (only one needed) will help store the peaks form both windings and "smooth" the avialable power.

Hope this helps

rp

[RP]

I think half-wave rectification only uses each coil half for half a cycle.  During the other half cycle, the diode is off so no current flows through that "half-winding".

Another possibility would be to fish out the internal wires where they join to the common center tap, disconnect them and connect each half coil to its own full-wave bridge rectifier.  With all the coils connected in parrallel you'd really have half the voltage and double the current.

my two cents...

[georgeodjungle]

ya ya, nice place.

is that a pvc prop?

[41south]

Hi George,


Yes it is a pvc prop, its a 2 blade 1 piece design from www.thebackshed.com.




The place is called Castle Point. Its on the south east coast of the North Island in NZ. We holiday here so it was a great place to test this little turbine.

[richhagen]

Hello, I built a turbine with a two phase stepper here:  http://www.fieldlines.com/story/2005/4/8/31534/30936

You can parallel the phases to generate more current.  I had the opposite problem with my stepper and swithed one of two I built to series.  That is a beautiful looking location.  Rich Hagen