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My Mini Geni isn't working very good
By wooferhound, Section Homebrewed Electricity Posted on Tue Dec 30th, 2003 at 02:35:48 PM MST
finally wound some coils for testing

I have been working on a Miniture Generator made by converting a Window Fan motor for use with permanent magnets.

I finished the rotor yesterday. Today i wound a coupla coils to test and see what I get before I wind the 12 coils that I'll need to complete the unit. But things don't look so good. I'm getting 25 millivolts at 1200rpm with a single coil. I'm spinning the rotor with it chucked into a hand drill rated at 1200rpm. The voltage is being measured after going through a bridge rectifer with a 4700mfd cap across the output. I was puzzled and wound another coil that I thought would give me better output. However the 2nd coil was just measurably better than the first.

The magnets are quite small and are probably the problem. They are 1/4 x 1/4 Disk Neodymium and are rated N38. They are grouped in sets of three with epoxy glue & tie wraps, the same polarity pointing out in each set. 12 groups are glued around the rotor alternating North-South all the way around.
The 1st coil I made was 36 turns of 19ga wire. The 2nd coils was 40 turns and wound to the size of a group of magnets better.
I wanted to see the voltage loss through my rectifers so I hooked a 9volt battery to it and measured the difference between the battery and the output. I was getting a 1.2 volt loss, so now I'm wondering if the little coils may possably be putting out as much as 1.2 volts and then getting promptly absorbed by going through the Bridge rectifier . . .

My Mini Geni isn't working very good | 20 comments (20 topical, 0 editorial)

Re: My Mini Geni isn't working very good (none / 0) (#1)
by Electric Ed on Tue Dec 30th, 2003 at 03:14:02 PM MST
(User Info) http://www.electric-ed.com

From the photos, the coil "span" appears to be somewhat less than the magnet pole center-to-center distance. I suspect that there may be some voltage cancelling happening.

Also, there appears that there is no stator iron, which would create a very inefficient magnetic circuit.

Electric Ed

Re: My Mini Geni isn't working very good (none / 0) (#6)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Dec 30th, 2003 at 06:33:57 PM MST
(User Info) http://wooferhound.com

When I was testing, I was only using 1 coil at a time. For the picture I just stuck those two coils in there so folks could see how I planned to place them. There will be 12 coils and 12 magnets and they will line up to each other 1 to 1.

The ring around the outside is the laminate material from the original fan motor. I was sure that would work for the stator iron.

}=- W o o f -={

[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#9)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Dec 30th, 2003 at 07:30:48 PM MST
(User Info) http://wooferhound.com

I should point out that I cut the slots out of the original fan stator, leaving me with an almost perfect circle of laminates.

}=- W o o f -={

[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#13)
by Norm (peppysue@suite224.net) on Wed Dec 31st, 2003 at 07:30:20 AM MST
(User Info)

I've got the same thing (even the same hacksaw, but yellow handle) get another junk fan motor (you know they're not that scarce) and start all over again, but don't cut the laminates, this time grind down the armature enough to allow for some of those small magnets that Ed on Windstuffnow has (99 cents each so they won't break you) Have Fun ( :>) Norm
( :>) Norm
[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#2)
by cevonk (cevonk(atsignhere)aol.com) on Tue Dec 30th, 2003 at 03:24:08 PM MST
(User Info)

Very interesting project! Getting things to work on a small scale is sometimes harder than on a large scale. If the magnets are 1/4" in diameter and 1/4" thick, it looks as if the field airgap between the magnets and the outside stator is about 3/4". With larger magnets, say 1/2" thick, that would work out to an airgap of 1 1/2", which would probably be a serious drawback.

It's neat to see the ideas that you are working on!

Re: My Mini Geni isn't working very good (none / 0) (#7)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Dec 30th, 2003 at 06:39:35 PM MST
(User Info) http://wooferhound.com

It's hard to tell the scale from the photos, but the airgap from the end of the magnet to the lamanates is slightly over 1/2 inch. was planning on making coils at 3/8 inch thick.

}=- W o o f -={

[ Parent ]

Its so obvious I think you are joking?? (none / 0) (#3)
by TomW on Tue Dec 30th, 2003 at 03:41:39 PM MST
(User Info)

Woofer;

You said:

The magnets are quite small and are probably the problem. They are 1/4 x 1/4 Disk Neodymium and are rated N38. They are grouped in sets of three with epoxy glue & tie wraps, the same polarity pointing out in each set.

Way back in alternators 101 we learned that the poles need to alternate N S N S N S etc.

That and the other drawbacks noted will produce a poor alternator.

Cheers.

TomW

"Education consists mainly of what we have unlearned."--Mark Twain

Re: Its so obvious I think you are joking?? (none / 0) (#8)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Dec 30th, 2003 at 07:21:34 PM MST
(User Info) http://wooferhound.com

Thanks TomW

let me quote what you quoted and add the rest of the paragraph...

--Quote-----
They are grouped in sets of three with epoxy glue & tie wraps, the same polarity pointing out in each set. 12 groups are glued around the rotor alternating North-South all the way around.
------------

Perhaps I could have described this more clearly.
As they say "A picture is worth a 1000 words" so here's a pic

The mags are grouped in sets of 3. Each set has all North or all South pointing out. putting the magnets together this way is very difficult as the mags are trying to run away from each other and flip around and stuff. Then these Sets are glued to the stator in alternating groups.
set of 3 Norths
set of 3 Souths
set of 3 Norths
set of 3 Souths
etc.

}=- W o o f -={

[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#4)
by Norm (peppysue@suite224.net) on Tue Dec 30th, 2003 at 03:43:51 PM MST
(User Info)

What happens if you just run the output of one coil thru one small 1 amp diode? or even try measuring the ac voltage? ,,,or check the voltage of the battery...then check the voltage of the battery thru the rectifier...you should be getting some kind of voltage ac or dc? even .oo1 volt? Hope this helps until you get a more expert advice....Like Zuck perhaps? Maybe with a different arrangement of magnets ( :>) Norm.
( :>) Norm

Re: My Mini Geni isn't working very good (none / 0) (#5)
by JB on Tue Dec 30th, 2003 at 04:34:52 PM MST
(User Info)

I did a little 1/6 hp motor something like that last week. it was a small 6 pole 7.8 amp 1000 rpm ac motor and had only 6 coils in series. They looked about 17 or 18 gauge. i put 6 of the 1/2 by 2 by 1/4 neos on it skewed ns ns ns. It still cogs pretty good. I wasnt terribly impressed with my results but it did show 4 amps 15.5 volts on the dc side of the bridge rectifier on my meter at 400 rpm and 5.3 amps 24 volts dc at 770rpm I think if i had doubled the magnets amd made them 1/2 thick I would have been able to bring the charging voltage down considerably. JB

[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#10)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Dec 30th, 2003 at 07:45:19 PM MST
(User Info) http://wooferhound.com

I did try to test the straight AC voltage, but after I disconnected everything I realized that it was'nt hooked up properly. I'll try again in the morning.

Also I did consider testing using a single diode, but the wife wanted the vacuum cleaner fixed so I went on to the higher priority project at the time.
Thanx

}=- W o o f -={

[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#11)
by kell on Tue Dec 30th, 2003 at 09:38:00 PM MST
(User Info)

For each bunch of little mags fighting each other you've got a distorted multipolar field with flux lines going every which way.
I think you'll do better with cheap ceramic magnets of the right size, so you know the flux lines will cut the coils where and when you want them to.

Re: My Mini Geni isn't working very good (none / 0) (#12)
by Norm (peppysue@suite224.net) on Wed Dec 31st, 2003 at 07:06:14 AM MST
(User Info)

I think you'll do better with cheap ceramic magnets of the right size, so you know the flux lines will cut the coils where and when you want them to.
I agree ...something like Ed has would have been a lot less fuss and bother:
http://www.windstuffnow.com/main/builders_corner.htm
and less fuss and bother = More Fun! ( :>) Norm
( :>) Norm
[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#14)
by Jerry on Wed Dec 31st, 2003 at 08:30:03 AM MST
(User Info) http://www.dplusv.com/Photo-03.html

I did 6 of the little Ed/Windstuff magnets on a smaller version of this motor. Didn't change a thing but machined the armature down to fit the magnets.

It dose cogg hard but I'm seeing 60 watts at 500 rpm. Just try getting 60 watts from a solar panel for 6 bux.
JK TAS Jerry

Airheads Page

[ Parent ]

Re: My Mini Geni isn't working very good (none / 0) (#15)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Wed Dec 31st, 2003 at 11:37:33 AM MST
(User Info) http://wooferhound.com

I was reading somewhere on the board that , lining up magnets like this created a magnetic field that was the same as a bar magnet with the poles on the sides. Thats why I built it this way.

Is this right or not, Many of Zubbly's designs are simular to this approach.

}=- W o o f -={

[ Parent ]

big gap..... (none / 0) (#16)
by Norm (peppysue@suite224.net) on Wed Dec 31st, 2003 at 12:51:12 PM MST
(User Info)

After taking a real close look at the pictures and especially the last ones ,I think I have the solution...a couple of the ones that replied and said about the gap were on the right track especially Electric Ed where he also referred to the width of the magnets to the width of the coil or something like that, so I'll be back with the solution as soon as I draw a couple of illustrations on one of your pictures. OK? Norm
( :>) Norm
[ Parent ]

Re: big gap..... (none / 0) (#17)
by Norm (peppysue@suite224.net) on Wed Dec 31st, 2003 at 02:48:13 PM MST
(User Info)

Okay....on the next one you get like this(this would be an alternative for someone with only simple handtools)after carefully unwinding each coil.....cut each pole straight down as on the red line, when you are finished it will look something like the first picture. Now center a block of wood as thick as the laminate and scribe the radius of the rotor and cut the ends of each pole off accordingly take a large half-round file and file the curve to allow clearance of the rotor. Then rewind the coils and put em back. This is far from ideal but it should work. The better way would be as Jerry suggested....Hope this helps....Have Fun! ( :>) Norm.
( :>) Norm
[ Parent ]

Re: big gap..... (3.00 / 0) (#19)
by hiker (hiker.wild[at]yahoo[dot]com) on Sat Jul 16th, 2005 at 03:14:53 PM MST
(User Info)

rewound with thicker wire--not so hot--lights up one 12v 50watt light
to full bright--but takes the full rpm on my hand drill.
WILD IN ALASKA
[ Parent ]

Re: big gap..... (3.00 / 0) (#20)
by ghurd on Sun Jul 17th, 2005 at 02:48:57 PM MST
(User Info)

How many turns?
What size wire?
Lowe's magnets?
G-

[ Parent ]

Re: big gap..... (none / 0) (#18)
by Harry Luubovv on Wed Dec 31st, 2003 at 08:30:05 PM MST
(User Info)

Ok Woofer,

Why not try using square magnets to line up one after another instead of round ones ? because the rounds do give troublle to the magnetic paths, that is, pulling and distorting the flux path. Square ones should behave more "Squarely" in this regard, no pun intended. :-

Love experimenters !
Luubovv

[ Parent ]

My Mini Geni isn't working very good | 20 comments (20 topical, 0 editorial)

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