Model Engine Maker

Supporting => Engine Ancillaries => Topic started by: cfellows on June 12, 2013, 09:50:18 PM

Title: Anybody guess what this is going to be???
Post by: cfellows on June 12, 2013, 09:50:18 PM
(https://dl.dropboxusercontent.com/u/29733857/_IGP2439.JPG)






Here's a hint...

(https://dl.dropboxusercontent.com/u/29733857/_IGP2441.JPG)

It's going to be an air core dynamo, obviously.  I started with a 4" square piece of 1" thick, HDPE (High Density Polyethylene).  Also sometimes called Seaboard. 

(https://dl.dropboxusercontent.com/u/29733857/_IGP2433.JPG)

It's used a lot in the boating industry.  It's pretty rigid, but does have some give to it.  Machines like a dream.  I decided to make the core out of plastic since it won't put out a lot of power and, more importantly, the Fairbanks compressed air engine should have enough power to run it and light up a few LED's.  Here I'm drilling a 1/4" hole in the center.

(https://dl.dropboxusercontent.com/u/29733857/_IGP2435.JPG)

Next I cut circular grooves on both sides.  These grooves will form the coil winding channel.

(https://dl.dropboxusercontent.com/u/29733857/_IGP2436.JPG)

I changed rotary tables and started whittling away everything that didn't look like a dynamo core.

(https://dl.dropboxusercontent.com/u/29733857/_IGP2438.JPG)

This will be a single phase AC alternator.  I used a lot of the information provided by Manfred Albert over here:

http://www.homemodelenginemachinist.com/f23/dynamo-build-castings-17756/ (http://www.homemodelenginemachinist.com/f23/dynamo-build-castings-17756/)

I'll be using #24 magnet wire, hoping to get 60 or 70 turns per coil.  They will all be hooked in series.  Not all sure what kind of voltage and current I'll get out of this thing, but since LED's will run on about 3 volts or less, I think it will be sufficient.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: vcutajar on June 12, 2013, 09:55:01 PM
This is going to be interesting.

Vince
Title: Re: Anybody guess what this is going to be???
Post by: tel on June 12, 2013, 09:59:28 PM
Interesting indeed - and a very nice start!
Title: Re: Anybody guess what this is going to be???
Post by: dale on June 12, 2013, 10:12:13 PM

Oh I get it! The engine turns the dyno,the dyno powers up the air compressor, the compressor supplies nourishing air to the engine! very ingenious :Lol: Seriously another great project, always interesting and informative
Title: Re: Anybody guess what this is going to be???
Post by: b.lindsey on June 12, 2013, 10:43:25 PM
Will definitely be following along Chuck....nice start on it!!

Bill
Title: Re: Anybody guess what this is going to be???
Post by: stevehuckss396 on June 12, 2013, 11:04:27 PM
I don't know Chuck! Something like this?

(http://i770.photobucket.com/albums/xx349/stevehuckss396/Misc/DSCN0590s.jpg) (http://s770.photobucket.com/user/stevehuckss396/media/Misc/DSCN0590s.jpg.html)

(http://i770.photobucket.com/albums/xx349/stevehuckss396/Misc/DSCN0597s.jpg) (http://s770.photobucket.com/user/stevehuckss396/media/Misc/DSCN0597s.jpg.html)

Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 12, 2013, 11:31:48 PM



Chuck


nicely done  :ThumbsUp:


I'll be very interested to see what sort of efficiency the air core has,


Of course you're gunna knock up an iron one, just  for the comparison aren't you?    :stir:


Bez
Title: Re: Anybody guess what this is going to be???
Post by: zeeprogrammer on June 13, 2013, 12:01:16 AM
"Anybody guess what this is going to be???"

Mine?  ;D
Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on June 13, 2013, 12:03:55 AM
Very interesting Chuck, I will be tagging along. Electrical devices always interest me.

Don
Title: Re: Anybody guess what this is going to be???
Post by: b.lindsey on June 13, 2013, 12:11:00 AM
Nice try zee....this from someone who has to wait till T goes out of town to to have chicken cheesesteak  :lolb: :lolb:

Bill
Title: Re: Anybody guess what this is going to be???
Post by: Jo on June 13, 2013, 07:27:01 AM
Chuck, I would like to be following this along but I should have said earlier that my internet provider  :hammerbash:  :hammerbash: won't let me see your photos because it has decided to block acess to where ever you are hosting them.  :-\

Jo
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 13, 2013, 07:44:39 AM
Hi Chuck
 
If you don't mind me asking how did you arrive at the 60-70 turns?
 :thinking:
 
If I do the maths it equates to coil height of 5mm to 5.5mm - it looks a bit bigger than that, maybe
1/4" which should give you about 95 turns (tight wound)
 
N=0.707*H2/d2
 
N= Number of turns
d=diameter of wire #24 = 0.55mm
H=Height of Coil(along the coil axis)
 
Where H=5,     N=60
Where H=5.5   N=70
Where H=6.35 N=95
 
of course there is a tidy factor. If I was winding them myself in a hurry you would have to half all those calculations   :Lol:
 
Bez
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 13, 2013, 01:44:13 PM
Ok I figured out why the difference.
   The  N=√2/2*H2/dassmes the coil is wound onto a regular flat former.  :embarassed:
 
But these formers are concave (same shape as the side of the endmill) so there is no room for windings in the corners at the top and bottom of the coil.   :facepalm:
 
 
I'm looking forward to seeing the real thing in action Chuck,  thanks for inviting us along.
 
Cheers
 
Bez
 
 
 
Title: Re: Anybody guess what this is going to be???
Post by: MuellerNick on June 13, 2013, 02:12:13 PM
Chuck,
do you intend the coils of the stator to be fake and have magnets inside? If not, a coil without (iron; better ferromagnetic) core is quite ineffective. For iron, r is 30010000, for ferrites, it is 415000. So that's the factor your field strength is reduced by not having a core.


Nick
Title: Re: Anybody guess what this is going to be???
Post by: Ian S C on June 13, 2013, 02:54:32 PM
I built a little alternator a few weeks ago, it was a little shaded pole motor, 850 rpm type. I took out the armature, and made a new one, it is a 6 finger claw (similar automotive alternator), with 3 ferrite magnets removed from old speakers inside, this will produce about 90V, and gives useful power when fed through a transformer, and a bridge rectifier, to give about 12V.  This alternator was designed for the Stuart S9 .
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 13, 2013, 03:01:54 PM
Chuck, I would like to be following this along but I should have said earlier that my internet provider  :hammerbash:  :hammerbash: won't let me see your photos because it has decided to block acess to where ever you are hosting them.  :-\

Jo

Jo, I've been hosting my photos in a public folder of http://www.dropbox.com for some months now. These include the Fairbanks and the radial 3 compressed air.  Are you not able to see pictures from any of my recent posts?  Is anybody else having a problem seeing them?
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 13, 2013, 03:12:52 PM
Chuck,
do you intend the coils of the stator to be fake and have magnets inside? If not, a coil without (iron; better ferromagnetic) core is quite ineffective. For iron, r is 30010000, for ferrites, it is 415000. So that's the factor your field strength is reduced by not having a core.


Nick

After following Manfred Albert's build on HMEM, I decided that non-ferromagnetic coils would be satisfactory for my model.  I know that ferromagnetic cored coils are more efficient and produce more power, particularly as generator size increases, but my little Fairbanks doesn't have much torque and although I'm pretty sure my generator will work, it's more for form than function.  I had spent some time looking at stators used on motorcycle alternators.  They are about the right size and are available used on Ebay for under $30.  I think a decent alternator for a model could be made from one but you'd need a pretty hefty engine to drive it.
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 13, 2013, 03:14:59 PM
Hi Chuck
 
If you don't mind me asking how did you arrive at the 60-70 turns?
 :thinking:
 
If I do the maths it equates to coil height of 5mm to 5.5mm - it looks a bit bigger than that, maybe
1/4" which should give you about 95 turns (tight wound)
 
N=0.707*H2/d2
 
N= Number of turns
d=diameter of wire #24 = 0.55mm
H=Height of Coil(along the coil axis)
 
Where H=5,     N=60
Where H=5.5   N=70
Where H=6.35 N=95
 
of course there is a tidy factor. If I was winding them myself in a hurry you would have to half all those calculations   :Lol:
 
Bez

My estimate is based half on calculation and half on SWAG.  The windings will not be particularly tidy based on having to wind them in place.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 13, 2013, 03:20:02 PM
I built a little alternator a few weeks ago, it was a little shaded pole motor, 850 rpm type. I took out the armature, and made a new one, it is a 6 finger claw (similar automotive alternator), with 3 ferrite magnets removed from old speakers inside, this will produce about 90V, and gives useful power when fed through a transformer, and a bridge rectifier, to give about 12V.  This alternator was designed for the Stuart S9 .

Yeah, I had looked at using a motor similar to one of these as the basis for an alternator.  They are typically referred to as fan motors.  I think you can also make a pretty decent brushless DC motor from one of these by replacing the armature with one containing permanent magnets.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Jo on June 13, 2013, 03:27:58 PM

Jo, I've been hosting my photos in a public folder of http://www.dropbox.com for some months now. These include the Fairbanks and the radial 3 compressed air.  Are you not able to see pictures from any of my recent posts?  Is anybody else having a problem seeing them?

Yes I have been having problems for a few months as you say. I thought I would mention it in case anyone else was having similar problems.

I have to remember to get my Linux computer out and access them in a bit of a convoluted way and normally I forget  :-[

Jo
Title: Re: Anybody guess what this is going to be???
Post by: Ian S C on June 13, 2013, 03:39:28 PM
Chuck, I wanted to remove the pole shading rings(they are just used for starting these motors), but I would have to remove the main windings, and I'm too lazy to do a rewind, although I could fit in heavier wire, which would be useful in increasing the current, it was a 150 watt motor.     Ian S C
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 13, 2013, 09:30:23 PM
OK, Jo, I'll start using Photobucket, just for you, even though it's more trouble...  :stickpoke:

I started work on the outboard stand for the armature today.  I started with a 1" x 1.25" x 3" piece of aluminum.  In this first picture I've drilled the pilot hole for the armature shaft and went all the way around the base with a 1/4" ball nose end mill.

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2797_zps8574177e.jpg)

Here I'm using an end mill and my rotary table to start shaping the front and back.

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2798_zpsd1b84853.jpg)

Finished rough cutting the front (or back :-\).

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2799_zps98b89628.jpg)

And here's a couple of pictures after all the shaping and filing is done. 

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2800_zps97f7f4c4.jpg)

The finish, such as it is, was made with my random orbital sander.

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2801_zpsc8c36147.jpg)

OK, Jo, you're off the hook.  Turned out not to be as much trouble as it used to be and now I get to save space on my Dropbox account for other things!
Title: Re: Anybody guess what this is going to be???
Post by: Jo on June 14, 2013, 07:36:59 AM
Brilliant I can see them  :whoohoo:

Following along  8)

Jo
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 14, 2013, 03:23:43 PM
Hi Chuck
 
I don't think you'll have much trouble making enough juice to drive a couple of Doz White LEDs at about 60mW each.
 
I guess we'll get to see eventually but some of us are impatient mugs..  ;D    so I'll ask now
 
What will you be using for your induction source?
 
and how will they be configured? by that I mean; with the eight windings were you aiming to get 60Hz at 900rpm?
 
There is just so many ways you could set this up.
 
Oh! By the way... if these questions are gettig in the way of building this thing... just skip the answers & go streight to the workshop so you can get more progress photos.
 
    :ThumbsUp: :ThumbsUp: :ThumbsUp:
 
Bez
 
 
Title: Re: Anybody guess what this is going to be???
Post by: Noitoen on June 14, 2013, 09:16:01 PM
Chuck, I wanted to remove the pole shading rings(they are just used for starting these motors), but I would have to remove the main windings, and I'm too lazy to do a rewind, although I could fit in heavier wire, which would be useful in increasing the current, it was a 150 watt motor.     Ian S C

You don't have to remove the shading rings, just cut them open. Is the motor you using a 6 pole one. The stator should have the same number of poles than the rotor.
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 14, 2013, 09:40:23 PM
Hi Chuck
 
I don't think you'll have much trouble making enough juice to drive a couple of Doz White LEDs at about 60mW each.
 
I guess we'll get to see eventually but some of us are impatient mugs..  ;D    so I'll ask now
 
What will you be using for your induction source?
 
and how will they be configured? by that I mean; with the eight windings were you aiming to get 60Hz at 900rpm?
 
There is just so many ways you could set this up.
 
Oh! By the way... if these questions are gettig in the way of building this thing... just skip the answers & go streight to the workshop so you can get more progress photos.
 
    :ThumbsUp: :ThumbsUp: :ThumbsUp:
 
Bez

Not sure what you mean by induction source.  The armature will have 16 bar magnets arranged with alternating N & S poles facing outward.  The coils will all be hooked in series.  This will allow all the south poles to pass the coils at once followed by all the north poles passing the coils at once.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 14, 2013, 09:45:58 PM
Got the stator frame and outboard armature support mounted on a common base.  Next I'll start on the armature and armature shaft.  I need to order the magnets.  I'll need 16, 1" x 3/8" x 1/8" bar magnets with the poles on the large flat face. Or I could use 1" x 1/4" x 1/4 with the poles on the long sides.  This would allow a bit more space between the magnets. 

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2806_zps22cd0720.jpg)

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2805_zps4c8caa0e.jpg)

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2803_zps59bf90bd.jpg)

I want to get the armature assembly finished before I start winding the coils so I can experiment a little with different numbers of turns in the coils.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 15, 2013, 10:08:32 AM
Nice progress Chuck  :ThumbsUp:
 
Not sure what you mean by induction source.  The armature will have 16 bar magnets arranged with alternating N & S poles facing outward.  The coils will all be hooked in series.  This will allow all the south poles to pass the coils at once followed by all the north poles passing the coils at once.

Chuck

Thanks. You have answered the question.
 
That should produce even more current and higher frequency per revolution than the very simple eight magnet version I was imagining.
 
Just to verify you correctly picked up what I meant by induction source, I meant the source of magnetic flux which when moving relative to stator coils will induce the EMF in the coil windings.
 
I thought it was easier than asking; permanent magnet? or wire wound? and if wire wound how is the initial excitation established? 
 
Cheers
Title: Re: Anybody guess what this is going to be???
Post by: Ian S C on June 15, 2013, 02:22:35 PM
Noitoen, the stator is 6 pole.  The shading loops are too buried to get at, but we'll see what happens.  I have done a similar modification to a larger induction motor.  Ian S C
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 24, 2013, 11:27:46 PM
I received my magnets from KJMagnetics and installed 8 of them on my armature.  I've done a bit of testing and results are a bit disappointing, but I think I will be able to get it where I want it.  Here's a picture with the armature withdrawn for illustrative purposes.

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2821_zps7ab8977c.jpg)

I've installed 8 magnets and have 200 turns of #27 wire on one pole of the stator.  Turning the armature at somewhere around 1500 RPM's and feeding the output through a full wave rectifier gives me .25 volts.  Multiplied by 8 would give me 2 volts.   That's probably enough to light an LED but if I add another 8 magnets, I'm thinking I'll get 4 volts and if I add 16 magnets I should get 6 volts.  Since the #27 wire is rated at .287 amps, I'm guessing an incandescent lamp is out of the question.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 25, 2013, 12:47:24 AM
Hi Chuck
 
If you skip the bridge rectifier you should be able pick up a bit of voltage.
 
Just wire your LEDs in pairs back to back with a series current limiter.
 
or set the LEDs in a bridge configuation themselves.   ;)
 
Bez
 
 
Title: Re: Anybody guess what this is going to be???
Post by: MuellerNick on June 25, 2013, 08:05:09 AM
Quote
Just wire your LEDs in pairs back to back with a series current limiter.


I think you mean to wire them anti-parallel. But LEDs will mostly fail at a reverse voltage above 5 V!
Chuck, I hope the magnets are properly oriented, you can get them in (at least) two orientations.


Nick
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 25, 2013, 06:07:26 PM
Quote
Just wire your LEDs in pairs back to back with a series current limiter.

I think you mean to wire them anti-parallel. But LEDs will mostly fail at a reverse voltage above 5 V!
Chuck, I hope the magnets are properly oriented, you can get them in (at least) two orientations.

Nick

I double checked the magnet orientation and they are all in correctly, alternating poles facing out.  I've ordered some more magnets, but will do some further testing in the meantime. 

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on June 25, 2013, 06:14:25 PM
Hi Chuck, the magnets you are using and this is just a question. When you purchased the magnets, did they specify that the north and south poles were end to end or front to back?

Don
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 25, 2013, 08:23:38 PM
Hi Chuck, the magnets you are using and this is just a question. When you purchased the magnets, did they specify that the north and south poles were end to end or front to back?

Don

The poles are on the large flat faces...

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 25, 2013, 10:45:09 PM
So I removed the single winding and then wound all eight stator coils, 200 turns each with alternating coils wound in the opposite direction.  Boy, glad I don't have do that 8 hours a day to pay the rent.  That is mind numbing work!

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2822_zpsa5bbbcd7.jpg)

I also epoxied another row of magnets on the armature.  I broke one in the process, so I'll need to await my order to install the last magnet.  As an aside, I discovered that JB weld does indeed have some kind of magnetic material in it.  Don't know if its steel, iron, cobalt or what, but the gooey mix is most definitely attracted to the magnets.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 27, 2013, 09:20:32 AM
Looking good Chuck
 
 
 Nick
 
Please tell me you're not saying anti-paralled LEDs will fail due to the reverse voltage?  Silliest thing I ever heard.  :lolb:
 
We both know the reverse bias voltage on one diode of the pair can never exceed the forward bias voltage of the other.  :happyreader:
 
Quote
Just wire your LEDs in pairs back to back with a series current limiter.


I think you mean to wire them anti-parallel. But LEDs will mostly fail at a reverse voltage above 5 V!
Chuck, I hope the magnets are properly oriented, you can get them in (at least) two orientations.


Nick

 
Title: Re: Anybody guess what this is going to be???
Post by: MuellerNick on June 27, 2013, 09:51:33 AM
Quote
We both know the reverse bias voltage on one diode of the pair can never exceed the forward bias voltage of the other.   


I stand corrected!  :embarassed:


Nick
Title: Re: Anybody guess what this is going to be???
Post by: Alan Haisley on June 27, 2013, 06:16:15 PM
I received my magnets from KJMagnetics and installed 8 of them on my armature.  I've done a bit of testing and results are a bit disappointing, but I think I will be able to get it where I want it. 

I've installed 8 magnets and have 200 turns of #27 wire on one pole of the stator.  Turning the armature at somewhere around 1500 RPM's and feeding the output through a full wave rectifier gives me .25 volts.  Multiplied by 8 would give me 2 volts.   That's probably enough to light an LED but if I add another 8 magnets, I'm thinking I'll get 4 volts and if I add 16 magnets I should get 6 volts.  Since the #27 wire is rated at .287 amps, I'm guessing an incandescent lamp is out of the question.

Chuck
After looking at your picture and at the K&J catalog, I think that you can use thicker magnets. Based on their specifications that would let you apply a higher Gauss field which might help. You may also be able to double them up. Another thought is to mount them slightly skewed or with NS in line with the armature chords.
It looks like you have a lot of orientation choices here that may change the output. At a slower speed you may be able to clamp the magnets with wire bands or something so that you can reuse them with a bunch of armature configurations and orientations without having to spend a fortune for magnets.
Alan
Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on June 28, 2013, 12:58:13 AM
I agree that the magnets need to be bigger as Alan has said, but also the magnet should be the same width as the pole piece for good magnet flux coverage.

Just my 2c

Don
Title: Re: Anybody guess what this is going to be???
Post by: Noitoen on June 28, 2013, 01:27:56 PM
it's very important that the polarity of the bar magnets, in your case be "top to bottom" and not like those old school magnets that where painted half red and blue along the length.

As for the size, if the polarity is right, some round segments of soft steel can be glued to the magnets to widen the magnetic field. the flux density on those neodymium magnets is much denser than the increased area of the little inserts are able to carry without saturating.
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 28, 2013, 03:11:44 PM
I'm still waiting for my second order of magnets to arrive.  I did do a trial run with the magnets doubled up, except for the one I broke.  I measured about 3.6 volts AC at around 1500 RPM and about 3.4 volts DC when I hooked up the full wave rectifier.

I was able to light a large LED with the full wave DC, but when I took out the rectifier, it wouldn't light with straight AC. 

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Stuart on June 28, 2013, 04:14:38 PM
a LED is a diode and therefore conducts one way some are back to back and will work either way sometimes for tow colour operation

you need DC for a LED at least you did when I was into electronics used to be G4IJX and built an early computer zilog Z80 based



but as usual i may be wrong
BTW yes it is mind numbing try a two pole High frequency stator for  a grinder 1 3/4 bore and three inches long there is not much room to do the winding on those

Stuart
Title: Re: Anybody guess what this is going to be???
Post by: steamer on June 28, 2013, 06:40:22 PM
Nice progress Chuck!... I really like the genset!....it's a nice thing to do with our small engines for shows and stuff....and it looks the part.

Glad we are all sorting out the electronics.....

Dave
Title: Re: Anybody guess what this is going to be???
Post by: Noitoen on June 28, 2013, 10:42:49 PM
I think there must be something wrong. I've worked for many years with motors and alternators and although they had a core, self exited alternators generate at least more than 3 volts when they are rotated at 1500 rpm with just the core's residual magnetic field and with few turns on their coils. Only when the regulator, using this voltage "wakes up", does the magnetic field grow to the get the full voltage. Neodymium magnets are so strong the leads me to believe you should double check your system.
Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on June 29, 2013, 02:30:35 AM

I was able to light a large LED with the full wave DC, but when I took out the rectifier, it wouldn't light with straight AC. 

Chuck
The reason they didn't lite is because with the rectifier you had both halves of the sine wave. The LED is a rectifier and only conducts one way so you only had half of a cycle and half voltage.
I still stand by the fact that the magnets need to be the size of the pole piece to get max flux coverage.

Don
Title: Re: Anybody guess what this is going to be???
Post by: MuellerNick on June 29, 2013, 11:47:34 AM
Looking at the basic physics of a generator, we see two things we want (or not) to get out of it: Voltage and amperage.


Voltage is a function of flux-change. The higher the speed of flux-change, the higher the voltage. That means more RPM and/or more poles for more voltage.
Amperage is a function of flux-strength. Need more amps? Stronger magnets and/or improve the flow of the flux through the coils. But not the problem here.


If you look at a motor, and keep in mind that it is just the reverse of a generator, things get more obvious. The higher the voltage, the faster it turns. The more poles, the faster it turns.
The higher the load, the more amps.

On edit, an addition:
If we see that the voltage is substantially higher without a load compared to with a loaded generator, we see that it doesn't provide enough current. So we need to improve flux-strength too to get what we want.



Nick
Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on June 29, 2013, 01:13:21 PM

If you look at a motor, and keep in mind that it is just the reverse of a generator, things get more obvious. The higher the voltage, the faster it turns. The more poles, the faster it turns.
The higher the load, the more amps.




Nick
Nick, I Think you are talking about a DC Motor, speed is a function of poles and Frequency of the source for AC motor.
Voltage is a function of coil turns and flux change for Generator. Speed will also cause higher voltage output.

Don
Title: Re: Anybody guess what this is going to be???
Post by: MuellerNick on June 29, 2013, 01:36:34 PM
Quote
Nick, I Think you are talking about a DC Motor, speed is a function of poles and Frequency of the source for AC motor.


Frequency is just an other means of speed of flux-change. Look at the collector as a mechanical VFD.


Nick
Title: Re: Anybody guess what this is going to be???
Post by: b.lindsey on June 29, 2013, 01:53:50 PM
This stuff is like greek to me...do you guys know of one or two good basic texts for explaining motors/generators/alternators for us non electrical types?

Bill
Title: Re: Anybody guess what this is going to be???
Post by: steamer on June 29, 2013, 03:11:39 PM
Though I haven't seen a schematic yet, If you take a google look at small wind turbine generators for home build...you'll find a lot of information....I have some of these articles somewhere....just can't put my hand on it at the moment..


Dave
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on June 29, 2013, 04:54:33 PM
The basics of a generator (or alternator) are much as Nick says.  However, you can also increase the voltage by increasing the number of windings.  And I think Don and Nick are right that I can increase the current (amperage) by increasing the number and/or strength of the magnets and by reducing the spacing between the magnets and the stator poles. 

I agree with Don that having the magnet(s) the same width as each stator pole, or in this case each stator winding, would be optimum and if I use the remaining magnets that I've ordered, my armature will have three magnets side by side that will add up to about the same width as a stator coil.  This will, of course, also add more magnetic strength which will increase the current.

So, the quandry is why 3.4 DC volts would light the bulb and 3.6 AC volts wouldn't.  I realize with the AC voltage, that current would only flow for 1/2 of each cycle and the other half is essentially wasted, but I would have thought that would still be enough to light the bulb.  Perhaps the amount of current being produced is so small, 1/2 a cycle just isn't enough.

I have to verify this but I believe my dynamo is set up like this: 

1.  There are 8 stator poles with the coils all hooked in series and alternating coils wound in the opposite direction.  Each coil is 200 turns of #27 wire.  The total resistance of the stator is about 22 ohms.

2.  There are 8 sets of magnets comprised of 2 magnets each, both with the same pole facing out.  Alternating sets have the opposite poles facing out.  The magnets seem pretty strong.  They are 1" long x 1/4" wide x 1/8" thick.  Don't know the Gaussian rating but the KJ Magnetics web site rates them at 7.34 pounds.  Adding one more magnet will add another 50% magnetic strength to the armature.

By the way, I'm assuming when I measure the AC at 3.6 volts, that means 3.6 volts positive wave followed by 3.6 volts negative wave.  Don't know if that is peak voltage or RMS.

Chuck

Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on June 29, 2013, 05:55:57 PM

So, the quandry is why 3.4 DC volts would light the bulb and 3.6 AC volts wouldn't.  I realize with the AC voltage, that current would only flow for 1/2 of each cycle and the other half is essentially wasted, but I would have thought that would still be enough to light the bulb.  Perhaps the amount of current being produced is so small, 1/2 a cycle just isn't enough.


By the way, I'm assuming when I measure the AC at 3.6 volts, that means 3.6 volts positive wave followed by 3.6 volts negative wave.  Don't know if that is peak voltage or RMS.

Chuck


One of the reasons the that would not illuminate  the LED lite, would be its turn on voltage, some require over 1.5 volts to light. Being half wave rectifier give half voltage on AC, so you my not have had enough to forward bias the LED.
The voltage you measured would be RMS if you used a meter to read it with.
By the way you should read less DC voltage that AC. Voltage. The rectifier will droop 1.4 volts across it and the conversion from AC to DC depending on the frequency will give you less.
This link should help you. http://cas.web.cern.ch/cas/Warrington/PDF/Visintini.pdf
Don
Title: Re: Anybody guess what this is going to be???
Post by: Admiral_dk on June 29, 2013, 09:14:00 PM
You need to pay premium prices to get at "True RMS" meter  :old:  all cheap multimeter's can't measure RMS .... or more correctly they can IF the voltage is a PURE sine - if not the measured voltage might be as much as 90% wrong  :old:

Since I often repair old tube amps for guitars (not pure sine out), I bought a "True RMS" meter years ago, and I can tell you it makes quite a difference on the result I get on power output.

Chucks alternator will deliver a pure sine (if the armature, windings and the magnets a perfectly equally spaced), when loaded with a pure resistive load !!!!

But loaded with a rectifier and / or LED's => all bets are off, except to say that the output is anything but a pure sine => all measurements with a non "True RMS" meter might be up to 90% off - so comparing the AC and DC voltages doesn't tell you anything usefull in explaining why one works and the other not.

I can admittedly not remember if you'll measure a higher of lower result in this case - sorry.

Alternative to the "True RMS" meter can be a oscilloscope - it will not be perfect, but it will give you a ballpark voltage across the load, within a few %.
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on June 30, 2013, 04:39:28 AM
So, the quandry is why 3.4 DC volts would light the bulb and 3.6 AC volts wouldn't.  I realize with the AC voltage, that current would only flow for 1/2 of each cycle and the other half is essentially wasted, but I would have thought that would still be enough to light the bulb.  Perhaps the amount of current being produced is so small, 1/2 a cycle just isn't enough.

Chuck

Hi Chuck
 
There are a number of factors that could be at play here.
 
1. What is the colour of the led you are trying to illuminate.
 
The higher the wavelength the higher the forward bias voltage you need to get it to conduct and illuminate.
 
2. what is the device you are using to measure the AC voltage.
 As you said you don't know whether it is RMS or not.
 
It will depend on a number of things.
 
If the meter is a galvanometer type the voltage will most likely be moving the coil meter movement by average rectified voltage of the waveform applied or 0.637 of the peak if it is a sin wave, in many voltmeters this is often calibrated to assume the waveform is sinusoidal  and therefore read the RMS voltage of 0.707 (or half the square root of two) of the peak voltage.
 
If the voltmeter is a DMM the possibilities are equally as vague - because the input can be either rectified averaged in the same way as the galvanometer type or in a more accurate meter, the input can be chopped at high frequencies and take instantaneous dc readings of each pulse and mathematically calculate the true RMS voltage whatever the waveform is.
 
I am guessing your meter is likely to be indicating a Pseudo RMS.
 
This leans us towards the likelyhood that the problem is LED colour, which if white could need as much as 3 to 4 volts to turn on because you need the full visible spectrum of wavelengths to get white light. ( often achieved by internally parallelling multiple LEDs of different colours, in the single package)
 
You could test this forward bias limitation issue by using clear lens red LEDs as they require lowest voltage to illuminate. If the red LEDs give you a good illumination then bias voltage threshold is probably the issue.
 
note that illuminating a LED with AC it will only lite up while the voltage is above the forward bias voltage.
 
so if your peak AC voltage is 4 volts and the turn on voltage of the LED is 3.5V, then the LED will only be conducting - maybe 10-15% of the time, with the result being of a very dim illumination and one that is probably not visible.
 
I hope this information will help you find the problem.
 
Of course all the other suggestions to help increase the voltage and current capabilities of the generator will most likely over come the issue any way, but it will be interesting to identify the real reason for the apparently buzzar behaviour of your LEDs. 
 
Bez
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on July 12, 2013, 07:15:38 PM
Just a quick progress report here.  I wasted a week thinking I had ordered more magnets when in fact I hadn't.  So it took another week to get a second batch of magnets delivered.  Previously, I had 2 magnets per pole but was missing 1 magnet on 1 pole (breakage). 

When the new magnets arrived, I installed the 1 magnet needed to complete the 2-magnets-per-pole armature.  When I test spun it with my cordless drill at around 1500 RPM, I measured right at 4.0 volts AC.  So, I (finally) located my stash of bright green LED's and hooked up 18 of them in parallel, every other one wired in the opposite direction.  Then I hooked up the alternator with no rectifier, just straight AC,  all 18 LED's lit up very brightly.  So I'm pretty happy with it at this point.  However, I'm planning to build another stator using a 1" length of 4" pipe, 1/4" wall.  The poles will be made up with steel cores that I can wind separately, then attach to the stator ring.  Probably won't be the most efficient set up in the world, but should give me more power.  I do want to put some kind of load on the engine and I don't think the current setup with LED's is going to do it.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Roger B on July 12, 2013, 07:22:04 PM
Definitely moving in the right direction  :ThumbsUp:

I always like to see engines driving something.
Title: Re: Anybody guess what this is going to be???
Post by: b.lindsey on July 13, 2013, 12:26:23 AM
That's good news Chuck, sounds like things are moving in the right direction :)

Bill
Title: Re: Anybody guess what this is going to be???
Post by: Rustkolector on July 13, 2013, 04:42:12 AM
Chuck,
You are definitely are the right track. Many poles, many turns, and a steel stator will give you a reasonably high voltage output at low RPM. How are you planning on managing the cogging effect that a steel stator and permanent magnets will create?

Jeff
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on July 13, 2013, 05:55:12 AM
Chuck,
You are definitely are the right track. Many poles, many turns, and a steel stator will give you a reasonably high voltage output at low RPM. How are you planning on managing the cogging effect that a steel stator and permanent magnets will create?

Jeff

At the moment I don't have a plan other than hoping it won't be too strong...

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Rustkolector on July 13, 2013, 04:08:14 PM
Chuck,
Depending on the magnets and air gap you use, cogging can be excessive. I made a alternator from an 18 pole ceiling fan motor. Anxious to test it's output, I stuck the magnets on my iron rotor and inserted it into the stator. Actually, the rotor was pulled from my hand into the stator ruining a couple of the neo magnets. I couldn't turn it nor could I remove it by hand due to the magnetic force. I was able to  minimize the cogging effect by angling the rotor magnets on the rotor so that one magnetic pole on the rotor spanned two stator poles. Cogging was still present but acceptable, however I still needed a plastic sleeve around the rotor magnets to protect them from damage as rotor insertion is still tricky. Using an 18 pole stator made it fairly easy for me to angle my magnets. Fewer poles makes angling between two stator poles more difficult. I suggest you try to use as many poles as you can fit into to stator.  A 4" stator will make this difficult. Mine was 6" dia. The other benefit of added poles is voltage at lower RPM. I am not sure a non magnetic rotor would be of any benefit, but it might have some relative to cogging, but not to electrical output.

Jeff
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on July 13, 2013, 04:18:14 PM
Hi Chuck
 
Great to hear the green LEDs worked out nice and bright.  :whoohoo:
 
Are you aiming for some filament lumins loomens lemings light bulbs to load up the alternator when you beef it up some more?
 
The circuit with 18 Green LEDs sounds like you calculated that out to be just right for using the alternator windings as your LED current limiter.
 
If you don't mind me stealing your thunder Chuck, I'll explain (for those interested) how you would have arrived at that magic number 18.
 
A typical forward Bias voltage for green LEDs is about 2.2V - the internal impedance of the alternator was measured at 22 ohm (IIRC) therefore out of the 4V measured at the alternator output (unloaded), 1.8V (=4v-2.2v) must be across the internal impedance of the windings when LED load is applied.
1.8V over 22 ohm will pass 80mA.
That should give about 9mA through each of the 9 conducting LEDs during each half wave of the AC cycle (close to the typical 10mA required)
 
Setting the circuit up this way there is no need for the usual current limiting resistor.  Neat trick Chuck  :praise2: 
 
I'm looking forward to seeing your next mods   :ThumbsUp: :ThumbsUp:
 
Cheers
 
Bez
 
 
 
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on July 15, 2013, 05:27:44 AM
Thanks, Bez.  Actually I started with 6 LED's, the went to 12, and finally 18, all that I had.  I suspect it would have driven more.  However, I'm also hoping to run the engine at about 600 or 700 RPM, not the 1500 that my cordless drill provided.

I started work on a steel core stator.  I'm using a 1 1/8" long piece of 4" OD, 3.5" ID steel pipe as the outer ring. 

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2870_zps7feababf.jpg)

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2871_zps3bf06c0e.jpg)

The coils are wound on HDPE plastic spools that started out 1" x 7/8" x 1/2" thick.  The center part of the spool is 3/8" diameter with a 1/4" hole through the center and winding space is about 1/4" x 1/4" or a little less since the windings don't go all the way out.  There are a total of about 260 turns of #28 copper wire per coil which is about 25% more than my other stator.

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2872_zpsb71b926b.jpg)

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2873_zps0a0d810b.jpg)

(http://i192.photobucket.com/albums/z195/cffellows/IMG_2874_zps4868ec0a.jpg)

I profiled the inner radius of the coil form using a fly cutter on my mill/drill to cut the concave curve with the coil form held vertically on the outside edge of the vice jaws.  I formed the outer radius by mounting the coil form on the end of a 1/4" diameter expanding mandrel, then clamping the mandrel in the round tool bit hole on one of my boring bars and swinging the outside of the coil form at the proper diameter in my lathe.  Each coil form will have a 1/4" diameter x .4" long steel  rod with a very thin, 5/16" diameter flat head on the inner end and a 6-32 threaded hole in the other end.  Recessed, 6-32 socket head cap screws from the outside will screw into the outer end of the rod and secure the coil forms to the stator ring.

Don't have any idea how much cogging will be an issure or what kind of power I will get out of this thing or if my engine will even turn it.  It's all a learning experience at this point.

Chuck
Title: Re: Anybody guess what this is going to be???
Post by: Don1966 on July 15, 2013, 05:45:48 AM
Chuck why are you using a steel stator? You should have no cogging because there are no steel pole pieces. The steel stator is only good if the pole pieces are steel to help distribute the magnetic lines of force. Sorry bud but this will not help much. The steel ring will increase eddy current losses.
Your orginal design should product more output then you have. Did you pass a compass inside the stator to check that the poles were north and south on every other poles. Just use a battery to power the stator with to do this. Do it just to double check they are correct.

Don
Title: Re: Anybody guess what this is going to be???
Post by: cfellows on July 15, 2013, 03:39:38 PM
Chuck why are you using a steel stator? You should have no cogging because there are no steel pole pieces. The steel stator is only good if the pole pieces are steel to help distribute the magnetic lines of force. Sorry bud but this will not help much. The steel ring will increase eddy current losses.
Your orginal design should product more output then you have. Did you pass a compass inside the stator to check that the poles were north and south on every other poles. Just use a battery to power the stator with to do this. Do it just to double check they are correct.

Don

There will be a 1/4" diameter steel core in the coil that holds the coil to the steel ring.
Title: Re: Anybody guess what this is going to be???
Post by: Bezalel on July 16, 2013, 01:07:17 PM
Thanks, Bez.  Actually I started with 6 LED's, the went to 12, and finally 18, all that I had.  I suspect it would have driven more.  However, I'm also hoping to run the engine at about 600 or 700 RPM, not the 1500 that my cordless drill provided.


Probably a good thing you didn't start with less than 6 LEDs -  the estimated 80mA is shared between the 3 forward biased diodes, 26 mA is pushing towards the limits. They tend to fritz out between 20-30mA.
 
Bez