# Determining Number of Turns for low voltage AC Generator

#### BabyHueyTAW

Ok, I did a quick search, and could not find answer.
I need to determine how many turns / windings of 24awg magnet wire are required to generate no less than 5VAC no greater than 20VAC single phase using 3 of the N45 Neo Magnets rated at 13800 gauss each with 275-pound pull. Y'all give me a clue how to figure this out?

#### Baluncore

Welcome to PF.
The number of turns needed will depend on the geometry of the magnetic circuit and the RPM of the alternator.
You need to define those physical parameters.

#### BabyHueyTAW

No spin, only vertical movement across coil images not to scale of course,

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#### Baluncore

Where does that diagram in post #3 come from?

#### jim hardy

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Y'all give me a clue
1. Volts is product of (rate of change of flux that's encircled by your turns) X (number of turns)
Flux is product of flux density(that's your Gausses) X area , adjusted for the geometry
How many of those 13,800 Gausses go down through your coil where they're encircled by your wires ?
And how fast does the magnet move?

2. Viewed from the top
your outer coil is wound clockwise
your inner coil is wound counterclockwise
so any voltage induced in one coil will cancel voltage induced in the other.
That the coil diameters differ by one wire thickness means they have unequal areas so the voltages won't exactly cancel,
but i think that machine is going to disappoint you.

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#### jim hardy

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Candidate for DIY forum ?

#### Baluncore

Yes, a candidate for DIY.
A weird idea. It would be nice to have a link to the theory. Without that I question the orientation of the magnets and the lack of a better defined magnetic path. As it is there will be significant cancellation.
If half the diagonal winding was not reversed there would be no reversal of flux between the ends of the movement where the coils do not overlay. As it is, a current sheet flows down the near side of the coil and up the back, but it is linear, not rotating. We will have to wait for further information.

#### BabyHueyTAW

Where does that diagram in post #3 come from?
This is something I cobbled together with MS Paint. trying to explain what I want to do.

#### BabyHueyTAW

Yes, a candidate for DIY.
A weird idea. It would be nice to have a link to the theory. Without that I question the orientation of the magnets and the lack of a better defined magnetic path. As it is there will be significant cancellation.
If half the diagonal winding was not reversed there would be no reversal of flux between the ends of the movement where the coils do not overlay. As it is, a current sheet flows down the near side of the coil and up the back, but it is linear, not rotating. We will have to wait for further information.
As far as the lay of the coils in the image, those are really just a visual for the idea in my head. I did not consider the cancellation. I think I may actually have better results trying this the old fashioned way of trial and error. I will repost over in DIY. Thank y'all!

#### anorlunda

Mentor
Gold Member
Candidate for DIY forum ?
Suggestions like that should be in a report so that the mentors can help.

Ok, I will repost in DIY. thank you
No don't do that, it would be a duplicate post which is against the rules. I moved this thread for you. If you need assistance, don't hesitate to click REPORT to ask the mentors for help.

#### BabyHueyTAW

As the magnet in the large disc move up and down the column which houses the coil. If this helps explain better

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#### berkeman

Mentor
As the magnet in the large disc move up and down the column which houses the coil. If this helps explain better
Looks like energy extraction from water wave motion? I don't think your magnet/coil geometry is optimized for that energy source. Have you looked at how existing wave energy conversion mechanisms work?

#### BabyHueyTAW

Looks like energy extraction from water wave motion? I don't think your magnet/coil geometry is optimized for that energy source. Have you looked at how existing wave energy conversion mechanisms work?
This is exactly the concept, just want to move the magnet not the coil

#### Baluncore

This is exactly the concept, just want to move the magnet not the coil
Efficient linear alternators usually employ a stack of magnets, the “mover”, moving inside a tube, with many coils wound around the tube. That makes it possible to generate many cycles of three phase energy per stroke of the “mover”. The magnetic path is then short, while the magnets and gap are sealed from the environment.

The mover can be a piston driven along the cylinder by a connecting rod, or by fluid pressure. Internal combustion, “free piston” engines, and external combustion “Stirling” engines, have been designed as alternators using that principle.
https://en.wikipedia.org/wiki/Free-piston_linear_generator

#### BabyHueyTAW

Inside the PVC I will have a wooden dowel, wrapped around the dowel is my coil. the magnet stack will be free moving vertical only.

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#### jim hardy

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That's clever construction there....

I mentioned up above 'rate of change of flux that's encircled..'

Encirled flux will only change near the top and bottom of your coil
here's a demonstration of that , at www.youtube.com/watch?v=jaZfTXUv_lI

which means bouncing a short magnet up and down about the middle of a tall coil won't do much in the way of generating electricity.

But you can experiment with varying ratios of magnet/coil tallness to find a combination that'll work.

I just tried dropping a ceramic ring magnet down around a copper tube to see if induction will work as well from the outside of a coil as it does from the inside(video below).
My magnets aren't nearly so strong as rare earth ones and i couldn't really tell whether the copper tube slowed down their fall or not.
Sorry,
maybe that's an experiment you can try with your stronger magnets and a yard of copper pipe...?

old jim

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#### BabyHueyTAW

That's clever construction there....

I mentioned up above 'rate of change of flux that's encircled..'

Encirled flux will only change near the top and bottom of your coil
here's a demonstration of that , at www.youtube.com/watch?v=jaZfTXUv_lI

View attachment 238474
which means bouncing a short magnet up and down about the middle of a tall coil won't do much in the way of generating electricity.

But you can experiment with varying ratios of magnet/coil tallness to find a combination that'll work.

I just tried dropping a ceramic ring magnet down around a copper tube to see if induction will work as well from the outside of a coil as it does from the inside(video below).
My magnets aren't nearly so strong as rare earth ones and i couldb't really tell whether the copper tube slowed down their fall or not.
Sorry,
maybe that's an experiment you can try with your stronger magnets and a yard of copper pipe...?

old jim

Hmm, so my coil does not necessarily need to be that tall as long as my magnetic field cuts both ends. I think I understand. I think my wife would shoot me if i bought a copper pipe right now just to play with. she was not thrilled with the price of my toy magnets...
I will keep playing with this more. I have 800 feet of 32awg magnet wire and 2pounds of 24 awg to play with my 3/8" OD wooden dowel, will post pictures and thoughts as I go. I really appreciate the thoughts and support as I tackle this.

#### jim hardy

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I think my wife would shoot me if i bought a copper pipe right now
Are you above "Dumpster Diving" ? Perhaps a piece of shower curtain rod ....
aluminum tubing is pretty common stuff.

#### BabyHueyTAW

So I am going to try this, and see what we see.

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#### BabyHueyTAW

Are you above "Dumpster Diving" ? Perhaps a piece of shower curtain rod ....
aluminum tubing is pretty common stuff.
Never above diving!!

#### BabyHueyTAW

!!!! I Now Understand what you mean on the enter and exit voltage!! My coil is much too long and not enough coils to cut with the magnetic field!!! I must shorten my coil and add layers to it!!! You guys are amazing!!

"Determining Number of Turns for low voltage AC Generator"

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