Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Acoustic magnetic generator.  (Read 132492 times)

Grumage

  • Hero Member
  • *****
  • Posts: 1113
Re: Acoustic magnetic generator.
« Reply #75 on: February 19, 2014, 09:15:16 PM »
Dear Verpies, Google and all.

I shall have to start this reply with a slight error report!!

I decided to revisit this experiment earlier today and found that some of the signal seen on the Oscilloscope was caused by EM radiation from the Amp and transformer. Undaunted, a leftover Sweetie / Candy tin was pressed into service as an Earth Spike grounded (not supply industry ground) Faraday cage. I was then able to ascertain without any doubt that the Ferrite was indeed generating a signal and not picking up any extraneous signals. The output was a lot weaker than before but resonance and harmonic sub frequencies were all there and in the correct sequence.

Yes there is a "sweet spot" between the core halves !! I found the optimum air gap was 3mm !!

Once again I apologise for my earlier error. I hope that these new findings will exonerate me ??  :)

Cheers Grum.

Grumage

  • Hero Member
  • *****
  • Posts: 1113
Re: Acoustic magnetic generator.
« Reply #76 on: February 19, 2014, 09:33:27 PM »
Dear Google ??

Quote from YT.
Sandeep Kapoor2 hours ago

Hi Grumage. Its very interesting. I made some observations.

1. You exited the core only with piezo and it gave voltage in pickup coil. I am assuming piezo was not connected to input coils.
2. You demonstrated that by adjusting the airgap, a sweet spot is obtained.
3. Piezo must touch the core physically for maximum aplitude of the output voltage.
4. At different input frequencies you got high nodes in the pickup coil. Are these frequencies related in anyway with each other in the ratios of PHI ?

Thanks for sharing. Looking forward to more tests eagerly. BTW verpies directed to this video from overunity dot com.

1. The Ferrite cores were just sat on the Piezo transducer. No, there is no electrical connection.
2. Correct. Around 2.5 to 3mm.
3. Correct.
4. Correct. Verpies did the mathematics some time ago. Although the resonant frequency signature did not alter there were minor resonant points at the "ODD" harmonic scale !! 3.5.7 etc.

Cheers Grum.

Google

  • Hero Member
  • *****
  • Posts: 568
Re: Acoustic magnetic generator.
« Reply #77 on: February 20, 2014, 03:39:53 AM »
Thanks a lot Grum and verpies  :) :)

Now I derive from this:

1.  if you replace the core by a magnet, you would get a much higher output for the same input power ?
2.  higher the number of turns of the pick up coil, higher the voltage generated ?
3.  thicker the pickup coil wire diameter, higher the amperage ?
4.  stronger the magnet, higher is the output power, for a fixed input power ?

5. If all 4 above are correct, what would limit the max power output for a fixed input power.

6. If all the parameters are optimised, can we get a cop of 1 by this arrangement ?

Best

verpies

  • Hero Member
  • *****
  • Posts: 3473
Re: Acoustic magnetic generator.
« Reply #78 on: February 20, 2014, 10:57:21 AM »
1.  if you replace the core by a magnet, you would get a much higher output for the same input power ?
Possibly ...or if this particular magnet is not susceptible to acoustic stimulation, the core can be kept with the magnet added as shown here.  Keeping the core has the additional benefit of closing the flux lines in a well controlled magnetic circuit and better guiding the magnetic flux under the pickup coil, because the relative permeability of a magnet is almost 1 and that of a core is usually above 1000.

2.  higher the number of turns of the pick up coil, higher the voltage generated ?
Yes, but voltage is not power.

3.  thicker the pickup coil wire diameter, higher the amperage ?
Not quite. Thicker wire lowers the resistance (R) of the winding and raises the current limit (IMAX=V/R).  In other words, it does not mean that higher current will flow - it only means that a higher current can flow through a thicker winding.

4.  the stronger the magnet, the higher is the output power, for a fixed input power ?
No, because the output power depends on the magnitude of variation in magnetic flux, not on the absolute level of magnetic flux density.

6. If all the parameters are optimized, can we get a COP of 1 by this arrangement ?
Maybe

Google

  • Hero Member
  • *****
  • Posts: 568
Re: Acoustic magnetic generator.
« Reply #79 on: February 20, 2014, 11:06:42 AM »
@verpies, thanks.

That implies, keep the core.
That also implies, the output will depend on flux variation in the core, may be maximisedassisted by a relatively weaker magnet also.
That implies, an efficient piezo which can create vibrations with lesser input power.

Best

tinman

  • Hero Member
  • *****
  • Posts: 5365
Re: Acoustic magnetic generator.
« Reply #80 on: February 20, 2014, 11:58:44 AM »
It does. 
I always am amazed how much the glass can bend before it breaks.  I could not squeeze the glass so much in a vise statically.  It would break much earlier than the dynamic deformation shown on that video.
As glass is a liquid,i would think that some how the structure of the liquid is being changed by the acoustics-making it more pliable.Maybe John Hutchinson was really onto something?.

I too,have not seen glass flex this much without breaking.I wonder if the same could be applied to that liquid we can use as fuel!water!. Can acoustic resonance break the bonds of water?

Google

  • Hero Member
  • *****
  • Posts: 568
Re: Acoustic magnetic generator.
« Reply #81 on: February 20, 2014, 12:25:50 PM »
@ tinman,

It can break, when placed in a crystal bowl and resonated at 42712.2 hz. Thats what John Keely observed. True or false, I dont know.

Best

itsu

  • Hero Member
  • *****
  • Posts: 1845
Re: Acoustic magnetic generator.
« Reply #82 on: February 21, 2014, 11:44:07 AM »

Would a setup like this work?
These are 16 ceramic magnets 8 on each side of the piezo element.

Pickup coils on each side moveable to find the acoustic nodes.

Regards Itsu


verpies

  • Hero Member
  • *****
  • Posts: 3473
Re: Acoustic magnetic generator.
« Reply #83 on: February 21, 2014, 02:45:34 PM »
Would a setup like this work?
If the material of these magnets is susceptible to acoustic stimulation...then maybe it will work a little.

These are 16 ceramic magnets 8 on each side of the piezo element.
Pickup coils on each side moveable to find the acoustic nodes.
The disadvantages of this arrangement are:
- open magnetic flux path (high reluctance)
- short acoustic path (short separation between acoustic nodes)
- open ends radiate acoustic energy to air (acoustic energy loss)
- segmented magnets will cause acoustic reflections inside the stack, which will confuse measurements
- segmented magnets might clap if the stack is not clamped, which will confuse measurements further
- no core for guiding the magnetic flux (magnets have almost the same permeability as air) thus flux can loop back in unexpected places, not necessarily under the pickup windings!


P.S.
Don't you have a large ferrite C-core or a toroidal core that you can cut with a Dremel tool + diamond wheel ?
It's easy to damage this type of piezos by soldering.  Clip-on contacts might be safer...

itsu

  • Hero Member
  • *****
  • Posts: 1845
Re: Acoustic magnetic generator.
« Reply #84 on: February 21, 2014, 03:25:47 PM »
P.S.
Don't you have a large ferrite C-core or a toroidal core that you can cut with a Dremel tool + diamond wheel ?
It's easy to damage this type of piezos by soldering.  Clip-on contacts might be safer...

Ok,  thanks, i have a ferrite C-core, but its not really large.  I do have some yoke halfs too, but those are not really large either.
By "a toroidal core that you can cut with a Dremel tool + diamond wheel ?" you mean cut it in half, or only one cut where the piezo would tightly fit in?

What about this setup (the rod is graphite which is conductive but not magnetic, so it would need to be a similar ferrite rod):

Regards itsu

verpies

  • Hero Member
  • *****
  • Posts: 3473
Re: Acoustic magnetic generator.
« Reply #85 on: February 21, 2014, 03:52:00 PM »
What about this setup (the rod is graphite which is conductive but not magnetic, so it would need to be a similar ferrite rod):
That size and proportion would be much better.  The rod would have to be ferrite not graphite, of course  ;D

One thing that's missing in this arrangement is the massive counterpoise on the other side of the piezo. 
The piezo must brace itself against something either mechanically or inertially.  The mass of the piezo is not enough to serve as a counterpoise (and it's bad for it).

An identical ferrite rod on the other side of the piezo would work as a counterpoise but it would affect the magnetic field a little because it is magnetically permeable, ...yet not an intended part of the magnetic circuit. 
Of course the counterpoise can be made a part of the magnetic circuit, too.   
If the counterpoise is not a part of the magnetic circuit then any hard paramagnetic material is fine ...even a glass rod or aluminum rod, as long as it has the same time-of-flight as the ferrite rod on the other side.

If a different material is used for an inertial counterpoise, then its length should be adjusted according to the speed of sound in it.
For example, aluminum has a high speed of sound, so an aluminum rod counterpoise should be longer than the ferrite rod, in order to make the reflection from its open end come back to the piezo at the same time as the reflection from the open end of the ferrite rod.


                     Speed of       Speed of       Loss factor         Loss factor
                    Longitudinal      Shear         Longitudinal          Shear
Material            waves          waves            waves               waves
---------------------------------------------------------------------------------------------
Diamond      12000m/s
Aluminum       6374m/s        3111m/s     0.00003-0.0001     0.0001
Hard Ferrite   6300m/s 
Steel              5960m/s       3235m/s      0.00002-0.0003
Iron               5957m/s        3224m/s     0.0001-0.0004        0.0002-0.0006
Soft Ferrite    5700m/s
Copper          4759m/s        2325m/s     0.002                      0.002
Brass             4372m/s        2100m/s     0.0002-0.001       <0.001
Gold               3240m/s       1200m/s      0.0003
Lead              2160m/s         700m/s      0.05 - 0.3                0.02

The table above is missing a column listing the slower longitudinal extensional speeds, which are more applicable to long rods
For example for a long Aluminum rod the extensional speed is only 5000m/s.  See here and click on "Speed of sound, solid phase".

WARNING: Graphite is porous, soft and has a high acoustic loss factor.  Its spongy structure makes it work better as an absorber than an acoustic reflector.

verpies

  • Hero Member
  • *****
  • Posts: 3473
Re: Acoustic magnetic generator.
« Reply #86 on: February 21, 2014, 04:36:43 PM »
By "a toroidal core that you can cut with a Dremel tool + diamond wheel ?" you mean
1) cut it in half, or
2) only one cut where the piezo would tightly fit in?
Both is feasible.
In the 1st case, the piezo would go in one gap and the magnet in the other gap.
In the 2nd case both the piezo and the magnet (magnets) would have to go in one gap.

Both cases are nicely illustrated here. (the pickup winding can be anywhere on the core. It can also span the entire circumference of the core for some experiments)

verpies

  • Hero Member
  • *****
  • Posts: 3473
Re: Acoustic magnetic generator.
« Reply #87 on: February 21, 2014, 04:46:48 PM »
In those experiments it's good to have a flat or concave horizontal surface that will hold fine sand in order to cheaply visualize the formation of acoustic standing waves.  Similar to this video but not in 2D nor transversely - only linearly (1D) and longitudinally.

I grinded a shallow groove in a rod to hold the sand when I was doing those experiments in school.
« Last Edit: February 21, 2014, 06:48:22 PM by verpies »

itsu

  • Hero Member
  • *****
  • Posts: 1845
Re: Acoustic magnetic generator.
« Reply #88 on: February 21, 2014, 04:49:33 PM »
Both is feasible.
In the 1st case, the piezo would go in one gap and the magnet in the other gap.
In the 2nd case both the piezo and the magnet (magnets) would have to go in one gap.

Both cases are nicely illustrated here. (the pickup winding can be anywhere on the core. It can also span the entire circumference of the core for some experiments)

What about using a ferrite magnet core like from a big speaker and use the one cut approach to insert the piezo only?
Or is the magnetisation wrong of such a speaker magnet?

Regards Itsu

verpies

  • Hero Member
  • *****
  • Posts: 3473
Re: Acoustic magnetic generator.
« Reply #89 on: February 21, 2014, 04:55:43 PM »
What about using a ferrite magnet core like from a big speaker and use the one cut approach to insert the piezo only?
Or is the magnetisation wrong of such a speaker magnet?
Unfortunately the magnetization is wrong.
It would have to be magnetized circumferentially, but it is axially :(