Longitudinal wave research

[MarkSnoswell]

The reason for posting this is to show just how many resonances there are and how high the Q is in a toroidal ferrite core. *NONE* of this would be detectable without a DC bias (magnetic field in the torroid), a coil mounting that allows mechanical resonance and a square wave drive into a non-inductive drive coil... if you don?t know what you are looking for it?s very unlikely that you will ever see anything!

Look at how high the Q?s are!! .. This is a quick test and I expect that I could dramatically improve those Q values with good design. The point is that if you drive a current at one of the resonances and modulate it at another then you can get a multiplier of the Q?s ? and it will be very easy to get into extremely high energy modulation modes with significant non-linear behaviour.

I don?t know if this will yield overunity ? but It?s an area that is completely unexplored and shares a lot of characteristics with Bob Boyces and SM TPU devices.

I?ll take photographs and write a up a clearer explanation when I have done more tests ? for now I thought that it is good to give people an idea of just how significant and complicated the resonance modes can be in toroidal cores.
Please keep this confidential  to this group.



Thursday 13th September 2007.
Preliminary experiment to identify magnetoacoustic resonance modes in a ferrite toroidal core.
Mark Snoswell, mark@ballisticmedia.net

These results are with a Ferroxcube torroidal core Type T140/106/25-3C90 (140 mm OD, 105 mm ID, 25mm high).
The core has three coils that are *not* wound tightly on the core. They are loose to allow the core to mechanically resonante.

The three coils are:
DC Bias. 28 turns.
Drive coil: Symmetric Counter-wound ? 5 turns in each direction (non inductive).
Probe Coil: 3 turns.

The following resonance modes were measured with:
4 amp DC bias current applied to the DC bias coil.
200 mill amp p-p signal driving the drive coil.

All observed resonances are dependent on the DC bias current being present. The amplitude of the resonances was directly proportional to the DC bias. There was a significant frequency dependence on the bias.

All resonances were measured with a square wave drive. Resonances could not be clearly observed with sine wave drive.
The following table denotes the number of nodes around the core at a particular resonance: resonance frequency: and Q.

The first 10 resonances (7th not observed) are for standing longitudinal magnetoacoustic waves around the toroidal circumference. The other (high frequency and one acoustic) resonant modes have not been matched with known resonant modes although the acoustic modes appears to be the fundamental flexural mode.

      Nodes   Hz   Q
      1   14,567.4   387
      2   20,277.5   711
      3   31,631.4   2228
      4   40,286.2   1857
      ~5   44,296.8   2260
      ~6   57,068.5   --
      ~7   Not observed.   --
      ~8   80,925.6   2636
      ~10   90,406.8   2659
            
            
2/3rd harmonic   1   64,305.8   3994
2/3rd harmonic   1   75,739.6   3030
            
2 nodes ?         192,913.8   4019
            
1 node?         194,599.8   3089
         227,234.8   
            
*Acoustic         8,010.8                    ~9

*no detectable signal in the probe coil but a very significant acoustic singnal.

[MarkSnoswell]

By establishing the magnetic field at one frequency and generating (modulating it) the magnetoacoustic standing waves with an harmonic-offset I will be able to make the standing wave pattern rotate at the offset beat frequency. This then matches the performance of the TPU closely -- a rotating static field generated only by intermodulation of two base signals. The rotating static field has remarkably low impediance (I know that from previous tests -- impedance ~= the DC resistance of the wire) and high amplitude -- this should certainly drive a significant current in a secondary coil. With the right feedback and control to keep it stable this feels remarkably close to a working design that is engineered to deliver the characteristics of the TPU -- hmm. I don't know if anyone is following me here, but this is quite remarkable... of course I have to engineer it and test it now, but with a working principal and solid repeatable resonance data to work with the guessing has been removed.

sigh -- I wont get a chance to do more experiments untill next week -- we have the big Pedal Prix race this weekend http://www.pedalprix.com.au/news.php

cheers

mark.

[MeggerMan]

Hi Mark,
Some good results there, how did you measure the Q value?
Were you able to move your probe coil to find the nodes?

I suppose to prove that the magna-accoustic wave is shifting you could place a dish containing some small plastic beads or water onto the core and look for the patterns while you change the frequency.

I received my sample AD9959 chips today - 2 off.
Next is to order up the AD9959 eval board.
I also have the programmable pulse chip now, so I can produce any pulse from 10ns to 250ns in 1ns steps, this coupled to the DDS 20 will give me good narrow pulses at any frequency up to 20Mhz.
I want to carry out your tests above using BB core.

Regards
Rob

[Jdo300]

HI Rob,

Where did you order the programmable pulse width chips from?

God Bless,
Jason O

[MarkSnoswell]

I want to carry out your tests above using BB core.

Excellent -- as I will be focusing on the ferroxcube core for a while.
I will do a prelimenary test on the Micrometals core to see if I can see any simillar resonances at all -- it's a much softer core with a large poloidal/toroidal ratio which will make it much harder to see the resoances... the effects will still be there but blured out (although the lower Q's could possible make the resoances easier to see?? )... wont know untill I do a test.


Quote from IM from Rob on the pulse timer chip:
"DS1023S-100+ I got from Farnell in One in the UK, not quite as good as the one you mentioned but OK.
: Digikey sell them cheaper
: Digikey have a minimum qty of 45 at 8.19USD each
: 368 USD for 45, a bit expensive"


The DS1023s is the 8 bit programmable pulse width chip. We really want the 22 bit probrammable width chips.

Suggestion:   perhaps we can do a bulk purchace if most of us want these chips. I would be prepared to buy up to 10 of them at USD 8.19 each.