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OverUnity Research > Benches > Grumage (Moderator: Grumage) > Ferrite Core Resonance investigation.
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Author Topic: Ferrite Core Resonance investigation.  (Read 48700 times)
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img  TutorialFE
Re: Ferrite Core Resonance investigation. « Reply #25 on: 2014-05-28, 12:59:56 »
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@itsu

The ferrite core seems to me that the russian pdf was then tested in a different way with a coil in the inner hole and another hole in the exterior.
   
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Re: Ferrite Core Resonance investigation. « Reply #26 on: 2014-05-28, 13:40:28 »

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Quote from: TutorialFE on 2014-05-28, 12:59:56
@itsu

The ferrite core seems to me that the russian pdf was then tested in a different way with a coil in the inner hole and another hole in the exterior.

Yes,  you mean like in the picture below.

Well, its kind of hard to implement that way, but i could give it a try.

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #27 on: 2014-05-28, 14:13:00 »
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It's turtles all the way down
Perhaps a different approach is needed. How about applying electrodes directly to the ferrite material, 4 in all, 2 for excitation, 2 for pickup. These could be in the same plane or orthogonal but some distance apart.

When I get time I will do this experiment by using a silver epoxy or paint to fix the copper foil contacts to the ferrite.

Alternately a combination of electrodes for excitation and coil for pickup, or use the coil to excite and electrodes for pickup.

With the electrodes, measure the resistance and try to get a good impedance match from the driver.

Regards, ION


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Re: Ferrite Core Resonance investigation. « Reply #28 on: 2014-05-29, 10:39:34 »

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Thanks ION,   

good idea, my ferrites Ohmic range differ enormous per ferrite so it should be tailored for each specific piece of ferrite i guess.

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #29 on: 2014-06-08, 21:48:57 »

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As suggested by ION, i tried to characterize one of my pot cores by inputting a sweeping frequency range (1KHz - 100MHz) directly into/onto the ferrite and measuring the response at the other side with my scope.
The pot core half's are separated by a piece of mica in the center.

It looks as if this specific pot core has a resonance peak around 42MHz which is kind of high i think.

Any comments are welcome if this could be a valid way to characterize a ferrite core.

Screenshot 1 shows the pot core frequency range starting at 1 KHz and ending at 100MHz with a strong peak around 42MHz.

I later on tried the same with a large U-core separated by 2 pieces of electrical tape:
Screenshot 2 shows a U-core with frequency range starting at 10Hz and ending at 100MHz with a peak around 25MHz.

Video here:  https://www.youtube.com/watch?v=XVWFd6w0xI0&feature=youtu.be


Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #30 on: 2014-08-04, 10:55:33 »

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Users Void, D3x0r and me are trying to replicate the shown ferromagnetic resonance of a flyback core demonstrated in a video by Akula.

The forum used is over on overunity.com in this thread:
http://www.overunity.com/14687/akula-eternal-lantern-4/msg412955/#new


Page 1 of this thread shows the complete diagram used, but we are concentrating on replicating the ferromagnetic resonance shown by using a very small part of this circuit as can be seen (and attached below) here:
http://www.overunity.com/14687/akula-eternal-lantern-4/msg412459/#msg412459

In this post:
http://www.overunity.com/14687/akula-eternal-lantern-4/msg412458/#msg412458
there are linked severall videos with translated text from Russia to English which gives good info what is trying to be done.

Up till now i have build this small circuit and found a pulse which seems to indicate this ferromagneticresonance of the core.
But making use of it like demonstrated by Akula is failing at the moment.

Screenshot of the pulse below, video here: https://www.youtube.com/watch?v=XJMx_BsUnms&feature=youtu.be 

Screenshot data:

blue   = collector transistor (MJE13005) signal
yellow = base transistor signal
purple = FG input signal (250Hz DC pulse, 2V amplitude, 4% duty cycle)
green  = current probe signal from plus lead (3V dc), current probe controller set to 200mA/div.

What i find strange is the peak in the middle of the blue trace, so middle in the active transistor window.
When pushing on the core (gap by 2 pieces of electrical tape) the peak moves to the right.

Any idea what the cause could be of this peak?

Regards itsu 
   
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Re: Ferrite Core Resonance investigation. « Reply #31 on: 2014-08-04, 16:00:32 »
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Itsu:

Sorry I missed this experiment in post #29 when you first posted it. I just now saw it.

Very nice experiment, however if I may, I would like to offer some suggestions for a more refined test.

Instead of a pot core, use a rod core or piece of 2 inch ferrite cut from a flyback transformer with square cross section.

The leads should be attached with conductive epoxy, (preferably silver) at two distant points on the rod on opposing faces.

The assembly should be put into a small aluminum box with BNC connectors at either end and 50 Ohm termination resistors.

Do not use probes, use BNC cables to connect to the generator and scope.

The test can also be repeated with a bar magnet instead of a ferrite rectangular rod.

I'll work up a sketch for you. Termination and shielding is important at these frequencies, and probe ground clips can pick up stray signals or be resonant loops at certain frequencies, so should be replaced with BNC cables terminated to 50 Ohms inside the shield box.

Thank you for doing this experiment. My generators lack the sweeping capability, and my 300 MHz scope is in repair with a triggering problem or I would try to duplicate this experiment. I am sorry that I cannot do the fine level of testing you are able to at this time because of equipment shortcomings. May be time for me to buy some new gear.

I got the idea from a video I saw where a fellow took a cut half section of a ring magnet (speaker magnet) and he attached leads to either end, four in all at distant points on the magnet section two connections at each end on the faces and was able to light a LED at a specific and very sharp frequency point. That video was later removed from youtube.

I thought this might also be used to characterize a ferrite resonance.

Thank you, Itsu for following up on this.

Kind Regards ION



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Re: Ferrite Core Resonance investigation. « Reply #32 on: 2014-08-04, 16:40:31 »
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Hi Itsu:

Regarding post #30 ,notice that the pulse coincides with the peak of the current waveform on the inductor.

To me this appears to be a parasitic turn off of the FET due to the high current drawn as the core tries to saturate or the breadboard layout is not stiff enough to support the current drawn at that point (some stray inductance or capacitance causing the turn off at the peak current.)

With additional stiffening of the power supply at the breadboard site by using quality capacitors and  keeping all gate leads and drive leads as short as possible, the parasitic turn off of the FET should be able to be eliminated.

I cannot stress enough that clip leads and plug boards do not make for a good breadboard test at high frequency pulsing. Better to use a piece of copper clad as ground plane with devices soldered to the ground plane where required, and BNC input for signal from SG, with good ground to the ground plane. Keep all wires as short as possible, and local bypassing of the V+ to the ground plane is a important.

Hope this has been helpful, Kind regards, ION

http://www.eevblog.com/2014/01/15/eevblog-568-solderless-breadboard-capacitance/

http://forum.allaboutcircuits.com/showthread.php?t=38094

http://electronics.stackexchange.com/questions/2103/when-to-avoid-using-a-breadboard
« Last Edit: 2014-08-04, 17:49:36 by ION »


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Re: Ferrite Core Resonance investigation. « Reply #33 on: 2014-08-04, 17:58:07 »
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Hi Itsu, For what it's worth I got the premature turn off when using a BJT with a low voltage circuit (runs down to under 1 Volt input voltage). I put it down to low base drive, due to the coil drawing current and dropping the voltage, then when the coil prematurely turns off the voltage rises and turns the BJT on again. I use mosfets rather than BJT's wherever possible or unless the application calls for it.

Just out of curiosity. What effect would exciting the ferrite to resonance have ? Would it vibrate the core and induce a current by way of a vibrating core and windings ?
What would be the mechanism for and nature of any extra energy to be harnessed ? What kind of resonance is desired ? mechanical, magnetic or other.

..
   
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Re: Ferrite Core Resonance investigation. « Reply #34 on: 2014-08-04, 18:23:50 »
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Here is a funny story from Bob Pease on the subject of breadboards.


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Re: Ferrite Core Resonance investigation. « Reply #35 on: 2014-08-04, 19:50:43 »

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Quote from: ION on 2014-08-04, 16:00:32
Itsu:

Sorry I missed this experiment in post #29 when you first posted it. I just now saw it.

Very nice experiment, however if I may, I would like to offer some suggestions for a more refined test.

.................


Thanks ION,   good advice as always i have some silver based conductive glue, so might try it again with these suggestions.
These Russian Pdf's make it look all very easy  :)  ,   but obviously its not.

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #36 on: 2014-08-04, 19:54:29 »

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Quote from: ION on 2014-08-04, 16:40:31
Hi Itsu:

Regarding post #30 ,notice that the pulse coincides with the peak of the current waveform on the inductor.

To me this appears to be a parasitic turn off of the FET due to the high current drawn as the core tries to saturate or the breadboard layout is not stiff enough to support the current drawn at that point (some stray inductance or capacitance causing the turn off at the peak current.)


Guess you are right, as i found out that even with an air coil (68uH) i have this peak in the middle of the transistor opening, so its not coming from the ferrite.
I will use a copper groundplane setup to put this little circuit together and see if the pulse is still there.

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #37 on: 2014-08-04, 20:03:03 »

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Quote from: Farmhand on 2014-08-04, 17:58:07
Hi Itsu, For what it's worth I got the premature turn off when using a BJT with a low voltage circuit (runs down to under 1 Volt input voltage). I put it down to low base drive, due to the coil drawing current and dropping the voltage, then when the coil prematurely turns off the voltage rises and turns the BJT on again. I use mosfets rather than BJT's wherever possible or unless the application calls for it.

Just out of curiosity. What effect would exciting the ferrite to resonance have ? Would it vibrate the core and induce a current by way of a vibrating core and windings ?
What would be the mechanism for and nature of any extra energy to be harnessed ? What kind of resonance is desired ? mechanical, magnetic or other.

..

Hi Farmhand,

thanks for the info, i noticed that when varying the input pulse amplitude (2 - 4 v) on the base, the pulse is moving across the opening window of the collector.
Also this pulse is there when using an air coil only, so nothing to do with ferrite resonance  :(

The effect we are after is as Akula demonstrated the eternal lightning of some leds   :D
This ferromagnetic resonance should be able to supply power for a long time, but nobody probably knows how (transmutation, mechanical vibration, magnetic vibration?).

Regards itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #38 on: 2014-08-05, 22:56:14 »
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Itsu:

Using a 2 inch x 1 inch x 1/4 inch bar magnet, I silvered copper electrodes 1/8 inch wide to the faces at the one inch ends.

The magnet is polarized on it's large faces, but I don't know what type it is. It was salvaged from an industrial "Printronix" printer

Driving with my signal generator at one end, I was able to light a LED two inches away connected at the other end and there was a peak at one frequency, but it was not very sharp, resembled a low Q LC resonant circuit.

My magnet was about 2000 Ohms on each end.

I will post more technical details and a photo when the glue is all dried and it is mounted in the shielding enclosure. (and when camera batteries are charged).

This is just a preliminary report. Next I will try with ferrites that have not been magnetized.


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Re: Ferrite Core Resonance investigation. « Reply #39 on: 2014-08-06, 15:26:29 »

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Thanks ION,

i have some 20/2cm (7.8/0.79 inch) ferrite rods which i could use, but not really sure about your setup, so i await the picture.

Also this  "My magnet was about 2000 Ohms on each end" is not clear, do you mean the resistance measured with a multimeter?
I remember my ferrite resistance measurements were in the 80KOhm or so with the leads 1cm apart.

 
Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #40 on: 2014-08-06, 15:40:18 »
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Attached is a picture of the magnet and box it will be put into for shielding and proper low noise connections.

There are two copper connections on each end, both left and right, a little hard to see in the picture.

2000 Ohms was measured on both the left two and the right two connections. I did not measure the resistance across the length, but will do so.

I drive input into the right two connections and scope the left two.

I'm having a little trouble with the conductive silver glue and may need to redo the contacts for lowest resistance.

Peak output was between 170kHz to 180 KHz.

I may also wrap a coil to around the magnet and look for output on it while driving various connections to the magnet (and vice versa).

Hope this helps.


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Re: Ferrite Core Resonance investigation. « Reply #41 on: 2014-08-06, 15:46:15 »

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OK,  got it,    do you plan to suspend the magnet in the air, only supported by the BNC connections, or will there be some support underneath?

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #42 on: 2014-08-06, 16:04:20 »
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Quote from: Itsu on 2014-08-06, 15:46:15
OK,  got it,    do you plan to suspend the magnet in the air, only supported by the BNC connections, or will there be some support underneath?

Regards Itsu

The magnet is rather heavy, I may use some small strips of double sided sponge tape at either end to fix it to the box or may float it from the connections if I get the glue to hold.

It does seem to be sensitive to damping with fingers.

BTW, the largest faces of the magnet is where the poles are located.

ION


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Re: Ferrite Core Resonance investigation. « Reply #43 on: 2014-08-07, 21:09:46 »

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I tried to do the same with a somewhat smaller ferrite magnet, but this silver conductive glue is not strong enough.
Guess i need to stiffen it up with some superglue over it.

I did not get any reading from the short time i was able to, so no 2000 Ohm or so.


Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #44 on: 2014-08-07, 21:42:59 »

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Quote from: ION on 2014-08-04, 16:40:31
Hi Itsu:

Regarding post #30 ,notice that the pulse coincides with the peak of the current waveform on the inductor.

To me this appears to be a parasitic turn off of the FET due to the high current drawn as the core tries to saturate or the breadboard layout is not stiff enough to support the current drawn at that point (some stray inductance or capacitance causing the turn off at the peak current.)

With additional stiffening of the power supply at the breadboard site by using quality capacitors and  keeping all gate leads and drive leads as short as possible, the parasitic turn off of the FET should be able to be eliminated.

I cannot stress enough that clip leads and plug boards do not make for a good breadboard test at high frequency pulsing. Better to use a piece of copper clad as ground plane with devices soldered to the ground plane where required, and BNC input for signal from SG, with good ground to the ground plane. Keep all wires as short as possible, and local bypassing of the V+ to the ground plane is a important.

Hope this has been helpful, Kind regards, ION

http://www.eevblog.com/2014/01/15/eevblog-568-solderless-breadboard-capacitance/

http://forum.allaboutcircuits.com/showthread.php?t=38094

http://electronics.stackexchange.com/questions/2103/when-to-avoid-using-a-breadboard


ION,

i made some changes like getting away from the breadboard and using a groundplane like PCB.
I did not go all the way by using BNC connectors for the input etc. or putting into a sealed box, as the frequency is very low (250Hz)
I also use a very stable 3V from 2 aaa batteries in series, but the mystery peak is still there.

So i guess its just the setup of this circuit that behaves this way and closes down the transistor early.

Video here:   https://www.youtube.com/watch?v=OOPsny2pmps&feature=youtu.be   

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #45 on: 2014-08-07, 22:56:34 »
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Itsu:

Try removing the 10nF capacitor and the 220pF cap one at a time to see what happens. It could be that the 10nF cap across the 10 ohm is providing a "leading current turn on" of the transistor which is then overcome when the inductor current exceeds  the base current (x transistor gain) that the capacitor can supply to keep the transistor on, so the transistor turns off then on again when the SG drive "catches up" with the required base drive.

 The copper clad breadboard looks good.
« Last Edit: 2014-08-08, 13:50:25 by ION »


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Re: Ferrite Core Resonance investigation. « Reply #46 on: 2014-08-08, 18:19:26 »

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Thanks.

Nope, removing the 220pF variable or the 10nF or both does not make any difference on this signal.

Regards Itsu
   
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Re: Ferrite Core Resonance investigation. « Reply #47 on: 2014-08-08, 18:56:20 »
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It's turtles all the way down
Thanks for trying that, sorry it didn't work.

When I get a break I will build the identical circuit and test it.

This has me puzzled now.


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Re: Ferrite Core Resonance investigation. « Reply #48 on: 2014-08-09, 17:15:35 »
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It's turtles all the way down
Itsu:

What is your power source to the circuit? Is it set to current limit?. I notice the waveform drops back to some lower amplitude and holds to the "on" condition after the first peak of the waveform discharges something (a capacitor on the output of the power supply but internal to it)? or possibly the bypassing at the board. Something is supplying an initial high current then the current drops back to a lower level.

A current shunt resistor (0.1 ohm) in the emitter would give us a better picture of the instantaneous current drawn by the circuit.


---------------------------
"Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy
   
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Re: Ferrite Core Resonance investigation. « Reply #49 on: 2014-08-09, 20:01:18 »

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ION,

in the latest video with the copper clad breadboard, i use 2x aaa batteries in series (3V).
In the earlier video with the breadboard i used my 10A bench PS set to 3V and current limiter all the way up (so to deliver max current).

I will put a 0.1 Ohm resistor in the emitter lead and measure the voltage across it using again the 2 aaa batteries as power source.


Regards Itsu 
   
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