Self running coil?

[mscoffman]

I have contacted Stefan about this user. All 14 of his posts are this kind of stuff

> Good.

I don't have a feeling his stay here will be a long one

> I don't know...computers can be very persistant...Gigo.

Luc

[gotoluc]

Hi Luc,

If the ORBO principle takes any advantage from core saturation caused by just the closeness of permanent magnets at a moment and this saturation helps reduce the input current need for reaching full or enough saturation to let the rotor escape from the attraction,  then the idea of increasing the inductance when the magnet(s) are close to the core sounds counterproductive because higher inductance demands higher input current to do saturation (if comparing to the previous ORBO example).  Somehow you have to defeat the extra flux the core possibly collected inside its volume from the strong magnet.
Of course this is what I think and the best would be to see the B-H curve of such core on a scope when the coil's self inductance on it has increased to a higher value due to a nearby magnet, how it would look like.

EDIT:  Luc, when I wrote on the higher current need for a higher inductance above I did not know this core has a square loop B-H curve. See my following letter to gravityblock too.

Yes Gyula thanks, I see you have reconsidered this. I will see if I can buy a large Finemet toroid to further experiment with it.

Maybe this inductance increase could be beneficial at your pulse coil in the oscillator because the copper loss could be decreased by using less wire for the given inductance needed for the oscillator. 

Yes!  I definitely agree, this maybe much better then what I have at this time. Needs to be tested.

By the way, would you tell the DC resistance of the pulse coil you have used in your latest oscillators? I think it is the coil from a shaded pole motor and you tune it by a ferrite rod?

I'm glad you ask this!  because it's hard to believe. Yes it is a shaded pole motor inductor that I use as pulse coil because it's easy to adjust the exact inductance needed by just sliding in or out a long ferrite rod that I made by super gluing 2 AM radio loop stick antenna ferrite rods together. With it I can vary the inductance from 35mH to 350mH. Anyways, it's DC resistance is 67 Ohms. I know many will say that it's a waste of energy but I tried it with my single wound 6.9 Ohm toroid coil and I see no difference. Perhaps because at resonance the coils resistance is not seen? Let me know what you think of this.

I wonder if you tried a normal toroidal core for the pulse coil between the gate-source electrodes? Or the toroidal core's tuneabilty by a magnet may  not give as a flexibility as the ferrite rod does?

Yes I tried the pulse coil with the toroid as stated above but found no gain.

Or a toroidal core has a much higher Q than the high DC Ohm motor coil and makes tuning (oscillating at all) very cumbersome?  I ask these because the resonant voltage across the gate-source surely depends also on the Q of the resonant circuit. Maybe you have found a certain low (or max a medium) Q value you have at present that  gives these <10uA results from the 3V and increasing the Q here would not be beneficial.

rgds,  Gyula

I don't know much about coil Q so I don't know what to answer

Hope what I could answer helps.

Luc

[void109]

Being new to electronics, if someone could point me toward how to build a circuit to see a B-H curve on my scope, I'll take video of the curve rendered by the core when under influence of the magnet and without.

My scope has the option of plotting via X/Y inputs.

[gotoluc]

FYI, I have encountered same effects on MetGlas cores a few weeks ago.
So, it's not only FineMet that shows this effect.
And I would not be surprised if this effect also works for normal ferrite cores.

The external magnet changes the B-H curve of the core material.
Changing the B-H curve means changing the permeability curve, and thus changing the coil value.

Note, that the optimum distance between magnet and toroid is dependent on the current being used (e.g. to measure the coil value).
This means that optimum distance can be different between the measured situation and the real 'in use' situation.
Using a DSO can help you to easily optimize the optimum distance for the 'in use' case (optimize the maximum current delay to a voltage step to find the maximum coil value).

Hi teslaalset,

thanks for posting your findings

Can you help me with what I would need to do to setup my DSO scope to measure this. I have no electronics background so I don't know. I've just been learning as I go. I would need an illustration or better a video tutorial as I learn much faster visually.

Thanks for sharing

Luc

[gotoluc]

Being new to electronics, if someone could point me toward how to build a circuit to see a B-H curve on my scope, I'll take video of the curve rendered by the core when under influence of the magnet and without.

My scope has the option of plotting via X/Y inputs.

Well that makes two of us . It would be great help if someone could make a video tutorial of this.

Luc