Self running coil?

[gyulasun]

Hi Gyula,

could you calculate an estimated amount of micro watts the switch could be leaking into the circuit using the scope shot I attached below?

I have the pickup coil at 1.85vdc on a 2% 1/2 watt 10K Ohm load = 0.00034 Watts. I'm also only using a half wave rectifier at this time.

The below is what's I scoped across the 5% 100 Ohm MOSFET gate resistor when the coil is adjusted at the neutral point (no current taken or returned).

Please keep in mind that the negative pulses are not used for the MOSFET.

Thanks

Luc

Hi Luc,

From the waveform data your scope shot shows we can approximate pretty well how much driving power goes INTO the MOSFET at its gate source input.
The current flowing across the 100 Ohm carbon resistor is I=.3438V/100=3.438mA.  Here I considered the RMS value of the peak to peak waveform of 3.44V (yellow trace).
This is the current actually flowing into the gate source path (and this path of course includes all the loading effects coming from the output side of the FET i.e. from the drain side).

So the input power to the gate source of the MOSFET is P_inp=4.5V*3.438mA=15.47mW
(I used half of the 9.06V peak to peak value of the gate source voltage (green trace) because for a regular square wave the RMS value is half of the peak to peak value and I took your wave form as a regular one to simplify things.)
We have to add to this the power dissipated in the 100 Ohm series resistor, which is about 1.18mW (.3438²/100).

So your signal generator provides about 15.47 + 1.18=16.65mW input to the MOSFET.  Now I cannot tell you how much from this leaks through to the tank circuit, maybe others can help here too. Will think about it.

rgds, Gyula

[NextGen67]

with a small mirror glued on the magnets and laser pointer you can amplify the vibration effect if exist .

great work!

@wings,

Actually thinking of it, the magnet would actually possibly vibrate a bit, considering the 5 layers... Some of the energy input is leaking out of the toroid wiring, and as such they *might* get the magnet to vibrate...

However, I'm not pointing to that effect.

It still will be very interesting to see if the magnet indeed vibrates.

--
NextGen67

[gotoluc]

Such could be indeed the case, however...

If the magnet would move/vibrate instead of the domains then [I think that]:

1) The [to receive] charge would go along the Y-ax [which means pick-up coil would be positioned wrong].
2) The core windings would [probably?] *not* have the effect [the cap charge back I mean here] that we notice now, because the magnet should have been positioned along the Z-ax in such a case, which would be very weird.

Which leads to a quick confirmation test:

When we place a small pick-up coil at the 'S' pole position, we would pick-up [considerable more] charge than what is being pick-up now(*), because *if* the magnet would move/vibrate, most of the charge would be able to receive at the magnet S and N pole.

(*) It is possible that when a small coil placed there, it *does* pick-up [a rather small] amount of charge, since the magnets field would [probably?] be affected by it's interaction with the core's domains [like see such as a Cemf, seen from magnet perspective!].  Also, actually Picking-up charge here *would* decrease what is being returned to the coil [and as such cap], because in *this* case the coils wire is being affected.

P.S.: Maybe someone could do a clean up of my quick copy and paste drawing?(**)

P.S.2: I wanted to make a similar drawing, but then seen from the coil [core] perspective, but since the wiring is not standard, I have trouble in seeing how such would be graphically represented... Maybe some of you here could draw up such ?

P.S.3:  It might become clear that if the magnet is placed TO near the coil, it's magnetic fieldwould pass the X-as border [the halve of the coil], which *could* reduce the effect [pick-up] we notice now. Also, placing an extra magnet [as shown in the drawing] might increase the effect we notice ?

P.S.4: The above description is not totally correct, as [small] parts of it *seem* to contradict Luc's scope results, but [at this point of time] to me, this seems a pretty close estimation of the effect we notice, and I have *indications* of why parts *seem* to contradict.

P.S.5: I do of course not argue about the fact that the magnet *its field* is vibrating.

(**) To ADD in the clean-up drawing:

Notice that we talk about a different than normal effect here... Normally (and it still does) the magnet interact with the coils wire, and in such influences with what is returned back into the coil [and in such cap]... However, the 2nd and greatly overlooked side effect [and *this* influences the pick-up coil(s)], is that charge seems to be radiated outwards of the coil [by means of magnetic field], which is at a 90 degree angle with the coils input energy... *This* also could be why the input and output energy do not inteference with each other, since they are not on the same phase.

Now, *if* the AE[Additional Energy] returned in the pick-up coil(s) would be *more* then what is being lost over the coil [and circuit] resistance, we could argue that this AE in, would in fact be enough to be able to redirect this AE energy back into the circuit, and we would have our first ever *confirmed* self runner.... However there are still a lot factors which might prohibit such.

--
NextGen67

Hi NextGen67,

thanks for your input and drawing. Adding magnets at both ends is something I was considering to test and is on my list of things to test.

I will report the results after doing the test or make a video if it works well.

Thanks for sharing

Luc

[skywatcher]

Now i have build my setup.   

First some data:

Ferrite core: 35 mm outer diameter, 23 mm inner diameter, height 15 mm
Exact material and permeability is unknown. I don't even know from where i got it.   

Coil: one layer of 0.4 mm wire, combined inductance 315 mH

Capacitor: 120000 uF / 15 V electrolytic

MOSFET: BUZ11, with 680 ohm resistor at the gate

Although my coil has a different inductance, the resonant frequency is also at about 15 kHz.   
I can clearly hear it, so the coil and/or the magnet vibrates.

And it's also 'self-running'. I can remove the power lines from the capacitor and it continues running. The peak voltage measured at the middle of the coil is about 35 V. But i'm still skeptical. I think the energy comes from the generator, through the gate of the MOSFET. It also runs without the magnet, at a slightly lower resonant frequency. But without the magnet i can not hear any sound.

[gyulasun]

@skywatcher

Would you tell what is the DC voltage in the electrolytic cap?

Also, you use the 680 Ohm in parallel with the input i.e. parallel with gate-source, right?  What is the input square wave amplitude I wonder.

Thanks, Gyula