gotoluc

As you powered led with extra coil what stopped you from connecting led back to the gate of mosfet and closing loop then disconnecting function generator ?  Or using more pickup coils and power directly an oscillator chip driving mosfet ?

I think that is what we all trying to work at, and certainly Luc his goal. Tough at this stage, he can't feed that back, since he needs the right pulse frequency and duty cycle. In a while maybe :-)    Also for now -that is my opinion- I am more interested in the effect of the generators added energy. It will be a good idea to have a final conclusion about that first.

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NextGen67

I'm interested in values of capacitor used and coil inductance compared to frequency driving circuit in stable state and in excess energy generated.Is resonant frequency in harmonic relation to best working frequency from function generator ? I can't find exact capacitor capacitance in comparison to running frequency from function generator.

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

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.

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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

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

gotoluc

As you powered led with extra coil what stopped you from connecting led back to the gate of mosfet and closing loop then disconnecting function generator ?  Or using more pickup coils and power directly an oscillator chip driving mosfet ?

To everyone

One way to Isolate the signal generator is to use an OPTO Isolator and connect the switching side of the OPTO to the capacitor bank to feed the mosfet gate. I do have a 4N35 and a H11D1 which I both tried last night but they are way too slow to shut off. At 1KHz they were at 95% duty and to full on with frequencies over that. My signal generator is fixed at 50% duty. So these are not working or I don't know how to connect them correctly. If someone with electronic knowledge can recommend an Isolator which could work a up to 50KHz and still keep the 50% duty cycle using a component that I can pickup locally please look at the two suppliers in my city for stock: http://www.resetelectronics.com/VALUE/index.asp  or http://www.active123.com/

The other way is using the pickup coil to trigger the mosfet. This is complicated because the pickup coil is a sine wave that it peaks are out of phase with the mosfet pulses. So again I'm at a loss of how to use this energy or build a circuit that could create the very exact frequency, gate drive voltage and current that is needed.

I'll see if I can pickup a CMOS 555 locally and try to power it from the cap bank by keeping it in the 10vdc range.

AT EVERYONE If you know how to close the loop please provide a complete drawing of how to build it. Please do not just say do this and that. I am willing to do everything I can and I think I have done all I can with my minimal electronic knowledge I have.

Thank you for your time

Hi Luc,

<...>
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

Gyula,

Would it not be possible to simply attach only the signal generator to the mosfet and then connect the Cap to the source and drain, and just observe what goes into the cap ?

Actually a [known] voltage/amperage could be supplied to get it at the correct working point, but this can with a calculation be subtracted from the cap value later again?

EDIT: No need to attach battery I guess, since the signal generator can easily deliver enough voltage ?  Anyhow, after say 5 minutes of charge, one could see how much the cap collected.

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NextGen67