Self running coil?

[gotoluc]

Hi Luc,

Interesting effect (but you make way to big steps as far as me concerned haha).

Why, does the circuit self resonance, and why do you need to 'trigger' it once to get going?

Well, see it as a normal L-C circuit, only now the C is made out of the [combination] of Ciss/Coss/Crss(voltage depended) and the small 2nf cap you placed parallel to the coil.

Why do you need to 'trigger' it, to get it going?

Because in initial stage, there is *no* voltage applied to the mosfet, so hence the system can't operate... Once you give it a 'one time shot' with the generator (could be battery also), you start the reaction....

The Bemf from the toroid coil provides the energy to get power the gate again.

Small calculation... your precision meter showed 0.000088 Amp (88uA).

What goes into the mosfet: 10.94 volt RMS (from the coil) which has a 6.9 ohm resistance...

So, 10.94 Volt / 6.9 Ohm = 1.5855 Amp.. Divide this through the Frequency 18120 Hz...  1,5855072463768115942028985507246 / 18120 = 0.0000875 A (87.5uA) which is pretty well what your precision meter shows also.

while your pick-up coil (with 1K resistor) delivers 0.00054A (540ua), the draw it takes from the circuit is only 0.000034A (34uA), that is a nice effect I would say.

It might get *really* interesting if you can get the 0.000088 down to -0.000001 at least

EDIT:  Luc, if you measure the mH of the coil, you would be able to derive the C provided by the mosfet, since you have placed a 2nf in parallel with it... at 18.12Khz and 2nf you are at 38.57mH.

EDIT2: Yes, you can bring down the 0.000088 still, with changing the small 2nf cap, though *how* far down
will you be able to go?  Did you read my info, on how you probably get *best possible* tuning ?
Your circuit is using 0.95mW at this stage [without pick-up coil]. Errr... That would be 1.13mW actually
The total circuit uses 1.13mW, the coil uses 0.95mW, so 1.13-0.95=0.18mW for the operating of the Mosfet (it's switching),
and it's resistance.

EDIT3: Luc, what is the resistance of your pick-up coil? Wonder if it is close to 10.85 or 14.01 Ohm?

--
NextGen67

Hi NextGen67,

thanks for your above details and also the new test details you asked for which I will do this weekend.

First, the toroids inductance in test 13 is 25.3mH and the pickup coil is 28mH and 24.8 Ohm DC resistance.

I tried to add more capacitance to the 2nf tuning capacitor to further drop the current draw to which results in frequency drop but it looks like it's at its maximum since adding more the circuit stops to self oscillate

I also found that I can have the pickup coil further 2" or 5cm and I can pickup the resonance effect If I inset and tune a ferrite in the pickup coil. I also moved it around the toroid with the ferrite inside and there maybe a point close to the magnet that the pickup coil give a good output without current increasing on the toroid. I did this by hand so this still needs to be confirmed with a fixed setup.

I will build a setup that I can adjust the distance between the magnets and toroid to better test all the effects in order to find idea settings.

Luc

[gotoluc]

luc  great job at looping the signal.

Well not quite OU but not far off.  1.57mw in  ,  .29mw out

What Im not sure of how the modem transformer is doing it by being across the source and gate. That would indicate that either the source is showing a variation to apply signal to the gate, or the gate is feeding back through the gate against the source and bouncing back to the gate through the modem transformer. Like a small delay.
Not really sure, but it is as I have talked about getting some feedback to run itself. Depending on the gate sig voltage as you have it now, I would try using the pu coil to apply sig to the gate. If that lil modem transformer is not shorted on the one end and instead, connected to the pu coil, phased one way or the other, you may be able to drive the gate higher.

Mags

Hi Mags,

it is interesting to see it working this way

If I remove the short on the unused side of the modem transformer the self oscillation stops.

Luc

[gyulasun]

Hi Luc,

Would you measure the inductance of the small 1:1 transformator that is connected to the gate-source? 
You mentioned in the latest video the other side of the transformator is short circuited with that piece of wire.  This bothers me if really so because it greatly reduces the inductance of the other coil.  You could test it too with the L meter: measure on one side, the other side is open,  then short this latter other side, and read the L meter.

Thanks,  Gyula

[Magluvin]

Hey luc
Yes I got that about the short on the opposing side of the modem transformer. =]
But what I was thinking was if you replaced the short with the pu coil instead, it might drive the gate a bit more, and then the output a bit more and then the gate a bit more...  lol  tiny Chernobyl.  =]  But just heat, no RA

Mags

[Magluvin]

Ah  but maybe even better to just hook up the pu coil to the gate and source? Maybe.
Just quick simple stuff to try.

Mags