Self running coil?

[gotoluc]

Hi all,

so now the modem coil is gone

It has been replaced (so far ) with a PC board 10mH inductor and a 22K pot adjusted to around 10K

It is working much better this way as much more resistance was needed between the gate and source then the modem transformer had. However the 10mH inductance is needed and maybe more. I will test this.

I'm now able to add more capacitance at the toroid. We are now at .0033uf or 3.3nf and resonating frequency is 12KHz. Current is down to .000070 with 12.88vdc feed.

One more step in the positive direction.

Luc

[NextGen67]

It cannot be that the 2SK MOSFET is not switching on,  you may wish to consider it switches on for every positive half wave and off for the negative ones. So the drain source capacitance must be some switched average value... with a value you calculated. 

Gyula

Should have made myself more clear.

Meaning: ...Which indicates that probably your mosfet is hardly switching on when adding Additional capacitance
[Certainly when you add a whole nF at once... Resonane will fall out of reach with magnet position, and thus less energy is
returned by the toroid coil, and thus the mosfet cease to operate, and halts the whole circuit].

@Luc... As per new testing method, you probably could keep it in resonance tough, and bring down the uA's

EDIT: and as seen in Luc's above message, when using a more economic way to drive the fet, it makes things better.

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NextGen67

[gotoluc]

I decided to try the pot (variable resistor) in series with the inductor instead of both inductor and 10K in parallel between the gate and source. It works this way but I only need a total resistance of 445 Ohms. 27 Ohms from the inductor and the balance from the variable resistor. However at the best setting it uses .000080

So for some reason the other way is better.

Luc

[mscoffman]

It has been replaced (so far ) with a PC board 10mH inductor and a 22K pot adjusted to around 10K

It is working much better this way as much more resistance was needed between the gate and source then the modem transformer had. However the 10mH inductance is needed and maybe more. I will test this.

I'm now able to add more capacitance at the toroid. We are now at .0033uf or 3.3nf and resonating frequency is 12KHz. Current is down to .000070 with 12.88vdc feed.

Just so you know...I think you are creating a: Phase Shift Oscillator. I predict
you are going to get all of your parameters tied up in one big ball in a moment.

[NextGen67]

Hi all,

so now the modem coil is gone

<...>  We are now at .0033uf or 3.3nf and resonating frequency is 12KHz. Current is down to .000070 with 12.88vdc feed.

One more step in the positive direction.

Luc

Luc, What is your CH1 RMS now... Guess a lot lower? (maybe somewhere around 5.8V ?)

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NextGen67