Self running coil?

[gyulasun]

HI Gyula, Gb,

Yes, those are the standard tools to find out either L, C or Freq...

However, to complete the picture, it would be nice to come up with a rule to determine the Capacitance of the mosfet being used (using the data from it's data sheet)...

Something Like:

Enter Ciss
Enter Coss
Enter Crss
Enter Rds(on)
Enter Vgs(th) [ or enter input voltage ]
Enter Vgs [ or enter tank voltage ]

And then the formula would spit out the C[apacitance] value that matches Luc's data (and for any given mosfet).

As for his IRF640 data, one can see that all Frequency's hang around 1533 to 1579 pF. The value of 1578.54 pF probably having the most accurate [and best/lowest 0.0000xx result ]

--
NextGen67

NextGen,

Sorry I do not fully get you, something is foggy: what kind of formula do you think of?
And for the IRF640, which capacitance is the 1578.54pF ? Ciss, Cgs, Coss? How did you get it?

By the way, would it not be better to wait for the person referred to by Luc what he comes up with first?

Gyula

[skywatcher]

I decided to make a video using the 2 identical toroid's of test 15 video to demonstrate what I had done for myself yesterday that the magnet affects a ferrite core toroid more than just dropping it's inductance.

It's clear that it does more. Imagine that the magnet brings the core close to saturation. If you are feeding a sine wave into your coil, without the magnet it would create a magnetic flux which changes its direction as the current changes its direction. Let's say, you get a megnetic flux inside the core which changes between -100 mT to +100 mT. If the core has a saturation flux of 1 T, and with the magnet you create a flux of 950 mT inside the core, you get a bias from the magnet, and if you apply your sine wave the flux is centered at 950 mT with +/- 100 mT, but because the saturation flux is 1000 mT it will be clipped. So you have some kind of asymmetric behavior here.

This could, as i already explained some days ago, also have the effect of 'magnetic rectification' which might explain some of the strange effects.

[skywatcher]

Yes skywatcher, you understood correctly. I can even start it just by tapping the positive connection. No signal generator even needed.

Luc

What about the battery ?  Is it connected only for startup, or all the time ?

[gotoluc]

Hi everyone,

Since I changed my cap bank meter to a 10 Ohm instead of the 1 Ohm resistor to get more resolution on my meter I'm getting confused. In my latest video test 16 I said the normal wound coil with no magnet was using 320uA and that is not correct!... it is 3.2uA used
Same goes for the toroid with magnet I said it was returning -350uA and it is -3.5uA returning.

It will take me some time to adjust using the 10 Ohm but it's worth it as it gives me much better resolution. Maybe I should even go to 100 Ohms!... but I don't have a 1%

I also decided to retest the 20KHz self pulse test I posted on page 26 first post. The more accurate reading is 17.5uA and not 14uA

I also took a new scope shot of it once it was tuned to the most efficient and is below.

Sorry for the confusion in video test 16

@Gyula, I'll do the test you asked by adding the capacitance and post the results.

Luc

[gotoluc]

What about the battery ?  Is it connected only for startup, or all the time ?

Hi skywatcher,

yes battery still needs to be connected as it is using 18uA but at least it is creating its own energy for the mosfet switch at 20KHz.

This is an accomplishment on its own! as I don't know of a pulse circuit that can create a 20KHz pulse of 7.19vpp with 3vdc at 18uA input. Can think of one?... or anyone else reading this topic?

Hopefully with a new main toroid coil of less DC resistance and a little more inductance we can come to unity or better.

Luc