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Author Topic: Self running coil?  (Read 302278 times)

gotoluc

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Re: Self running coil?
« Reply #330 on: March 26, 2010, 03:11:50 PM »
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 :P

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

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Re: Self running coil?
« Reply #331 on: March 26, 2010, 03:16:29 PM »
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 ;D

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

Luc

gyulasun

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Re: Self running coil?
« Reply #332 on: March 26, 2010, 03:22:48 PM »
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

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Re: Self running coil?
« Reply #333 on: March 26, 2010, 03:27:34 PM »
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

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Re: Self running coil?
« Reply #334 on: March 26, 2010, 03:29:22 PM »
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

gotoluc

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Re: Self running coil?
« Reply #335 on: March 26, 2010, 03:38:59 PM »
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

Yes, you're right!... glad you are all here helping.

The inductance when not shorted is higher then my meter can measure (20H)

When shorted it's 10mH

I'll add a 5K pot on the normally shorted side of the modem transformer and vary it to see the effect on the self oscillation in hope to find the ideal inductance. I'll then match it with a coil of that value and see if it still works.

Thanks for bringing this to my attention :)

Luc

NextGen67

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Re: Self running coil?
« Reply #336 on: March 26, 2010, 03:40:26 PM »
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 :P

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

Ha, that explains my numbers 10.85 or 14.01 [10.85+14.01 = 24.86 !]...
About the resistance of your pickup coil. Good that I could predict it.

The toroid inductance of 25.3 mH... I guess then the C's of the mosfet were
3049pF - 2000pF (2nF) = 1049 Pf.... Which indicates that probably your mosfet is hardly
switching on... That would then be also why the mosfet shuts off when adding more Capacitance.

Yeah, when you have the build done, you will be able to have more control.

--
NextGen67

gyulasun

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Re: Self running coil?
« Reply #337 on: March 26, 2010, 03:50:30 PM »
Yes, you're right!... A you are all here helping.

The inductance when not shorted is higher then my meter can measure (20H)

When shorted it's 10mH

I'll add a 5K pot on the normally shorted side of the modem transformer and vary it to see the effect on the self oscillation in hope to find the ideal inductance. I'll then match it with a coil of that value and see if it still works.

A for bringing this to my attention :)

Luc

Luc,  the 5K pot is also good but maybe you could test the inductance change with a separate magnet attached to very near the core of the modem transformer,  just like at the toroidal core.   Good thing is you can use the L meter for both tests separately and see the effect. 

Gyula

gyulasun

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Re: Self running coil?
« Reply #338 on: March 26, 2010, 03:56:27 PM »
Quote from: NextGen67 link=topic=8892.msg234686#msg234686 A=1269614426
... I guess then the C's of the mosfet were
3049pF - 2000pF (2nF) = 1049 Pf.... Which indicates that probably your mosfet is hardly
switching on...

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

mscoffman

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Re: Self running coil?
« Reply #339 on: March 26, 2010, 04:35:20 PM »
@gotoluc;

(1)
Excellent and innovative solutions. I am glad we got that out of the way as
I am convinced we were seeing groundloop problems, with no apologies to
the user with that screenname.  ::)  So it would be best to keep the signal
generator ground disconnected…We have a very sensitive analog energy
balance. And a groundloop can pump energy into the circuit derived from
the utility lines! There may be a small metal shunt on the back of the signal
generator that can be opened (for a quick AB test) the isolates power line
ground from the signal ground in the SigGen. I wouldn’t run The SigGen with
that shunt opened forever. Alternatively you can one of those small grey
plastic 2 prong plug to 3 prong outlet converters with the little green
ground pigtail left open, to do the same thing. These things are power line
ground isolation techniques.


(2)
What you may want to do is to totally stop now and re-design an oscillator
circuit patterned on the JT Joule Thief circuit with the official toroid coil
totally removed from the circuit. This would use an audio transformer *in
place of a JT toroid*. (a one to one transformer is often not a best choice
for use in an oscillator though). Once the (power) oscillator circuit was
working *then* remove a load resistor and insert the official large toroid
Drain to Vcc. Your circuit will then be self starting with frequency
determined by a cap across the transformer. I can tell this 1:1 transformer
is trying to pull the circuit frequency down to its self resonance design
frequency of 18KHz which isn’t that good. You could also wind a small JT
osc. toroid transformer for this app. I’d stick with mosfet transistors.

Alternatively the transistor in the drive oscillator could be replaced by a
small signal mosfet and use that output of that => to drive main mosfet +
coil. Either way would be a more operationally stable situation.

(3)
I think you can boost the efficiency of the pickup coil by making one like
the J. Naudin’s coil (one with the leds) around the magnet stack. That
alone may do it in terms of ou.

(4)
Use a capacitive voltage multiplier to charge the bulk capacitor from pickup
coil energy. The circuit as from a disposable flash camera driven by a three
volt battery comes to mind. This could use the main oscillator frequency to
switch a small signal mosfet to pump a capacitor and diode linked backed to
the main capacitor. Be real with this information;
http://en.wikipedia.org/wiki/Voltage_multiplier

PS: Connect the bridge rectifier, across the pickup coil unless a diode is
blown out, it will boost 59.uf capacitor charging efficiency!

Thanks and good work so far… Now let's get cleanly beyond a unity gain
situation. :)

:S:MarkSCoffman

« Last Edit: March 26, 2010, 05:06:36 PM by mscoffman »

gotoluc

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Re: Self running coil?
« Reply #340 on: March 26, 2010, 05:09:10 PM »
Hi all,

so now the modem coil is gone ;D

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

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Re: Self running coil?
« Reply #341 on: March 26, 2010, 05:20:32 PM »
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

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Re: Self running coil?
« Reply #342 on: March 26, 2010, 05:34:48 PM »
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

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Re: Self running coil?
« Reply #343 on: March 26, 2010, 05:58:48 PM »

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

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Re: Self running coil?
« Reply #344 on: March 26, 2010, 06:11:44 PM »
Hi all,

so now the modem coil is gone ;D

<...>  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 ?)

--
NextGen67