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Author Topic: Self running coil?  (Read 302290 times)

gyulasun

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Re: Self running coil?
« Reply #315 on: March 25, 2010, 10:45:10 PM »
Hi Mark,

here are the scope shots. First is with 50 resistor and second is without resistor. I do agree that it makes the pulses square but it takes more current then without the resistor.

Both were adjusted to minimum voltage to trigger gate.

Any idea why this is ???... this is the problem I have when I connect the 555. It keeps the pulses square and does not give as good of results compared to using the wavetek with rounded pulses.

Luc

Hi Luc,

The near sinusoid waveform with the spikes across the 100 Ohm resistor comes from the fact that you use a 10:1 probe backwards i.e. its output goes to the signal generator and its input tip (which includes a series 9 MOhm resistor as usual) goes to the gate of the MOSFET.
This means that this series 9 MOhm makes the gate high impedance and this way the gate can easily pick up the stray E field from the toroid coil (the sinusoid voltage also has the same freq like the signal generator output, 33.7 kHz), or if it does not pickup the the E field, then this sinusoid voltage may also come from the drain side via the Crss drain gate capacitance and it is as big as the scope shows because the gate has a high impedance.

How to solve?  Could use a piece of 50 Ohm coax cable directly from the signal generator input to the gate, a cable length of 0.5-1 meter long.

EDIT  Maybe the 50 Ohm low impedance the gate now will "see" from the signal gen output would mean you will find similar NOT as good results like you find with the 555.

You would have to 'tinker' again for achieving the same good sweet point if you change to coax cable.

Thanks for answering my earlier questions.

Re on you ebay MOSFET types: they have very good low value threshold voltages, a .5 to 1V advantage wrt the 2SK... type, maybe this can compensate for the moderately high 700-800pF input capacitance. If you are careful with the voltages, the P channel type can be "handled".
(The third type is out of question indeed because of its 4.3nF input cap.)
So the first two types are worth trying, hopefully they have good prices.

rgds,  Gyula

PS Or you use an 1:1 probe, not a 10:1 from the signal gen? Cannot recall.

mscoffman

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Re: Self running coil?
« Reply #316 on: March 25, 2010, 11:04:07 PM »
Hi Mark,

here are the scope shots. First is with 50 resistor and second is without resistor. I do agree that it makes the pulses square but it takes more current then without the resistor.

Both were adjusted to minimum voltage to trigger gate.

Any idea why this is ???... this is the problem I have when I connect the 555. It keeps the pulses square and does not give as good of results compared to using the wavetek with rounded pulses.

Luc

Excellent scope pic's. Well both the signal and the noise has to flow
through the terminating resistor and the signal is winning power wise
with the resistor. Notice how the signal *Transistions* are much more
rapid and much squarer. The Fourier decomposition to sinewaves
would show much greater high frequency action with the squarer wave. 

The other thing is that clearly your coil seems to be resonating at
the frequency you are driving it at. This is seen in the one to one
lower power sinewave base seen in the gate current. The pulses
are due to coil inductance. The sinewave is due to coil re sonace and
you are *not* seeing it in the generator voltage with the t-resistor.
The coil power is beginning to overpower the transistor. And that
is beginning to effect your signal generator leads as noise in those
drooping high levels. With the cleaner signal you can tell that
the resonance sinewave is not a function of drive voltage.

On the NE555 how are you powering it? It may make sense to use
an external ~5volt dc supply for the NE555 then a voltage divider
to set the voltage. for comparison to the SigGen. You need to look
at the *exact upper and lower gate voltage levels* If you just want to
convert the signal to be *more* sinewave like and slower use an RC filter.
Hopefully you have already tried that gate series variable resistor. ie VrCiss =
RC when used with the NE555. In this circuit you won't necessarily get any
operational browny points for using clean digital signal level drives. It's
nicer to look at though. RC filter = series resistor then cap to ground.
put the scope on the actual gate. If you still come up with the same
answers then perhaps OU is based more in coil resonance and less in
the high speed inductive kick?

So:

a) set up variable gate resistor, tune with t-resistor vs tune with remote
powered NE555. Should be same. Also *maybe* same now as witout Vr and
t-resistor.

b) Set up RC filter, tune with t-resistor vs tune with remote powered NE555
Should be the same. Also should be same now without RC filter and
without t-resistor.

c) NE555 under remote power vs NE555 under bulk or pickup power with
voltage set exactly the same - difference in operation? = difference of
power drain of NE555 on operation of circuit.

:S:MarkSCoffman

gotoluc

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Re: Self running coil?
« Reply #317 on: March 25, 2010, 11:52:05 PM »
Hi Luc,

The near sinusoid waveform with the spikes across the 100 Ohm resistor comes from the fact that you use a 10:1 probe backwards i.e. its output goes to the signal generator and its input tip (which includes a series 9 MOhm resistor as usual) goes to the gate of the MOSFET.
This means that this series 9 MOhm makes the gate high impedance and this way the gate can easily pick up the stray E field from the toroid coil (the sinusoid voltage also has the same freq like the signal generator output, 33.7 kHz), or if it does not pickup the the E field, then this sinusoid voltage may also come from the drain side via the Crss drain gate capacitance and it is as big as the scope shows because the gate has a high impedance.

How to solve?  Could use a piece of 50 Ohm coax cable directly from the signal generator input to the gate, a cable length of 0.5-1 meter long.

EDIT  Maybe the 50 Ohm low impedance the gate now will "see" from the signal gen output would mean you will find similar NOT as good results like you find with the 555.

You would have to 'tinker' again for achieving the same good sweet point if you change to coax cable.

Thanks for answering my earlier questions.

Re on you ebay MOSFET types: they have very good low value threshold voltages, a .5 to 1V advantage wrt the 2SK... type, maybe this can compensate for the moderately high 700-800pF input capacitance. If you are careful with the voltages, the P channel type can be "handled".
(The third type is out of question indeed because of its 4.3nF input cap.)
So the first two types are worth trying, hopefully they have good prices.

rgds,  Gyula

PS Or you use an 1:1 probe, not a 10:1 from the signal gen? Cannot recall.

Hi Gyula,

thanks for the details. The scope probe I use on the Generator output has both X1 and X10. I only use it on the X1 setting which has a 220 Ohm resistance from what I can measure.

In the first scope shot of the post in question: http://www.overunity.com/index.php?topic=8892.msg234503#msg234503  The scope probe is not used. I have my alligator clips (50cm or 20" long) connected at the 50 Ohm resistor across the Hot and Ground of the BNC output connector of the Wavetek and still have the sine wave. So I don't think it's coming from the probe.

Thanks for your opinion on the ebay mosfet's

Luc

gyulasun

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Re: Self running coil?
« Reply #318 on: March 25, 2010, 11:59:40 PM »
Luc,  it is interesting that with the triangle waves the waveform across the 100 Ohm looks like correct. 

Then the sinusoid wave is still a mistery... Maybe it is picked up by simple induction from the main toroid coil?

Gyula

mscoffman

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Re: Self running coil?
« Reply #319 on: March 26, 2010, 12:18:53 AM »
Hi Luc,

The near sinusoid waveform with the spikes across the 100 Ohm resistor comes from the fact that you use a 10:1 probe backwards i.e. its output goes to the signal generator and its input tip (which includes a series 9 MOhm resistor as usual) goes to the gate of the MOSFET.
This means that this series 9 MOhm makes the gate high impedance and this way the gate can easily pick up the stray E field from the toroid coil (the sinusoid voltage also has the same freq like the signal generator output, 33.7 kHz), or if it does not pickup the the E field, then this sinusoid voltage may also come from the drain side via the Crss drain gate capacitance and it is as big as the scope shows because the gate has a high impedance.

How to solve?  Could use a piece of 50 Ohm coax cable directly from the signal generator input to the gate, a cable length of 0.5-1 meter long.

EDIT  Maybe the 50 Ohm low impedance the gate now will "see" from the signal gen output would mean you will find similar NOT as good results like you find with the 555.

You would have to 'tinker' again for achieving the same good sweet point if you change to coax cable.

Thanks for answering my earlier questions.

Re on you ebay MOSFET types: they have very good low value threshold voltages, a .5 to 1V advantage wrt the 2SK... type, maybe this can compensate for the moderately high 700-800pF input capacitance. If you are careful with the voltages, the P channel type can be "handled".
(The third type is out of question indeed because of its 4.3nF input cap.)
So the first two types are worth trying, hopefully they have good prices.

rgds,  Gyula

PS Or you use an 1:1 probe, not a 10:1 from the signal gen? Cannot recall.

@gyulason,

I can't believe there is either a 1meg or 9meg R in series with the signal
generator as it wouldn't drive into a 50Ohms resistor at all....Measure
with DVM ohmmeter. Scope probes are generally 20Ohms impedance coax
at their highest frequency range so unless we are running at many MHz
the difference 20 vs 50Ohms won't matter. 20Ohms=RC || RL + dcR
So 50ohm video coax for a lab would be nice but not necessary at
these low frequencies. The t-resistor is desirable for Sig Gen.

---

@gotoluc

Well, try a sinewave then. Maybe OU doesn't like inductive kicks?
A sinewave is it's own Fourier Decomposition. It doesn't have any
additional HF signal components or steps. Resonance is a sinewave.
NE555 + RC filter ~= waveform. There is an Intersil cmos IC
somewhat like the NE555 that outputs a sinewave and squarewave
too. I think there is an app note that shows triangle wave generation.
It takes extra energy to generate a squarewave.

---

Man this looks close! You should boost the resistor up on pickup coil
to get 4.2Vdc like 6Kohm - perhaps insert the full diode bridge across
the pickup coil.

:S:MarkSCoffman

gotoluc

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Re: Self running coil?
« Reply #320 on: March 26, 2010, 12:22:04 AM »
Excellent scope pic's. Well both the signal and the noise has to flow
through the terminating resistor and the signal is winning power wise
with the resistor. Notice how the signal *Transistions* are much more
rapid and much squarer. The Fourier decomposition to sinewaves
would show much greater high frequency action with the squarer wave. 

The other thing is that clearly your coil seems to be resonating at
the frequency you are driving it at. This is seen in the one to one
lower power sinewave base seen in the gate current. The pulses
are due to coil inductance. The sinewave is due to coil re sonace and
you are *not* seeing it in the generator voltage with the t-resistor.
The coil power is beginning to overpower the transistor. And that
is beginning to effect your signal generator leads as noise in those
drooping high levels. With the cleaner signal you can tell that
the resonance sinewave is not a function of drive voltage.

On the NE555 how are you powering it? It may make sense to use
an external ~5volt dc supply for the NE555 then a voltage divider
to set the voltage. for comparison to the SigGen. You need to look
at the *exact upper and lower gate voltage levels* If you just want to
convert the signal to be *more* sinewave like and slower use an RC filter.
Hopefully you have already tried that gate series variable resistor. ie VrCiss =
RC when used with the NE555. In this circuit you won't necessarily get any
operational browny points for using clean digital signal level drives. It's
nicer to look at though. RC filter = series resistor then cap to ground.
put the scope on the actual gate. If you still come up with the same
answers then perhaps OU is based more in coil resonance and less in
the high speed inductive kick?

So:

a) set up variable gate resistor, tune with t-resistor vs tune with remote
powered NE555. Should be same. Also *maybe* same now as witout Vr and
t-resistor.

b) Set up RC filter, tune with t-resistor vs tune with remote powered NE555
Should be the same. Also should be same now without RC filter and
without t-resistor.

c) NE555 under remote power vs NE555 under bulk or pickup power with
voltage set exactly the same - difference in operation? = difference of
power drain of NE555 on operation of circuit.

:S:MarkSCoffman

Hi Mark.

I think we are getting closer to what is needed to make this circuit work.

If I use the 555 and match the pulses to the exact specs as the Wavetek output (I mean perfect match) and connect the 555 to the gate then the sine wave is gone and so is the coil sending back energy. I connect the Wavetek and all is back.

Something inside the Wavetek is allowing the gate to switch and the coil resonance to come through the switch and shunt resistor. Using the 555 it loses this since you don't see the sine wave on across the shunt resistor, which maybe a braking effect on the resonating coil.

Could it be that the Wavetek output has an impedance matching transformer and this is what is helping not to cancel the coils resonance as what is leaking trough the switch is resonating in the Wavetek impedance matching coil?

If this is what is happening then the sine wave that is going back through the shunt resistor should not be calculated as power that is coming from the generator but rather from the coils supply.

Are you following me on this? Let me know what you think

Luc

mscoffman

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Re: Self running coil?
« Reply #321 on: March 26, 2010, 01:48:28 AM »
Hi Mark.

I think we are getting closer to what is needed to make this circuit work.

If I use the 555 and match the pulses to the exact specs as the Wavetek output (I mean perfect match) and connect the 555 to the gate then the sine wave is gone and so is the coil sending back energy. I connect the Wavetek and all is back.

Something inside the Wavetek is allowing the gate to switch and the coil resonance to come through the switch and shunt resistor. Using the 555 it loses this since you don't see the sine wave on across the shunt resistor, which maybe a braking effect on the resonating coil.

Could it be that the Wavetek output has an impedance matching transformer and this is what is helping not to cancel the coils resonance as what is leaking trough the switch is resonating in the Wavetek impedance matching coil?

If this is what is happening then the sine wave that is going back through the shunt resistor should not be calculated as power that is coming from the generator but rather from the coils supply.

Are you following me on this? Let me know what you think

Luc

Yes, I think it has something to do with the
100 ohm resistor in the ground lead of the signal
generator. The sinewave is possibly fake as current
goes.

Is the NE555 grounded? Or is it grounded through
100ohms?
Is the NE555 remotely powered by a dc supply?

Try implacing and unimplacing a 10.0ohm resistor
across the 100ohm resistor and see if that doesn't
cause a relative decrease in the ratio of this sinewave
to the rest of the signal. Try to see if shorting the
100Ohm resistor changes circuit OU behavior.

Try attaching a 100ohm resistor in the ground lead
of the NE555? Finally it may be time to implement
the opto remotely powered by a dc supply. That
should behave just like the NE555 when led is
driven by signal generator. You know a 1:1
isolating transformer in the SigGen leads could
show something too.

If the NE555 is grounded then the output driver
impedance of the NE555 can inhibit formation of that
sinewave but the mosfet transistor may be reverse
amplifying it when it exists. Making a resistor-to-
ground makes the NE555 effectively less powerful.
Also try leaving the SigGen Ground in place when
operating with the NE555.

Something in the above should help determine the
problem. The main things are the probable grounding
of the NE555 and the probable bulk capacitor or
pickup coil suppling the NE555 power.

Secondary is 100ohm resistor in the ground lead
of the signal generator. Or some 60Hz AC pickup
in the ground lead of the signal generator. Or a
SigGen signal on the ground lead between it's
ground and utility ground.
 
:S:MarkCoffman

forest

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Re: Self running coil?
« Reply #322 on: March 26, 2010, 02:34:49 AM »
To eliminate ground you have to connect 555 to capacitor bank as a power source.
Can you precharge capacitors , connect 555 into it ,connect battery for a moment to start oscillations and look what next ?

gotoluc

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Re: Self running coil?
« Reply #323 on: March 26, 2010, 05:01:12 AM »
Hi everyone,

I have an update video: http://www.youtube.com/watch?v=1Gy-kkJKNOU

Scope shot is from video test.

Luc

gravityblock

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Re: Self running coil?
« Reply #324 on: March 26, 2010, 05:14:11 AM »
Tutorial of Series and Parallel LC Resonant Circuits, http://www.scribd.com/doc/28956060/Resonance-Tutorial

[Edit:]  @Luc, Good update on the SK2806-01 Mosfet and the modem transformer to self-oscillate with the sine wave.  Good work!

GB

gravityblock

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Re: Self running coil?
« Reply #325 on: March 26, 2010, 05:48:07 AM »
One shot from the signal generator will re-start the circuit and cause it to self-oscillate again.  This is truly amazing.  A "perfectly" tuned circuit would produce a continuous sine wave and oscillate indefinitely.  I believe this is what I'm seeing.  Please correct me if I'm over-looking something.

GB 


gotoluc

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Re: Self running coil?
« Reply #326 on: March 26, 2010, 06:12:17 AM »
Yes gravityblock, you are seeing a circuit that creates its own resonant frequency oscillation ;)

It's not perfect!  but it works. I think this maybe one more step in the right direction.

Now!... we need to better understand how to tune for maximum output with minimum input.

So it still needs lots of work to go OU if possible ;D

Stay tuned for more tuning

Luc

NextGen67

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Re: Self running coil?
« Reply #327 on: March 26, 2010, 09:32:23 AM »
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


« Last Edit: March 26, 2010, 11:05:13 AM by NextGen67 »

NextGen67

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Re: Self running coil?
« Reply #328 on: March 26, 2010, 09:37:53 AM »
One shot from the signal generator will re-start the circuit and cause it to self-oscillate again.  This is truly amazing.  A "perfectly" tuned circuit would produce a continuous sine wave and oscillate indefinitely.  I believe this is what I'm seeing.  Please correct me if I'm over-looking something.

GB

Still some 0.000088 from that.... Once it get to -0.000001 it is self sustaining (e.g. no battery necessary) and able to give energy back.

--
NextGen67

Magluvin

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Re: Self running coil?
« Reply #329 on: March 26, 2010, 10:12:43 AM »
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