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Author Topic: Self running coil?  (Read 302219 times)

mscoffman

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Re: Self running coil?
« Reply #225 on: March 21, 2010, 01:15:53 AM »
Luc,

Ha so there seem to be two choices of mosfet now.

Either the RF510;   Ciss =135pf,    Rds =0.4ohms
Or the si1026x; Ciss =60pf,    Rds = 0.7ohms  [the build in set combined]

Gyula was that in series or parallel? Also, could a 2nd si1026x be added, and by such create something like: 2* si1026x; Ciss =120pf,    Rds = 0.35ohms  [the build in sets combined] without having negative other things happening?

Now if we only could find a single one that has Ciss=<120pf,    Rds=<0.35ohm

Anyhow, a little problem [for Luc] that could happen is that the frequency factor goes so far up that he might need to put his magnet closer to the coil... So Luc, if you go for any of the above mosfet types, and you can't get a good charge back [but still notice some effect], you probably would need to come closer with your magnet. You might having a hard time for a while finding the sweet spot back again.

NextGen67


If you study the data sheet: http://www.vishay.com/docs/71434/si1026x.pdf 

Rds ohms max = 1.4
Id amps = .5
Vgs(th) min = 1
Vgs (th) max = 2.5
Vdss Volts =  60
Ciss pf Max = 30
Crss pf Max  = 3
ton ns max = 15
toff ns max = 20

And these data are for a single device and I suggested using two in parallel because they are manufactured as double devices in a single SC89 SMD case.  NextGen has just mentioned using two such SMD cases also in parallel, which would mean 4 single MOSFET in parallel, this would still have about 120pF input capacitance but Rds would be  about  .35 Ohm.

rgds, Gyula

---

another selection:

STMicroelectronics  STS2DNF30L,  Dual transistor Surface mount SO-8
each transistor;
Ciss =  121pf, Rds(on) Static drain-source on resistance = 0.09ohms


NextGen67

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Re: Self running coil?
« Reply #226 on: March 21, 2010, 01:38:27 AM »
---

another selection:

STMicroelectronics  STS2DNF30L,  Dual transistor Surface mount SO-8
each transistor;
Ciss =  121pf, Rds(on) Static drain-source on resistance = 0.09ohms

mscoffman, Very good :)

Vds 30V
Vdgr 30v
Vgs 18v
Vgs 2.5v max
Rds 0.15ohm max [0.09 typ]
Ciss 121pf
Coss 45pf
Crss 11pf

Data sheet attached.

--
NextGen67

gravityblock

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Re: Self running coil?
« Reply #227 on: March 21, 2010, 01:40:22 AM »
When I click the link I am asked to logged in when I am already logged in. whats up with that?

There has been 8 downloads of this file so far.  The problem may be on your end or a temporary issue with the server.  Maybe try to log out, then log back in.  If the problem persists, then you can view or download the file on Scribd, http://www.scribd.com/doc/25248289/How-to-Build-Solid-State-Electrical-Over-Unity-Devices

If you have any additional problems, send me a PM and I'll send the file to you.  Thanks for bringing this to my attention.

GB

LightRider

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Re: Self running coil?
« Reply #228 on: March 21, 2010, 06:00:28 AM »
Hi all,

here is a new video demonstrating a pickup coil and a LED as load.

Link: http://www.youtube.com/watch?v=bgPR9r14zWE

Luc

Hi Luc,

I gather the material to make a replica of your experience  ;D
But until now, it seems that I can't make the necessary adjustments to succeed  ???

Would it be possible to make a video of the steps to adjust the frequency, duty cycle, voltage, space between the coil and magnet ... etc...

And of course to show your connections to your measuring devices (capacitor bank at the back with the precision 1 ohm resistor ... this part hasen't been clearly filmed).

Thanks,
LightRider

NextGen67

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Re: Self running coil?
« Reply #229 on: March 21, 2010, 10:35:54 AM »
Having taken a close look at Luc's scope shots [the non tuned and tuned ones], it clearly seems to show some capacitive effects at the begin of the ON pulse [see below enlarged image fragments].

For the NON tuned scope shot:

Instead of the vertical rise and then horizontal line we would normally see in a square wave, this one is like

1) Rise (normal - start of ON signal)
2) Horizontal, but below max amplitude [ capacitance effect ?]
3) Slope up [ capacitance effect, the capacitance seems NON fixed here ?]
4) Horizontal line (normal)
5) Fall (normal - end of ON signal)

This effect takes roughly some 14+17 = 31 percent of the ON phase. It is likely that this is caused by the capacitive properties of the FET. I have no good explanation yet as of *why* the capacitance effect is build out of 2 parts [one(1) the horizontal below max amplitude, the other a slope up to max amplitude], but this might have to do with the FET's switch on technique used].

Note that the end part of the ON signal [the fall] looks rather as what would normally expect [thus no capacitance effects happening here], and this could be explained by the fact that since the energy to from the signal generator wend off, the capacitance of  the FET is 'virtually' not there anymore [the capacitance is only there when the FET is in operation modes].

The 'fine tuning' [getting optimal resonance frequency], seems to have particular strong effects on *this* part of the ON signal. ( See some posts back where I posted Luc's non tuned and tuned scope shot, but with the yellow trace inverted and moved over the green one, to make the difference clear between non tuned and tuned ).

When a better type FET is used [one with the lowest possible Ciss] the 'length' of this effect will become much smaller and thus less important... It actually would make tuning more easy, since *exact* matching becomes a less important factor.

Also, with the better type fet, it seem appear to me that the 'charge back' factor [charging up the Cap bank] would *increase* , which is of course a good thing.

As for the TUNED scope shot,

You can clearly notice that step 2 and 3 mentioned above are 'corrected' by Luc, by having an *exact* tuned frequency.

in my earlier posted scope shots [the one with the red circles], the difference is pointed out, and one can see that the non tuned one has a mismatch, and this shows *why* the cap is unable to charge up [loss of energy, due to frequency tuning mismatch].

So, basically the FET capacitance is *NOT* really so important for the charge back (since only some 31 percent [less then 3 percent! with the correct FET] are accounting for the frequency 'mismatch'

Later on [when the better type FET is used], new scope shots like these could actually give some indications as for *where* the charge back is coming from.

also, with the new type FET, the tuning will have *more* effectiveness because the tuning part could *never* 'correct' the slope [step 3] part totally, because it is a variance capacitance there[that also is why there is a little ring signal afterward]. this slope part is almost totally removed with the new type FET, thus *more* effectiveness for he tuned frequency [thus *more* charge back].

A side note for the Cap bank charging.... Although you see Luc's meter gaining upwards very quickly, the actual charge going into the Cap is still at the very low border... Charging happens with some 62.4 uA, and if my calculations are correct, this will translate in some 0.005 mW.   This will become slightly better -hopefully- with the new FET, and if after all this we still get the charging effect, the resonance coil could be tweaked for lower ohmic resistance.

P.S.: At the end of the ON signal [the fall] it shows a rather *non* direct decay at the last 20 to 25 percent of the fall edge... what effect is responsible for causing this ?

--
NextGen67
« Last Edit: March 21, 2010, 01:28:07 PM by NextGen67 »

skywatcher

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Re: Self running coil?
« Reply #230 on: March 21, 2010, 12:57:53 PM »
Now i have 2 different coils (one with 315 mH (1 layer), the other with 2480 mH (3 layers) combined inductance).

But i'm not able to replicate any of the interesting effects.   :(

There is no clearly visible resonant frequency. I tried it with frequencies from 100 Hz up to more than 100 kHz. I looked at the voltage measured across one half of the coil. It changes it's shape (sometimes it's more rectangular, sometimes it looks more than one half of a sine wave) and it changes also its magnitude but only slightly.

The voltage measured across the 1 ohm resistor is generally very low. With 5 mV/div resolution of my scope i can barely see any differences.

Also the magnet has no visible effects. It reduces the inductance only slightly (about half the value measured without magnet) although it's a very strong neo magnet (N48, 10 mm diameter x 10 mm).

Maybe the ferrite core is not suitable to see the effects. I don't know. But i'm not motivated to make dozens of new coils with other cores to try this out.   :-[

LightRider

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Re: Self running coil?
« Reply #231 on: March 21, 2010, 01:45:57 PM »
Now i have 2 different coils (one with 315 mH (1 layer), the other with 2480 mH (3 layers) combined inductance).

But i'm not able to replicate any of the interesting effects.   :(

There is no clearly visible resonant frequency. I tried it with frequencies from 100 Hz up to more than 100 kHz. I looked at the voltage measured across one half of the coil. It changes it's shape (sometimes it's more rectangular, sometimes it looks more than one half of a sine wave) and it changes also its magnitude but only slightly.

The voltage measured across the 1 ohm resistor is generally very low. With 5 mV/div resolution of my scope i can barely see any differences.

Also the magnet has no visible effects. It reduces the inductance only slightly (about half the value measured without magnet) although it's a very strong neo magnet (N48, 10 mm diameter x 10 mm).

Maybe the ferrite core is not suitable to see the effects. I don't know. But i'm not motivated to make dozens of new coils with other cores to try this out.   :-[

Similar result on my side  :( ???
LightRider

gyulasun

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Re: Self running coil?
« Reply #232 on: March 21, 2010, 02:12:54 PM »
Hi Skywatcher,

Here is what I would do:

use the 315mH coil

Try to use 25V DC supply or so (because your BUZ11 has an output capacitance of 750pF at Vds=25V

Give 10.5kHz input pulse frequency to the gate source from your freq source because the 315mH resonates with the 750pF about that frequency, see: http://www.whatcircuits.com/lc-resonance-frequency-calculator/
and data sheet for your FET: http://skory.gylcomp.hu/alkatresz/buz11.pdf

Of course you wish to sweep the frequency up and down near the 10kHZ frequency because there is no garantie for your FET to have just 750pF at 25V.

You may repeat this procedure with the other coil, just use the near correct values. If you do not have a variable power supply, use one or two batteries in series and estimate the output capacitance from the data sheet, (Coss in Fig. 10).

EDIT: With the magnets on, you have to measure the mH value of the coil to bring the circuit readily into resonance. Otherwise, much trial and error as Luc found.

rgds, Gyula

EDIT: if you measure with the scope between the drain source, you have to see amplitude increase at or near resonance, together with the waveform becoming nearly sinusoidal (input is square wave).
« Last Edit: March 21, 2010, 02:35:05 PM by gyulasun »

skywatcher

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Re: Self running coil?
« Reply #233 on: March 21, 2010, 02:42:41 PM »
My cap (120000 uF) is only rated 15 V. So i can not go up to 25 V with this one.

I have found a 33 uF film cap (250 V). Maybe i can try this one.

NextGen67

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Re: Self running coil?
« Reply #234 on: March 21, 2010, 02:53:22 PM »
@Gyula,

Send you a PM again.. you should see it :-)

--
NextGen67

NextGen67

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Re: Self running coil?
« Reply #235 on: March 21, 2010, 02:55:04 PM »
My cap (120000 uF) is only rated 15 V. So i can not go up to 25 V with this one.

I have found a 33 uF film cap (250 V). Maybe i can try this one.

Skywatcher,

You still have your previous [somewhat working one] intact?

--
NextGen67

skywatcher

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Re: Self running coil?
« Reply #236 on: March 21, 2010, 03:36:07 PM »
Skywatcher,

You still have your previous [somewhat working one] intact?

--
NextGen67

Yes...

I wonder why the magnet has such a low impact on the inductance. Maybe the permeability of the core is too low.

NextGen67

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Re: Self running coil?
« Reply #237 on: March 21, 2010, 03:47:01 PM »
Yes...

I wonder why the magnet has such a low impact on the inductance. Maybe the permeability of the core is too low.

yes, your core material and magnet do not match up.

You did not time exactly how long it 'ran' last time - right?    You may want to give it another try with that [working] one, and time how long it keeps going.  After that, try to clamp your magnet a bit to the coil, so that its movement get strongly restricted [you may need to re-tune the frequency after that a bit], and 'run' it again... sere how long it can run now.... If I'm right [and you re-tuned correctly], your 2nd run should be longer :)

Also, be sure to have NO metallic objects in near vicinity.

--
NextGen67

mscoffman

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Re: Self running coil?
« Reply #238 on: March 21, 2010, 03:51:04 PM »

Also the magnet has no visible effects. It reduces the inductance only slightly (about half the value measured without magnet) although it's a very strong neo magnet (N48, 10 mm diameter x 10 mm).

Maybe the ferrite core is not suitable to see the effects. I don't know. But i'm not motivated to make dozens of new coils with other cores to try this out.   :-[


My cap (120000 uF) is only rated 15 V. So i can not go up to 25 V with this one.


@skywatcher

I think, there was a video of the measurement of the toroid coil with
and without the magnet stack right at the surface of the coil. The
measurement were 1040mh [without] and 44mheneries [with]. I would
submit that this nearly 25 times difference represents the action of a high
performance ferrite material possibly traceable to Metglass. I also notice
sometimes the gotoluc diagrams are showing lines like the toroid may
be split by small gaps into halves. That also might make a difference.

So I don't think I would attempt duplicating this experiment until I got
measurements somewhat similar to his or else could invalidate, correct
or explain what was shown with a coil at least somewhat similar to his.
Yours sounds like what I might expect, maybe low, but his values
seem extraordinary. I've heard that metglass material is like this.

---

You don't happen to have two of these 120Kuf capacitors do you?  8)

If so...place them in series...According to theory, equal
values of series capacitors divide their capacitance by
two so you have 60Kuf and they would split the Q charge,
so the working voltage of the two combined would be
doubled to 30Volts.

When I was using them I would check to see, once in a while,
that they were dividing the sum of the DC voltage between
them equally, and not continue if they were not. (due to
unbalanced DC leakage current, and unbalanced delta C)

:S:MarkSCoffman

skywatcher

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Re: Self running coil?
« Reply #239 on: March 21, 2010, 04:01:15 PM »
You did not time exactly how long it 'ran' last time - right?    You may want to give it another try with that [working] one, and time how long it keeps going.  After that, try to clamp your magnet a bit to the coil, so that its movement get strongly restricted [you may need to re-tune the frequency after that a bit], and 'run' it again... sere how long it can run now.... If I'm right [and you re-tuned correctly], your 2nd run should be longer :) 

At the moment, i can not even replicate the 'long' runtime o got last Friday. I don't know exactly how long it was running then, but today it's much less.

Quote
Also, be sure to have NO metallic objects in near vicinity.

That's not possible. If you look at Luc's videos, there are also plenty of metallic objects...