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Author Topic: Slayer driven neon-producing DC via resistor ?.  (Read 21782 times)

tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #15 on: August 22, 2014, 03:04:55 AM »
This goes back to the issue of "what is AC and what is DC". Alternating means just that, alternating.

Take a neon and a resistor in series and connect them to an AC supply. Now consider the polarity of the voltage at one neon terminal. The voltage is positive during half the AC cycle, and it is negative during the other half of the cycle. Right? And the other electrode of the neon, connected to the other side of the mains supply line,  is negative while the other is positive, and is positive while the other is negative. Right? So the electrodes glow alternately, at the line frequency. One is on, the other is off. Then the one is off and the other is on. The negative-most electrode is the only one that glows, as the DC case shows.

Now... voltage is _relative_ and so is polarity. In the DC case, where two electrodes are connected together, but one is glowing and the other is not... they are both at the same _potential_ wrt some external reference like true Earth ground.... but with respect to the supply voltage to the stack, you can see that the "polarity" at any point is also relative. Consider two batteries connected in series. Look at the "middle terminal" where the positive of one battery is connected to the negative of the other battery. What is the polarity of this point? Is it negative, or positive? It is Positive wrt the Negative of the entire stack, but it is Negative wrt the Positive of the entire stack. In the neon stack, the two connected electrodes are at the same potential, but in one tube this is negative wrt the other electrode so it glows, and in the other tube that same potential is positive wrt the other electrode so it does not glow.

In the apparatus above, the neons are lit by the DC output of the HV Wireless Receptor, that I demonstrated in one of the microQEG videos.
http://www.youtube.com/watch?v=jcGTBA7NoVI
Well im not sure how using a DC reference in this case(the batteries in series)is the same as what we have here,as we are dealing with an AC source. So insted of having two batteries conected in series,we have a center taped transformer,say 12/0/12 AC. I can clearly see in my neon that both pins are glowing. Further testing shows it is the line with the resistor in series that has the +DC component,regardless of which side of the cap it is on.This can only mean that the resistor is offsetting the charge rate of one side of the cap-some how?.

What you are showing TK,is that the pin in the neon that has the negative polarity is the one that glow's-this we knew. What im showing is how a resistor some how offsets the charge rate to the plates in the cap. Now oddly enough,(and this seems ass about) is that the higher the value of the resistor,the higher the DC value in the cap is reached.

MarkE

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #16 on: August 22, 2014, 03:23:27 AM »
The rectification effect is weak.  If it were strong you would see a good percentage of the neon hold voltage on the capacitor.  You can try scoping the neon bulb, but the probe is likely to distort the voltage.  You also want to be careful not to hurt your scope.  If you are going to try that, I would do it through a series 1Meg resistor.  That will cost some bandwidth.  At these frequencies that should not be a problem, and it is a lot better than frying your vertical amplifier.  You are looking for asymmetry in the waveform.

tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #17 on: August 22, 2014, 05:35:57 AM »
Below is a simple test i carried out. It would seem one pin in the neon is recieving a higher charge than the other. Although both wave forms are in phase,we can see a potential difference between the two.There dosnt seem to be any offset in either trace though.

MarkE

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #18 on: August 22, 2014, 06:33:42 AM »
That's just where each of the wires are in the RF field.  The capacitor charges from the difference potential.  You want to measure from TP1 to TP2 or vice versa.  You also want the connections in your test set up from the bulb towards your scope to have as little exposure to RF as possible.  You could use a piece of coax from the bulb to get away from the field.  Or you could use nice short connections such as soldering the two bulb side resistors to the bulb with short leads and wrapping the ground clip lead around the probe hook to minimize the ground clip loop area.  The difference may still be hard to see because it is only about 1% of the signal.

tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #19 on: August 22, 2014, 07:09:16 AM »
That's just where each of the wires are in the RF field.  The capacitor charges from the difference potential.  You want to measure from TP1 to TP2 or vice versa.  You also want the connections in your test set up from the bulb towards your scope to have as little exposure to RF as possible.  You could use a piece of coax from the bulb to get away from the field.  Or you could use nice short connections such as soldering the two bulb side resistors to the bulb with short leads and wrapping the ground clip lead around the probe hook to minimize the ground clip loop area.  The difference may still be hard to see because it is only about 1% of the signal.
As all the cables run together,and are of same length,i dont see this as being the cause for the cap charging up. There is also the issue that it seems to be the pin in the neon that has the positive charge,is the one that light's up in my setup-this will be seen in the next video,as soon as it has uploaded. The resistor determonds as to which side of the AC cap has the negative potential-the side with the resistor is negative. resistor value also determonds the voltage potential reached in the cap.

MarkE

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #20 on: August 22, 2014, 07:26:27 AM »
As all the cables run together,and are of same length,i dont see this as being the cause for the cap charging up. There is also the issue that it seems to be the pin in the neon that has the positive charge,is the one that light's up in my setup-this will be seen in the next video,as soon as it has uploaded. The resistor determonds as to which side of the AC cap has the negative potential-the side with the resistor is negative. resistor value also determonds the voltage potential reached in the cap.
This is a matter of getting a clean measurement, so that we can figure out where the rectification effect is coming from.  The energy to charge is a function of the field strength and the exposed area.  You want to measure what is across the bulb and not what the scope leads pick-up on their own.  You could take a pair of 24 AWG or finer wire and tightly twist that to make a sense wire set to the bulb maybe five feet long to keep the scope ground clip away from the intense RF field.

What I think that we know:
1) Cap charges to less than 100mV without the resistor.
2) Cap charges to ~1V with a resistor of xxx Ohms.
3) Scope confirms it is a real DC offset and not RF fouling the DMM.
4) Resistor orientation does not change the charging polarity.
5) Pick-up at the neon bulb looks sinusoidal.
6) Side of the cap with the resistor is negative. (I take your word.)
7) It takes non-linear behavior to rectify even weakly.  This is not a function of linear: resistance, capacitance, inductance, and conductance.


tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #21 on: August 22, 2014, 07:52:04 AM »
This is a matter of getting a clean measurement, so that we can figure out where the rectification effect is coming from.  The energy to charge is a function of the field strength and the exposed area.  You want to measure what is across the bulb and not what the scope leads pick-up on their own.  You could take a pair of 24 AWG or finer wire and tightly twist that to make a sense wire set to the bulb maybe five feet long to keep the scope ground clip away from the intense RF field.

What I think that we know:
1) Cap charges to less than 100mV without the resistor.
2) Cap charges to ~1V with a resistor of xxx Ohms.
3) Scope confirms it is a real DC offset and not RF fouling the DMM.
4) Resistor orientation does not change the charging polarity.
5) Pick-up at the neon bulb looks sinusoidal.
6) Side of the cap with the resistor is negative. (I take your word.)
7) It takes non-linear behavior to rectify even weakly.  This is not a function of linear: resistance, capacitance, inductance, and conductance.
Video upload is taking for ever-very slow this time of day.
I will post it as soon as it's done,and maybe we can get some answers from it.

Some more details known so far.

1) Higher the resistor value,the higher DC voltage achieved in the cap.
2) The side of the neon pin that glow's,is the side hooked to the positive potential on the cap.
3) Any type of AC cap seems to work.
And 4)-confusion is growing fast lol.

tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #22 on: August 22, 2014, 07:53:46 AM »
This is a simple little setup,maybe you(Mark) or TK could throw it together,and look for your selve's.You guys are much more at home than me with this stuff-im just a mechanic.

tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #23 on: August 22, 2014, 09:18:41 AM »
Here is the last video on this,as it's time to move onto other things.
P.S-I joined the video's ass about,so first part is last,and last part is first.
https://www.youtube.com/watch?v=uj0-8SEGyUg

MarkE

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #24 on: August 22, 2014, 10:42:21 AM »
The miracle of induction is such that the voltage at one end of the wire is the opposite as at the other end of the wire.  So, assuming that it is the length of wire acting as the antenna: the times when the capacitor is positive on the probe, the neon is negative on that right hand wire, and that is when the neon glows on that side.

tinman

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #25 on: August 22, 2014, 01:04:10 PM »
The miracle of induction is such that the voltage at one end of the wire is the opposite as at the other end of the wire.  So, assuming that it is the length of wire acting as the antenna: the times when the capacitor is positive on the probe, the neon is negative on that right hand wire, and that is when the neon glows on that side.
Err ???-no,not seeing how that can be-makes no sence at all to me in this situation. How can it be negative at one end of the wire,and positive at the other end at the same time in regards to this setup.Dont forget that the two wires are side by side(speaker wire),and if we use your analogy,we would have two negative voltages at the neon,and two positive voltages at the cap through half the AC wave,then inverted through the second half of the wave.. First up,the wire isnt acting as an antenna-well not that much anyway. I say this because if i remove the neon,we get near no voltage at all at the cap.

TinselKoala

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #26 on: August 22, 2014, 01:27:13 PM »
Oh, you are using the oscillating E field from the slayer to light your neons. I didn't realize this. Ok here is what is happening, I think. Two things. First you are driving the neons with a rapidly oscillating AC RF voltage. So the electrodes of the neon are experiencing alternately, positive and negative _relative_ voltages. The negative one glows but they are switching back and forth at the RF frequency so there is no hope of picking up the event visually or photographically and it may even be shorter than the persistence time of the plasma glow itself, so perhaps both electrodes are constantly illuminated even though the plasma is only energised by the negative-most electrode in the gas.
The second effect is the field gradient. You should be able to take a bare neon, extend the leads sideways, grip it in a non-conductive holder and bring it close to the Slayer and have it light up, by "shorting" across the electric field with the neon's legs. Hold the neon so that the legs are tangent to the coil and it won't glow because you are parallel to the Efield gradient, hold it so that it is radial to the coil, "shorting" the Efield, and it will glow.  I use neons in this manner to determine the polarity of DC HV fields like from static machines like VDG, Bonetti, etc. You  poke the field and see if the electrode nearest the device glows, or the one nearest you glows, and this tells you the polarity of the DC field. If you turn the neon sideways it no longer is in the direction of the _gradient_ so no voltage develops across it and it doesn't glow.

So perhaps it's the field gradient that is doing the "rectification" you are seeing with your resistive antenna pickup system. I'm set up for other stuff right now and don't exactly  have room to pull down the Slayer and play around with it, but I might be able to get to it later on today.

MarkE

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #27 on: August 22, 2014, 01:35:25 PM »
Err ???-no,not seeing how that can be-makes no sence at all to me in this situation. How can it be negative at one end of the wire,and positive at the other end at the same time in regards to this setup.Dont forget that the two wires are side by side(speaker wire),and if we use your analogy,we would have two negative voltages at the neon,and two positive voltages at the cap through half the AC wave,then inverted through the second half of the wave.. First up,the wire isnt acting as an antenna-well not that much anyway. I say this because if i remove the neon,we get near no voltage at all at the cap.
The voltage develops around loops. 

TinselKoala

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #28 on: August 22, 2014, 01:38:43 PM »
Below is a simple test i carried out. It would seem one pin in the neon is recieving a higher charge than the other. Although both wave forms are in phase,we can see a potential difference between the two.There dosnt seem to be any offset in either trace though.
It looks like you have the Yellow trace baseline set a half a minor division below the center marker. This may be masking a little offset. You have cursors on that scope? Can you do a shot with just the yellow trace displayed at about 3/4 full screen height, with the baseline set exactly at the center graticule marker, and then use the cursors or the measurements to identify the max and the min of the waveform? It looks to me like there may be a little vertical asymmetry happening. P-p is less useful than max-min in this case, I think. If we have max and min we can get p-p from that easily enough.

ETA: Another useful technique is to deliberately set the scope's timebase to much slower than usual for the signal. This will turn the trace into a ribbon with clear top and bottom edges. This will also reveal if there is any lower frequency envelope modulation that you can't see by zooming in on the main sinus oscillation at 3 MHz for example.

TinselKoala

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Re: Slayer driven neon-producing DC via resistor ?.
« Reply #29 on: August 22, 2014, 01:46:23 PM »
"7) It takes non-linear behavior to rectify even weakly.  This is not a function of linear: resistance, capacitance, inductance, and conductance."

You can't find a more non-linear circuit element than a neon, unless it's a raw spark gap. Them thangs is whacky for certain. Once you get them good and lit up they are great, used as voltage regulators in all kinds of old kit, like plasma Zeners. But between the firing threshold and the cutoff voltage they are strange beasts indeed and if they are biased to just below the firing threshold all kinds of things can set them off.

Got LN2? Try immersing a running LED in some. Also try with the neon.   ;)