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woelen
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Glow in near vacuum gas ampoules
I purchased a set of gas ampoules: http://www.ebay.nl/itm/261808224080?_trksid=p2060353.m2749.l...
I want to use them for my element collection. They have a nice size and I intend to put them in special vials with a conductor at both ends, to which
I can apply a high frequency high voltage.
I did tests with these ampoules and it is fairly easy to make them glow. What I see though is that I do not get nice pure colors when I make them
glow.
The neon tube gives bright orange light, but there also are places where it produces pale blue light.
The other tubes have similar issues, but much stronger. E.g. the nitrogen tube gives a pink/purple light with grey/white spots and pale blue spots at
other places. The glow does not look as nice and colorful as on the picture on eBay.
What do I need to do in order to get a nice even glow in these tubes with constant colors?
I had the impression that any high frequency HV AC source of sufficient voltage would do the job, but apparently this is not the case. I tried the ZVS
driver I made, but it is too powerful. I get arcs in these ampoules and I hear a strong hissing noise! I also have a small AC high frequency high
voltage generator (according to seller: 2200 Vss output when input is 12 volts) with a max power output of a few Watts. This device, however, only is
capable of letting the neon tube and helium tube glow.
Any idea of what kind of device I need for making these ampoules glow nicely? If you know of a (not too complicated) schematic which I can solder
together, then that also would be very helpful.
[Edited on 22-2-16 by woelen]
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j_sum1
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Glad you asked this woelen. I have a similar issue. I have ampoules of Kr and Ne and will in time get (or make) others.
I am awaiting arrival of one of these to make them glow. I will let you know how I get on.
(I wwas considering making my own power supply but figured that I would easily spend as much on bits and waste a lot of time.)
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woelen
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Making these ampoules yourself is not easy at all. You have to work at very low pressure and you need to preheat the ampoules in order to be sure that
after sealing and drawing vacuum you do not have the issue of the glass gassing out into the vacuum. If e.g. you fill such a thing with 99.99% Xe and
the ampoule gases out some N2, O2 and H2O, then your ampoule is spoiled and does not show the pure Xe-spectrum anymore when it is made to glow.
That power supply you show looks strange to me. I only see one electrical pole (the sphere). I'm quite sure that you can get a neon bulb glowing with
such a thing (neon is excited easily) and a helium bulb may be borderline. I hope that you can get the krypton tube to glow with this device. To my
experience, I need a much higher field strength for all gases, other than Ne and He, and for the others I need two poles, connected to the glass
ampoule. I did tests with Al-foil, wrapped a few mm around the tips of the ampoules, with a wire sticking into the Al-foil for good contact. I will
make special vials, with foam and Al-foil at both sides, wires sticking in this and then clamped between bottom and top, in such a way that the
ampoule can be seen nicely. You also need high frequency AC, the glass does not conduct DC (if it does, it is punctured, due to arcing).
Maybe IrC can jump in, he has a lot of knowledge and experience with HV-electronics, much more than I have.
[Edited on 22-2-16 by woelen]
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IrC
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I had a friend in Phoenix back in the 80's that spent much time in his home lab building gas lasers and I think one of the solutions he devised
applies. After getting his vacuum down to under 1 micron he would gently heat the glass tube and tap on it end to end with a plastic tool he created,
he used the plastic handle of a small Xcelite screwdriver as the hammer and a fiberglass rod for handle. He only went to this extra bother for his
HeNe lasers, not wanting any gas molecules to poison the laser. I never tried building a HeNe laser as in my opinion it is the hardest gas laser to
get working well, if at all. But I think the problem of glass holding onto gas impurities applies in your case the same as it did for him. He said the
holding the glass under high vacuum, hot combined with intermittent tapping was a mandatory step. To me it seemed the real trouble was all about
getting the optical cavity aligned. This I know from spending long hours trying to get them working again after one was misaligned. The people at
Meredith Instruments were friends so I had a decent supply of next to zero cost HeNe lasers to experiment with. Anyway as to your impurity issue I
think you should try the heating/tapping under high vacuum to your ampoules before filling them. The mini Tesla coil idea of Jsum1 sounds interesting.
I would think assuming the output is high enough it would work. A better idea using your end contacts would be build your own adjustable flyback
driver. One where you could vary the voltage as well as frequency. Say from 15 to 50 KHZ since depending upon numerous factors you would see modes in
the tube and a nice uniform glow is what you desire. The color impurities in my mind can only be contamination, no doubt you can do a better job than
the tubes you bought off eBay. Forgot to mention he also repeated the glass cleaning steps by filling with the gas to be used, then pumping back down,
repeating the heating/tapping steps before final filling.
"Science is the belief in the ignorance of the experts" Richard Feynman
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j_sum1
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Interesting IrC. What exactly does the tapping achieve?
Making the ampoules is probably a project for much further down the track. I have more than enough projects right now. It might be that I short-cut
and just buy what I want.
As far as power supplies go, I have little experience with building my own electronic devices and so picked something that would at least give me a
starting point. My main concern with what I have chosen is that it lacks power. But I think that having a play with a small one is a sensible
precursor to building something larger. I have seen some YT vids. Some of those sparky devices look positively frightening.
I also have a CRT to disassemble and retrieve the flyback. I am probably going to need a tutorial to follow so that I don't do something stupid.
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woelen
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@IrC: I also am not in the process of making my own ampoules, but I could make my own driver with adjustable voltage and frequency. For variable
voltage I could use a variable voltage power supply (with ZVS driver you have output more or less proportional to power supply voltage, isn't it?).
Variable frequency sounds somewhat more difficult for me. That would require a variable high voltage capacitor or some adaptive inductor. Do you have
schematics of low power (fairly safe) variable voltage variable frequency power supplies?
@j_sum1: If you start doing high voltage things, know what you are doing. A mistake with high voltage can easily be fatal. To my opinion, HV is more
dangerous than nearly all home chemistry. A single touch at the wrong place can kill you. I never feel comfortable when working with HV, e.g. working
with the ZVS-driver I made always makes me somewhat scary that I accidently touch something which I should not touch. For this reason I want a low
power device for my gas ampoules (I think that a few hundreds of mW is enough for making the gas glow).
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j_sum1
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Ok. So 1 Watt might be enough.
Good to know.
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woelen
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Yes, glowing a small cm-sized gas ampoule only takes a small power. What is more important is field strength and having sufficiently high frequency.
The glass of the ampoule works as isolator, and hence DC and very low frequency AC cannot pass through the glass. For high frequencies, however, the
glass allows a current to flow, positive charge builds up on one side of the glass and negative charge builds up on the other side of the glass (it
works like a capacitor) and during the AC-cycle the charge buildup, on each side of the glass, alternates. The net effect is an alternating current on
each side of the glass, while inside the glass there is no current. The higher the frequency (at least up to several 100 kHz, above that other effects
may kick in), the less the glass is a barrier for the current. The standard "high frequency" high voltage power supplies, like your plasma globe, and
my ZVS driver, operate at something in the tens of kHz, maybe 20 kHz, but it can also be 10 kHz, or 40 kHz, but this is the order of magnitude for the
frequency.
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IrC
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I assume he was creating vibrations in the glass walls that he thought would help impart motion to anything loosely bound to them but that is just my
guess. I was relating what I watched him do while hanging out experimenting with lasers he built. If there is scientific validity to the idea I think
I would use ultrasonics.
http://uzzors2k.4hv.org/index.php?page=flybacktransformerdri...
I cannot think of anything simpler or cheaper than a 555 flyback driver where a pot was used to adjust frequency. The change I would make to the
examples in the link is to feed the flyback primary with an adjustable DC voltage. This would allow the power level to be adjusted. A ZVS circuit is
not a good idea in this application for multiple reasons. The result would be dangerous and difficult to adjust. Better to have a supply that could
bite but not actually hurt you.
I drew up a quick circuit and scanned it to give you an idea of what I was thinking on the flyback driver. Cheap, low power and pretty safe. The fet
can be what you have handy if its ratings are adequate. I did not do a lot of math on the circuit so no doubt there is room for improvement. At low
power levels the snubber may not be needed although many people lose fets with these circuits by not having a snubber circuit. I did not do any
calculations here either just added what I have used before. The PDF is a good read on the subject if you wish to improve the protection for the
mosfet.
Attachment: AN-4147.pdf (152kB)
This file has been downloaded 472 times
"Ok. So 1 Watt might be enough."
Actually with efficient power transfer I think one or two tenths of a watt would light something the size of these ampoules.
Just realized I forgot to label the regulator, should be along the lines of a 2N3055 or TIP3055 and should have some sort of heat sinking.
[Edited on 2-22-2016 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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woelen
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I have a working ZVS circuit lying here (based on the IRFP264 transistors you suggested me to use one and a half year ago). If I put a 20 kV/ 10 MOhm
resistor in series with the output of the transformer, what would you expect with the gas tubes? Would it be "safe"? In such a setup I can use the ZVS
driver as is for other more powerful experiments, and for lighting my bulbs. By adjusting the input voltage between 12 V and 18 V I can adjust the
output voltage, while staying well inside the range allowable for the ZVS driver. What is your opinion on that?
I read quite a lot of negative comments on the 555-drivers. They seem to be unreliable and easily break down if I am to believe diverse comments on
high voltage forums. They need very good cooling and the 555 can easily be blown out by capacitive coupling between the high voltage on the flyback
transformer primary side and the gate of the MOSFET. Is this really true? I can imagine that adding a zener diode can protect against this effect.
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IrC
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Too many unknowns to answer your ZVS/high ohm resistor question but I firmly believe for what you are doing here it is overkill, too powerful, and
unneeded danger for a project requiring such low energy input. As to would it work, obviously so well it could melt the tube if pushed but control
over parameters would be limited and harder to implement. Certainly not as convenient as dialing two pots to the right setting for each type tube
desired.
No doubt the many 555 complaints stem from poorly skilled in the art experimenters. I would bet none of them even considered snubber circuits for the
flyback and this would have greatly reduced bad transients hitting both the fet and the 555. Trying to reach high drive levels and thus severe
inductive kickback which were better suited for a ZVS or other power circuit. Yes you could blow the fet or 555 if you crank the circuit I posted way
up but the point is at the low energy required for this project the circuit shown is cheap, safe, reliable. If you study the link I gave the 2nd 555
circuit used a complementary pair of 2N3904-06 transistors to help isolate the 555. You could take that snippet out and add it to the circuit I drew,
or use their circuit and just rob the adjustable DC source to the flyback primary in my circuit. I have used circuits similar to the one I drew today
trouble free for years to power gas lamps larger than your ampoules without blowing things but as I said I was not going for high power. For that I
would use something like the ZVS unless adjustable frequency was also desired. If so I would design a circuit around something like the TL494. However
for your needs in this thread I fail to see the need for high power.
I should add I assume your ZVS question is due to you already having it and the high value resistor on hand and want to try it out. Do so but start
low on voltage, keep in mind below 10 volts that eBay ZVS board (or the similar circuit we have been building and using in the ZVS thread) may not
start reliably resulting in overheating fets so pay attention to input current draw (and lack of output high voltage). Not knowing the flyback voltage
nor the gas lamp characteristics I am not sure how to answer your resistor question. If I had to pull numbers out of a hat I would guess 80 volts more
or less, 0.3 to 2 ma, Considering a gas tube of relatively small size with terminals, as with a Neon lamp brightly lit (no radioactive source inside
the lamp). Other gasses no doubt will vary widely and of course your tubes contain more gas than my Neon lamp example. Also obviously things will vary
with no connection through the glass, as well differences exist with the mini Tesla coil approach. You will have to experiment to find the right
values for each tube. Using the circuit I drew you can merely start at the bottom on the voltage adjust with frequency set at say 17 KHZ, slowly
bringing voltage up to where the tube lights properly. The flyback is likely going to have peak efficiency around 15 to 20 KHZ. Next step
experimenting with frequency and voltage adjustments to get a uniform glow. Make a scale for both pots and record the settings for each type gas tube.
Possibly you may find a single frequency which works well for all tubes and can replace that control with fixed values leaving you with a single
voltage adjust control with a best setting for each type gas you could record. That way when you wish to try each different gas you can preset the
level for it. I imagine variations in how you make each ampoule would also affect the setting. I was trying to keep the duty cycle near 50 percent but
this may not be the best value for what its worth.
[Edited on 2-23-2016 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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woelen
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Thanks for your clear answer. I indeed asked my question on using the ZVS driver, because I already have it and I have a big resistor 10 MOhm / 20 kV
(its almost 10 cm long!).
You convinced me, however, that building the simple 555 circuit at the top of your link is the best option. I will not use the ZVS circuit for these
lamps, I value my life and I also do not want to destroy these beautiful ampoules.
Indeed, all the horror stories about blown MOSFETs and even exploding 555 chips are from people who want to squeeze maximum power from the little
circuit.
I will build the first 555 circuit from your link and I will do some research on snubbers in order to make it even more reliable. I still have three
IRFP264s left over from my ZVS project, so I will put one of them to good use in that simple 555 circuit.
Thanks again for your valuable input. If I have results, then I certainly will post them here.
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j_sum1
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Quote: Originally posted by woelen  | | That power supply you show looks strange to me. I only see one electrical pole (the sphere). I'm quite sure that you can get a neon bulb glowing with
such a thing (neon is excited easily) and a helium bulb may be borderline. I hope that you can get the krypton tube to glow with this device. To my
experience, I need a much higher field strength for all gases, other than Ne and He, and for the others I need two poles, connected to the glass
ampoule. [Edited on 22-2-16 by woelen] |
Device arrived. It gets little neon bulbs to glow. Ditto a little argon(?) bulb that came with it. It lights up compact fluorescents rather well
which is quite impressive.
It didn't do anything visible with the gas ampoules I have. I guess I am back looking for another solution.
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woelen
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Actually what you describe is what I expected. From a small USB-device I do not expect sufficient field strength to get the ampoules glowing. The main
issue is that the glass of the ampoules is a strong barrier. You need a flyback circuit like IrC posted, with some snubber circuit added to assure
that the transistor is not destroyed easily.
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careysub
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I think the advice about being very cautious working with HV is good, and indeed I would much prefer to use ready-made units, like neon-sign
transformer or a sufficiently powerful Tesla coil.
In the Tesla coil category vacuum tester probes look interesting, they produce up to 50 KV at 500 KHZ, 40 watts and are available from $150 (used) to
$250 (new). I might get one to try.
It appears that modern NSTs have an output frequency in the low 10s of kilohertz range, though not all of them specify an output frequency I assume
all modern switching based ones have similar output frequencies.
This listing:
http://www.ebay.com/itm/Complete-Set-of-noble-gases-sealed-i...
is interesting, since it shows the ampoules he provides glowing with a 2 KV NST, although he asserts that his ampoules are specially made to glow.
NSTs with output voltages of up to 12 KV are easily found on eBay and elsewhere.
Since NSTs are relatively inexpensive and would be straightforward to wire up a display, using suitable high voltage wiring obviously, I am
considering experimenting with using one to illuminate gas ampoules off of eBay, there are some quite inexpensive ones.
Any advice about what voltage I should try and any other safety advice?
The 2 KV seemed low to me, I was considering trying 9 KV. There are also "self adjusting" transformers with outputs listed as (for example) 2 KV - 12
KV. Do they vary the voltage based on current drawn?
[Edited on 6-6-2016 by careysub]
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Heavy Walter
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Fellows
There are two aspects about those ampoules.
Neat colors are related mostly with gas purity. As woelen and IrC stated, ampoules need to be well evacuated, with degassing procedures and filled
with spectroscopic quality gases.
Glow discharge for those electrodeless ampoules depends on HV and HF and pressure filling. I doubt you will be able to ignite them with a NST.
Vintage "violet" electric massage/therapy devices are a good power source for igniting low pressure ampoules.
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careysub
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| Quote: Originally posted by Heavy Walter | ...
Glow discharge for those electrodeless ampoules depends on HV and HF and pressure filling. I doubt you will be able to ignite them with a NST.
Vintage "violet" electric massage/therapy devices are a good power source for igniting low pressure ampoules.
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The properties of the "violet ray" devices (high voltage, high frequency, low current) sound like the operating properties of Tesla coils. Sounds like
those Tesla coil vacuum testers are the best bet.
I guess I believe the "the-element-shop" guy on eBay when he states that his gas tubes are specially prepared to work with an NST (especially a low
voltage like 2 KV).
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woelen
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Interesting link, but only for people
outside of the EU  This seller does not sell anything to EU-countries, although he
himself is located in the EU.
I purchased one of these a few months ago, besides the small ones I already had purchased earlier:
http://www.ebay.nl/itm/Complete-Set-of-noble-gases-sealed-in...
http://www.ebay.nl/itm/Complete-Set-of-Noble-Gases-Sealed-in...
They are twice as big as the ones from the other link, but they are MUCH harder to ignite. The glass is thick. This makes the ampoules robust and
good-looking, but the downside is that making the glass glow requires much higher voltage. I only managed to light the Ar, Kr and Xe tubes with my
ZVS-driver at 20 volts input, which probably is well over 10 kV output. The Ne-tube and He-tube are easier to light, but still require the use of my
high power ZVS-driver.
The tubes do not take much power from the ZVS-driver, they only require high voltage, not much power.
[Edited on 6-6-16 by woelen]
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careysub
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| Quote: Originally posted by woelen | Interesting link, but only for people
outside of the EU This seller does not sell anything to EU-countries, although he
himself is located in the EU.
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There are ways around this. EU people can U2U me if interested.
[Edited on 6-6-2016 by careysub]
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careysub
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| Quote: Originally posted by woelen |
...
I purchased one of these a few months ago, besides the small ones I already had purchased earlier:
http://www.ebay.nl/itm/Complete-Set-of-noble-gases-sealed-in...
http://www.ebay.nl/itm/Complete-Set-of-Noble-Gases-Sealed-in...
They are twice as big as the ones from the other link, but they are MUCH harder to ignite. The glass is thick. This makes the ampoules robust and
good-looking, but the downside is that making the glass glow requires much higher voltage. I only managed to light the Ar, Kr and Xe tubes with my
ZVS-driver at 20 volts input, which probably is well over 10 kV output. The Ne-tube and He-tube are easier to light, but still require the use of my
high power ZVS-driver.
The tubes do not take much power from the ZVS-driver, they only require high voltage, not much power.
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Looking at the image of the argon tube here:
http://www.ebay.com/itm/Argon-gas-ampoule-purity-99-999-elem...
It looks to me like they are lighting it with a Tesla coil, notice the single electrode and the spark current jumping to the tube.
I will procure one along with some Chinese gas tubes and run some tests. Stay tuned.
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woelen
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I can recommend this yaolihong2013 seller. She sells good materials and when something is wrong (I once had an ampoule with 2 grams of Li from her,
which had a small crack), then you get a replacement without any hassle.
She sells many other interesting things. Most noticeably, 25 grams of very pure and shiny lithium metal for a very good price, and other element
samples in ampoules.
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careysub
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I went with oneworldonedream who I have done business with before. It looks like the same product.
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j_sum1
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I have nearly a full set of these that I have bought one at a time. (I don't have Xe yet.) I have not yet got a power source that works.
For something that looks like an empty glass tube they actually look quite nice.
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woelen
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I now found a circuit, based on a simple astable oscillator and using TIP2955 and TIP3055 as driver transistors:
http://tmms.co.jp/EFD/Lab_&_experiments/Corona_Lab/Power...
I will use BDX53 and BDX54 for these, I just ordered two sets of these. This circuit allows limitation of current to tens of uA.
I will replace the astable oscillator with a NE555 circuit, the driver part will use BDX53/54. I have a good flyback transformer lying around, which
only has a secondary. I wind my own primary.
This should be the final answer to my quest. Relatively safe, low power, and robust.
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careysub
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I see quite a number of new-old stock TV fly-back transformers on eBay. There are no specs on any of them.
Are they good choices for a project like this?
[Edited on 9-6-2016 by careysub]
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