Flashlamp Video

I would think that would work, these type of NST are mid point grounded so it's basically a center taped transformer with the center tap at ground and due to there construction they self current limit, at least the transformer types, i dont have any experience with the switcher units that are now mandatory in new installations for neon.
I have 5 of these types of transformers and i can do a test with a variac if need, mine are made by fransformer are are a different mounting style from the one in the video that he made.

That said i would still not be comfortable with a that type of transformer and would want the floating pole to be covered over with a insulating cap. NST transformers generally are higher voltage but a 5kvac unit using the case min point ground and one side should be 2.5kvac. I have one NST that is 15kvac terminal to terminal and seems to be half the voltage from terminal to case.
i would not use an ignition transformer from a fuel oil furnace, NST where usually more reliable

but for what it's worth thats my 2 pennies worth

I don't condone this, but if you mount the mid-tap grounded NST 100% surrounded by a double later plastic box, Ie Plastic, Air gap, Plastic,
It becomes a floating transformer.. With the caveat that IF you do not properly insulate it, touching the case of the floating transformer is an instant, perhaps LETHAL, nasty shock...

I would not normally suggest this.. Hence the call for double insulation and other precautions..

Steve

I would avoid the complexity of the NST conversion. If it were me, I would get a MOT (and two MOT's in series if you are using 230V), pick a suitable ballet resistor in series with the input and then send the output to a voltage multiplier circuit. Microwave rectifiers and capacitors are just the right capacity for this set up. With a 20:1 step ratio for the 120 V MOTs, a 230 V source will give you 5,000V DC with a simple doubler, at as many A as your heart desires (and much more than it will withstand). Use a cheap variac as the limiting resistor and you have a very powerful capacitor charging circuit for very low cost and work load.

What is an MOT? Microwave oven transformer?

I think i would prefer a microwave transformer but they are not current limited and can deliver a lethal shock with out the capacitors but i think are more predictable then an NST
The NST on it's own is a hell of a painful shock but 30ma generally wont kill you until rectified and sent to the cap's they just put out too much voltage, say with my system, my caps are 2.5kvdc one side of the nst is 2.5kvac or 6kvac and rectified. one pole of my smallest NST comes out to 3,535 volts, so a slip of the variac and i would have a catastrophic accident. but i digress the breakdown tester i have can do the same thing, it can do just over 2,000ac and i am using a doubler so i can stay in a safe range on the supply

I guess this means i am mixed on this, treat the transformer as lethal, put it behind plexiglass, I have not had a fault of the internal ground on the NST and have always used them with my Tesla coils, the transformer was always out of reach when i displayed the coil

another option i guess would be a cheap switcher that you can get from ebay, there are a lot of options for less then 100 bucks,, they just take a long time to charge the caps. I even used a Dynamotor at one point in this experiment.

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Originally Posted by planters

I would avoid the complexity of the NST conversion. If it were me, I would get a MOT (and two MOT's in series if you are using 230V), pick a suitable ballet resistor in series with the input and then send the output to a voltage multiplier circuit. Microwave rectifiers and capacitors are just the right capacity for this set up. With a 20:1 step ratio for the 120 V MOTs, a 230 V source will give you 5,000V DC with a simple doubler, at as many A as your heart desires (and much more than it will withstand). Use a cheap variac as the limiting resistor and you have a very powerful capacitor charging circuit for very low cost and work load.

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This would probably be the route I would go if I were to set something like this up. I use MOTs for my tesla coil. They are very beefy. I have yet to burn one out.

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Originally Posted by Draco

What is an MOT?

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Microwave Oven Transformer

I used to use MOT's to literally blow stuff up and melt things, oddly up to now that's what i used my breakdown voltage tester for.

I had always been too nervous to use them for a Tesla coil, a NST has an inductive current limit built into them, a microwave transformer does not, drawing an arc from one can draw over 20 amps on the primary side, so some experiments ate fuses like candy and dimmed the lights in the room...fun times

You can use a very restrictive current limiting resistor on the MOT. You could limit the current to whatever value you want. The variac can be placed upstreem of this in order to limit the ultimate charge the caps can reach.

I had forgot about using a variac for current control and a bit embarrassing because i was building a system for a distribution transformer, one was to limit the current and the second variac to control the voltage, i dont know what they are called over seas but we call them Pole Pigs, the 300 pound transformer that takes 14,400 volts from the grid to a 240 volt center taped for the house, the one i have can have the secondaries put in parallel and use it backwards, 120 or 240 in and 14,400 volts of fun out at huge amounts of current, i need to find oil for mine and repair the case, same morons that destroyed 3 of my 160mfd caps badly damaged my pig as well, i have new bushings i got from a salvage yard, now it's just fear that slows my progress and besides it looks cool sitting in my laundry room, i had to make it's own cart with wheels, at the time i got it i wanted to build a coin crusher, pole pigs rarely come up for sale to the public, at-lest at a cheap cost.
back on topic I am using a 100k 50 watt resistor to bleed down my caps, i was wondering what values you use Planters for your cap ? am ok or under or over? I am thinking of using a high voltage relay to switch in more if needed as well

here is the latest version of my doubler , the two caps are 2mfd, 4kvdc the diodes are a fast recovery at 12,000 volts at 800ma if my data sheet was right and it can sustain around 200-300ma when fast charging the bank, ramp up with the dial, I doubt it would tolerate a full input with a discharged bank, and it's all made from stuff i had laying around the lair. front is inlet and upper side is the outlet, old meter is inlet current
Attachment 48801

Most rectifier diodes have a peak current rating that is 20-30 x the average rating and the rating you indicate is almost certainly an average rating. Don't worry about charging the cap bank with those.

Another name for a pole pig (there are probably others) is a line transformer. I will be using one of those. Like the MOTs they are very robust. The concept is to set up a working system with all the bits and components working together and then when the only limitation is say average power then move to a more powerful component to remedy that.

Your resistor seems a little off. If you intend to bring the caps to 4,000V then the bleed rate with that resistor will be 40mA. The peak dissipation will be 160W and depending on your duty cycle this resistor would get pretty hot. If the resistor was a switched dump resistor (I use both) then the resistor should be able to absorb an occasional load.

What are you going to do for a lamp?
Are you going to use a vacuum pump or a sealed commercial lamp?

I am going to use a commercial lamp that i have now to help me get a triggering system that reliably works then i will experiment with the home made lamps, i have two quartz tubes the exact size that you recommended to start from, I now have a drill press that has some of the features i need to use with brass, i still need a cutting insert and that may happen this week for that, i need to bolt the press vice down as well, i am hoping that will work, the cheapest metal lathe i have seen so far is about 550 dolor's, for a table top one and i cant afford that. I have a fried that works at a machine shop so if i butcher the brass i can have him make them.
I looked in my shed and found a 100k at 225 watts. i dont know if that's the current draw i want though. What values do you use? The 225 watt one is the highest value in ohms in a power resistor, all my other ones are 2.5 k and lower, and as my luck goes i accidentally knocked over a bin full of vacuum tubes, that's- a mess even though most survived
my vacuum pump should be ready for the task, it's vacuum "idiot lights" no longer function and Omega is useless for help but it will still get a deep enough vacuum to make "plasma in a jar" i don't remember what that is in Torr, the pump is a direct drive single stage omega fpuv91 i cant find anything on it. I have a dual stage one as well that was for HVAC I got it "kit form", it had a bad motor start cap and the moron took the vacuum section apart, so for a 10cm long lamp i am thinking the single stage will be fine, i still need valves and the tubing

What do you want the resistor for? If it is to bleed then 1Mohm is in the range. That will "waste" at most 15W and should make your caps safe quickly. If it is to dump then both your 100K resistors should be able to handle the occasional one time load.

Your shed seems to have a lot of clumsy folks wandering through it.
Your single stage should be fine if it is able to allow a plasma in a sealed container. If it is not enough then wire your caps into a doubler circuit for charging and discharge them in series for twice the potential through the lamp.

I would skip the lathe. Get some brass rod approximately the same OD as whatever lamp tube you will use. Mount it in your vise and drill a hole in its center, part way through. Drill a small hole parallel to this main hole, lateral to it and all the way through from one flat face of the brass cylinder (rod) to the other. Pick up a tungsten welding rod, The doped ones such as the 2% cerium rods work a little better. Use a Dremmel tool and cut the rod to whatever length you like(1-2inches is fine) and hammer it into the main hole until it bottoms out. If it is a loose fit then clamp the brass at its edge in a vise and crimp it a bit to grab the tungsten. Polish the brass so that any scratches in its outer surface run circumstantially and so that when you use the tube to seal it to the glass you will have few if any scratch-based micro leaks. Attach tubing to the outer ends of the rods for the pump on one end and the needle valve on the other and you are ready to go. No excuses.:p

If i am interpreting this correctly the the main hole does not go all the way through and just slightly smaller in diameter and the gas port would a smaller hole directly next to the main hole with the rod pressed in, but the gas port is at a right angle just before the arc face and the smaller hole then exit's out the back for connection to the gas and vacuum, this i think i can do
The brass got here last week, i could not find it local in the OD i needed so ebay saved the day, i have rod that is about 1 mm bigger then the ID of the quartz, I am going to need to order the tubing to hold the electrodes in place as i cant find that local as well.
I took my caps to 5,000 volts, i was not expecting to get to 5kv but the power supply puts out just enough past it's own rating, i found out that the unit was made to run on 100 volts ac, my nominal here is 118vac but it worked out well.
i am still unsure what i want to do for a trigger source, i figured out how to program the one timer that came with no info so i have reliable timing.

I remember the first time i connected a huge cap to a camera's flash unit, i was told i would get more flashes because of the added capacitance from a local tech, needless to say it exploded :eek:

I wanted to ask another question, for the dump load do you and it set up where if there is no voltage on the main relay so it stays connected until the command signla opens the relay allowing to use the cap or is it not that important because of the resistors that bleed down the cap's charge? basically the relay being normally closed when not in use


on a new note i can charge to 4kvdc in less then 1.5 seconds, the current whent off scale of my meter but it did do it

With bleeders in place you can forgo the dump resistor.
The gas port does not need the right angle. The tungsten will keep the discharge mostly near its end and away from the gas port.
Carefull...your caps will not live long at 25% above their rated voltage.

That makes it easier to make the electrode.

The 5,000 volts is the rated voltage and i am under by almost 50% in the doubler, I built the doubler for a rating of 8,000 volts. I am getting the parts from an old device that was used to seal plastic with rf energy, from a employer held auction and i got it for 2 bucks, there are more goodies inside, the main power transformer has a 4,000 and 8,000 volt output and a multi tapped primary to select the voltage in steps, i believe this the main plate voltage for the tube in the device, i had always wanted it inside to hold what i am doing now but that never happened, my main caps are too tall and i dont want to start making new holes in the thing yet, i did not do any unresolvable harm to it yet
The breakdown tester is what is slightly over voltage but it has no caps in the path, just the variac, power transformer and some odd ac doubler that has no ratings on it, just ac in and ac out at the same frequency i am guessing it's just an auto transformer and the third terminal is ground though the mounting bolts, it has an overload alarm on it as well, i tend to think the do not go over 1.5kvac was more for testing wire insulation then a warning of internal damage, like other crap i have i can't find any info online.
I cleaned the shed and almost burned it down, i tried starting my quad and it ignited rather then starting, that is a mess in the shed, i am ok and so is the @#$*quad, can't say the same about the floor

i have a question, i can find the tungsten but in two flavors , one set contains 2% thorium and then other set is 2% cerium, witch one should i pick or just use thorium for one and cerium for the other? i have the quartz for 2 lamps.

(Your shed seems to have a lot of clumsy folks wandering through it.) my shed developed a new simptiom, it likes to suddenly catch fire, the float valve was stuck open

So, I have been following this thread because it interesting. There has been talk about the transformers used to charge the caps. I don't want to de-rail the thread... But I removed this from a lab down the street today and figured its worth posting a pic in this thread. My neighbor's foot is in the pic for size reference.
Attachment 48857

It has two 120V primaries and a single 2400V secondary. Its rated at 50KVA!!!! So, after the hooking it up backwards and melting a few screwdrivers etc Im not sure what to do with it...

give it to me of course :devil:

what does it weigh ?

This also generates a real question on my line transformer, mine is 3kva and has an option for 7200 or 14,400 and was originally in an oil filled can, is it "safe" to use out of the oil? I know it helps with HV insulation and dissipates heat but would it beable to operate for short times with no oil? I would build a plexiglass box to go around it

I am slow to respond because PL is no longer notifying me of updates for some reason.

Thorium and cerium both work. Cut the thorium outside because the dust contains a small amount of radioactivity. Don't worry, these electrodes are used frequently today and the radioactive risk is EXTREMELY low, but if there is any risk it is in the dust.

3kva is very low for a line transformer. This is probably some kind of small tap to power equipment from line voltage. The specific voltages are the give away.

I would not operate it out of oil. The oil helps to cool the wingdings, but at this low power rating it is probably included for its insulating properties as well.

I have some experience with radioactive items, i even have some of the fused sand from the trinity site(took me some time to find it from a credible company, lot of you find online is fake) and i have a clock that will put thorium to shame when it comes to radioactivity lol, at lest for the welding rods, i am still trying to locate the rods.

I will work on repairing the case, the dent in it violated any safe clearance to the transformer. I may be wrong on the 3kva or the documentation i have is wrong,the calculator puts it closer to 5kva. The switch on the case connects to a switch to select the primary voltage and the secondary is 240 center tapped and whats nice is it's a dual secondary so i can parallel it for 120. with oil it weights 330 pounds, new copper secondary and the primary is made from aluminum.
finding the top bushings took the most time, the ceramic for the low voltage side was cracked as well but i think i can make and interconnect with bolts or just glue them. since the transformer is in a stable place i put the case to a low priority. i may even contact http://www.t-r.com/ they refurbished it and sold directly to me, they may have the secondary terminals i need and a seal for the lid.
the transformer as been out of the contaminated oil for over a year now, i have thought about making a bag to fit in it to draw vacuum on it to see if i can get any more gook out of it. any ideas? due to the cost of new oil i was wondering if there are any substitutes i could use for cleaning any possible water out, lol it at-lest smells like it should now

I know i face something near impossible with the dang pole pig but it did not fail while energized and ever since that damned fire i have never applied voltage to it since, oddly the windings are insulated with fabric that would soak in the oil, it's in rough shape but i believe i can fix it , water did damage spacers made from paper but other parts seem just fine, the dang thing had just been refurbished and PCB free oil, i still have the lab report for that.
i had gotten it for use in a Tesla coil that has yet to be built, using this to charge caps is some thing i had not considered till this thread got going, i just want to make sure this thing is clean before i put it in new oil due to the cost of the oil, it will still be ugly as sin but should function. I will be configuring it for 120, i do have a step up transformer but my variacs are 120 only

I found the Thoriated rods , i got them in 3.17mm size, thats the largest practical that i can work with, oddly i cant wait to get my Geiger counter on it to see how much above background they are, i have the view that is standard precaution of not inhaling dust that most radioactive things are over blown, our species as adapted to deal with the minimum radiation as long as it's not inhaled. i have always been fascinated with radioactive items and low level stuff is not the work of demons. humans forget the square inverse law for this stuff, so basically dont eat it or inhale the dust. if there is interest i can upload some pictures of my stuff, i was damn lucky to get Trinitite, it's restricted and only certain places have it but i find it so awesome that i have a direct connection to the USA's first atomic test. I have a thorium mantel that was used in the older gas fed camping lights and i have some uranium metal shavings as well , that is some strong stuff, i expected it ro be more soft, most of my stuff i got from united nuclear , i try to be an element collector in the works, i just we could plutonium, it's not currently.
The Square Inverse law means if you dubble your distance to the source your exposure is attenuated 4 times so you get .25% of the total exposure so the souce would need to be powerful,
I have a working turn of the last century geissler tube and i cant get my dad near it and the ironic thing is he has recived radiation treatments so he know's the level is not dangerous.
http://s124.photobucket.com/user/dra...4.jpg.html?o=0
when i can take pictures i will upload in a different thread. the golden hour clock i mentioned with a date pre to 1957 used radium and i had 3, now just one and the hands to the other two and with the beta window open and right on the tube they over range both of my meters of is a civil defense cdv-700 and the other is an arduino based kit i built from a kit, it;s in a nesting interlocking hobby cases i think i got at Walmart, i have a hole cut into the box so i can atlest get some beta sensitivity.

as i had mentioned before that i am autistic so my hobbies drift around like that, it can some times shift quick

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Sorry my English is very bad!

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Once again, let me repeat. Your English is quite good and better than my Deutsch and infinitely better than my French. I can understand you quite well, so you should be assured that your posts are appreciated.

Now, lets talk! The ablation regime begins around 30J/cm^3. We discussed this earlier on this forum. There is evidence of Si and O2 lines appearing in the spectrum at this energy level and the gas removed from these lamps contains SI and O2 and the quantity of this gas has been quantified. In fact, as the discharge energy increases the quantity of ablated material increases, becoming nearly proportional to the energy deposited.

An interesting fact is that the duration of the discharge is not well described as to its relationship to the onset of ablation. In the two papers that I refer to, the pulse durations were on the order of several usec, but this was not varied or studied.

I still do not understand the appearance of your flash lamp envelope. If the material is quartz or borosillicate and the surface is slowly ablating due to the discharge process then it should be clear. There may be small scratches due to ejected electrode material or a little of this electrode material itself, lying within the tube (I have seen both these phenomena), but not a blue haze.

For what it is worth, I am using a 100uF x 5,500V capacitor. This is one of the capacitors that make up the 4 capacitor bank in the laser you see in the background in the video. In that laser, with a system inductance of 1.050 uH, the 22,000V system has a discharge time of 10 usec, a laser pulse width of 4 usec at threshold and 9usec at high energy.

I have discovered a few interesting facts about these high energy lamps. They saturate! As you increase the energy to a given lamp, the output, both the total and the peak increase rapidly. When you reach approximately 20J/ cm^2 of internal surface area, the output will continue to increase, but only due to duration. The peak ceases to increase. No matter how fast the discharge, this 20J/cm^2 barrier remains. This is probably why the very highest energy dye lasers (to date:)) have succeeded with coaxial lamps with their high surface to volume ratio. Yet, if I remember correctly, because these lamps operate as a black body, placing a reflector on the outside does not increase the peak energies of these lasers. It acts to return energy to the plasma which re-radiates it and increases the output by increasing the duration of the pulse.

Despite its high UV transmittance, quartz tends to block radiation much below 200nm. At temperatures of 10's of K degrees substantial amounts of the short wavelength light is unable to leave the lamp, no matter what the design. Even the detector response and the atmosphere become limitations in the VUV region.

Fromm what understand is that UV below 200nm ionizes the air as well, the low end of the UVC my rock lights generate is said to only travel not even a foot before it's blocked by air, items that need the very short wavelengths needs to be in vacuum.
Now i wish i had a dye laser to try this with, if you sealed and pumped the air out of optical cavity if there would be a measurable difference in laser output.

VUV vacuum ultraviolet?

I just got outbid on 1/8th thick thorated tungsten rods so the search still goes on.
I wanted to start with 1/8 as i have the tooling for that in plenty and atlest online the rods are fairly cheap, ironically I enjoy TIG welding, i had an employer that would let me learn on stainless steel scrap they had laying around
in my younger days we would try to find stuff to put in thermite and got a kick out of the tungsten and another alloy used for jet engine parts where unaffected by the heat, this was before i knew the melting temp of these metals is much higher then thermite

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if you sealed and pumped the air out of optical cavity if there would be a measurable difference in laser output.

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No. The solvents don't transmit well either. Only pure water will get down to 200nm or so and the organics begin to cut out around 240nm. The best, methanol and ethanol cut out by about 220nm.

Pure tungsten works nearly as well, You're probably going to face more limitations due to your gas handling/vacuum system and quartz tube than the differences in the rods. You don't have to knock yourself out obtaining a rod.

is 1/8th over kill or ok? i normally would go metric but my tools are not.

china for the win on electrodes, i found a vendor that has them for about a buck each, and i can use them for a check source for my Geiger counters :D

The diameter needs to be related to the ID of the tube. Too small and the discharge is going to make a lot of contact with your bulk electrode and if that's brass then it will erode. I'm using 1/4" in a 13mm ID tube. This works well.

Ok cool, the id i have is 10mm so i can up it a bit more if i can find the rods that large

I amm thinking of putting my caps on this http://www.harborfreight.com/18-in-x...lly-61899.html
make themm more mobile and more isolation from the floor, i can they make a plexie box a lot easier to then

my polepig transformer is one one i built from 2x4 and industrial casters

How heavy are your capacitors? The uneven surface of the dolly will probably require you to put a piece of plastic between it and the capacitors. You might consider what you will do with these capacitors and build an enclosure that can support or house the other components such as rectifiers, transformers pressure gauges etc.

from my measurements the bottom flange on each capacitor will be on the carpeted section so almost over the wheels, i can then bolt the caps to the dolly. a cart will come about in the future, i have a cart in the back yard that i plan on using but it's just an aluminum skeleton, they originally supported the full weight of a heart bypass machine during assembly but that has since been discontinued so they have very nice wheels i just need to make the shelves
but right now the power supply will be on a table and the caps under the table with that set up i can glue or use 3m VHB tape to hold the plexi to the caps until i can make something better.

just a running thought for now

I dug out another cart but the caps would need to be on the top and i would lose my tool cart

I made another small change (I hope for the better) in my flash lamps yesterday. After hundreds of high energy discharges there is a build up of deposits very close to the electrodes and most of it, outboard from where the discharge should have terminated. There is some degradation of the silicone "O" rings and I suspect they are the source. So, I took a short length of indium wire, .5mm thick and placed one wrap and twisted it off right on top of the new "O" rings. This is too thick to fall into the gap between the electrode and the glass, but so thin that it is nearly as flexible as the silicone. Hopefully this will protect the organic from the discharge energy that sneaks around the electrode.

i think i forgot to ask this long ago but what are you using to trigger the HV pulse to fire the lamp? "other then smurfs being thrown in to circuit :)

I dont have a dedicated system yet to do this on an output pulse from the master clock

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what are you using to trigger the HV pulse to fire the lamp?

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Happy thoughts and fairy dust. The details of the fairy dust are kinda...

Actually, you have a lot of choices. I use an automotive trigger transformer for the step up and line voltage (230) with a basic doubler circuit to charge some large snubber capacitors (10-100uF) to approx 630V. You can use a cheap timer circuit (eBay) or a mechanical, momentary switch to then switch a mechanical relay or thyrister to in turn dump the snubbers to the coil. Place the ground of the coil in contact with the ground of the discharge capacitor and the high voltage lead around the discharge tube

very cool, i have a few spare spark coils from cars (one even from a model t, and an actual REO Speed wagon from the 1920's . )
I did obtain 2 different interval timers from ebay, i had to teach my self how to program it due to the lac of into, I was going to use a higher power transistor to trigger the coil but never built it
it would have been for a gas operated tennis ball cannon that worked beyond my expectations but i cant find it's original ignition coil.
The only concern i had with thyristor is they conduct untill the cap is discharged, but my thinking is i have two timers, i can sync one to the other so i can interupt the cap's charging supply while triggering a flash, my concern is that the charging supply may hold the thyristor in an on state but a smaller charger should still go below the threshold of the thyristor.
oddly and off subject i was going to make an electronic Que for fireworks, the it would have charged caps to about 200 volts and then dump that via a thyristor into the iginther of the firework, i wanted to hit the thing hard for reliability

I did not think the spark coil would survive a hit from that much voltage, i did find mine today, the type with out any internal electronics, I am thinking that the way you are hitting a 12 volt device with that much input voltage that the output must be close to or exceed 100kv >:)

Typical coil step up ratios are 100:1. The MSD coil I am using has a step up of 70:1. So, with some inefficiency, I expect 40KV. In an electronic ignition, the coil is hit with several hundred volts.

ok, i dont have anything that new, the coils i have where fired from 12 volts and can get a generous amount of "spark" if you will, The vehicles they came from did not have a CDI or any other means of driving it with a greater voltage, just points that switched 12 volts with a snubber cap.

drivers i have built in the past ran from a 555 timer and used a power transistor as the switch, the updated one i want to build has a FET instead.

I honestly have not come across a coil pack or ignition coil driven by such a high voltage, the ones on my car have a 12 volt VCC and a trigger signal, I can scan in the service manual for my car to show that's it's low voltage. i have yet had the honor of working on a coil over plug types yet or any of MSD's stuff I guess i need to spend more time at the track and not on stock systems.

what model coil if you don't mind me asking?

http://www.msdignition.com/Products/...Ignitions.aspx

Very cool, thanks for the link, that will be on my Christmas list.

I built the 555 driver to night, not as impressive but it was scrap, at lest the coil was, i fear it may lack the "punch" i might need but i do get about a cm or so of dc goodness. and the way the FET is connected i can up the supply voltage only to the coil, i did not mount the heat sink yet as the FET i used is not the one i wanted, an IRF740, i think i want to use an IRF640, less voltage but 18 amps instead of 10.
Attachment 48965

I found plans for one powered from the mains but with no isolation, and well, see for your self http://www.instructables.com/id/Vari...-power-supply/

I am still going to try and find that MSD coil you use Planters, they are expensive here so i will be looking for used if i can, new they are about 180-220 bucks, i have found some local but not the type that use the higher input voltage, I also have what i think is from a stun gun, they run on 3-4 volts and output about 40kvdc. The problem is they over heat rather quickly so i am thinking of trying to put one in oil
https://www.sparkfun.com/products/retired/11218
I have 5 of these scattered about my lair but out of the original order i had 2 that where defective from the start and sparkfun replaced them, these suck current like it's going out of style and the arc is very loud, well over 100 db. I am hoping to pick your mind a bit over these, i rate them as a hazard, not deadly but they need to be respected, they are almost are as loud as the spark gap on my Tesla Coil and will reliably trigger smaller flash lamps, I don't know why i just thought of using them for this project until now but i think they will work to trigger the larger lamps and if they don't i would be really surprised. I am going to try a .5 second pulse to start but it may take less and best of all they are cheap, i just need a high current low voltage to turn it on, the turn on delay may be too slow for a laser but for these i think it will work.
I also came up with a compromise for a dolly for the caps to sit on until i put them in a cart, it's a plastic wheeled base that is the right size for the caps and at 15 bucks is a steal and i can use it for many other things.
I have aluminum bar stock for the bus bars on the caps and i found some older fiber glass type (50's-1960's) boards that i can use for spacers, i have seen that stuff in older high voltage equipment and is thick enough to stand up to 5 kv and is cheaper then plexiglass.
Please correct me if i am in error but i believe the trigger is connected to the anode side of the lamp with respect to ground, it will be in it's own box for safety as well, now i just need transformer oil, i made the mistake many years ago and used cooking oil in my Tesla project back in the 1990's, that was a mess when the oil spoiled and got really nasty.
but this brings a new problem, i have no supplier for transformer oil, would medical grade mineral oil work as a sub for the transformer oil? I just need a means of trying to remove the heat from the trigger coil, the device it's self is potted in epoxy. I may attempt to flash a commercial lamp this weekend, i am a borderline hoarder and live in a mobile home so space is limited, i still need to clean off my bench to correctly alighn that 473 nm laser you are helping me with, sadly i am a lazy dragon, :cool:

Thank you agan for your help in these projects !

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sadly i am a lazy dragon,

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Sorry, that is my only gripe. No excuse. A limited amount of money... no problem, but limited effort...not acceptable.

Your trigger will likely work because a low pressure lamp can be set to self trigger at JUST ABOVE the charge voltage. It requires very little additional ionization to pulse. I question a heat issue with your trigger. How frequently do you anticipate you will pulse your lamp? Normally, it will be your capacitor charging circuit or lamp heating that will limit your system. Placing an already potted device in oil to keep it cool will be of limited effectiveness. The epoxy will prevent the heat from being efficiently transferred to the oil.

The trigger ground and the lamp ground are connected. The trigger anode is wrapped around the tube and is otherwise connected to nothing. It hangs loose and is not in electrical contact with anything. The high voltage (electron deficient) anode is capacitively coupled through the low pressure gas vs the ground. The high potential field causes ionization of this gas which then provides the carriers to allow the capacitor to discharge through this less insulating gas.

Thank you for the info, i think my planned duty cycle will be once every 5-10 seconds so yeah heating should not be a problem, the car coil driver i made may also work for this, i did not know the trigger voltage is low enough so i will use that one to start, i had been thinking and i believe the other device i linked does not like an open circuit but i could be wrong.
I found the way you tie off the trigger line is the same i have seen on commercial lamps, i need more practice at it lol.

I am using aluminum bar stock to connect the caps to each other, i literally found the lost aluminum bar in my yard, it seems more then thick enough to handle the current

The trigger tying will be much harder/easier depending on the wire you use. There is no limit on thinness; the current is minuscule. I've used aluminum wire and this works well. The Ni-chrome works even better. Do not use stranded wire, the wire needs to retain a bend. And, if it is very thin it will be possible to nail the position of each loop as you tighten it down. My approach may be a little compulsive. If you just run a couple of wraps around the middle of the tube and the pressure is adjusted to just hold off the capacitor then it will trigger reliably.

The capacitor interconnects can be very thin. I link up to 5,500J at 15kA through 4cm wide x 1/2mm thick copper straps with no problems.

Excellent!
I now have a working system! For testing i am using a commercial xenon lamp with an arc length of 125mm.
I have Ni-chrome wire as well and i need practice with it though.

with a commercial xenon of 125mm long what would be the self conduction be at? I don't have enough energy to blow up this lamp but was just wondering?

quick question, i have read that these type of caps can build a charge when unconnected, does this have some fact to it? I usually short them in storage just to be on the safe side and the bleed resistor would do the same thing but is this true? I try to always error on the safe side but i have always wondered if this happens? I am tingling with excitement that i now have a working system!
I was also wondering what the thin (about maby the thickness of 10 sheets of paper but still can with stand 5kvdc) flexible plexiglass is called? i want to make a spacer in the middle of the cap bank to keep the cases isolated, i can't find a reasonably priced full sized sheet locally and it's not the vinyl i can find at the craft shop, i used most of it when i made the first version of the voltage blubber, what i like is i can cut it with out a scribe and is cheaper then what i can get at the hardware store but i can't remember where i got it from, i usually use the stuff for protecting the top cabinet of my antique tv's and radios, i only need it at this time as a spacer between the caps, the outer case will be thinker that i can get locally. The reason i want the the cases isolated is i heard a static discharge when charging, since these have some case damage i want to keep them floating

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with a commercial xenon of 125mm long what would be the self conduction be at?

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My guess would be around 1000V. This guess is so dependent on the fill pressure (150 -450 torr) and the condition of the electrodes that It could be off by a factor of two. When I first got into this, it was the low self breakdown in my commercial lamps that lead me to look into the low pressure lamps. You see, if you want a fast breakdown you can only lower the inductance so much and the lamp impedance dominates anyway. So, to get high energy you have to go to higher voltage than the lamp alone will hold off. You can add series spark gaps (been there) or a thyratron, but these also mean more inductance and cost. The lamp as load and as the switch is elegant. I have moved from external triggering to an interesting "injection" triggering that requires at least two lamps in series. But, once again, if you want to go to high energy then go to low pressure lamps.

Separating your capacitors with a flat sheet of something is a good idea. Remember that the sheet only blocks discharge away from its edges. The edges of the sheet, unless they are hermetically bonded to the case, have to extend far enough beyond the edges of the capacitors to make the air pathway around them too long to break down. Despite what I have heard, dry plywood works well. Most plastics will hold off at least 200-300V/mil. So, even 1 mm (40 mil) will hold off 8000V in addition to any added air gap between the capacitors. Plywood will probably hold off less/mil, but 1/4" (250 mil) is very cheap. Test it with your CN trigger. Will 40kV penetrate a 1/2" of plywood?

cool, i did test the commercial lamp to 1,000 volts just not past that point

I my experience using plywood has some variance depending on humidity, dry 1/2 inch ply wood should hold off 40kvdc but only when bone dry as you stated. i used to use the stuff for a lot of high voltage projects but at the higher voltages i got unpredictable performance and can get leakage currents at the higher voltages that can lead to an unsafe condition. Humidity here can run high at times and that is why i dont like wood for this.
In the past to keep costs down i tried a few different materials and found wood to be unreliable. I still find my self saving glass from copy machines and flat bed scanners as it tends to be tempered and worked well. I did find just recently fiberglass that was made for high voltage projects I just can't get it in big enough sheets, right now that is what i am using to keep my ground wires off the case of the cap bank