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Senior Member
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.
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/
Last edited by Draco; 11-30-2015 at 18:27.
Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu
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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,
Thank you agan for your help in these projects !
Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu
Senior Member
Sorry, that is my only gripe. No excuse. A limited amount of money... no problem, but limited effort...not acceptable.sadly i am a lazy dragon,
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.
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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
Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu
Senior Member
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.
Senior Member
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?
Last edited by Draco; 12-05-2015 at 20:05.
Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu
Senior Member
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
Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu
Senior Member
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.with a commercial xenon of 125mm long what would be the self conduction be at?
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?
Senior Member
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
Remember Remember The 8th of November, When No One Stood, but Kneel, In Surrender
In a popular government when the laws have ceased to be executed, as this can come only from the corruption of the republic, the state is already lost. Montesquieu
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