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Insulation?

Discussion in 'High Voltage' started by adalast, Mar 7, 2010.

  1. adalast

    adalast New Member

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    do you have any suggestions on good places to find those? i am checking with local computer repair shops for some dead monitors i can scrap parts out of (hopefully it's just the tube and not the flyback).

    will wrapping my own primary coil help to limit the problem with overvolting the flyback? i would think that it would have some effect on it since i am putting more insulation in the way which should make it able to handle more voltage. i guess i could buy a couple and just see. the guy who made the instructable told me to put a 100-200 watt light bulb in series with the flyback to act as a current governor. i am calling the computer repair shops now trying to find some flybacks, but no go for a few days on any of them so far.
     
  2. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    You are obviously just producing more voltage than the insulation can withstand and that is all there is to it.
    There is nothing that can be done other than reduce the voltage or find a different fly back transformer that is designed to run at the voltage and power levels you are working with.

    Check with your local TV repair places for parts. They would be the ones who could have used or surplus fly backs or HV multiplier bricks for the large screen CRT based TV's that run at much higher drive voltages.
     
  3. Hero999

    Hero999 Banned

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    Just to recap: I suggested reducing the number of turns on the primary because it will reduce secondary voltage, because the CFL driver will have a constant current output. The reduction in interwinding capacitance should also minimise the risk of arcing to the primary side.
     
  4. dave

    Dave New Member

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  5. adalast

    adalast New Member

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    ok... so what would my voltage output be? i still need at least 30kV coming out of it to be able to do the lifter. it won't function under 25kV and i want to make sure to have some margin of error on the pressure and temperature.
     
  6. Hero999

    Hero999 Banned

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    I didn't realise that.

    In that case you need a better flyback transformer or look into some other way of getting the voltage you require.

    The trouble is, the flyback will probably have a built-in rectifier so adding a voltage doubler is not an option.

    You could connect two flybacks in series, but they would certainly need to be kept a fair distance from each other or immersed in oil to prevent arcing.

    You could try a neon sign transformer or an ignition coil.

    You could also try adding a multiplier to the output of the CFL transformer but you'll need a huge number of stages to get 30kV so it really isn't feasible.
     
  7. adalast

    adalast New Member

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    any good sources of neon sign transformers? that was my original plan, but my dad had pitched his about 4 months before i got to him. i would imagine that doing flybacks in series would be even more of a headache than what i have now as far as them self destructing. this link was on another thread on this site asking about lifter power supplies (i found it in a google search just last night). it looks like they use a multiplier of some sort to step up the voltage. i can only assume that it is a CW multiplier from the description.

    i would love to be able to get a stable output of much higher than the 30kV floor that i'm looking for so i can do experiments with some of the designs that become possible with larger voltages, so the design does have some limitations. i would love to be able to get up to 100kV if possible, but i know that will require a fair bit of engineering and some hoil and toil. i did pick up a 28" tv and a 17" monitor today that i'm waiting on taking apart for a bit in an effort to try to just use the tv/monitor HV output to get the lifter off the ground. i have seen youtube videos where this method was used. so it should be possible. i am just a little scared to pull the HV line off of the top of the tv tube since i know that the bigger the tube the more capacitance it has and 17" and 28" is a huge differance when electricity is concerned. the tv screen doesn't work anymore, but i can hear the coils charge up when i turn it on, so something inside the tube must have died. should i just be able to disconnect the HV line on the TV without worrying about getting a shock as long as i'm holding onto the rubber cup around it? i tried the monitor, but it doesn't seem to want to stay on without a computer hooked up to it, so i will just get the flyback out of it later.

    how well do ignition coils work as far as sustained high voltage output and are the compatible with voltage multipliers? also, how much do they generally run at a junk yard?
     
  8. shortbus=

    shortbus= Well-Known Member

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  9. adalast

    adalast New Member

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    that looks like a good site shortbus. i will have to look it over in more detail once i get rid of my headache. would it be more stable to replace the flyback with an ignition coil in the power supply i'm using? somehow i don't think so since the voltage coming out of the driver circuit is already >1kv vs the 12 v of the circuits described in the literature on that site. i guess i could have my fiance call some places and see how much they cost (she works at an auto body and mechanical repair shop). maybe i can get them cheap and won't have to fight with the disposal of the monitor/tv remnants.

    on that note, what else can i look for on those boards that can be salvaged and used for some fun stuff. i've got 3 of them laying around now and i would like to salvage what i can off of them before pitching them.
     
  10. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Ignition coils and sign transformers are low frequency devices. The transformers are usually a center tapped system so at best you only get 7.5 KV AC from either output of a 15 KV transformer.
    Ignition coils dont take open circuit High voltage operation any better than an over driven fly back. They will suffer from internal insulation break downs just as fast as the small fly backs do.

    Your best bet is the larger fly backs from the old TV's. I have found many over the years that had no output rectifiers but relied totally on a bypass diodes on the input coil and the CRTs unwillingness to conduct in reverse to produce the HV DC that the CRTs used. Those type work well with voltage multiplier circuits.

    Years ago in high school I found a fly back out of a old 28 inch TV that I could push to the point of jumping a 3 inch arc without problems. Any wider gap than that and it would just turn the whole HV secondary into a purple fuzz donut from the corona discharge.

    For higher voltages you may need to consider designing an air core type transformer that works more like a Tesla coil Or a Vandergraph type static generator.
     
    Last edited: Mar 9, 2010
  11. adalast

    adalast New Member

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    i've considered a van der graaff generator for the lifter, but i've never heard of someone doing that and i'm not sure if it will work. i've thought about a tesla coil, but i was really hoping that i could use an off the shelf unit like i see everyone else doing on their power supplies. there are so many people out there who make these lifters... it can't be this complicated to generate the 20-30kv that is needed. youtube is just full of people with these damn things flying... it can't be so hard to get a generator that works. i've heard of people making ignition coils run at over 60kV. i see all of this in my research, but when i try to get it working... it just breaks down and fails. it's really quite discouraging, but i'm more resilient than that and i know i can get this stuff working. is it really this hard to make it all work without arcing and killing itself. i haven't come across anyone that has had this problem and actually brought it up. i've read on at least six sites about lifters and making them and such... but nobody ever mentions having this much trouble with a power supply blowing up. what am i doing wrong?
     

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