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Thread: Tingle from homemade projectors

  1. #11
    Join Date
    Dec 2007
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    NorCal / Western Caribbean
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    The generator is probably 3 miles away. There are all osrts of transformer things along the street/road. I know we have three phase on the property. At one point we had one phase running at 210V another at 110V and another at 70V. Its pretty screwed up. Some many things get damaged here and the power company doesn't give a shit.

    Quote Originally Posted by steve-o View Post
    How many miles away is that generator? Ground potentials can change. Do you have experience with high voltage electrical wiring? It can be fatal if you don't know exactly what you are doing.

  2. #12
    Join Date
    Jul 2010
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    Brazil
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    Live - Neutral 128.2V OK
    Live - Earth 11.5V Should be close to 0V, yours is definitely on the high side
    Neutral - Earth 8.0V Should never be above a couple of volts in worst case... definitely too high

    If your installs are like we have in Brazil... I can feel your pain buddy
    Here the neutral is earthed at every building entrance...This causes tons of leakage, that's why I always try to take 2 phases for 240V and forget about the neutral altogether!
    Sometimes having some appliances plug inverted seems to magically solve the problem (plugs are sometimes not polarized)

    Good luck there, keep us posted!

  3. #13
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    Dec 2007
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    I guess Brazil and here are kind of alike then!

    So when I am plugging into the wall socket. What should be live could be neutral and vice versa and this could cause the tingle? Maybe I will try and pick up a 1:1 isolation transformer like massivesound suggested.

    It doesn't just happen in this building but at various other locations across the island.

    Its soooo frustrating!

    Thanks for the advise so far. I think it is pretty tough to do anything with the mains supply. I just have to do something inbetween the supply and the projector. or wear rubber gloves!

    Cheers
    Rich

  4. #14
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    Brazil
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    1:1 isolation transformer is a good choice... would also kinda protect against high frequency noise!

  5. #15
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    What sort of isolation transformer am I looking for. ebay brings up all sorts of wierd and wonderful things.

  6. #16
    Join Date
    Aug 2010
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    I have experience of this situation from years ago in Ibiza !.

    Problem is that when there is a lot of clay in the soil and an active tourist industry (discos using triac or thyristor controlled lighting or machinery in general) you can get quite large induced currents floating down the mains supply causing local grounds to differ from each other.

    I have seen a car light bulb giving a reasonable glow when just connected to two stakes in the ground with less than 100yards between them " VIVA ESPANYA" !

    I think you may have this type of problem aggravated by your use of high frequency switch mode PSUs !

    BTW this is extremely dodgy when using hire power water cooled gas lasers !

    You need a transformer (not a module) with its primary winding isolated from its secondary winding (NOT autotransformer).
    This is called (in some places) an isolation transformer. Unfortunately, where you are, it is probable that no one will have the faintest clue what you are talking about since most local tradesmen will be working from empirical experience and a healthy distrust of any concept involving "magnetic fields".
    The name doesn't help much!
    Result is that they will think you are totally nuts asking for a transformer with 220vac IN and 220vac OUT !

    However this type of transformer actually exists and would allow your secondary (the bit you use) to float free. You can then make your own earth (just for this secondary circuit) by driving a stake (preferably copper) into the earth outside your building (best piss on it occasionally or better still get the local dogs to do it).

    If isolation transformer (same voltage in as out) is not available get a step up and also a step down one and make sure that at least one of them has an isolated secondary winding. The bigger the voltage difference between input and output the more likely that the primary and secondary windings are separate and isolated. Unfortunately this also reduces the efficiency of the setup.
    To check this just put a meter on one of the primary leads and one of the secondary leads and make sure the is no continuity. EG same high resistance (megohms) that you get from air (no connection at all).

    I have been a "High Tech" artizan most of my life so I understand that Yanqui, EU or UK "health and safety" rules are hardly applicable here. So only trust yourself and just use a decent voltmeter between you and anything dubious before touching it and you should be OK.

    Cheers

    PS. Be very careful of the fridge and the washing machine when going barefoot !

  7. #17
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    Jan 2007
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    Florida
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    (best piss on it occasionally or better still get the local dogs to do it).
    LOL!! I don't know if that's the best advice or not .. maybe for the dogs a tingle while trickling would be ok, occasionally .. ..just don't hold on to anything metal while doing it ..

  8. #18
    Join Date
    Feb 2008
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    East Sussex, England
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    Well, its the best advice if you want the earth to be effective
    http://www.facebook.com/SubsonicSystems
    http://www.frikkinlazors.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

  9. #19
    Join Date
    Aug 2008
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    UK
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    Vaseline's quite effective...

    ...for keeping the earth wire to rod junction corrosion free.

    I put an earth rod in for my electric fence 10 or more years ago - solid copper large bore tube and attached the earth from the fence to it via a screw, ring terminal and vaseline. Still going strong and junction still ok under the vaseline. Excluding the air is good as is getting the lower half of the post well down in the ground - mines at least 2 feet into the ground with about 6 inches above ground.

    BTW electrical contact cleaner is a good alternative to dog piss.

  10. #20
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    Aug 2008
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    UK
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    Vaseline's quite effective...

    ...for keeping the earth wire to rod junction corrosion free.

    I put an earth rod in for my electric fence 10 or more years ago - solid copper large bore tube and attached the earth from the fence to it via a screw, ring terminal and vaseline. Still going strong and junction still ok under the vaseline. Excluding the air is good as is getting the lower half of the post well down in the ground - mines at least 2 feet into the ground with about 6 inches above ground.

    BTW electrical contact cleaner is a good alternative to dog piss, albeit dog piss is cheaper but only if you have the dog in the 1st place!

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