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Thread: Tingle from homemade projectors

  1. #21
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    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!
    We've been stuck for hours squeezing the dog, couldn't get a drop out!
    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.

  2. #22
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    Thanks for all the advice.

    The island here is either volcanic rock or reclaimed swamp. I wish I could get proper ground rods in here but that would be difficult for every location I go to. I do this for fun with friends.
    There are only a few bars and none of them have dimming systems so I shouldn't have problems with triac or thyristor controlled lighting. I get shipments from the USA every couple of weeks so ordering online isn't a problem. I will try and google 120V:120V transformers and see what comes up.

    As the lasers can run between 80V and 240V would a 120V to 220V stepup transformer work to do the isolation?

    Cheers
    Rich

  3. #23
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    Quote Originally Posted by neutrino View Post
    Thanks for all the advice.
    The island here is either volcanic rock or reclaimed swamp. I wish I could get proper ground rods in here but that would be difficult for every location I go to. I do this for fun with friends.
    There are only a few bars and none of them have dimming systems so I shouldn't have problems with triac or thyristor controlled lighting. I get shipments from the USA every couple of weeks so ordering online isn't a problem. I will try and google 120V:120V transformers and see what comes up.
    As the lasers can run between 80V and 240V would a 120V to 220V stepup transformer work to do the isolation?
    Cheers
    Rich
    Strange.... reclaimed swamp does not sound very resistive to me so maybe the Varying Local Earth isn't such a relevant detail after all. As for volcanic rock, well that sounds somewhat porous and unless very dry doesn't sound like a good candidate either. Could well be wrong here but a quick check with a local geologist should clear that up!.
    Also you don't mention either the fridge or the washing machine so I am beginning to doubt that the VLE theory somewhat, although induced spikes (from your own switch mode PSU and total lack of earthing is still top of the list as far as "tingles are concerned.
    If you can get stuff from USA then "Isolation Transformer" as suggested by Bruno (Laserdj) is by far the best solution. Problem with step-up transformers is that they are normally "autotransformers" which means that the the secondary winding is just a continuation of the primary winding (or vice versa ) which will NOT give you any electrical isolation at all.

    So you MUST CHECK THIS DETAIL BEFORE PURCHASING !

    The other thing you don't mention is whether the USA supplies arrive by boat or by air !
    Isolation transformers are HEAVY BUGGERS, precisely due to their primary and secondary windings not having sections in common. I would recommend one that is AT LEAST 1kva so that any gear you plug in with interconnections can be used with a common earth. (eg.Lights/sound//computer etc.). If you need more just get another one since they can happily share the same earth.


    Once you have an Isolation Transformer you can put easily check if you have a crossed wire of your own
    using your own "copper tube/stake" earth and an "RCD" (residual current detector). This is a circuit breaker which detects any difference between the neutral wire current and the live wire current and trips out when this difference is above about 30ma (domestic) or 300ma (industrial) since it assumes that any difference is flowing to earth (possible via someone touching a wire).


    The other things you might want to look at are INVERTERS !

    Some of my projectors run from the roof of a car (reducing setup time to zero) and they run of the car battery itself (or an auxiliary one which charges from the car alternator). They run using 220vac derived from chopping the 12vdc source and transforming up to the required output voltage.
    They drain the battery very fast however! Last but not least are small portable generators which would also liberate you entirely from the dodgy sounding mains supply. Both of these solutions allow you to use a local earth with no risk whatsoever but they do cost a bit.


    I hope all this helps.

    Cheers

    PS. @Norty Try giving the poor sod something to drink occasionally !
    Last edited by catalanjo; 08-20-2011 at 10:56. Reason: Thirsty pooch !

  4. #24
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    Thanks for the info. Everything is wet here, the water table is really high. Its only 3 x 7 miles or so. Google Utila, Honduras

    All my shipments come in via boat so weight isn;t an issue - carting it around will be!

    I will have alook at the 1kva isolation transformers later thsi weekend. The two satallites I'm not too concerned about at the moment as the cases are fully isolated. Its the other two projectors and the laptop then that can be connected to the isolation transformer.

    I'll look into the inverters too. Could I run one off a big 12V PSU like the ones that are used for VHF radio base stations? I beleive they can supply 20-30A or so.

    CHeers
    Rich

    Quote Originally Posted by catalanjo View Post
    Strange.... reclaimed swamp does not sound very resistive to me so maybe the Varying Local Earth isn't such a relevant detail after all. As for volcanic rock, well that sounds somewhat porous and unless very dry doesn't sound like a good candidate either. Could well be wrong here but a quick check with a local geologist should clear that up!.
    Also you don't mention either the fridge or the washing machine so I am beginning to doubt that the VLE theory somewhat, although induced spikes (from your own switch mode PSU and total lack of earthing is still top of the list as far as "tingles are concerned.
    If you can get stuff from USA then "Isolation Transformer" as suggested by Bruno (Laserdj) is by far the best solution. Problem with step-up transformers is that they are normally "autotransformers" which means that the the secondary winding is just a continuation of the primary winding (or vice versa ) which will NOT give you any electrical isolation at all.

    So you MUST CHECK THIS DETAIL BEFORE PURCHASING !

    The other thing you don't mention is whether the USA supplies arrive by boat or by air !
    Isolation transformers are HEAVY BUGGERS, precisely due to their primary and secondary windings not having sections in common. I would recommend one that is AT LEAST 1kva so that any gear you plug in with interconnections can be used with a common earth. (eg.Lights/sound//computer etc.). If you need more just get another one since they can happily share the same earth.


    Once you have an Isolation Transformer you can put easily check if you have a crossed wire of your own
    using your own "copper tube/stake" earth and an "RCD" (residual current detector). This is a circuit breaker which detects any difference between the neutral wire current and the live wire current and trips out when this difference is above about 30ma (domestic) or 300ma (industrial) since it assumes that any difference is flowing to earth (possible via someone touching a wire).


    The other things you might want to look at are INVERTERS !

    Some of my projectors run from the roof of a car (reducing setup time to zero) and they run of the car battery itself (or an auxiliary one which charges from the car alternator). They run using 220vac derived from chopping the 12vdc source and transforming up to the required output voltage.
    They drain the battery very fast however! Last but not least are small portable generators which would also liberate you entirely from the dodgy sounding mains supply. Both of these solutions allow you to use a local earth with no risk whatsoever but they do cost a bit.


    I hope all this helps.

    Cheers

    PS. @Norty Try giving the poor sod something to drink occasionally !

  5. #25
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    Sorry mate ! you have to power the satelites from the trafo as well since they connect to the controller and if they don't have a common earth things will get "jittery".

    Cheers

  6. #26
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    Thanks for the heads up. So I need to power all three projectors from the tranformer along with the laptop and the USB hub for the FB3s?

    Cheers
    Rich

    Quote Originally Posted by catalanjo View Post
    Sorry mate ! you have to power the satelites from the trafo as well since they connect to the controller and if they don't have a common earth things will get "jittery".

    Cheers

  7. #27
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    Lightbulb

    hey Sir Rich -

    Quote Originally Posted by neutrino View Post
    ..will have a look at the 1kva isolation transformers later thsi weekend.
    I'll have to check in to the rating on them, but we toss-out the 208-240 1:1 iso-transformers from every laserscope-conversion, cause they are about 150# of just 'dead-weight', since the iso-tranny is not needed for most show-rigs, here...

    We do-have 2x sitting in the back-shop, and would be more than happy to *give* them to-ya, but, since they're ~150# each, they'd prolly cost a good-bit to ship-down... I think we could just bolt to a good-size pallete, with a decent alum. 'base-plate' (to aid with avoiding pall't blow-out), and ship it 'nekkid' to further-save on cost...

    Lemme see if I can do some 'digging' on the rating for those puppies, and get back to ya.... But, like ya said - 1-2 of those, even on a big-tire 'rolling cart' ain't gonna be very 'spine-friendly' You might-be best-off with the inverter-idea, if you're not cranking 8hrs on a gig, etc...

    Anyhoo, hope this might help, lemme know yer thoughts...
    cheers.. er, Salud!
    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  8. #28
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    Quote Originally Posted by neutrino View Post
    Thanks for the heads up. So I need to power all three projectors from the tranformer along with the laptop and the USB hub for the FB3s?

    Cheers
    Rich

    Fraid so.... and any connected sound ....!

    Jon's offer sounds good but may be a bit "big" for your needs!

    Cheers

  9. #29
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    Thanks for that Jon. Probably too heavy to shift around down here. Cheers anyway

    Quote Originally Posted by dsli_jon View Post
    hey Sir Rich -



    I'll have to check in to the rating on them, but we toss-out the 208-240 1:1 iso-transformers from every laserscope-conversion, cause they are about 150# of just 'dead-weight', since the iso-tranny is not needed for most show-rigs, here...

    We do-have 2x sitting in the back-shop, and would be more than happy to *give* them to-ya, but, since they're ~150# each, they'd prolly cost a good-bit to ship-down... I think we could just bolt to a good-size pallete, with a decent alum. 'base-plate' (to aid with avoiding pall't blow-out), and ship it 'nekkid' to further-save on cost...

    Lemme see if I can do some 'digging' on the rating for those puppies, and get back to ya.... But, like ya said - 1-2 of those, even on a big-tire 'rolling cart' ain't gonna be very 'spine-friendly' You might-be best-off with the inverter-idea, if you're not cranking 8hrs on a gig, etc...

    Anyhoo, hope this might help, lemme know yer thoughts...
    cheers.. er, Salud!
    j

  10. #30
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    I think the guy that does the sound has a little isolation transformer for his DJ kit - not sure if the amps are on it or not.
    What will happen if the lasers and control are on an iso-tran and the sound kit isn;t?

    Cheers
    Rich

    Quote Originally Posted by catalanjo View Post
    Fraid so.... and any connected sound ....!

    Jon's offer sounds good but may be a bit "big" for your needs!

    Cheers

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