How good of an electrical insulator is cardboard?

Discussion in 'General Electronics Chat' started by Ingeniir, Jul 16, 2011.

  1. Ingeniir

    Thread Starter New Member

    Jun 29, 2011
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    I'm attempting to build a disco light with 4 lightbulbs powered by mains power, controlled by a microcontroller. At the moment, I'm trying to figure out what to use for the housing. I know a plastic case would work well, but all the plastic cases I have all have non-ideal dimensions, whereas some shoeboxes I have would be perfect. I tried looking up the dielectric constant of cardboard, but the closest thing I could find was the dielectric constant and dielectric breakdown voltage of paper, but different sites had values on different orders of magnitude. I'm guessing this is because of the different types of paper that exist. I'm inclined to go ahead and do it because I know lightbulb screw shells are insulated from the outer metal casing with cardboard, but I thought I should check. Can cardboard insulate against mains voltage?
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    As long as the cardboard does not get wet, you will be fine at mains power.

    Any exposed metal casing should be earthed
     
  3. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    You think your going to run live mains inside a cardboard box? HA! I laugh at you and your post. Cardboard is weak and no one with no electronic experience should go near the mains. I suggest you go away, look up the dangers of high voltage and realize that using something as cheap as cardboard. what on earth is going through your mind?
     
  4. Robin Mitchell

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    Oct 25, 2009
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    WHAT ARE YOU SAYING YOU IDIOT????
    DONT USE CARDBOARD! Its not strong. if it rips you are going to suffer the conciquence.

    How can people be soo ignorant
     
  5. R!f@@

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    Aint card board made of wood ???

    Here we have wooden card boards you know...
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Cardboard can be made of pressed paper.
    This will not isolate any more when it gets wet.

    Bertus
     
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  7. R!f@@

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    Apr 2, 2009
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    sheeesh !! you came on a bit strong mitch...:eek:
    my bad....:D

    So it means what you have is different from what we use.
    But still any one shud know that anything made of paper isn't strong enuf to build things like disco lights.

    A fool would attempt to use thick paper such as "your" cardboards to make a heavy disco light and hang it over head.
     
  8. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    Cardboard is used in kids projects who use pva glue to keep it together. But im sure your a professional and use SELLOTAPE. That stuff is for real experienced people. If you made a box out for cardboard and a REAL electronic engineer or authorized persons to QC pass it they would look at it and throw it away.

    Let me make this VERY clear. If you think using high voltage without proper equipment or knowledge is fine then you wont have my sympathy if you should get hurt or killed. If anything you deserve to be hurt!

    PS This is not aimed primarily at you R!f@@ as your cardboard is wood based which i think is not safe but miles better than cardboard
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Actually card board is an insulator but not a very good one.
    It's unreliable and catches fire quite easily
     
  10. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    im just angry at the moment ¬_¬
    I did not get a straw with my orange juice....and i downed tonic water for my cramps i got during the war....hang on??? i wasent around then?
    ....
    ....
    Back in the war, i jumped out of a plane, landed on top of a Jerry, punched him in the face, drank my whiskey and used the bottle to kill five of em!
     
  11. R!f@@

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    'm confused...:confused:
     
  12. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    I don't think he'll care if he gets killed...:D

    Also, he's "Student of Mechanical Engineering", that's why he was asking, so don't be so severe...
     
  13. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    a mechanical engineer can do better that cardboard!
    embarrassing...so embarrassing
     
  14. Ingeniir

    Thread Starter New Member

    Jun 29, 2011
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    Hey all,

    I just wanted to clear a few things up. I am not concerned with the structural properties of cardboard. I plan to minimize any loads on the disco light housing. I am certainly NOT going to hang it up on the ceiling. The form of the disco light will be similar to this one: http://electronics.rory.co.nz/projects/lighting/disco_lights.php.

    What I AM concerned about is whether or not cardboard will insulate against 120VAC at 1A. I think there is miscommunication regarding the variety of cardboard being discussed. The type of cardboard I want to discuss is that of shoeboxes, but comments on other types of cardboard are also welcome. I think it's obvious that when cardboard is wet, it is not a good insulator.

    So far the comments have warned me that cardboard is structurally weak, that it is a bad insulator when its wet, that cardboard is made out of paper, and that ignorant people deserve to get hurt -_-. While this advice is very welcome, it is unfortunately unhelpful.

    According to one website, the dielectric constant of paper is 3.0 and it has a dielectric breakdown voltage of 200 V/mm. According to another website, paper has a dielectric constant of 3.3 and has a dielectric breakdown voltage of 14MV/m. Does anyone have values from credible sources that they trust? Or can anyone offer personal experience?
     
  15. Robin Mitchell

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    Oct 25, 2009
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    Please oh god please dont use cardboard. Spend the money to have it made out of plastic, metal lined with think insulator or something besides cardboard.



    That made me laugh XD
     
  16. Ingeniir

    Thread Starter New Member

    Jun 29, 2011
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    I would consider your advice if you would explain it. Why shouldn't I use cardboard? Do you think it is a bad insulator? How bad of an insulator is it? What is its dielectric constant and what is its dielectric breakdown voltage?
     
  17. praondevou

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    Jul 9, 2011
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    Forget the 1A. Yes it will probably isolate against 120VAC. BUT if you use as a disco light there might be the problem that the box gets damaged, for example if someone steps on it. It's just not professional and you'd have to make sure that nobody could get near the box and accidentally damage it and consequently get hurt/killed/shocked. ;) That's why it would be safer to use other readymade boxes made out of plastic for example.
     
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  18. Ingeniir

    Thread Starter New Member

    Jun 29, 2011
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    Alright, since it seems everyone is so worried about the structural integrity of the housing, I will explain what I have in mind so everyone stops commenting on it XD. If I do end up using cardboard, I will almost definitely reinforce it with additional layers of cardboard on the outside. Furthermore, when in use, the box would be on a high shelf out of reach. It will not be hanging. If I ever complete this, I wouldn't want my project to be damaged anymore than anyone would want to be shocked. I will protect it from damage. I understand the dangers of mains power, which is why I asked this question in the first place.
     
  19. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    paper was actually used as an insulator for wire back when plastics weren't widely available. Many capacitors used paper as an insulator.

    But your question shouldn't be if cardboard is an insulator. Consider that your shoe box was actually carefully engineered to perform admirably for a specific task, which you may have guessed, to hold shoes.

    Your question should be, will this choice of housing provide sufficient mechanical integrity, fire prevention, and electrical containment. In my estimation it fails all three. I'm with Mitch on this one. DO NOT play where you can get hurt.
     
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  20. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    I agree. If you are using light bulbs, consider the heat the produce.
    If this no mass production you should be able to find something better... You obviously don't want to spend much money, or NO money, but people are throwing so many things away... I'd be surprised if you don't find something else more appropriate.
     
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