Basic heating circuit - Complete noob needs prod in the right direction

Discussion in 'The Projects Forum' started by Lexman, Jul 3, 2010.

  1. Lexman

    Thread Starter New Member

    Jul 3, 2010
    2
    0
    Hi all,

    I'm in a little over my head here but would be very grateful of any advice.

    I need to build a very basic circuit but have no experience in electronics other than basic bits at school over 15 years ago.

    I need to create a simple portable heating element consisting of a length of straight nichrome wire (8cm), running off 2 AA batteries and able to reach temps hot enough to cut polystyrene.

    Very early stages, so suggestions very welcome.

    Thank you in advance.

    Best,
    Lexman
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    Well, you can look at some completed projects to get ideas.

    Google "nichrome wire foam cutter circuits"
     
  3. Dx3

    Member

    Jun 19, 2010
    87
    7
    Have you tried connecting the nichrome to the batteries?

    That would quickly tell you if the batteries have enough power to cut styrofoam.
    After it is established that the cutting is possible, then comes the limiting circuit to cause longer battery life and such as that.
     
  4. Lexman

    Thread Starter New Member

    Jul 3, 2010
    2
    0
    Thanks guys, seems like trial and error is the way to go then. Would nichrome be the best to go for? What thickness would you recommend?
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
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    Nichrome would not be the best, as it is typically too thin. It will cool too quickly while transferring heat to the foam. A thicker wire will hold more heat.

    Guitar strings are popular for these devices.

    A place I worked at as a youth used quite thick wire..almost clothes hanger wire.

    The reason for that was to create shapes for edging and "routing" of the foam for a truer "chiseled" look.

    If you just want a standard shaper, the guitar string will hold up much longer than nichrome.

    Oh, Unless you are cutting only a few cm of foam, I dont think your 2 AAs are going to do the trick for very long.
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I use .005", .025", &.03" NiCr wire. Using 8cm of .005 wire, 6.3V @ 700mA cuts blue board and white board even faster with nice clean full width cuts.
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    well, there goes my theory.

    I have little experience with styro, but the foam-rubber I used for a base for fiberglass sculps did not like such thin wire. Oddly enough, I had to use more current, and got un-even heating to the point where it would start to burn the foam in some areas, and not cut in others.

    We would work with 3ft x 3ft x 3ft cubes, so it was more of an issue over a larger surface, I suppose.
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I've had lousy results cutting foam rubber.
     
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