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carbon or metal film resistors ?

Discussion in 'Electronic Components' started by vroemm, Sep 4, 2006.

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  1. vroemm

    vroemm Guest

    I would like to buy bundles of 100 resistors.
    100 metal film cost 1.76 euro.
    100 carbon resistors cost 1.41 euro.

    Not much difference.
    I think i will buy the metal film.

    Or are there situations where carbon resistors are better, perhaps even
    needed ?

    Its just for general hobby use.
     
  2. Carbon resistors can be better at high voltages (above 1000V), as there is
    volume to absorb and dissipate energy rather than a thin film that can
    easily be burned out. For most uses metal film is far better though, and
    even at 1% tolerance they're cheap. You can get more choices for values
    too.
     
  3. Tim Shoppa

    Tim Shoppa Guest

    If he's talking about "100 carbon resistors cost 1.41 euro", he's not
    talking about carbon composition, but carbon film.

    And at the prices he's talking about the resistors probably are rated
    for no more than 500V, I'm guessing he's talking about 1/2W or 1/4W
    units or less.

    In my experience I would rate typical metal films as far better at
    handling massive overloads than carbon films. Of course there are
    fundamentally different types of metal films (some are high-precision,
    others have safety ratings, some might even have both but not at the
    price he's talking about!)
    Tim.
     
  4. I hadn't thought of that.. carbon film.. I'd never use them at all, unless
    someone can tell me a reason to. I thought they were purely a cost saving
    thing where poor tolerances didn't matter, made redundant for most uses
    once metal film became cheap.

    I still rate the solid carbon ones though, they don't cost that much. I
    made a HeNe laser current limit resistor out of 4 2W solid carbons in
    adhesive lined heatskrink tubing, and they work well. First tests were with
    metal film resistors, but they burned out spectacularly like they might if
    I'd microwaved them for fun. I bet carbon film types would be even worse.

    I use standard 1% 0.6W metal film types for nearly everything I do, I think
    there's no point in trying to save money by using anything less, except
    maybe if you're into huge volume production. The difference on cost is far
    less than the worth of time lost in solving problems with bad resistors.
     
  5. vroemm

    vroemm Guest

    1/4 W metal film.

    Max working voltage 300 volt.
    Max overload voltage 600 volt.

    Order number 407917-89 at http://www.conrad.nl
     
  6. vroemm

    vroemm Guest

    100 0.25 watt metal film resistors 1.76 euro. ordernumber 408280-89
    100 0.6 watt metal film resistors 7.00 euro ordernumber 418374-89
    At http://www.conrad.nl

    That is 4 times more expensive for 0.6 watt compared to 0.25.
    A bit much for a hobbist, when buying many values.
     
  7. Fair enough. I didn't think there would be that much difference. There
    wasn't last time I looked, but if you can get that much difference go for
    it. Or check to see if there's a cheaper source of 0.6W, as a difference
    that strong suggests you might find one.
     
  8. The differences are more marked in low volumes. At the 1000+pces end of the
    market they are cheaper, and a lot of stuff is available surplus as companies go
    over to surface mount.

    We started stockpiling leaded resistors a couple of years ago when the majors
    started reducing their manufacturing programmes. We won't ever go to surface
    mount so need to ensure supplies for a few year yet, or at least until I retire!

    Peter
     
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