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Voltage and heating circuits?

Discussion in 'Electronic Basics' started by Guntar Gunderson, Jan 13, 2011.

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  1. I have a simple heating circuit that takes 16V @ 3.5A. I want to run
    it on a 12V-48A/hr deep-cycle battery.

    Now, I can get a DC-DC boost converter for $80, NBD.

    What will happen (generally) if I hook it up to the 12 volt source?
    It doesn't have any solid state circuits... it's simply a resistance
    device; I don't expect it to burst into flames. Am I violating any
    basic safety rules if I plug into a lower voltage?

    Gunz
     
  2. Rich Grise

    Rich Grise Guest

    If the heater is indeed nothing but resistance, it won't do any
    harm at all, but you'll get a drastically reduced heat output. I'm
    way too lazy to do the math; if it's nichrome, the difference would
    be exaggerated, because nichrome has some insane tempco of resistance.

    But there's very little danger that you'll burn the house down. :)

    Cheers!
    Rich
     
  3. Jasen Betts

    Jasen Betts Guest

    it will heat less powerfully by the ratio 12^2/16^2
    which is 144/256, 9/16, or about 56%

    but it's not that bad, lead-acid batteries are usually around 13-14V

    ballpark 70-80%
     
  4. Jasen Betts

    Jasen Betts Guest

    nichrome's tempco is very close to 0, stainless steel on the other
    hand goes up quite a bit from room temp to red-hot.
     
  5. Guntar Gunderson:
    If you need more heath than half of the rated, maybe it's less expensive to
    buy another battery to be put in series with the one you have and build a
    simple, very low frequency, PWM controller, that will cost you about $5.
     
  6. Rich Grise

    Rich Grise Guest

    Hm. I must have been thinking tungsten, as in bulb filaments.

    Thanks!
    Rich
     
  7. Phil Allison

    Phil Allison Guest

    "Rich Grise is off his Drugs":


    ** Ni-Chrome has a large tempco ??

    News to everyone that has ever used any.

    Wot a moron.


    ..... Phil
     
  8. Phil Allison

    Phil Allison Guest

    "Rich Grise"

    ** Still wrong - dickwad.

    In practice, the heat difference would be diminished compared to a simple
    resistance - cos as the applied voltage drops, so does the resistance of
    tungsten.



    ...... Phil
     
  9. Rich Grise

    Rich Grise Guest

    Uh, yeah, that's what I just said.

    Thanks,
    Rich
     
  10. Phil Allison

    Phil Allison Guest

    "Rich Grise"
    ** No dickwad - you said the direct opposite in fact:

    " if it's nichrome, the difference would
    be exaggerated, because nichrome has some insane tempco of resistance."


    Piss off - IDIOT !!


    ...... Phil
     
  11. Rich Grise

    Rich Grise Guest

    Yeah, and I stood corrected: After I was duly informed of my error, (see
    upthread, if you're a man) I said, and you can look above, "Hm. I must
    have been thinking tungsten, as in bulb filaments."

    "Dickwad?"

    Oh, well, guess you missed your Tourette's meds today.

    But thanks for playing!
    Rich
     
  12. Phil Allison

    Phil Allison Guest

    "Rich Grise is a Fucking MORON "

    ** And that is where you made the second error - fuckhed.

    Now you've made a third and forth time just to prove how thick you are.




    ...... Phil
     
  13. Rich Grise

    Rich Grise Guest

    You can't insult me if you can't even spell "fuckhead."

    Please go take your meds.

    Thanks,
    Rich
     
  14. Guntar, are you still there?
    Just ignore the silly little flame wars. Phil has been doing that for
    years.
    Others have pointed out that heat from a resistor varies with the square of
    the voltage, so you might be able to get by with a single 12 volt battery,
    or two of them in series if you need more heat. But you don't have much
    control over the amount of heat you're getting that way.
    You could have an adjustable heater if you go with two batteries and a
    simple controller, whereupon you could simply turn a knob and get just
    exactly the amount of heat you need.
    I googled "adjustable duty cycle heater controller" and found some that run
    on 12 volts, but you would probably want two batteries in series (nominally
    24 volts).
    If you're comforatable with a soldering iron, you could make your own
    controller -- it's a simple project, because all you need is a circuit that
    turns on and off at a low frequency, like once a second. You adjust the
    duty cycle and therefore the amount of heat.
    We haven't heard back from you, but there are people here that just love to
    offer their know-how on stuff like this. But you've gotta talk to us!
     
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