heater-help please!

Discussion in 'Homework Help' started by jahzece, Nov 29, 2011.

  1. jahzece

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    Hello everyone,
    I am in so much need of a variable heater circuit which is DC supplied and rechargeable in nature. I am targeting a maximum temperature of 40°C. Can anyone help me on this? please answer me soon im unfortunately in a rush.:(
     
  2. jahzece

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    anyone?? :(
     
  3. jimkeith

    Active Member

    Oct 26, 2011
    539
    99
    Need as many specifics as possible before any intelligent discussion...
    Battery operated?
    Approx power required?
     
    jahzece likes this.
  4. jahzece

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    there is actually no power required. all i need is a heater that is battery operated and is portable.
    thanks there. :)
     
  5. jahzece

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    i was required to design a 'hot compress belt' which is battery operated and rechargeable in nature. this is for dysmenorrhea cure.
     
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    what is the heater load mate.?
    What is the battery voltage ?
     
  7. jimkeith

    Active Member

    Oct 26, 2011
    539
    99
    Since this appears to be a new task for you, this is how I would start:

    Fabricate a crude belt of the correct size and line it with ½W resistors (perhaps 10Ω). Insulate the outside with a layer of flexible packing foam to reduce heat loss.
    Instrument with a temperture measuring device next to the skin.
    Apply power from an isolated DC supply and crank it up gradually until you obtain the desired temp rise--feeling of 'hotness' may be too subjective a measurement.
    Measure power required
    Select battery type, size and number of cells to obtain desired run time.
    Calculate required resistance from total battery voltage and required power
    Select resistor /resistance wire /conductive plastic resistor...
     
  8. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    I very much doubt that this is a wise project for an amateur. A home-made heating belt could easily produce serious burns if things went wrong. Constructing it out of small resistors, which would act as concentrated heat sources, would seem to be a particularly bad idea.

    Commercially made heated clothing / heat pads /heated blankets normally use resistance wire woven into fabric designed to diffuse the heat safely, avoiding excessive hot spots.
     
  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    A silicone rubber heating strip would be a good place to start.
     
  10. wayneh

    Expert

    Sep 9, 2010
    12,120
    3,046
    +1
    Just buy some electric socks and cut and sew them into a belt. You'll obviously have to pay attention to the conductive elements and not cut them.

    Actually, now that I think about it, I bet you'd be much happier with a reusable hot pack. They look sort of like breast implants and contain supersaturated sodium acetate, I think, that holds a constant warm temp as it all crystallizes. You recharge them in hot water, and they stay liquid until you snap a little clicker to initiate the crystallization. Very nice.
     
    Last edited: Nov 29, 2011
  11. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    jimkeith idea would probably work quite well; I used same idea to to keep a small fish boll at a constant temperature via thermistor & control. Cant find print but used circlesf 33Ω, 1/2W. believe it used a 9VDC wall wart for power.
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Actually they get very hot, then cools as it crystallizes, good for 4 hours. I had some a long while back, but my kids played with them to death, in the freezer. At least the freezer survived.

    Where do you get them? I've been looking for replacements for a decade. I recharged them in the microwave, which matched the instructions I was given.
     
  13. wayneh

    Expert

    Sep 9, 2010
    12,120
    3,046
    Last year, they were doing demos at Sams Club for the holiday season. Haven't see them this year, but there are many suppliers online. I must admit never using them, but as a chemist I was intrigued.
     
  14. jahzece

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    can anyone suggest me for a thesis proposal? please?
     
  15. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    how about belt that is a semipermeable hose, like a garden soaker hose, and have a hair blow dryer at one end?

    A blow dryer is actually overkill and would rain too much juice, but you could take the idea proposed earlier about using resistors as heaters and use a much smaller brushless fan (like PC CPU fan?) and blow over them. you wouldn't need much air flow really.
     
  16. wayneh

    Expert

    Sep 9, 2010
    12,120
    3,046
    Good grief, this is for school? You should have said so. To get any useful help, you should specify the constraints (money, time, design goals, etc. etc.) AND, most importantly, discuss your own ideas and interests, and work you've already done.

    Few here will help you do your homework without serious evidence of effort on your part.
     
  17. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Since this appears to be homework I have moved the thread to the appropriate forum.
     
Loading...