heater-help please!

Thread Starter

jahzece

Joined Nov 29, 2011
5
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.:(
 

Thread Starter

jahzece

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

Thread Starter

jahzece

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

jimkeith

Joined Oct 26, 2011
540
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...
 

Adjuster

Joined Dec 26, 2010
2,148
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.
 

wayneh

Joined Sep 9, 2010
16,114
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.
+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:

Bernard

Joined Aug 7, 2008
5,285
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.
 

Wendy

Joined Mar 24, 2008
21,906
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.
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.
 

strantor

Joined Oct 3, 2010
5,158
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.
 

wayneh

Joined Sep 9, 2010
16,114
can anyone suggest me for a thesis proposal? please?
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.
 
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