a Problem in making a heating element using resistance wire, need some help?

Question

I want to make a small heating element, using resistance wire and a battery. The point is that I need a small hot rectangular surface (only about 1cm x 2cm).
I was thinking of using a small copper plate (for its high thermal conductivity) and "zig zagging" some NiCr wire along one side of it (so that the other side will be the hot flat surface I need), but the problem is that that will short the circuit since the resistance wire is not insulated. I've been looking for coated resistance wire but I cannot seem to find anything like that.

I need the temperature to be fairly high so I doubt I can use tape to insulate the plate. Maybe I could use another material but I can't think of anything (a ceramic plate could handle the temperature but its thermal conductivity is bad and I wouldn't know where to get it)

so If you have any suggestions on this, just shout

Thanks for the replies so far, I've heard good things.. Those ceramic adhessives seemed perfect, but doesn't seem easy to find around here..
For additional info:
I'm using this to melt cut nylon wristbands back together, temperature will be around 500°F (it will be nylon 6/6 at most)
I am aware of the high current draw and finite capacity of a battery, but thats okay, its not meanth for extensive use..

Answer 1

Go to this web site: http://www.cotronics.com/vo/cotr/ca_electricallyresistant.htm

They hace an adhesve that doesn't degrade up to temperatures of 2800 degrees.

Answer 2

Are you heating metal?
If not why dont you try this? Use the ceramic plate as the base and place the copper wire on top of that in the zig Zag fashion. This way you can place whatever it is you need to heat (hopefully non-metal) directly onto the wire. Using this set up, you actually don't need a material with a high thermal conductivity, actually the worse the better.

If you are heating a metal try covering the wire with a very thin(sanded down) piece of ceramic.

Answer 3

Its an assumption that a ceramic has poor thermal conductivity. Some ceramics have pretty good thermal conductivity.

You might be able to use a thin glass insulator between the copper and the nichrome. (think microscope slide cover).

You could also run an ac current instead of a dc current. A simple circuit can do a DC to AC conversion. With it you could get more resistive losses (heating) that you might otherwise get with a specific length of wire.

Answer 4

There a variety of solutions to your problem but specifically cannot propose one until the notion of temperature is know.
> I need the temperature to be fairly high
There are different material choices to be made and we need to
identify the temperature range. Also be aware that batteries are finite power sources and converting electrical energy to heat is a very consumptive process that will eat into the battery supply quickly. As the batteries become discharges the power may drop off as well as the temperature.

Answer 5

Hi,

I think maybe you could varnish one side of your copper plate using wire enamel, that way you would isolate the NiCr wire from the copper. I don't know what is a fairly high temperature so I don't know if this will work.

In the following address you can find a table with different kind of enamels that support different temperatures up to 220 ºC

http://www.calfinewire.com/datasheets/enamel.htm

Hope this helps.
Greetings
ASK

Answer 6

You can use a resistor with flat, rectangular sides, and clamp or glue your plate to it. The Yageo 5 W resistors are 1 cm x 2.2 cm, almost the exact size you need.

You can order them from http://www.digikey.com . Here is info from the Digi-Key catalog:
http://dkc3.digikey.com/PDF/T062/1307.pdf

You want the Yageo 5W type (they're 2.2 cm long). You just to need to figure out a suitable resistance value for whatever voltage or current you plan to run them at.

They're just 33 cents each, but you'd also have to pay shipping and handling charges.

Answer 7

See what temperature epoxy is good to. In that small an area is the thermal conductivity of the rectangle really that critical?

Answer 8

Curly said "With (a.c.) you could get more resistive losses (heating) that you might otherwise get with a specific length of wire."


Curly is confused.

Answer 9

can u try for shaving blade