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Does copper wire work well for heating coil?

I want to make a diy hair dryer (https://youtu.be/NyXi30acGO0) however the heat coil is a tricky part. I have seen that video saying you need 32 AWG nichrome wire; and another video similar that uses 25 AWG nichrome wire. 
I got an old long ethernet cable, however it uses 25 AWG copper wire. 
Does anyone know if copper wire will work well for heat coil?

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bwrussell3 months ago

Copper will not work well, or at all really. The reason is resistance, or lack thereof. Copper has low resistance, which is why it's used for wiring, and so it won't heat up significantly without absurd current draw.

In fact, under no circumstances should you use copper wire as a heating coil. If you're pumping enough current through your coil to heat it then you're drawing enough current through your house wiring to heat it too. You'll burn your house down.

It appears nichrome 80/20 is the way to go.

ADRIANT28 (author)  bwrussell3 months ago
Thanks. But do you know what I can take apart to find nichrome wire?

I suggest taking apart an old hair dryer.

;-)

ADRIANT28 (author)  Jack A Lopez2 months ago

I already have a toaster to take apart however I don't have a hair dryer.

And yes thankfully my mom hasn't thrown away the old toaster.

Yeah. The heating wire in a toaster is nichrome, so that should work too.

I put a smiley following that comment I wrote three weeks ago, because there might be some absurdity, in taking apart a hair dryer, for to get parts, for to build a hair dryer. After all, would it not be less work, to use a hair dryer as a hair dryer, without the trouble of taking it apart for parts?

Although, I have seen similar things. I have seen somebody take apart a carbon-zinc battery, for to get material, specifically zinc metal, to use to build a homemade battery. There might be some absurdity in that too. Here:

https://www.instructables.com/id/Make-a-Zinc-Air-B...

ADRIANT28 (author)  Jack A Lopez2 months ago

Yeah that would be absurd to take apart a hair dryer to make a hair dryer. I also do have an old hair dryer but it would be too absurd to do it. The old hair dryer isn't safe to use with what I assume. Frequently there would be green plasma flashes inside, don't know what that is but I am assuming it isn't safe. I have no idea what it is that is causing green plasma flashes, do you? I guess I could salvage the motor (If it isn't bad) and the heating coil. I might use it to make a space heater (I am still in a dilemma of how to power it, I don't know if I should connect it to an AC adapter which would make it not so hot but I want to use an old case fan; or use some kind of power transformer, maybe a doorbell transformer or what should I use?)

I am guessing the, what you call, "green plasma flashes", are due to an intermittent (alternately open or closed) connection that is arcing

https://en.wikipedia.org/wiki/Electric_arc

briefly every time it is open.

If the arcing is happening in the motor brushes, this is mostly harmless. It is worse if the arcing is happening somewhere else, like a broken heating element wire. Although for both those cases, the arcing is not really a danger to the user, I mean unless it is like making an intense hot spot where the arc is, and starting to melt a hole through the plastic case of the hair dryer.

You would probably smell burning plastic if that was happening... which reminds me, arcs make a smell too. Arcs make ozone, and that has a unique smell.

https://en.wikipedia.org/wiki/Ozone

Regarding the question of choosing a voltage source for a heating element, the way to do that is using Ohm's law, V=I*R, and the formula for power, P=V*I.

I think I tried to explain this, in an answer I wrote to this topic, 19 days ago?

Well, actually I don't remember how many days ago it was, but the widgits in this page are telling me it was that number. Just scroll down a little bit, and you'll see it.

ADRIANT28 (author)  Jack A Lopez2 months ago

The same thing also happens with the old toaster I mentioned. Like when it finishes toasting or if yoy press the cancel button, it would flash green plasma.

Thanks for letting me know. The old hair dryer heats fine and also the motor works fine. Also does the motor use a power transformer or does it use 120V AC motor?

The last hair dryer I took apart had a low voltage, permanent magnet, DC motor. Moreover, I seem to recall the voltage across the motor was only around 10 volts or so, and there was some clever, and cheap, way, that this was done.

Like for example, a diode, a heating coil, and a DC motor, all wired in series together. The diode acts as a half-wave rectifier, and most of the voltage during the half of the time when the diode is forward biased, most of the line voltage, perhaps 90% of it, falls across the heating coil, with the remaining 10% across the motor.

Then as some cleverness on top of that, the designers might also have made a way to switch the size, i.e. resistance, of the heating coil in series with the motor, or switch on other heating coils, to effect more than one fan speed, and to effect more than one level of heat being dissipated.

As seen by the user, these switches will have some friendly and descriptive labels, like: HIGH/LOW for the fan speed, and HOT/WARM for the heat.

Something else with a heating element. Not sure it's used for much else.

Yea a toaster.

Toga_Dan3 months ago

in increasing order of resistance:

Copper

Steel

Stainless steel

NiCr

ADRIANT28 (author) 3 months ago

Ok Thanks for all the comments! And yes I have an old toaster to take apart. I hope my mom hasn't thrown it out yet.

Jack A Lopez3 months ago

The secret to understanding heating elements, is to think of the heating element as a resistor, as imagined by Ohm's law,

V=I*R

And also consider the formula for electric power,

P=V*I

The usual first step in designing a heating element is to have some number in mind for power dissipation, P, like, for example, P= 100 watts = 100 W.

The next step is to have a voltage source in mind, like for example, a 12 volt DC supply, so V = 12 V DC

Then figure out what size resistor R would be needed for dissipate P watts of power, when a voltage of V volts is across it. In other words, solve P= V^2/R, for R.

R = V/I = V/(P/V) = V^2/P

For V=12 V and P = 100 W, this is

R = V^2/P = 12*12/100 = 144/100 = R = 1.44 ohm

The next step is to think about building that resistor from a length of wire. The wire has resistance proportional to its length, and the value of that constant of proportionality is different for different wire thickness, and different kinds of metal (e.g. copper versus nichrome). This number for resistance per unit length is a number you can look up in a table.

There are other considerations too, particularly if the wire is going to get really hot.

Generally speaking, chemical reactions between solid metal and air are slow at room temperature (think "rusting"), but a lot faster at glowing hot temperature (think "burning").

For some reason, nichrome wire can survive glowing, orange hot, temperatures in air, without burning itself up.

But this is NOT the case for copper wire. So copper wire is only good for heating elements that get warm, not glowing hot.

Moreover when you do the math for finding the length and thickness (or AWG) of a copper wire needed for a particular resistance, e.g. R =1.44 ohm, it turns out you need a very long piece of very thin wire.

In fact, it might be the case that the volume of the wire, equal to its length times its cross-section area, L*A, is a number bigger than the physical space you want to heat.

I remember one time I took apart an electric blanket, and its heating element was, what appeared to be, a really long length (like 10 meters) of really thin (like 32 AWG) copper wire.

I think that was the last place I observed, in a product found in the wild, an instance of a heating element intentionally made from copper wire.

seandogue3 months ago

short answer, it is not an effective material for heat coils.

Copper will not work well as a heating element; to little resistance and to low of a melting point.