Nichrome Wire

[MrJammin]

I am looking into using Nichrome Wire for a current project that requires a heating element. I did a little research and found out that Nichrome wire is the heating element most commonly used in toasters and hair dryers. Does anyone have any idea how long the heat up time is for this kind of wire? If a I put a large amount of current through it (a couple of amperes), could I get it to a couple of 100 degrees Farenheit in a few seconds?

 

[jpanhalt]

If a I put a large amount of current through it (a couple of amperes), could I get it to a couple of 100 degrees Farenheit in a few seconds?

Yes, depending on the size of the wire and current, you can get it red hot in a second or less. John

 

[mneary]

And your next question would be: how much current?

I would suggest starting with something less than the rated current of the appliance you got the wire from.

 

[Pommie]

You can also use wire wound resistors. Just break off the porcelain (hit with hammer) and you end up with a nice length of resistance wire thats already terminated at each end. An added advantage is that by choosing different values you get a nice selection of different thicknesses.

Mike.

 

[Leftyretro]

Just out of curiosity does anyone know the calculation(s) needed to figure out the max temp a small oven would rise too given the power dissipated, given the E (say 120vac) and the total R (say 12 ohm) of the wire) in the wire? Is it a watts to BTU type calc and then on to the internal volume being heated?

Thanks

Lefty

 

[jpanhalt]

Just out of curiosity does anyone know the calculation(s) needed to figure out the max temp a small oven would rise too given the power dissipated, given the E (say 120vac) and the total R (say 12 ohm) of the wire) in the wire? Is it a watts to BTU type calc and then on to the internal volume being heated?

A calculation of the steady state temperature (max temperature) would depend on the specific heat of the oven and its contents, their masses, and the rates at which heat is added and lost. The rate of loss, of course, will vary with the environment and the temperature, and the oven can never get hotter than the heater. If you wanted to do a very simplified calculation with just water in a perfect thermos, you need 1 calorie to raise the temperature of 1 gm 1 degree C, which would be approximately 4 watt-seconds.

It's easier to just add the heat, measure the temperature, and adjust the heat input accordingly. John

 

[Leftyretro]

A calculation of the steady state temperature (max temperature) would depend on the specific heat of the oven and its contents, their masses, and the rates at which heat is added and lost. The rate of loss, of course, will vary with the environment and the temperature, and the oven can never get hotter than the heater. If you wanted to do a very simplified calculation with just water in a perfect thermos, you need 1 calorie to raise the temperature of 1 gm 1 degree C, which would be approximately 4 watt-seconds.

It's easier to just add the heat, measure the temperature, and adjust the heat input accordingly. John

Thanks, I figured it would be somewhat complicated with lots of factors. Anyway most applications use a thermostat or temp control and don't really try to let the system reach max possible temp.

Lefty

 

[Krumlink]

With my PSU for a Flyback I can heat up a 100ohm 50Watt Power Resistor to about 150F in about 1 minute

 

[ericgibbs]

I am looking into using Nichrome Wire for a current project that requires a heating element. I did a little research and found out that Nichrome wire is the heating element most commonly used in toasters and hair dryers. Does anyone have any idea how long the heat up time is for this kind of wire? If a I put a large amount of current through it (a couple of amperes), could I get it to a couple of 100 degrees Farenheit in a few seconds?

hi,
You can cannablise an old 'steam iron', [ ironing clothes type], the elements are a 'flat sheet' , the temperature sensing element could also be remounted inside the oven, with the iron temperature setting control on the outside of the oven.

Another quick sort of heat are halogen or IR lamps.

 

[eblc1388]

Unfortunately suitable temperature sensor for "a couple of 100 degrees Fahrenheits" required by the OP is either using thermocouple or via a bimetallic temperature switch. I have seen temperature controller with a "small tail" used to sense the temperature.

 

[Pommie]

A "couple of hundred degrees Fahrenheit", that's not even boiling water. An LM35 should handle that.

Mike.

 

[ericgibbs]

A "couple of hundred degrees Fahrenheit", that's not even boiling water. An LM35 should handle that.

Mike.

G' day Mike,
As you say a LM35 is happy upto 150Cdeg. [302Fdeg].

 

[Nigel Goodwin]

hi,
You can cannablise an old 'steam iron', [ ironing clothes type], the elements are a 'flat sheet'.

You're not kidding about 'old' - irons haven't used seperate elements for over 30 years - the elements then became an integral part of the soleplate.

Probably one of the last was the Morphy Richards CA75 (non-steam), I used to repair them in the early 70's.

 

[things]

With my PSU for a Flyback I can heat up a 100ohm 50Watt Power Resistor to about 150F in about 1 minute

With my flyback driver, i can heat up a 2N3055 in about 2 minutes, and it gets wayyy to hot to touch I had to put it on a heatsink after that, and the heatsink still gets hot enough to melt the hot glue holding everything underneath it

 

[Gordz]

Cheap hair dryers are a great source for nichrome wire etc. We needed a low voltage heat source ( hot air @ 220c ) for a special printing application and used hairdryer guts for the prototypes.

 

[Nigel Goodwin]

I always use replacement elements for silica tube heaters - they come as a simple coil of wire that you pull through the old tube with a piece of string, so there's no dismatling to do!

 

[bryan1]

I scored a few old 240 volt nichrome hot water heating elements to use as a dumpload for my solar array's. When I measured the resistance they were around 82 ohms which was too big for a 24 volt array so I re-wired them to 5.6 ohms and now when the batteries are floating i'm heating water

Too easy

Cheers Bryan