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Nichrome wire heat up

Johnson77

Mar 10, 2020
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I'm working on a project that heats 2 pieces of nichrome wire. They are complete circuit loops. I've run both loops by themselves and works fine. When I combine them to make 1 line (parrellel), it pops the fuse. Is their any reason nichrome can't be heated in a parrellel circuit ??? I look forward to your council. Thanks in advance

chris
 

duke37

Jan 9, 2011
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You are taking too much current for the fuse. Two similar pices of wire in parallel will take double the current of one.
You could try running them in series but may not have sufficient voltage.
 

Johnson77

Mar 10, 2020
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Thanks Duke. I bought a couple of toasters and clipped the cords from them. But I’m heating 20 gauge nichrome. I think I will drop that to 26 or 32 gauge. See how that works
 

duke37

Jan 9, 2011
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If you are changing the wire guage, then you can get details of resistance per metre to suit. The resistor will depend on the length.

Give us details of the power supply and show us a picture of what you are trying to do.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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Nichrome, a nickle-chrome alloy, is typically used as an incandescent (red hot) heater element in electric ranges and small home appliances such as toasters. It has the nifty property of not "burning up" when heated in air. At lower temperatures, nichrome wire is used to cleanly cut styrofoam.

Nichrome wire has a positive temperature coefficient of resistance, meaning it has a resistance when cold that is much less than its resistance when hot. Most metallic electrical conductors behave this way, which is fortunate because the property can be used to prevent thermal runaway when electrical power is applied. But it also means the initial electrical current can be substantially larger than the current needed at the final operating temperature. For heating purposes, the voltage is specified first and then the initial (cold) and final (hot) resistances are used to calculate the current required. This is not a trivial computation because the final hot resistance depends also on thermodynamic factors that govern how heat is lost or transferred. Sometimes, for one-off projects, trial-and-error is used to find a solution.

Please tell us what you are trying to DO rather than describe your failed attempts to do it. Clearly, you have little or no knowledge of electricity, but we are here to help with that.
 

Bluejets

Oct 5, 2014
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Sometimes, for one-off projects, trial-and-error is used to find a solution.

Found that with the foam cutter for r/c aircraft wings etc. where the blank size varied.
Used a large transformer from an ice machine cutter circuit with a 400va dimmer on the AC input to control the output.
Nichrome wire here varied in both gauge and length anywhere from perhaps 30mm to over 1 metre in length.
Marked each setting as the need arose for future reference.
25 years and still working fine.

Some modellers used output control with 2 auto batteries in series with another piece of nichrome as a "dropper" with battery fed in one end and a sliding clip as a tap.
2 batteries were essential for the fine wire used on the wing core cuts.
Use of heavy gauge undercut the profiles.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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I have never had much success cutting either open-cell or closed-cell Styrofoam or any other kind of "foamed" plastic, probably because I lacked the patience to find the right temperature for the nichrome cutting wire. My fallback position was to use a really sharp knife, which is clumsy and time-consuming even with straight-line cuts. Fugettaboutit for round or anything resembling wavy cuts.

I think a lot of hobby-type experimentation is of the trial-and-error persuasion. I know that's how I approached it while growing up and trying to figure out what electricity and (later) electronics was all about. Luckily, I didn't electrocute myself or burn the house down, although I have been electrically shocked many times and have on several occasions accidentally started small electrical fires.

The key to learning by trial-and-error is to keep careful records, completely describing (as much as possible) what you are trying to do, how you are trying to do it, and the outcome from your efforts. @Bluejets indirectly referred to this methodology with his comment, "Marked each setting as the need arose for future reference."

"Trial-and-error" also requires at least some understanding of what you are trying to do. This understanding will assist in allowing you to set parameters for the experiment. For example, in @Bluejets nichrome wire cutting experiments on Styrofoam there were limits he self-imposed on the voltage, current, and nichrome wire diameter and length. He probably acquired knowledge of these limits from earlier attempts to control the electrical heating of nichrome wire and applied them to cutting Styrofoam. Clearly (perhaps) a red-hot wire would melt too much "stuff" while a luke-warm to the touch wire wouldn't melt anything at all. The devil is in the details of finding out exactly how much voltage and how much current is needed to make a clean cut. I would imagine that how fast you moved the cutting wire through the Styrofoam would be a factor to consider, but perhaps not easy to control.
 
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