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home made fuse?

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Philipc

New Member
I've ran some experiments and found that 41awg wire will blow a little over 3 amps, and 44awg a little over 1 amp. Would it be a bad idea to use this in experiments in place of a fuse?
Thanks
Philip
 

mozikluv

New Member
homebrewed fuse

:D hi,

since you have already figured out at what current the wires trip off, why not. but my suggestion is use those wires only to replace fuses of such rating only like if it is 3A or 1A. i dont suggest you use that for permanent replacement. you might encounter a wire like the 41 that you said would break at 3A, but in reality it will break or it might not break. :D
 

Johnson777717

New Member
I agree with moziklov on this one. Small irregularitites in the wire, due to the manufacturing standards, may cause each individual section of the wire to "perform" differently than the other sections. Also, ambient air temperature can play a major role in the fluctuation of the "breaking point." Finally, the elements and metallurgical composition of the wire can fluctuate from manufacturer to manufacturer, and lot to lot.

I imagine the "wire" used in fuses has been tested extensively, and performs more precisely than regular wire.

If you're still interested in creating your own fuses, you may be interested in performing a R&R study on the wire that you are using. R&R stands for repeatability and reproducability. Basicly, run a test lot and see at which voltage, amperege the wire breaks. 32 trials at each setting is pretty substantial, statistically speaking. Then find the reproducability and repeatability of each test lot. You may be able to compare this with an R& R study performed by fuse makers (If the data is available?). This should give you a pretty good view of the confidence of your wire.

Good luck!
 

Dean Huster

Well-Known Member
Wire fuses

I don't like that idea at all. It will work only for dead shorts (and then imprecisely as stated above because of wire/alloy/drawing variations) but not for overloads. Fuses are rated to not only blow at certain currents, but to also include a time factor. A typical fast-blow fuse may operate at its rated current forever, blow with a 20% overload within 60 seconds, blow with a 50% overload within 30 seconds, a 100% overload within 5 seconds, etc. Wire, on the other hand, cannot be trusted to have similar characteristics. Although you may find a piece of wire to handle all current up to 5 amps, that doesn't mean that it will blow quickly with a 10a load vs. a 20 a load. There are also voltage and energy concerns to deal with. You don't want to play with a makeshift fuse like that in a high-energy 460vac 3-phase system. Another way to look at it is that using wire for a fuse isn't much different than putting a penny behind one of the old Edison base fuses or wrapping foil around a cartridge fuse.

Dean
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Re: Wire fuses

Dean Huster said:
Another way to look at it is that using wire for a fuse isn't much different than putting a penny behind one of the old Edison base fuses or wrapping foil around a cartridge fuse.
I beg to differ, it's completely different! - although I personally wouldn't suggest replacing a fuse by a piece of suitably rated wire, it's still going to be reasonably close to the original - using a penny, or foil, is completely (100%) removing any protection. With a piece of suitably rated wire you just can't be sure of the exact protection level given, it 'might' even offer a greater level of protection?.
 

stevez

Active Member
I'd say it's an "all depends on" kind of answer as is suggested in some of the responses. If the consequences of a home made fuse are not extreme - and the systems or components that need protection are properly protected then the thin wire might be acceptable.

An example of where I might use just such an arrangement - on my workbench with a power supply that is properly protected and wired for higher current levels (let's say 5 amps) I might use the thin wire to let go at 3 amps just to keep from replacing 5 amp fuses however I'd be certain that the operation of the fuse (melting of the wire) doesn't result in a dangerous arc or spray of vaporized metal. I'd only do something like this at very low voltages.

If you really aren't sure then avoid doing this. Safety is most important.
 

Johnson777717

New Member
Stevez, I like your idea about creating the fuse for the fuse.

It's great to see the open-mindedness and curiosity of you folks, seriously.
 

ChrisP

Member
Just to throw another thought into the pot... this concept is exactly that which is applied in the use of a "fusible link" as found for many years in most automobiles. In that application, a circuit designed for a given load and wired with a given gauge wire was protected by a short and easily replaced length of lighter-gauge wire. For example, a circuit wired with 12-gauge wire might be protected at the source by a 16-gauge link. Thus, the highest current that will flow in the circuit is governed by the capacity of the link.

These links were generally not standard primary wire, however. In many cases, the links were more flexible than standard wire, and another difference is that the wire would often melt through without visibly damaging the jacket of the wire. This made continuity testing necessary rather than simply being able to confirm an open link visibly.

It should be noted however that most auto makers have now gotten away from fusible link wire, and gone to the more predictable maxi-fuses instead.
 

Philipc

New Member
Guess I should of mentioned where I have been using it??
I'm currently an EE student and just finished Physics II, unfortunately that is the extent of my knowledge with electronics, but any how I've built a little lab in my bedroom and have been running some various experiments using my variac as a power supply. The variac has a 10 amp fuse, but after one of my homemade experiments blew the fuse, I've been using the 41 awg wire to prevent me from doing this again. I’m still using the 10 amp fuse in the variac, but also the homemade fuse in series. So I'm not really using the wire to protect my circuits, but instead my variac. My main concern with using the 41 and 44 awg wire, is the resistance of the wire effecting any thing? I’m not sure how the resistance of my fuse may compare to a real fuse? It just seems that 2-3 amps passing through such a thin wire is not a good thing?

I've ran several experiments on the home made fuse, and found that regardless of the voltage, the wire tends to blow around the same current levels.
And far as consistency between batches, I have a two pound spool of each, so I have miles and miles of wire to work with.

Thanks everyone for your input.
Philip
 
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