Need advice: Jumper cable making

[Herath]

I bought some female connectors which i suppose are called dupont connectors. They are 2.54mm in size. And i bought few meters of heat shrink tubes too.
But i did not buy the required cables. i am basically looking for steel core or single wire(strand?) cables.
and my problem is, where can i find them locally and most importantly, what gauge should i buy?.
Thanks

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[SevenZero]

I'm not too clear on the jumper wire you refer. Are you referring small jumper wires with 2.54mm socket ? If you need that, since these are usually used for low currents, you can use normal flexible cable we use for circuits.

[Herath]

I am going to use these for micro controller work. i am looking for wires like the ones inside those UTP network cables. are they avaible like the normal flexible ones?. flexibles are hard to work with.

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[SevenZero]

Description for your knowledge.....

Solid wire, also called solid-core or single-strand wire, consists of one piece of metal wire. Stranded wire is composed of a bundle wires to make a larger conductor.

Stranded wire is more flexible than solid wire of the same total cross-sectional area. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire. Solid wire also provides mechanical ruggedness; and, because it has relatively less surface area which is exposed to attack by corrosives, protection against the environment. Stranded wire is used when higher resistance to metal fatigue is required. Such situations include connections between circuit boards in multi-printed-circuit-board devices, where the rigidity of solid wire would produce too much stress as a result of movement during assembly or servicing; A.C. line cords for appliances; musical instrument cables; computer mouse cables; welding electrode cables; control cables connecting moving machine parts; mining machine cables; trailing machine cables; and numerous others.

At high frequencies, current travels near the surface of the wire because of the skin effect, resulting in increased power loss in the wire. Stranded wire might seem to reduce this effect, since the total surface area of the strands is greater than the surface area of the equivalent solid wire, but ordinary stranded wire does not reduce the skin effect because all the strands are short-circuited together and behave as a single conductor. A stranded wire will have higher resistance than a solid wire of the same diameter because the cross-section of the stranded wire is not all copper, there are unavoidable gaps between the strands (this is the circle packing problem for circles within a circle). A stranded wire with the same cross-section of conductor as a solid wire is said to have the same equivalent gauge and is always a larger diameter.

However, for many high-frequency applications, proximity effect is more severe than skin effect, and in some limited cases, simple stranded wire can reduce proximity effect. For better performance at high frequencies, litz wire, which has the individual strands insulated and twisted in special patterns, may be used.

There are quite a lot of information at http://en.wikipedia.org/wiki/Copper_wire_and_cable

If you are going to work on a project board, you are correct, solid wire would be more easy to use. However, you might solder the edge of the stranded cable with some lead to make it stiff and straight so that you can use it for the project boards.

The reason I suggest the stranded one over the solid one is because I found the solid one tends to crack within the wire without our knowledge when we use to bend it more often. I have bad experience with this. I have never found a problem with stranded one since it is flexible than the solid ad when prepared as mentioned above, I don't see any difference.

Up to you to handle it from here....

[Herath]

i will use the flexible ones. however stripping them is a pain without breaking the strands inside. i donot have a wire stripper. i will try with a thicker wire.

[SevenZero]

Use a blade to cut a round about 0.7mm before tip and then you'll be able to strip it by hand. When you become skilled, you will be able to cut the round without breaking wires inside.