Single or Muti-strand Wire? (+ Gauge Qs

hi all!

I would like to ask about the best choice for a high current applications, like 2.8Amp and above.

Which is the best choice? Multistrand wire is more flexible but is it needed, electrically speaking?

I know the reason why multistrand is used, here in Greece we call it "epidermic phenomenon". It is the tendency of the electrons to flow on the surface of the conductor....so with multstrand you multiply the area to good effect.

But does this apply to high current flashlights?

and the bonus question....

I have a problem with the wire thickness in a mod of mine, and I must minimize it.....

what is the smaller gauge suggested for 1.2A to the emitter and can i use single strand?

kosPap said:

here in Greece we call it "epidermic phenomenon"

Click to expand...

Same in English "Skin effect" epidermis = Skin
Cheers Norm

i doubt you will notice any difference if you use stranded, or solid wire of the same gauge, made of the same material.
2.8 amps i assume is p7 mod,
i,ve used many different wires for my p7 mods, from silver coated Teflon wire, to radio shack copper solid wire, stranded wire, also used wire from intercom cable, it is 2 pair cable, had thicker, stranded copper core but thinner insulation, but still sufficient for all my projects.
all worked great, all depended on what i had available at the time.

i don't see why you cant use single strand, many ppl use lacquer coated wire , single strand, for 3xp7 drop ins, works fine.

in 1 of my mods i needed relatively thin flexible cable with 7 conductors, i couldn't find one, what i found was a monitor cable, it had like 15 thin conductors, meant for signal, not for current, but i used 3 conductors for 1.6amps current, it worked out fine, i was expecting too much resistance, or overheating the wires, but nothing like that happened. wire stayed cold, and my dmm showed no drop in amps that was big enough to worry about.

I prefer stranded wire mainly for mechanical reasons. Solid wire of the same gauge seems to fatigue more easily and break, often at the through hole insertion point where the hookup wire is soldered to a driver board.

For 1.2A, 26 gauge should be fine. Is 26 ga too large for your application? Even the relatively small 14mm Sandwich Shoppe drivers all can fit 26 ga -- at least the ones I've used (GD, BBNG, SOB).

Skin effect is a high frequency phenomenon, so for filtered DC LED drive current it isn't an issue.

Since I have a 'junk' store nearby I prefer to use silver plated multistranded teflon insulated wire. Teflon insulation is great for its resistance to abrasion and doesn't 'melt back' when you solder the wire ends. It does need the 'correct' wire stripper to do a good job though.

cheers,
george.

According to the chassis wiring column of this chart, 29AWG is the absolute minimum gauge for 1.2A. 28AWG or larger is a better choice.

The frequency at which the skin effect becomes significant in a conductor is the rightmost column in the linked chart. For the conductors you're concerned with, the frequency is around 1.5*10^5 Hz, so I think you'll be fine with this 0Hz project.

Stranded or solid, just use whatever's a big enough gauge and you'll be fine. Personally, I find that stranded wire is easier to work with.

Great resource....saved for feature reference...

BTW there is a calculator on this.....what is the biggest volatge drop in percentage that we should aim for/tolerate?

kosPap said:

BTW there is a calculator on this.....what is the biggest volatge drop in percentage that we should aim for/tolerate?

Click to expand...

You should select your wire gauges so that you don't have to account for significant voltage- and, by extension, power drops across the wires.

A 2.5cm length of 28AWG solid copper wire will have a resistance of R = 212.9Ohm/1000m*1m/100cm*2.5cm = 0.00532Ohm. With your current I=1.2A and V=IR, the voltage drop across your wire will be 0.0064V, which is 0.21% of a 3V drive voltage. At 1.2A, the power dissipated in the wire will be 0.0077W. The voltage and power lost in the wire are small enough so as to not matter for a flashlight.

somehow i am getting different numbers fropm the calculator....

woudl you think that a 1 percent is a good goal?

I made a calculation on 2.8A and 28G and got 2%

28 ga is listed at 212.872 ohms per km. You have 2.5cm of wire, or 0.025m, or 0.025x10^-3 km. Thus, resistance for the 2.5cm length is 212.872*0.025x10^-3 ~0.0053 ohms. From V=IR and I=2.8A and R=0.0053 ohms, Vdrop ~0.015V.

If we assume Vf=3V, then the % voltage drop is 0.015/3*100 ~0.5%.

LukeA said:

You should select your wire gauges so that you don't have to account for significant voltage- and, by extension, power drops across the wires.

A 2.5cm length of 28AWG solid copper wire will have a resistance of R = 212.9Ohm/1000m*1m/100cm*2.5cm = 0.00532Ohm. With your current I=1.2A and V=IR, the voltage drop across your wire will be 0.0064V, which is 0.21% of a 3V drive voltage. At 1.2A, the power dissipated in the wire will be 0.0077W. The voltage and power lost in the wire are small enough so as to not matter for a flashlight.

Click to expand...

i'd agree with this if you are set on using 28awg for your application.

i've always been told to use the largest wire that is practical for the application. if you go up to a larger gauge you will have to worry even less about voltage drop. in any case you would want to use the shortest amount of wire possible.

No 28Gauge was an example only....

I now have a good range of wires (in mm here in greece) but lacking anything between 30 and 26 gauge equivalents...unless I am lucky to score a multiwire cable to cannibilize...

My main concern is that for P60 XPG builds reflector height is critical and 31 gauge is the only option tickness-wise....
In a desperate effort to use the exact thickness needed, I am considering the thicker of the single strand pieces DX incude with the drivers....(insulation thickness plays the biggest role actually)

regarding length I know all too well (in order to put up my home HAM antenna there was so much wire needed that made the purpose pointless).
Since I became good with installing wires on the driver PCB I now trim to needed length + 3mm....