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Choosing the Correct AWG

Discussion in 'General Electronics Discussion' started by sall, Feb 4, 2011.

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  1. sall

    sall

    51
    0
    Jan 29, 2010
    I am wrapping up a few things for my LED project. I have 14 LED arrays. Each have 32 LEDs in series of 4 running @ 58mA. I am trying to figure out the correct wire gauge to use. So each array is drawing 464mA or .464A max for signal/brake intensity.

    Each array is triggered by a power supply which is either triggered by a dual intensity PWM for driving or by a soon to be designed microprocessor for some special effects (sequential, etc). The wiring in question is ran from the power supply (Sharp 12v regs with a transistor doing on/off switching on pin 4 of the reg) to each individual 32 LED array. The power supply will also be fused for the max output of the entire power supply.

    Circuit Schematic: (Note arrays are different than on schematic)
    [​IMG]

    Uploaded with ImageShack.us

    I have found several links with tables for this purpose but I would like to be absolutely certain.

    [​IMG]

    Going by this I am assuming 30 AWG would be sufficient. Correct? No? I was under the impression wire length was taken into account for this as well?

    I initially wanted to use ethernet cable to keep it all neat since i had plenty of connector from outdated laptops. Until I looked up ethernet specs and from I could find maxed out at about 350mA. Ethernet cable is 24 AWG IIRC so, why the low current rating? I guess that may be another question entirely but if I can use that it would be great.

    If you need more info about specs of the project I will be more than happy to provide what I can! I appreciate your input! :D
     
    Last edited: Feb 4, 2011
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    Unless you have any pressing reason to use the smallest wire possible, you might like to choose a larger wire size as it will be mechanically more reliable. You probably want to use a multi-stranded wire for the same reason.

    The resistance of the wire will not be an issue since your series resistance for the LEDs will be so large as to swamp it.

    If these are break lights, then their duty cycle will be low and the odds of overheating wires is pretty low. The current ratings are pretty conservative too.
     
  3. sall

    sall

    51
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    Jan 29, 2010

    The reason for choosing the smallest possible is because I have to run these wires through a small trunk grommet. I appreciate your input, what would your suggestion be for for the gauge?
     
  4. shrtrnd

    shrtrnd

    3,767
    487
    Jan 15, 2010
    I'm with *steve*, I'd concentrate on a multi-strand wire, just because you're fishing it through a grommet, and you don't want to break a single strand here or there.
    Have you checked the commercially available types, to see what they're using?
    Current-wise, you should be able to use smaller gauge, but I see a lot of 26-gauge multi-strand out there. Would a bundle of 26-gauge make it through your grommet?
    Just things to consider.
     
  5. sall

    sall

    51
    0
    Jan 29, 2010
    Yes, I should be able get 26-24 gauge through the grommet.

    This is why I initially thought Ethernet cable would be a good choice. Since, I have plenty of it and spare connectors to solder to pcb. It's my understanding that most Ethernet cables are 24awg. So, why the low 350mA current rating I have found in data sheets where the table states 2.1A?

    I ran two 194 bulbs through the Ethernet cable on the same wire for about 15 minutes yesterday. I did notice any heat or anything out of the norm. The 194 bulbs draw 0.33A so, two together was drawing more than my array would.

    I think I should be safe but would like opinions on using the Ethernet cable vs. stranded 24 or 26 awg.

    Thanks for input thus far.:)
     
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