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Choosing correct wire

Discussion in 'General Electronics Discussion' started by Ronnie_Space, Jun 27, 2017.

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  1. Ronnie_Space


    Jun 19, 2014
    For a simple hobby circuit with x10 1W LED's running at 3.4V 200mA, (power supply 5V dc) how does one select an appropriate wire gauge for this load? Is there a rule of thumb or calculation anyone can advise?

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
  3. Ronnie_Space


    Jun 19, 2014
    Thank you.

    Acceptable loss 3%

    5V dc

    2 amps

    1m Length

    = 19AWG
  4. dave9


    Mar 5, 2017
    Practically speaking, I select the highest gauge (regular) insulated wire I have in stock... buying spools of wire gauge higher than needed for that, doesn't seem as cost effective to me as buying more of a gauge that can handle *most* low current projects, not having to (invest in) stock wire that's barely capable.

    However I question the use of 5VDC, presuming that a simple hobby circuit would use a resistive current limiter for each, so you're losing [ (5V - 3.4V) / 5V ] * 100 = 32% power as heat at the resistors alone. If you were to switch to using a 12V supply and ran 3 x LEDs in series for 10.2V sum forward voltage, you more than cut your resistor loss in half. j Granted, 3 x series doesn't divide into 10 evenly, but you're running them at under 1W each so perhaps running 9 LEDs at 222mA each instead of 10 LEDs?
  5. Lionel44


    Jan 11, 2014
    The wire gauge is governed by the maximum current drawn. It is always wise to check with the suppliers data sheet. However as a rule of thumb wire can be calculated by a factor of 10. eg a 1mm diameter wire (18 gauge) will safely carry 10 amps, 1.5 mm - 15 amps etc.
    It is the insulation on the wire that governs the voltage. For that reason a 1mm wire used on a low voltage hobby project or an automobile circuit cannot replace a 1mm wire used on 110 or 240volt household system.
    There is also something called voltage drop that has to be considered. Although it is unlikely to affect most hobby projects, it will have to be taken into account if long distances are involved (such as installing a doorbell or a motion sensor down at the garden gate) Because of the resistance of the wire (18 gauge 22 ohms/1000ft), volts will be lost over long distances and a larger gauge maybe required.
    Last edited: Jul 3, 2017
    Ronnie_Space likes this.
  6. xryz


    Jun 24, 2013
    i usually go with what is available which is usually a bit of old cat5 or telephone wire for this sort of project.
    Ronnie_Space likes this.
  7. Ronnie_Space


    Jun 19, 2014

    Good point regarding the loss. However, 5VDC comes from the powerbank I am using as my fixed power source.
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