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Cable Size (DC Long run)

Discussion in 'General Electronics Discussion' started by shockuk, Oct 29, 2013.

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  1. shockuk


    Jul 25, 2010
    Hi all,

    Wondering if you could help me size up cable for a stair lighting project.

    I would like to create a "string" of led lights, however this project differs from a conventional LED lighting project.

    Lots of stair lighting projects are designed without the ability to change LEDs.

    The "bulbs" / diodes need to be replaceable in the future, so I was thinking of using LED W5W (car sidelights), they're single LEDs and rated at 12v 0.02a (basically a LED and resistor in a convenient form factor). (Example: )

    W5W sockets and W5W LEDs can be purchased very cheaply online, especially when direct from manufacturer.

    There is approx 5 metres between the transformer and the first LED (the whole string would be approx 10metres total). There would be 13 LEDs in total, approx 0.26 amps, 3.12 watts.

    I would hope that I could use 1.5mm twin cable for this project. Please see picture for details :)

    Would 1.5mm cable be adequate, or will the voltage drop be too high for such a long run?

    Let me know what you think, and i'm curious if people think using W5W lights is a good idea or if you think it's a bad idea. ;)

    Thanks very much,

    Attached Files:

    • leds.png
      File size:
      24.4 KB
  2. duke37


    Jan 9, 2011
    My data book is old with a mixture of imperial and metric units but I think that 20m at 0.26A would drop 0.05V which is neither here or there.
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