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Warning about 12vdc pixel strings and specified power ratings

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by fasteddy, Sep 5, 2012.

  1. fasteddy

    fasteddy I have C.L.A.P Global Moderator

    Apr 26, 2010
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    Albion Park NSW
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    Today I had a very good discussion with Lithgow Lights about the power requirements of 12vdc pixel strings compared to 5vdc pixel strings and that the specifications state 0.3watts for both 12vdc and 5vdc pixels

    So if the stated power is 0.3watts for both 12v and 5v then the only thing that can be changed is the current going through the LED, so instead of putting 20mA through the LED they instead use around 10mA so they then get the same power used regardless

    We will only use the Green LED as an example here in an RGB LED

    Green - 20mA - 5V
    total power dissapated: 104milliwatts
    40mW through the resistor
    64mW through the LED

    Green - 20mA - 12V
    total power dissapated: 252milliwatts
    188mW through the resistor
    64mW through the LED

    Green - 10mA - 12 volts
    total power dissapated: 131milliwatts
    100mW through the resistor
    31mW through the LED

    But this can be incorrect and Lithgow Lights has a string that puts 20mA through the LED and this is measured, so effectively this string will draw nearly 2.5 x the power than what is stated and this can be very misleading. This will also explain why Lithgow Lights said that they ran very hot as there is a lot of heat energy being dissapated through the resistor.

    So just a heads up for those using 12vdc pixel strings

    So in summary if using 12vdc strings then it is best to actually measure the current drawn by the string as it appears the rated manufacturer specs may be incorrect and misleading which can make a huge difference in how many power supplies and the guage cable used.

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