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Calculate the power supply for 10 LED Screen's

Discussion in 'Power Electronics' started by dvid, Mar 31, 2013.

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  1. dvid


    Mar 31, 2013
    Hello guys!

    i have a pretty simple question, but im not sure and i dont want to burn anything :p

    I need to make an installation of 10 LED monitor of 18.5", but we dont have space to put a power supply for each one, so we are gonna put a bigger power supply for the 10 devices.

    I bought a power supply for a laptop for this application, it has 150w, 19,5v and 7.7A

    This is the specs of the LG screen:
    V = 19v
    A = 1,2 A
    Cnsumption = 14,4 Wh

    So, if we take the data of the monitor, we have:

    Power = ( 19 * 1,2 ) = 22,8w -------- 228w for the 10 screen's
    Consumption = (14,4wh) --------------------- 144w for the 10 screen's

    So i dont know what value is the right one, maybe if the monitors only takes 14,4 watts i can use the laptop power supply... but what you say???

    I'm gonna supply the 10 screens with a main cord of AWG 14 cable, with a cable for each monitor of AWG 22 cable.
    Original power supply of the screen = 19v, 1,3A

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    This data doesn't make sense to me. As you correctly calculated the power required to operate one LCD is 22.8W. If you operate 1 LCD for 1hour the Energy used is 22.8W*1H=22.8Wh.
    Since the 19V are surely DC, you can't even blame a power factor less than 1 for the discrepancy.
    I suggest you measure the real current consumption (at full brightness of the LCD). Add a reserve of e.g. 10%
    If the result is higher than the rating on the LCD's rating label, use the measured values for designing the installation.
    If the measured value is lower than rated, use the rating.
  3. BobK


    Jan 5, 2010
    1. If the lcd is rated for 1.2A at 19V, it might draw more current than that at 19.5V.
    2. You have to multiply the current by 10 for th 10 displays, so 12A is required.

    So your laptop supply is not sufficient.

  4. dvid


    Mar 31, 2013
    Yeah, the consumption is supossed to be 22,8wh, but the label says 14,4wh!

    The monitor is an LG E1942C, in the specifications of the website, says that the monitor consumption is 15w.

    I supossed that the 22,8w is the value of "Peak power", when the monitor is starting and something like that.

    And the 14,4w is the normal consumption...

    I will try to measure the real current of the circuit, but i think the 150w PSU can works in this case..

    ¿What do you think?
  5. BobK


    Jan 5, 2010
    I think you ignoring the fact that the voltage is too high.

  6. dvid


    Mar 31, 2013
    Im confussed about your last response bob.

    Yeah, we have 20v, but just 1A for monitor?

    If the consumption is 15w, the total power is150w, so my PSU of 150w can works right?
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    1V extra is *probably* not going to be an issue.

    I suggest you power 1 monitor from the power supply and make sure it works.

    Then add one more, and re-test, then keep going until smoke comes out of something. At that point you've added too many.

    But seriously, you may have added too many *before* you even got to that point.

    I would power no more than 5 based on the probability that the monitors draw more than 1A at some point (as they power up, for example)
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