DC 12V@20A Toggle ON/OFF Switch for DC 19v@3.42A laptop power supply?

Discussion in 'General Electronics Chat' started by kerosen_720, Oct 8, 2015.

  1. kerosen_720

    Thread Starter New Member

    Oct 8, 2015
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    Hello, everyone!

    I need to install an on/off switch on a DC 19v@3.42A laptop power supply (used to power an amp board).
    I searched the web and I found out that the safest way to do it is to choose a DC switch that does not prevent the current from passing, based on wattage calculated (19v x 3.42A=64.98 watts/sec for the power supply).
    I found a DC 12v@20A toggle on/off switch (http://www.ebay.ca/itm/Car-Boat-Lig...-LX-/262000740204?hash=item3d0076076c&vxp=mtr) that I think would work as it has 12v x 20A=240 watts/sec. (it allows more electrical power to pass per sec than the input).
    I would like to know if I can install this switch and if the 12v is a too low value for this circuit.
    Thank you :)
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the ratings for dc switches voltage hae to do with how far the contacts open up, 19 volts o a 12 volt switch should be fine. the current ratings are for how much curent the conacts will handle and break without either welding themselvs together or melting. the 20 amp should work fine too.
    that 12 volt 20 a switch should be fine.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    This is a generic switch that would work to make/break your load. The 12V rating comes from the built-in LED on-indicator. If you use the switch on 19V, you should not hook up the third terminal that makes the LED light up. 19V is likely too much for the LED
     
  4. kerosen_720

    Thread Starter New Member

    Oct 8, 2015
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    Thank you very much, alfacliff :)
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Make sure you read my response. I think cliff missed the LED detail...

    The LED indicator in that switch is designed specifically for automotive applications where the input voltage is <15V. It might survive 19V, then again, it might not. You might be able to put an external current-limiting resistor in series with the third terminal, and be able to use it on 19V.
     
  6. kerosen_720

    Thread Starter New Member

    Oct 8, 2015
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    @MikeML: I didn't think of that, but it is rather logical: if there is light, there is power used :).I will not connect the ground, then.
    Thank you, MikeML :)
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    sw.gif

    WAG for an initial value = E/I = (19-14)/0.02 = 270Ω
     
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  8. kerosen_720

    Thread Starter New Member

    Oct 8, 2015
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    Great :) this means that I have to use a 270Ω resistor between the third terminal and the ground wire? I'm sorry, I do not have much experience in electronics :(
     
  9. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Try it, and then measure the voltage as shown above. If the voltage between 2 and 3 is much less than 12V, then decrease R2. If much less, then increase it. Goal is to wind up with about 12 to 14V between 2 and 3.
     
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  10. kerosen_720

    Thread Starter New Member

    Oct 8, 2015
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    Ok, got it, MikeML, I will follow the diagram and make the measurements.Thank you :)
     
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