Laptop cooler

Discussion in 'General Electronics Chat' started by Alec_t, Jan 1, 2014.

  1. Alec_t

    Thread Starter AAC Fanatic!

    Sep 17, 2013
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    I have a Targus Lap Chill Mat for cooling my Vaio laptop. The Mat has twin fans driven from a USB port but I have been unable to discover the current draw from the spec or online searching.
    I note that the area of the air intake beneath the Vaio is considerably less than the combined swept area of the two fans.
    Question: how efficient is the cooler? I haven't noticed any obvious reduction in laptop temperature in use.
    Clearly, by drawing its power from USB the Mat actually increases the power consumption of (hence heat produced by) the laptop; so that means the laptop's internal fan will be working harder and itself using more power!
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Isn't the current listed on the labels on the fans?

    The regular computer fans has the current on the label.
     
  3. Alec_t

    Thread Starter AAC Fanatic!

    Sep 17, 2013
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    Without wrecking the Mat I can't get to the fans to read their labels :(
     
  4. shteii01

    AAC Fanatic!

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    Ah! I was afraid of that.

    You could fall back on the USB current rating. I think there is defined maximum in USB specification. So you can take that, at least you will have the maximum.
     
  5. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    What about making a custom adapter in order to measure what you want? ???? Have you taken a look at the spec or the manual for the information you seek??
     
  6. wayneh

    Expert

    Sep 9, 2010
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    This reminds me of an age-old problem: Does fanning yourself on a hot day actually work to cool you? A human is only about 25% efficient when producing mechanical work, so more than 3 times the fanning energy has to get dissipated just to come out ahead. Humans sweat, and I believe that's the crucial difference that makes fanning worthwhile.

    Your laptop doesn't sweat, but even still, more energy devoted to cooling fans should - in theory - help cool it. Your internal fans speed up - draw more power - when cooling is needed. This should be true of external fans as well, if they're effective in the first place.
     
  7. t06afre

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    May 11, 2009
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    Is not the current in USB limited to around 100mA. Unless the device "negotiate" for more power.
     
  8. Alec_t

    Thread Starter AAC Fanatic!

    Sep 17, 2013
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    Yes. Zilch about current draw. The only tech info is that it's powered by USB!
    I doubt there's any smarts in the Mat for negotiation.
    I'm assuming that's so; but in practice the cooling is not as great as I was hoping for.
     
  9. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Generally speaking. The whole bottom of the lappy becomes the heat sink. Obviously since it is plastic it is not very good heat sink, but it is better than nothing.

    By applying the fans to the bottom of the lappy, you help to remove the heat by moving the heated air away from the bottom.

    However, we now entering the question of air flow. Is there enough space between the heat sink (bottom of the lappy) and the fans to actually have the air flow? To move the hot air out and cool air in? Or are you just cycling the hot air?

    One somewhat interesting example is the rear of computer tower too close to the wall. The rear of the computer tower has a fan that moves the hot air from inside of the case. But the case is so close to the wall of the room, that the hot air just sort of bounces back at the case. So right outside of the case you have sort of pool of hot air. The overall effect is that inside and outside of the case is sort of equally hot and the case fans run as fast as they can, and not really provide much cooling.
     
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