Auto-Fan for TV Cooling

Discussion in 'The Projects Forum' started by frank1492, Dec 7, 2010.

  1. frank1492

    Thread Starter Active Member

    Dec 7, 2010
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    Hi-
    I need a circuit that will detect current flow through the power cord when I turn on my new LCD-LED TV and close an external switch to start a small computer fan. The TV is housed in a cabinet and for safety's sake I'm installing a small computer fan to exhaust the hot air. (.2a) So I'd like the fan to turn on when I turn on the TV.
    Is this simple? I never see these "off the shelf" though I think people might want them.
    Thanks for any help!
    Frank
     
  2. tom66

    Senior Member

    May 9, 2009
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    Hmm, have a look at mains operated fans, you can usually get them in 120mm packages, which is the size of most computer fans. Here's one in the UK. Operates off 230V mains (AC), so it can be plugged in if wired into an appropriate fused plug. I imagine you can find something similar for where you live, and at a better price. That way, when you turn the power to the set off the fan will also switch off. You might want to insert a series resistor, about 1k ohm high voltage (at least 400V) 2W power rated (try several values), to limit the speed.
     
  3. Markd77

    Senior Member

    Sep 7, 2009
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    How about just detecting the temperature for turning the fan on?
    It would be simpler and just as effective, maybe better, because the fan would run after the TV was turned off until it has cooled down.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Markd77's idea could be effective.
    Also when the temperature is low( and the fan is off), you do not have the noise of the fan.
    On this page the last circuit is for a 12 Volts fan using a FET to switch it.
    http://www.bcae1.com/coolfans.htm

    Bertus
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
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    My questions in return is:
    1) Is this TV New?
    2) Why would it need additional cooling?

    Tapping directly from the TV's main input and using a simple 12V wall adapter connected to the fan would be all that is necessary.

    Can you explain to us why you think it needs additional cooling?

    iONic
     
  6. DigitalReaper

    Member

    Aug 7, 2010
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    You can get extension cables with that sort of functionality built in. See http://www.maplin.co.uk/Search.aspx?MenuNo=95171 for a couple of examples. The slave sockets only turn on when the device connected to the master socket is drawing power.

    I have to agree with the above posters though, are you sure you need extra cooling? The temperature controlled fan would be the method I would use if I were doing it.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Does your TV have any outputs, for instance a USB port? Could really simplify things. Even digital audio-out could provide a useful trigger.

    It's not hard to build a temperature-based fan controller and I've posted such a circuit here not long ago. But that said, it would be far easier to use off-the-shelf stuff if you can.
     
  8. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    My thoughts exactly. LCDs don't get terribly hot, plasmas do.
     
  9. frank1492

    Thread Starter Active Member

    Dec 7, 2010
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    The fan is just a precaution because I have housed the TV in a cabinet. The vents at the top of the set are about 1" from the bottom surface of the top of the cabinet. There is a margin of 1" on the sides as well, but the back of the cabinet is closed except for a few 2" holes. (I'd like to keep it that way for dust protection.) Of course when the cabinet doors are open for TV viewing the heat can escape out the front as well. And the face of the screen is within 1/2" of the cabinet front. Feel free to give me reasonable assurances that I don't need anything...:)
    I had thought of the thermostat idea but I'd prefer the fan run constantly rather than cycling on and off. Still I may go this route if I think I need to because thermostat circuits are easy to find.
    I had guessed what I really wanted to do would not be trivial because I had never come across such a circuit when I had wanted to do this before.
    The set has several HDMI outputs and a USB input for service and reading JPEG files. There are audio outputs both digital and analog as well. I'd be curious to have someone explain in detail how I might use the signal from any of the TV's outputs as a trigger for a relay.
    Thank you all.
     
  10. frank1492

    Thread Starter Active Member

    Dec 7, 2010
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    BTW I am examining the idea of power strips with slave sockets as some of you have suggested this. But I haven't found much for sale online in the U.S. One that was reco'd was discontinued. Can someone suggests some key words to try in my search?
    Just to be sure I am clear: These slave sockets will only be active when current is being drawn through the main socket, is that correct? If so that's what I want!
     
  11. frank1492

    Thread Starter Active Member

    Dec 7, 2010
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  12. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    The Idea of keeping the cabinet cool is good. And is advised. Just to get the air refreshed is enuf to cool LCD's.

    If you are a tech then you can tap off from it's supply to switch on a relay , but if not I do not recommend to open it up. U might need something like a small LDR placednear the screen out of site. use it to Bias a transistor accurately to turn at the level of LCD light out put. from that u can use anything from a relay to a 12V ATX fan
     
  13. wayneh

    Expert

    Sep 9, 2010
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    A hole big enough for the fan, and an inlet below, may well be enough all by itself.

    OP, what's the power draw rating on this thing? That should give some idea of how much heat needs to be removed.
     
  14. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I am using such a smart (master / slave) switch for years.
    It powers the periphials (slaves) of my computer (master) when I switch it on.

    Bertus
     
  15. wayneh

    Expert

    Sep 9, 2010
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    That does look sweet, and I can think of places I could use one. However, it sounds like it needs at least ~60 watts load to trigger the switch. I guess even an LED backlit LCD TV will have no trouble reaching that?
     
  16. frank1492

    Thread Starter Active Member

    Dec 7, 2010
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    The idea of the light sensor is very cool- never would have thought of that! When the set turns on the Vizio logo is very bright- and not adjustable. Seems that might be a perfect spot to locate the sensor.
    Still....I'm probably going to go the easy route and get the Smart Strip.
    Does Bartus have any tips on the pot adjustment? I sense this can be tricky.
    Thanks again to all.
    Frank
     
  17. frank1492

    Thread Starter Active Member

    Dec 7, 2010
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    BTW I wouldn't open the set while under warranty.
    As for the set's power consumption, I was getting nervous since this uses LED for the backlight, not fluorescent. The specs say the set draws 57.1 watts average. Do you think that is enough??
     
  18. wayneh

    Expert

    Sep 9, 2010
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    It probably uses more at startup but when a black scene comes along and the LEDs all turn off, I wonder if the strip would then switch off, coming back on when a bright scene re-triggers it. Sure would be nice to try before buy.
     
  19. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The smart switch I use has a sensitivity adjustment, so I can adjust the switchpoint.

    Bertus
     
  20. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Umm!! I like to throw some light on this.

    LCD back lit is always active as long as the set is on, it's the LCD it self that produces black. Not the led strip going off.

    U can tell this if you service them.
    U shud look at my LCD TV thread that I posted about mixing two completely separate brands into one
     
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