Complex problem, simple solution needed :)

Discussion in 'The Projects Forum' started by Edmunds, Jun 28, 2011.

  1. Edmunds

    Thread Starter Active Member

    Sep 27, 2010
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    0
    Hi all,

    My iCamper project, as I have started to call it (putting lots of "i" devices and trying out some smart home/home automation stuff in a camper) is rolling along nicely with some significant help of this forum. I have a new problem.

    I have Apple TV running now from a 12V to 5V DC/DC converter. This might seem simple, but the crazy thing can draw like 20A so it took a while to find the right converter. The problem is, the Apple TV restarts every time I switch on the TV. I have had a digital voltmeter connected to the terminals and it shows between 4.99 and 5.15V. At the moment of switching on the TV, it shows like 5.33V for one moment. It does not seem like a big spike, but a)Apple TV might be very sensitive to higher voltage; b)my digital voltmeter could not be quick enough to detect a much bigger spike. Or, it could be, the problem is an actual drop, not a spike that my voltmeter is not showing. Either way, I need some kind of filter which sounds like a big fat capacitor.

    Questions:
    1) Am I talking any sense here?
    2) Can this be addressed with some kind of capacitor filter?
    3) If yes for (2), what would that look like?

    Thank you and BR,

    /Edmunds
     
  2. #12

    Expert

    Nov 30, 2010
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    Yes. A big, fat, capacitor would probably fix it. Place the cap physically near the Apple TV and quit buying 5 volt televisions when you can get 12 volt televisions. 20 amps of 5 volts is only a hundred watts. No surprise that a TV could use 100 watts.

    I really can't guess the size, but there are some massive caps available in the 5.5 volt range and some other massive caps in the automotive range. Time for a search of "what's available".

    edit: I found .022F for $1.07 at Mouser so the price is not as bad as I thought.
     
    Last edited: Jun 28, 2011
  3. wayneh

    Expert

    Sep 9, 2010
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    The AppleTV has an internal 6W power supply. Something's not right here.
     
  4. #12

    Expert

    Nov 30, 2010
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    Now there is something I didn't know! A 6 watt TV!

    If wayneh is right, my answer is wrong.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    It's not me, that's a spec from Apple.

    Note that the "AppleTV" isn't a TV, it's a device for browsing and playing digital content such as Youtube and movie rentals, on a TV or HDTV. It has no screen to power, although it has a wireless router and that probably requires most of the power that the ATV uses.
     
  6. #12

    Expert

    Nov 30, 2010
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    Whew! For a minute there I thought TV's were getting magical.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Depending on your perspective, they already are. I wonder how Ben Franklin would feel about his whole "early to bed" thing if he had an HDTV! :D
     
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