12V LCD Monitor Power Supply??

Discussion in 'OnBoard Electronics & Controls' started by olivermr, Mar 16, 2009.

  1. olivermr
    Joined: Mar 2009
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    olivermr New Member

    Hi Guys

    Heres the vibe. I am trying to find a good solution to running an LCD screen at our navigation desk for an upcoming yacht race. We would like to run the unit off a hidden laptop but realise that it requires power. I have done some research and it seems that using an inverter type system would put quite a bit of strain on our power system ie. an inverter converts battery 12V to say 240V then back down to 12V for the LCD. The other option i believe is to run a 12 DC-DC regulator / converter system. Any suggestions as to how to go about this? I understand i would have to buy an LCD screen that has an independant power unit or wall wart unit but not to sure about matching the LCD regultor / converter and the battery system and how power consumption / isolation would maybe affect the yacht power system.

    If you're in the know and willing to help i would be more than stoked!!!

  2. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member


    The title "12V LCD Monitor Power Supply??" is the LCD screen a 12VDC screen or is it a 240VAC svreen (power input)?

    If it is actually a 12VDC screen, just run it directly from the battery, if it is a 240VAC screen, the cheapest supply is going to be an inverter, but as the screen is an LCD, you will have to use a true sine wave inverter, they do cost a bit more than the average modified wave inverter.
  3. Mylestec
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    Mylestec Junior Member

  4. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    not too sure what you are about but why not mount the laptop to the roof if you have one and bring the screen down like a sun visor ...done this in the car and ok.....check your computer has a suitable output to match the LCD some have video out some VGA handbook will tell you how to invert the screen or switch to external monitor
  5. Luckless
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    Luckless Senior Member

    2 key things here. How large of a screen do you want (And how small can you actually get away with?) and what video out puts does your laptop have?

    I know there are small, 6-12 inch LCD screens that run on a standard 12 (in a few cases 9) volt systems, and take various inputs. You could look around for those rather than using a full sized desktop model. Just be warned you will pay more for the size of the screen compared to a 'normal' desktop one. You will however have more efficient use of your battery than relying on an inverter.
  6. john schroeder
    Joined: May 2009
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    john schroeder john P schroeder

    I run all my navigation off my laptop. I power a flat screen in the cockpit behind a plexiglass cover . Its 110 volt This is powered by a converter bought from a radio shack . The flat screen is a best buy item with extended warenty I have been using it 6 years no problem its shaded by the dodger and when not navigating Ill watch a movie !But not when driving of course
  7. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Unless you have already bought the TV I would really look at the line of car and RV TV's designed to work off of 12V power. Just do a google search for 12v tv and they pop up all over the place.
  8. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    There are lots of 12v powered LCD screens and many that are 120v but they converted to 12v before it get to screen.
  9. RoyHB
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    RoyHB Junior Member

    Interpreting the question

    I think the original question has to do with a concern about the cleanliness of onboard 12vdc power being supplied 'raw' to domestic equipment that is designed to be supplied by a 'brick' power supply.

    I have the same concern about some equipment I plan to install. On-board 12vdc power should be relatively clean except when inductive loads start up (fridge compressor, windlass, electric winches, macerators, etc).
    Also, depending on how it's connected the engine starter motor may induce some 'spikes' - though often it won't as it's on a separate circuit.

    The other consideration is that on many boats, the house bank batteries are cycled from full charge down to some nominal level (50% or 12.2 volts or whatever). Some cranky equipment may not appreciate the lower or upper end of the scale, battery chargers often send 14.2 volts or thereabouts which is present on the 12 volt bus as well as on the batteries.

    Hence the original posters question about DC/DC converters - I think what he's asking is whether it is necessary or wise to use such a beast to stabilize and clean up the dc power provided to some sensitive on-board electronics.

    I'd appreciate the views of people with actual expertise/experience/knowledge about this. I hope I don't sound unappreciative but this is one of those kind of topics that seems to elicit replies from well intentioned people who relate their personal experience rather than a technically correct answer from an engineer or professional electronics tech/installer.
  10. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The laptop running on 12V generates its own working voltages, so the video output floats and can be connected to any Asian 12V LCD monitor.

    There are however certain brands (i.e. Nfren) with exceptional sensitivity for supply voltage negative spikes. They display a black screen after such an event and need to be switched off and on to recover. In such a case an LC mains filter is required.
  11. TerryKing
    Joined: Feb 2007
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    TerryKing On The Water SOON

    I need to do some digging for a "Good" answer. The Car PC guys have done work on this, but I didn't find where I 'saved' it :)

    The biggest worry is the engine starter motor puts out 100+ Volt spikes as it is switched off as the engine starts.

    There are two basic approaches: (1) "Filter", consisting of a series-inductance and parallel-capacitance configuration, and often adding a parallel "Shunt" voltage spike suppressor. (2) A functionally-separate supply such as a DC-DC converter (a 'black box' with a 12 or 24 volt DC input and an isolated 12volt DC output).

    My cheap-and-dirty approach on my small boat: A simple L-C filter from the engine battery to a 24 Ampere-Hour 12V GelCell battery with a 16 volt Zener diode 'suppressor'. A manual switch isolates the Gelcell when the engine is off. I know this is error-prone, it's just what I have. Better solution would have a low-drop Power FET as the automagic switch. But if the Engine battery dies or blows up, my GPS and Radio still work...

    I'll try to find that Car PC filter stuff...

    Regards, Terry King ..On the Red Sea at KAUST.edu.sa
    Newsletter: http://redseanews.info Community Information: http://kcomm.info
  12. SheetWise
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    SheetWise All Beach -- No Water.

  13. TerryKing
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    TerryKing On The Water SOON

    Thanks for these pointers! Better than what I had seen about Car PC's

    This looks really good for onboard nav and safety / radio gear!
  14. gonzo
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    gonzo Senior Member

    I think that the key to the question is that he wants the PC hidden.
    Olivermr: Are you trying to use a computer when the race rules don't allow you? If not, they make all kind of waterproof laptops.

  15. SheetWise
    Joined: Jul 2004
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    SheetWise All Beach -- No Water.

    I'm not sure I see your point -- I assume he wants the battery and power connections hidden as well. This would be a daylight LCD touchscreen if used in the cockpit.
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