Amps...

Discussion in 'Motorhome Chat' started by DBSilverfox, Jun 22, 2012.

  1. DBSilverfox

    DBSilverfox Read Only Funster

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    I just bought an Avtex TV for the motorhome, and although I am sure it is obvious, I just want to check :RollEyes:

    TV is 35 Watt, runs on 12V and also 230V stepped down to 12V through the transformer.

    So if i run it off 12V socket it is pulling just under 3 amps. If I am on hookup, and using the mains socket, does that therefore mean it is only pulling 0.15 Amps?

    cannot get my head round whether it is the 230 volt supply or the stepped down 12volt consumption I should be considering :Doh:

    Thanks a lot

    David
     
  2. JeanLuc

    JeanLuc Funster

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    The current drawn by the TV will be the same in both cases since it is always running from a 12V potential, whether directly or via the power pack. So your calculation of approx. 3 amps when powered directly from a 12V socket is correct. When using the power pack from a 230V AC supply, the current drawn from the mains will depend on the specification of the power pack rather than the 35W power needed by the TV. (It is unlikely to be a transformer by the way - today, most small devices use switched-mode power packs.) Does the power pack state the input current somewhere, or perhaps the power consumption in watts? In practice, I am not sure why you would need to know the current drawn when on mains anyway since a 230V AC supply will be overwhelmingly sufficient for such a small device.
     
  3. DBSilverfox

    DBSilverfox Read Only Funster

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    Thanks Philip. The adaptor says input 1.5 A, output 3.33 A. So that seems to agree.

    As for why? Curiosity for one, because i don't like not knowing things. Also because when on 10A hookup i just like to know how much i am using before letting swmbo plug in her hair straighteners ...

    David
     
  4. Wildman

    Wildman Read Only Funster

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    As to why the answer is a simple one.
    Watts are the product of amps and voltage conversely amps are watts divided by voltage. As the Watts are constant irrespective of the supply voltage it is obvious that if you change the voltage the amps will also change
     
  5. Terry

    Terry Funster

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    Hi David if you are running off the 12v plug it is running off the L/Batt so will not effect your amp /watt usage anyway :BigGrin: Let the boss use her straighteners :Wink:
    terry
     
  6. JeanLuc

    JeanLuc Funster

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    Ah, now I understand: caution at the possibility of 'blowing' the supply post when the GHDs (or whatever brand) are unleashed in anger. Very unlikely in the UK, but I guess it's possible on some continental sites with 5 amp supplies.
    I rarely use a hookup (solar panel and 2 batteries suffice) but even when / if I do, I tend still to connect the TV via a 12V socket. That way I don't have to bother finding the 230V power pack or changing leads. If hooked up to 230V, the onboard charger will be more than able to exceed the 3 amp drain from the battery(ies).

    Regards,
     

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