Wiring question (12v TV)

Discussion in 'Tech/Mech General' started by Ridgeway, Mar 27, 2012.

  1. Ridgeway

    Ridgeway Funster

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    Just installing a 12v TV, make MOOVE 16", it's a French brand. I've made the installation of the bracket and now need to pick up a 12v supply. Just behind the TV location there are some 12v lights with easy access to the cables and connectors. Now not being anything like a sparky, far from it in fact I always prefer to check..

    I have a standard cigarette socket supply for the 12v to the TV and with one red and one black wire, then on the lighting circuit I have a red wire and white supply wire which feeds as follows to the lights, red supply to black lighting and white supply to blue lighting

    Question is which of the red and black for the TV goes to which on the red and white ?

    I am correct in assuming that with 12v DC that it doesn't matter which way round it goes or is my memory failing me....
     
  2. gozomike

    gozomike Funster Life Member Life Member

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    Hi

    Yes it does matter which way round a 12 volt DC supply is connected, reversal could damage the TV.

    I am not sure that the lighting circuit will have thick enough cables and fuse to supply a TV. If you are not sure on doing the wiring it would be much safer to get it done professionally.

    Mike
     
  3. Ridgeway

    Ridgeway Funster

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    Thanks Mike,

    The lighting units are supplied by twin, 1.5mm flex which is the same as a standard power cord on most electrical devices so I assume that it will be enough, the sockets 12and 240 have the same flex to them as well.

    Glad you said it does matter about the wiring directions, saves a costly mistake. Is there a way to establish which way around ?
     
  4. slobadoberbob

    slobadoberbob Read Only Funster

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    use a multimeter

    Test it with a multimeter to establish the positive and negative.

    Bob
     
  5. JeanLuc

    JeanLuc Funster

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    Forget standards for 230V AC mains. With 12V DC you have to use much thicker cable for an equivalent load. This is because of the inescapable formula:
    current = watts / volts

    So a 60 watt item running from a 230V supply draws 60/230 = 0.26 amps
    But the same 60 watt item running on 12V draws 60/12 = 5 amps

    Also, you need to consider voltage drop which occurs over the run of cable. The longer the run, the thicker the cable needs to be. TVs can be sensitive to voltage, so if your cable is too thin, what started out at the battery as 13 V can end up being rather less at the TV.

    In your case, I think 1.5 sq mm cable should be OK, but it might be a bit 'near'. If you are running lights at the same time, be prepared for problems. Also, if you overload the cable, it will get hot and this represents a fire hazard.

    Most motorhomes have a dedicated 12V feed installed for a TV, separately fused. Is there no socket available in the TV cupboard / location, or somewhere near it?

    P.S. don't assume in a continental motorhome, that red (or brown) cable = positive. In mine, positive is blue. Check with a multimeter before connecting anything.
     
    Last edited: Mar 27, 2012
  6. Gromett

    Gromett Funster

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    I wouldn't use the lighting circuit if I was you. I would run a fresh cable to the distribution unit or use a cigar lighter socket if it is specced for enough current.

    A tv using 100Watts will pull 8amps or so (bit less)...
     
  7. TheBig1

    TheBig1 Funster Life Member

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    As already mentioned, the lighting circuit is not suited to powering a tv. It is fused far too low to protect the circuit and you will overload it

    As a general rule, the white wire would be ground in the lighting circuit and red the live. The cigar socket can supply 10amps generally and should be wired red positive and black negative.

    Always check first though with a meter as wiring backwards would damage the tv
     
  8. Ridgeway

    Ridgeway Funster

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    Thanks guys, really appreciate the knowledge sharing. Shame i can't use the lighting circuit as it's close by, the only 12v socket in the habitation area is a long distance away and on other other side of the van:Doh: I have found the wiring for that and it's looks like 2mm flex so it now makes sense to me about the higher ampage draw on 12v vs a 230v supply.

    Checked the TV and it's rated at min 4w and max 21w so it is very low although appreciate still worth taking either a socket supply or direct.

    Is it normal to have only 1 x 12v socket in the habitation area ? seems not enough to me, also there are only 2 x 230v sockets which also seems low, our caravan had more.
     
  9. Gromett

    Gromett Funster

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    I couldn't agree more. Most motorhomes I have seen do not have anywhere near enough sockets and those that do have are always in the wrong place.

    I have yet to see an MH that had even one socket next to the seats so you can plug a laptop in.

    It's one of the reason I went self build so that stuff is in the right place....

    My personal choice in your case would be to run a decent 6mm cable from the battery to where you want your TV. You can take splits off this cable and put a few extra sockets in while you are at it. If you are adding a TV, chances are in the future you may want to add a 12V satellite box and maybe a laptop charging point. It is worth putting a hefty cable in on the first job to cut down redoing work 2nd and 3rd time round....
     
  10. Ridgeway

    Ridgeway Funster

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    Sounds like a plan, fancy coming around, only about 800 miles:Rofl1:

    I take it the supply would be from the leisure battery consumer unit and I need to find a spare socket on it and then fuse it suitably, what size fuse would you say for a TV plus 2 sockets (laptop, iPad). 6mm wow that's some flex, you mean flex rather than cable in this case ? also what size cable/flex would the spurs be of the main 6mm ?
     
  11. Ridgeway

    Ridgeway Funster

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    OK had a look at the leisure battery fuse board and there is an outlet marked "TV" wonder what that's for:Doh: It has a 10amp fuse on it which seems correct and today I bought some 2.5mm flex that I'll use for a direct supply to the TV, makes sense in the end

    Crikey I've loads to learn on these MH's
     
  12. Ridgeway

    Ridgeway Funster

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    Job done, 2.5mm direct from consumer unit to TV, tested it and all looks good.

    Thanks
     
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