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Old 21st August 2008, 07:00 PM   #1
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Default Flat screen TV install in Van, reducing amperage

Hi,

I'm a Newbie to this forum, and very inexperienced at installing auto audio/video systems. I tried unsuccessfully searching threads here for an answer and decided to post my questions.

I'm installing a new LCD TV into my VW van. The power source for the new TV has a converter, reducing 110V AC house current, down to 12V DC, 4-5 AMPS, which then connects to the back of the TV with a DC coaxial power plug.

The Van has the typical 12V system, so I'm thinking I can dump the converter that came with the TV, and wire it directly into the van's electrical system. The van has a second battery, so I'm not worried about the power drain on the starting battery.

Here are a few questions ...

1.) The TV's power source (the converter) outputs 12V DC, 5 AMPS, and the vans' electrical system outputs 12v DC, 10-11 AMPS. How do I reduce the amps so I don't burn-up the TV when it's directly wired into the van's electrical system?

2.) Presently, the output wire from the TV's power converter has a small plastic (magnetic?) canister near the coax plug. It's a small plastic cylinder (approx. .5" dia x 1.5" long), and the wire runs through it. I'm not sure what this does. Would I need to apply this type of unit onto any wiring that I do as well?

Any insights are appreciated.
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Old 21st August 2008, 08:55 PM   #2
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Default Re: Flat screen TV install in Van, reducing amperage

Quote:
Originally posted by YSquared
1.) The TV's power source (the converter) outputs 12V DC, 5 AMPS, and the vans' electrical system outputs 12v DC, 10-11 AMPS. How do I reduce the amps so I don't burn-up the TV when it's directly wired into the van's electrical system?

2.) Presently, the output wire from the TV's power converter has a small plastic (magnetic?) canister near the coax plug. It's a small plastic cylinder (approx. .5" dia x 1.5" long), and the wire runs through it. I'm not sure what this does. Would I need to apply this type of unit onto any wiring that I do as well?
1) You don't need to do anything for the difference in amperage. The TV will draw 5 amps from the van's electrical system. The electrical system system won't push extra current into the TV.

1a) If this is a pricey TV and/or you are the paranoid type, you can add a 12V regulator circuit, since a car's electrical system isn't literally 12V, it varies.

2) Sounds like an EMI filter core. I would leave it off your new wiring, unless I ran into problems.
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Old 22nd August 2008, 02:43 AM   #3
Eva is offline Eva  Spain
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Some TV sets actually expect 12V clean and regulated from their external power supply. Connecting these models to the 12V system of a vehicle may result in malfunction or damage.

In vehicles the voltage may be anywhere between 8V (when starting) and 15V, with brief inductive transients exceeding 30V or so when things are switched on and off.
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Old 22nd August 2008, 10:38 PM   #4
star882 is offline star882  United States
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What TV is it? What is the unloaded voltage of the supplied power supply?

You could use a MOSFET-based LDO with a very large capacitor on the output. Use a Schottky diode so the capacitor can only be charged through the MOSFET along with a current limiting loop to limit inrush.
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Old 14th May 2009, 04:24 PM   #5
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---or, just do one of the following: 1) Simple flyback; 2) Transformer-operated Push-pull; or 3) SEPIC, if input-output isolation is not required......

Any of these strategies will work well for a +12V automotive environment, as they will take input voltages above and below the output voltage.

Steve
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