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How to reduce voltage by 0.5v - TV from 12v socket


D-Hill
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I have an LCD TV which is powered by a 240v AC adapter, output voltage is 19v ideally I'd like to power the TV using the 12v socket. I have a 12v DC adapter from a DELL laptop which is 19.5v output, the AMPS will be sufficient. I'd like to know what's the best way to reduced the voltage by 0.5v, I've seen other posts that suggesting the 0.5v difference should be OK but I don't want to take the chance and blow the TV.

 

I need to convert the plug and was hoping that I could make a converter cable that has an inline fuse that reduces the voltage, is this a viable solution if it is what resistor should I use, if not what alternatives should I consider?

 

Thanks for any help.

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I can't see the 1/2 volt making any difference as the TV will drop the incoming voltage to 12V anyway.

Graham

Unless otherwise stated all posts are my personal opinion 

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Putting a suitably rated diode in series with the live wire will  drop  0.6V

2018 Passat B8 Estate 150GT TDi150 towing a 2018 Bailey Unicorn S4 Seville

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I use one of these

https://www.ebay.co.uk/itm/UK-DC-DC-5-32V-to-12V3A-Automatic-Voltage-Stabilizer-Power-Converter-Regulator-/313220835322?

To smooth out the variance from the alternator voltage (12.2-14.7)  to feed my 12v router on the boat. Should work for your needs provided current is below 3amps.

Having said that if your adapter is supplied with a cigarette lighter plug fitted then it will already be able to do this. Make sure the DC is the right way round at the plug to the Television as they are not all centre positive.

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15 hours ago, Idleness said:

I use one of these

https://www.ebay.co.uk/itm/UK-DC-DC-5-32V-to-12V3A-Automatic-Voltage-Stabilizer-Power-Converter-Regulator-/313220835322?

To smooth out the variance from the alternator voltage (12.2-14.7)  to feed my 12v router on the boat. Should work for your needs provided current is below 3amps.

Having said that if your adapter is supplied with a cigarette lighter plug fitted then it will already be able to do this. Make sure the DC is the right way round at the plug to the Television as they are not all centre positive.

My required voltage is 19v current transformer is 19.5v, it’s the output  that’s the issue, but thanks for the post.

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9 hours ago, D-Hill said:

My required voltage is 19v current transformer is 19.5v, it’s the output  that’s the issue, but thanks for the post.

For some reason, known only to my brain, I read that you needed to drop the 12v side to protect the adapter not the 19v side😱

 

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On 27/09/2021 at 19:39, D-Hill said:

I have an LCD TV which is powered by a 240v AC adapter, output voltage is 19v ideally I'd like to power the TV using the 12v socket. I have a 12v DC adapter from a DELL laptop which is 19.5v output, the AMPS will be sufficient. I'd like to know what's the best way to reduced the voltage by 0.5v, I've seen other posts that suggesting the 0.5v difference should be OK but I don't want to take the chance and blow the TV.

 

I need to convert the plug and was hoping that I could make a converter cable that has an inline fuse that reduces the voltage, is this a viable solution if it is what resistor should I use, if not what alternatives should I consider?

 

Thanks for any help.

So your 240V AC adaptor gives a 19V O/P (is this AC or DC?)

Your 12V DC power supply provides a 19.5V O/P (presumably DC for a laptop)

If the two supplies are both DC then forget the 0.5V difference as it will be accommodated within the input circuitry of the TV. Just replace the plug to match the input socket of the TV. 

If however the TV requires an AC supply, you'll have to think again.

 

I have a 12V DC to 18V DC converter that allows me to run and charge a laptop directly from a 12V car socket, similarly my 240V AC unit outputs 19V DC and does the same.

image.png

Fourwinds Hurricane 31D Motorhome. Also MGTF135 1. 8i Roadster (fun) & Volvo V70 3.2Ltr LPG (everyday car)
Unless otherwise stated, my posts will be my personal thoughts and have the same standing as any other member of Caravan and Motorhome Talk.

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  • 3 months later...

I would recommend using a 12v inverter just plug in to 12v and plug your tv's 240 adapter in the inverter's 13a socket. No fitting of voltage stabilizers, transformers, certainly not diodes or non oem equipment that could be a fire risk. 

Pic is of 200w unit you can get larger  I would check the tv power rating to make sure it will cope but it has safety features built in to shut down if overloaded.

It will work with most low powered equipment,  chargers radios tv's. Defo not heaters and kettles.

I would stick to plug and play rather than adapting your vans electrical system.:excl:

20220129_084352.png

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On 29/09/2021 at 08:49, Guest said:

f your TV requires 19v , a 12v supply isn't going to work. Or am I missing something ?

 

Yes it a DC to DC converter 12Volt to 19.5 volt - i have one for my dell laptop to run from the car

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One of these. I've used one successfully to provide 8 volts from a 6 volt supply on a motorcycle. https://www.ebay.co.uk/itm/334237098344

Ian.
2013 Freelander 2 SD4 Auto / 2005 Bailey Pageant Vendée; 1952 Norton ES2

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Just purchase a boost converter. Dozens to choose from on eBay & Amazon. 
They are basically a DC to DC Step up unit, usually with adjustable output voltage. Just ensure the output current capacity is greater than your needs

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That's exactly what I pointed to.

Ian.
2013 Freelander 2 SD4 Auto / 2005 Bailey Pageant Vendée; 1952 Norton ES2

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On 29/01/2022 at 10:08, iansoady said:

One of these. I've used one successfully to provide 8 volts from a 6 volt supply on a motorcycle. https://www.ebay.co.uk/itm/334237098344

These things are rated at 2 amps with a recommendation of running at 1amp. They are made and shipped from China so unsure if they comply to any  uk safety standards.  If you do use them please check the power consumption of your tv. 20 watts at 9v  is 2.2 amps which will either blow the converter or worse start a fire!

You would be wise to fit a 1 amp in-line fuse between the output and the tv if that blows no damage done.

Good luck but i wouldn't chance it unless the tv was 10 watts or less.

 

 

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Yes, miised the current requirement. It's fine for my application which is only LED indicators.

Ian.
2013 Freelander 2 SD4 Auto / 2005 Bailey Pageant Vendée; 1952 Norton ES2

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