How to make go from 12V to 19V with resistors

Discussion in 'General Electronics Chat' started by Batista230, Jul 9, 2011.

  1. Batista230

    Thread Starter Member

    Feb 11, 2009
    14
    0
    Hi
    I have a bag of different size resistors and I want to run a 19 volt laptop from a 12 volt DC car battery

    I have been told if I run the resistors in parallel it would increase the voltage
    I don’t know as of yet the amperage use of the laptop but I know it will be 19v
    I know little of ohms law

    The question is what size resistors do I need

    Also could I run my laptop and charge it direct from my 12 volt source

    Thanks
    Batista230
     
  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    What you have been told is wrong. It is not possible to increase voltage using a circuit built only of resistors.

    What you really need is a switched mode converter, but these are not easy things for a beginner to make. Commercial adaptors are made for running laptops from a 12V supply, I would suggest you try to obtain one of those.
     
  3. Batista230

    Thread Starter Member

    Feb 11, 2009
    14
    0
    Can it be done with capacitors?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Not just with capacitors and resistors. It also requires an inductor or broadband transformer, transistors or MOSFETs, and controller ICs.

    Laptops usually require several Amperes of current.

    This would not be something for a beginner to try to make. It requires much more advanced skills, and at a minimum an O-scope (oscilloscope) for test/troubleshooting.
     
  5. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    Technically you can build a charge pump with capacitors and a few MOSFETs, but they aren't much good for anything more than 50mA. ;)

    To the OP, here is an adapter sold by Dell. I bet you that all the money you will spend developing your own will be more than this one.

    Other manufacturers make their own.
     
  6. Batista230

    Thread Starter Member

    Feb 11, 2009
    14
    0
    OK best forget about building one then, as I dont have the parts anyway
    Would my laptop run direct from 12v?
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,793
    Probably not, but the brick will run fine from say a 400Watt Inverter. It doesn't even have to be a true sine wave inverter.
     
  8. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Just look for the matching power adapter on ebay and take the cost bite. It will get you going faster and for less money and stress.
     
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