How to KNow?

Discussion in 'General Electronics Chat' started by sangpo, Aug 29, 2013.

  1. sangpo

    Thread Starter Member

    Aug 17, 2013
    74
    1
    Hellow sir/madam,

    I am self learning basic electronic.

    Suppose I have a potable MP3 player which is rated for 3 Volt Dc. The ampere is not mention. I have a car battery of 12 volt DC and want to connect that to my player at the same time I dont want my palyer to damaged. Since it does not mention ampere, I dont know how to calculate the value of resistor ( if I have to use resistor) using Ohm's Law.

    Please do help me here.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    You need a voltage regulator - a "smart" resistor - set to 3V. Then you don't have to worry about current so long as the regulator can supply what the player needs, which is likely quite small and varies depending on what the player is doing. A simple resistor won't work. The LM317 regulator would work but there may be other options. You can also buy DC-DC buck converters cheaply these days, and this would be more efficient (not as hot).
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    I could think of a lighter source for a Portable MP3.! :p
    I would be more concerned my back get damaged than the player? :D
    Max.
     
  4. sangpo

    Thread Starter Member

    Aug 17, 2013
    74
    1
    Thanks you all for the commensts
     
Loading...