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In car MP3 power?

Discussion in 'Electronic Basics' started by taimou, Feb 14, 2004.

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  1. taimou

    taimou Guest

    Hi All

    I am keen to get a kitstream MP3 circuit board to work with a 3.5" drive in
    my car, (this kitstream looks very neat)

    The kitstream board requires 5V 75 mA; the HD that is a standard ATA drive
    is 12V (I think).

    Can I use a PC power supply with an inverter to supply the 5V to the
    kitstream via the floppy power cable?

    Or is there a better, simple, smaller, (cheaper) way I can get 5V and 12V
    (suitable to run the board and HD) from my 12V car power system?

  2. You can get the 12V straight from your car's power system and either
    use a 5V linear regulator or a 5V switching regulator, like the
    following, to create the 5V from the 12V supply.

  3. Feasible, but a PC supply may require an additional load to function properly e.g. a motherboard and processor
    Perhaps you could investigate some of the low voltage switching converters/supplies that RS or Farnell sell
  4. George

    George Guest

    Make sure you take it straight from the battery, not the cigarette
    lighter. The 12V from there is prone to noise and spikes. Also, the
    fact is that while running, the voltage off the battery might not be
    that clean as you are really getting the 14~ voltage off the
    alternator, which may not be that clean either. An inverter will clean
    that noise up for you, assuming it is good quality. Otherwise you may
    want to try some line conditioning before you regulate the voltage.
  5. The car "12 V" system will provide in fact about 13.5 V (depending on
    how well charged the battery is), so you need some regulation.

    An inverter to convert to mains voltage, followed by a computer power
    unit would work, but is a waste of energy and money.

    A "low drop" voltage regulator could easily provide the stable 12 V for
    the hard disk and, if required, an amplifier.

    For the 5 V lines one could either use a standard 7805 3-leg voltage
    regulator or a switch mode regulator. The latter would be more energy
    efficient, but at 75 mA the hassle may not be worthwhile ((12 V - 5 V) *
    75 mA = 530 mW, much less than the 20 or 30 W sound system in most
    cars). Be sure to mount the regulator onto a small heat sink though.
  6. Patrick

    Patrick Guest

    I am intested in a similar project. do you need a add-on ampliflier
    to hook up the speakers? since I saw that only have a
    headphone port.


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