getting 11.5V out of a battery ;)

Discussion in 'General Electronics Chat' started by Garry, Jul 20, 2005.

  1. Garry

    Thread Starter Member

    Jul 1, 2005
    Got a small problem... I'm trying to feed an LED display off a car battery (it's a timing display), and need ~11.5V for the LEDs. Using a voltage regulator is more or less not working, as the voltage drop of 1.5-2.5V between input and output is too much for reliable operation (car batteries run around 13.5V when fully charged ... but dropping into 12.xV ranges later on ... (haven't tried at what charge amount, though). I need a total of around 3A peak, but can split it up between the single display elements (10pcs) if necessary ...

    Any ideas?

  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    Low Drop-out regulator

    Here is the link to the LD1585 low drop-out adjustable regulator datasheet. It has a maximum voltage drop of 1 volt at 3 amps. You may want to consider this as a solution. The component is available at


    7-21-05 - Corrected spelling errors...
  3. jobarker

    New Member

    Aug 18, 2005
    LEDs are not sensitive to voltage as long as the diode is forward biased.
    Simply use a resistor to limit current to 20 mA or so. The LED should be lit any
    time the battery is on
  4. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    ya, that's right provided he's not concerned with the LED brightness. but if he's concerned with that then the regulator would serve his purpose.

  5. Garry

    Thread Starter Member

    Jul 1, 2005
    Yup ... Brightness is the issue here ... did some more tests, looks like I do need a bit higher voltage after all ... I will stick to running it off a regulated power supply and just set to whatever V I need after all ...

    Tnx @all ...