GB BOY COLOUR irritating power LED

Discussion in 'Other Handhelds' started by romanaOne, May 3, 2014.

  1. romanaOne

    romanaOne GBAtemp Fan

    Apr 18, 2014
    United States
    where the potential goes to zero
    I got one of these knock-offs on ali baba and it works well. I tried a bunch of games on the 64 megabit smart card and they all work ok. Yes, there are a few minor graphics defects- Link kind of tears when he walks around in Zelda--but overall, it is amazing to be able to actually see the screen on a GBC in my favorite games! In darkness, the screen is even a little too bright.

    Does anyone else notice that the red power LED is bright as all hell? I put a piece of black electrical tape over it. But that LED is probably wasting 30mA, or about 1 to 2 % of the current in a 2400 mAh NIMH AA. (I don't know the true capacity of the batteries, but I'll bet it is less than what's scrawled on the side. Salesmans' mAh, LOL.)

    Then I noticed the Smart Card has a big bright green LED that lights up when you are using bank 2. Not too annoying since it's on the back, but there goes another 30+ mA....

    So LEDs are wasting like 5% of the battery and they're annoying.

    That's assuming a BRAND NEW set of NiMH batteries. Nominally, the LEDs are probably drawing closer to 10%.

    What would be a good current-limiting resistor to replace them with? i.e. what is the resistance of a forward biased LED and will it mess anything up if I replace the LED with a larger resistance?
  2. mikeyt1998

    mikeyt1998 YouTube Glitcher

    Aug 11, 2007
    Dalton-in-furness, north west
    In response to: 'Will it mess anything up if replaced'

    I don't think that replacing it with another LED of larger resistance would cause any harm, I imagine that the circuit that the LED comes from is literally just to indicate that the GBC is turned on, but then I don't know the circuitry for a GBC so can't be 100%... :(
  3. WigWrm

    WigWrm GBAtemp Regular

    Apr 17, 2007
    United States
    I=V/R. I around 3-5mA will significantly reduce the brightness. Assuming this runs off of 3.3V then, .005=3.3/R and R=3.3/.005 = 660 ohms.

    The resistance of the diode when it is on should be negligible (mili ohms to under 10 ohm range).

    Seems like Vcc might be 5V, so.....
    5/.005 = R = 1000 ohms or 1kohm (when I = 5mA)
    5./003 = R = 1666 ohms or 1.67kohm (when I = 3mA)
  4. cracker

    cracker Nyah!

    Aug 24, 2005
    United States
    Yoi could always totally remove the power LED since it is basically useless as you can tell if the GBC is on or not.
    pelago likes this.