Need to replace 100ua meter with LED indicator

Discussion in 'General Electronics Chat' started by doug08, Jul 24, 2011.

  1. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    Any ideas how? Ideally would like to see the brightness of the LED increase as the current goes up. I can settle for the LED lighting up when the slightest ua current is detected.

    Thanks.
     
  2. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    How about a bar of 10 LEDs lighting up? They make ICs that can drive such LED bars. I'm too pooped to do any looking for you though (I was out digging a sprinkler line in 100 deg F weather).
     
  3. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    You'll need to look at where that 100ua meter is in your circuit and whether it's a true ammeter or one masquerading as a voltmeter.
    If one side of the meter is at ground potential, this should be pretty easy. If the meter is floating, you'll need a current sensing amplifier.
    The 10 LED chip Someonesdad referred to is the LM3915, available everywhere.
    If you want LED intensity to vary with current, then you'll want to PWM the LED.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
  5. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    I'll get my hands on a lm3914. :)
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    To get your 100uA signal translated to a voltage, you could run it across a 10k resistor; 100uA * 10000 Ohms = 1 volt. You would need a high impedance buffer for that signal, like an opamp set up as a voltage follower.
     
  7. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    Aw c'mon, I was only off by 1 that's only 0.026%:)
     
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