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LED Power on Indicator

Discussion in 'LEDs and Optoelectronics' started by efiste2, Aug 23, 2013.

  1. efiste2

    efiste2

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    Jul 30, 2013
    I have built a very basic Pre-Amp unit to solve a low volume output problem on another project I have been working on.....It works very well, but I now wish I had fitted an LED into the circuit to show when power is ON, ( i fitted a simple switch that is a push to lock on which by sight tells you nothing)
    My question to you learned chaps is If i fit an LED across the SWITCH WIRE and the NEGATIVE connection, when the unit is switched on, will the LED light up. I know I will also need a resistor in series with the LED, so my next question is what value resistor will i need.
    here is the "fag-packet" drawing of my unit. The unit is powered via a 9v Battery

    [​IMG]
     
  2. BobK

    BobK

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    1,648
    Jan 5, 2010
    Yes, put an LED with appopriate resistor between the wires labelled + and - on your diagram.

    Bob
     
  3. efiste2

    efiste2

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    Jul 30, 2013
    Thanks, all sorted now, used a 560 ohm, working fine.......
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    This is toooooo weird. This topic was solved by Bob with only one (1) reply!
    Is this an EP record book moment?

    Chris
     
  5. eman12

    eman12

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    Aug 24, 2013
    As efiste2 Stated You can use something between 330 to 1k ohm. But You can calculate the exact value of the resistor if you know the Voltage and the current of your LED. The formula is so simple and You can find it simply via internet.
     
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