Power Status LED

Discussion in 'General Electronics Chat' started by Zapnologica, Jul 6, 2012.

  1. Zapnologica

    Thread Starter Member

    Jun 15, 2012
    Good day,

    I am trying to add a power status led to my circuit.

    I have a input voltage range from 24v to 9v.

    Now when my board as power i want a small green led to light up so that i can see that the board has power.

    But i am not sure how to do this with the potential of different voltages.
    and i don't really want to add a voltage regulator just for the power LED.

    Is there a way in which i can do this?

  2. takao21203

    AAC Fanatic!

    Apr 28, 2012
    1. Use high brightness LED + 2.2K or 3.3K resistor. There will be difference in brightness but usually this is neglible for indication.

    2. Use a Z-Diode to clamp voltage.
  3. Zapnologica

    Thread Starter Member

    Jun 15, 2012

    2.2k resister worked :)
  4. JMac3108

    Active Member

    Aug 16, 2010
    Zapno ...

    This is a common problem. I also recently had a system where I needed to drive an LED over a wide range of voltage without being able to see the difference in brightness. The simple solution is to drive the LED with a current source. You get constant brightness regardles sof the voltage (withing limits of the current source).

    An LM317 makes a very easy current source. Just look in any LM317 datasheet and you'll find a sample circuit. And of course there are lots of other ways to make current sources.