LED switch status indicator

Discussion in 'The Projects Forum' started by deanspy, Jul 2, 2006.

  1. deanspy

    Thread Starter New Member

    Jul 2, 2006
    Hello folks,

    I have a circuit that uses a DPDT switch to choose two possible audio paths. I would like to add an LED(s) to show which path has been chosen. Yes, I could use a 3PDT switch, but I would rather not. I cannot modify the wiring of the switch, as the two paths (+ and - of a balanced microphone running phantom power) must be switched as-is.

    The solution must not colour the audio in any way.

    Any thoughts would be most appreciated
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    You can try a resistor on one path going to the LED and completing circuit Since the circuit is using phantom power it should light. It may however interfere with the audio. YMMV

  3. thingmaker3

    Retired Moderator

    May 16, 2005
    The LEDs could be driven by opamps. Since opamps have high input impedence, they should not interfere with fidelity.

    A modification of the "bar graph generator" in this tutorial should work: http://www.allaboutcircuits.com/vol_3/chpt_8/3.html

    Note that the LEDs would only light when a signal was present. One would still have to look at the switch when no input was present.
  4. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    how about using 2 DPDT. the other pole to take care of the audio path and the other pole to power up your LED. that way there is no audio interference.

  5. deanspy

    Thread Starter New Member

    Jul 2, 2006
    Thanks people!! I'm thinking I might "merge" your thoughts and use 2 small DPDT relays controlled by a single SPST pushbutton.