How to cut power to R+L speakers - When current in 3 other circuits?

Discussion in 'The Projects Forum' started by aid545, Feb 17, 2018.

  1. aid545

    Thread Starter New Member

    Jul 10, 2017
    11
    1
    Hi,


    Can anyone show on a drawing/schematic how I would wire up the following:

    I have 3 wires going to a soundboard (normally no current flowing)

    When a current is applied to any of the 3 wires, it plays a corresponding audio message on the sound board

    I want the power in the left and right speakers from the main boat stereo system to turn off for for the time the current is flowing in either of the 3 wires (so I can hear the soundboard audio), and the power to return to the stereo speakers when current in 3 wires stops flowing.

    I think SPDT Relay is the way to do this .. just not sure what type of SPDT Relay would be needed or what to wire to what terminals.


    Thanks so much for any advice.
     
  2. crutschow

    Expert

    Mar 14, 2008
    19,539
    5,445
    What is the value of the voltage applied to soundboard input?
     
  3. aid545

    Thread Starter New Member

    Jul 10, 2017
    11
    1
    hi crutschow .. i think the voltage applied to the soundboard input is 12v.

    Soundboard : https://www.adafruit.com/product/2220


    The setup is :

    GPS tracking unit (powered by 12v battery)
    GPS tracking unit has 3 output wires
    When certain conditions occur the GPS unit turn's on current in one of the 3 output wires
    The output wire activates audio on soundboard
    The current continues to output as long as conditions exist


    Below is specs from GPS unit I/O (not sure if that means 150ma on output?):

    Digital Inputs : 3 (1 fixed, 2 programmable bias)
    1-Wire™ Interface : 1 (driver ID, temperature sense)
    Digital Outputs : 3 open collector (150mA)
    Analog Input : 1 External ADC input
    Status LEDs : 2 (GPS and Cellular)
    Serial Interface : Serial port (TTL Level)
     
  4. wayneh

    Expert

    Sep 9, 2010
    14,709
    5,229
    You need an audio mixer that can mute one signal A when a signal B is detected. It's done at the line-level output of the soundboard and whatever the input to your stereo is normally. I've seen such a thing but can't recall where. :(
     
  5. crutschow

    Expert

    Mar 14, 2008
    19,539
    5,445
    It's a nit but the normal nomenclature is: the unit turns on voltage, not current.
    Current then flows from the voltage as determined by the load.
     
  6. aid545

    Thread Starter New Member

    Jul 10, 2017
    11
    1
    The soundboard has its own amp and speaker. Is an audio mixer still what is needed?

    Anyone know how I can achieve this with SPDT Relay (s)

    Thanks
     
  7. crutschow

    Expert

    Mar 14, 2008
    19,539
    5,445
    If the 3 wires actually have 12V when active then you could use a 12V coil DPDT relay with a 1N400x diode (x is any number from 1 through 7) from each of the 3 wires to the coil (cathode to coil).
    The other end of the coil goes to circuit common (ground).
    Also add a diode across the relay coil (cathode to where the other three diodes are connected) to suppress inductive transients.
     
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