Constant 12vdc signal to momentary relay contact AdaFruit MINI FX board

Discussion in 'The Projects Forum' started by Joshua Herald, Jun 11, 2015.

  1. Joshua Herald

    Thread Starter New Member

    Jun 11, 2015
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    I am working on a project for my job that is just a simple door bell that says "welcome " when a door is open.

    So the main operation is this.
    When conditions are met a relay will trip.The relay will close and provide PIN1 to ground on my ADAfruit MINI fx board that has been loaded with a wav file that says welcome to our home.
    The audio will be ran through an amplifier and then through hidden speakers.

    Pretty simple.


    Well i received my FX board today and found out that it needs some modification to work.
    If i momentarily close the circuit(pin 01 to ground) it will play the audio file once and stop. (exactly what i want)
    If the circuit is closed for longer than the WAV file is, it repeats. (I leave the door open and it says welcome welcome welcome welcome until i close it)
    I cant get any help from the people at ADAFruit some im coming here.

    My needs.
    I need to take a constant 12v and have it close a contact for 1-3 seconds and then release so even if the 12v signal is there for 5 minuites, the fx board will only play the wav file once.

    Any thoughts?

    Additional info
    I also have one of these but i don't think it will help.
    http://www.amazon.com/gp/product/B0...rd_t=36701&pf_rd_p=2091268722&pf_rd_i=desktop

    https://learn.adafruit.com/adafruit-audio-fx-sound-board/overview
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  3. Joshua Herald

    Thread Starter New Member

    Jun 11, 2015
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  4. Joshua Herald

    Thread Starter New Member

    Jun 11, 2015
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    If i understand the correctly it will switch the state of the relay after a time.
    If i wire the contact through the NO contact it would not be on for (delay) then on untill power is released.
    If i were to wire to the NC contact, the welcome would be playing all the time before power is applied and then it would turn off after delay
     
  5. Joshua Herald

    Thread Starter New Member

    Jun 11, 2015
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    All is well i used a simple RC circut on a relay.
    Also if i were trying to stick to a small circut, a simple NAND gate would have worked also.

    When the input is low, the NAND gate sees low on its upper input and high on the lower one, so its output will be high. If the input jumps high, the RC network on the lower input will hold that pin high for about 200ms. The NAND gate will see high on both inputs, so its output will go low, triggering the FX board. After 200ms, the RC network will have pulled the lower input to a logical low, so the NAND gate's output will go high again. When the input jumps low, the NAND gate will see both of its inputs low, which still holds the output high.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    No the relay clicks on at power up, then drops out after the delay,

    Or you can use a cd4093 Schmidt gate.
     
  7. Joshua Herald

    Thread Starter New Member

    Jun 11, 2015
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    0
    I just had a chance to test this board and we may have 2 different boards. I have attached pictures that show the state of the relay only changing once.

    I only connected to one of the contacts in the pictures but have tested both.
    With only the top left amber LED, that is with power applied but still timing
    With both the top left amber LED and the red LED next to the 555, that is with power and after relay has switched.

    Com to CK
    Initial Power up = Open Line
    After Delay = Closed

    Com to CB
    Initial Power up = Closed
    After Delay = Open Line

    Once power is removed, all states return to Initial Power up state.
    Mine does not change from Open to closed to open
     
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