Audio Camera Flash Trigger

Discussion in 'The Projects Forum' started by newcube, Jan 22, 2012.

  1. newcube

    Thread Starter New Member

    Jan 22, 2012
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    Hi All,

    I'm a rank amateur at electronics (although I did A Level physics 20 years ago). I'm attempting to build a camera flash sound trigger similar to this http://hiviz.com/tools/triggers/makeown.htm#st but I've not got an SCR (yet).

    The two circuits I've cobbled together work, but only if I rap the piezo disc with a pen or something. The flash does not fire if I clap my hands, etc.

    The version with the op amp seems to be more sensitive but it's hard to tell!

    Can someone give me some tips to increase the sound sensitivity please or should I just wait for the SCR to arrive?

    Thanks in advance,
    Nic
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    You can try using a microphone.
     
  3. newcube

    Thread Starter New Member

    Jan 22, 2012
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    can i just do a direct replacement for the piezo disc? I've not got one to hand, but i can cannibalise an old pair of headphones...
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    What is inside the flash hotshoe?
     
  5. newcube

    Thread Starter New Member

    Jan 22, 2012
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    nothing - if the centre pin and side contact are connected (via the 2N2222) the flash fires. A paperclip would do it too.
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    If you keep it connected will it flash or does it require a pulse?
     
  7. newcube

    Thread Starter New Member

    Jan 22, 2012
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    with a paperclip, the flash fires once on connecting the pins, then does nothing with they remain connected. Disconnecting the pins then connecting again fires the flash as before.
     
  8. mik3

    Senior Member

    Feb 4, 2008
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    Then he needs a trigger circuit with some kind of reset, it can be a push button or a time out reset.
     
  9. newcube

    Thread Starter New Member

    Jan 22, 2012
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    the circuit with the op amp does fire the flash once per rap of a pen on the piezo disc though which implies the connection is broken between pen taps. I just need it to hear a balloon bursting, not just a pen hitting it!!
     
  10. mik3

    Senior Member

    Feb 4, 2008
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    You can use a comparator wihtout positive feddback to sense the output of a microphone. If the output of the microphne is greater than a voltage level, the output of the comparator will short the pins of the flash. If the short time is not enough (i.e. sound of bursting ballon to short) you will need a comparator with positive feedback and some means to reset it. The reset signal can be a push button or a time out reset for automatic reset.
     
  11. newcube

    Thread Starter New Member

    Jan 22, 2012
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    Aaaaaaaaaand I'm lost!

    Thanks for your help though!
     
  12. mik3

    Senior Member

    Feb 4, 2008
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    The flash needs a short on its pins for a few microseconds or milliseconds I guess. You need a device which does this. My suggestion was in my previous post.

    Use a microphone or your piezo (if it works) and a comparator with some threshold level.
     
  13. newcube

    Thread Starter New Member

    Jan 22, 2012
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    Thanks for all that. I'll see what I can see.
     
  14. Wendy

    Moderator

    Mar 24, 2008
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    A pizeo speaker is not much of a microphone. It sounds like a sensitivity issue to me.
     
  15. newcube

    Thread Starter New Member

    Jan 22, 2012
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    Last edited: Jan 23, 2012
  16. newcube

    Thread Starter New Member

    Jan 22, 2012
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  17. newcube

    Thread Starter New Member

    Jan 22, 2012
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