Need help with a simple project

Discussion in 'The Projects Forum' started by Vatch, Sep 21, 2016.

  1. Vatch

    Thread Starter New Member

    Sep 21, 2016
    I am fairly new to circuits(I know how to solder without melting the breadboard) and I have a simple project that I am trying to complete. I want to know how to wire it without breaking anything. I would also like to learn a thing or two.

    I have a small sound board akin to that of a greeting card. The board has a button that activates it and plays a sound.
    A 5mW laser diode
    An 8 ohm 0.1 W speaker
    A 2.5 watt mono amplifier from
    And a battery pack that holds 3 AA batteries
    An assortment of resistors

    I would like to wire the amplifier's out to the 8 ohm 0.1watt speaker and the sound board's output to the amplifier(via removing it's leads from the incuded speaker and connecting them to the amplifier). I also need the button that activates the soundboard to turn on the laser diode. I would like to be able to have all of this run off of the 3 AA batteries without overloading anything.

    Any help is greatly appreciated as I have very little idea of how to figure this out myself.
  2. ian field

    AAC Fanatic!

    Oct 27, 2012
    The laser can be tricky - they're easy to damage.

    You need to set up a textbook constant current circuit, set to around 60% of the maximum rated laser current. Couple the audio in via a DC blocking capacitor to modulate the current.

    How/where you inject the AC depends on which textbook example circuit you chose.