Sound to Light Project

Discussion in 'The Projects Forum' started by sunnysun, Oct 4, 2013.

  1. sunnysun

    Thread Starter New Member

    Jun 15, 2013
    Good day guys. We have constructed a project called sound to light modulator but we don't know how the circuit really works, because we haven't taken a deeper course into circuit analysis. We don't know anything about triacs and optocouplers. Could you please explain to me in detail how this circuit works. Any help will be very much appreciated. Thanks in advance. :)

    This is the schematic:
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    The led in the opto triac IC1 conducts when voltage is applied, this fires the triac inside, which connects the terminals Mt1 and Mt2 together, these terminals are connected to the Main Q1 triac Mt2 and Gate, when these are connected together the triac conducts. The triac disconnects when the AC voltage goes to zero, ready for the next cycle, as they will conduct on both posative and negative cycles.
  3. tracecom

    AAC Fanatic!

    Apr 16, 2010
    You must not have gotten the instruction sheet with Kit 12 from Kits R Us. Here's their explanation of how it works.

    The audio signal is applied
    across the LED of the opto-triac. The
    potentiometer adjusts the input sensitivity
    while R2 limits the LED current. The LED
    emits infrared light in response to the input
    signal. The triac driver inside the MOC3021
    package is sensitive to the IR light, and
    activates a slave triac which controls the load.
    R3 limits the gate current of the power triac
    A triac is a bilateral switch, similar to an SCR,
    but conducts in both directions. Current flow
    between the two main terminals is controlled
    by the gate, and the series voltage drop is low
    when turned on. The mains voltage applied to
    X2 is thus fed to the lamp at X3 when the input
    signal is large enough for the triacs to conduct,
    and switched off when the signal level drops
    and the triacs turn off. The triacs will turn on
    for each half cycle of mains frequency that
    their gates are triggered. The lamp is therefore
    turned on and off very rapidly, depending on
    the music level. Because of the thermal lag in
    the lamps themselves, this appears as a
    pulsating change in light intensity rather than
    an on/off strobe effect.
  4. sunnysun

    Thread Starter New Member

    Jun 15, 2013
    Thank you very much! :)