I’m working on a sound flash trigger, and I found this circuit: http://courses.ncssm.edu/hsi/pacsci/text.html. I’m having some trouble getting it to work, so I want to first make sure I understand how it works. As far as I can tell, initially, current flows through the two 5 Kohm resistors to the transistor’s collector. Current also flows through the 68 Kohm base resistor and switches the transistor on. Current flows through the transistor. When the pizeo trigger is activated, current is directed through it and away from the base, switching off the transistor. Current then moves through the SCR gate instead of the transistor, activating the flash.
Does decreasing the value of the variable resistor increase sensitivity? By permitting more current to reach that portion of the circuit, do smaller changes in the collector-to-emitter current make it easier to push the gate current above the threshold value?