Sound trigger for flash unit

The circuit is based on operational amplifier IC1 used in the noninverting amplifier mode. Rl and 2 set the gain at about 500. RV1 (sensitivity) biases the noninverting input to the negative supply. Ql provides the relatively high trigger current required by the triac. When a signal is received by the microphone, the signals are amplified (by IC1). The triac is triggered and a low resistance appears across its Al and A2 terminals which are connected via the fiashlead to the strobe.
Sound trigger for flash unit  - schematic

The circuit operates almost instantly, giving very little delay between the commencement of the sound and the flashgun being triggered.

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