Sound Detector - inverting Gate output issues

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Sound Detector - inverting Gate output issues

Post by maxt » Fri Aug 10, 2018 9:38 am

Hi– I'm using the SparkFun Sound Detector's Gate output to wake up an ESP8266 board (Adafruit Feather).

The Gate pin goes high when sound is detected, while the ESP needs its Reset pin pulled low to wake it up. I'm inverting this with a resistor-biased NPN transistor (this one) hooked up like so:

See schematic here
Base -> Detector GATE
Collector -> ESP8266 RESET
Emitter -> GROUND

This works great most of the time, but every once in a while (not following any pattern I can tell) the sound detector gets stuck in a loop where the gate pulses at roughly 4Hz (onboard LED blinks & ESP8266 continuously resets). Sometimes this happens immediately when I turn the system on, other times it will work fine for hours before it happens. Since I intend to leave this unattended, this unpredictability is a dealbreaker.

The device is powered by a single cell LiPo battery so the detector should have a stable power supply. There is no other connection between the ESP and sound detector besides the Gate and shared ground. If I unhook the Gate connection and just monitor the detector's LED then this issue never happens.

Any advice to make this more reliable would be appreciated– happy to provide any other details needed. Thanks!

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