PVDF Acoustic Sensing Platform for Community Water Quality Monitoring: An Open-Source Hardware and Firmware Architecture

This technical note describes an open-source hardware and firmware architecture for community water quality monitoring using polyvinylidene fluoride (PVDF) piezoelectric acoustic sensing on commodity microcontroller substrate. The platform comprises a PVDF sensor element, optional 16-bit analog-to-digital converter (ADS1115), ESP32 microcontroller, optional LoRa mesh networking, and solar-rechargeable battery supply. The architecture targets bulk water quality changes detectable through acoustic transduction — turbidity variation, flow disruption events, suspended solids presence, structural fault events, and broad density anomalies relative to a calibrated local baseline. Specific contaminant identification (bacterial species, dissolved heavy metal ions at trace concentrations, trace organic compounds) is explicitly outside the detection scope of acoustic sensing alone and requires complementary sensor modalities, which the platform supports via standard I2C, SPI, and analog interfaces. A minimal-component signal-chain variant is documented for budget-constrained deployment contexts, using the PVDF film's native capacitance with a 1 MΩ shunt resistor to form a passive RC high-pass filter (corner frequency approximately 30–120 Hz depending on film thickness), which attenuates mains-frequency electromagnetic interference and low-frequency thermal drift without requiring active filtering. The platform monitors water quality state; it does not treat, filter, or purify water. Deployment supplements rather than replaces laboratory testing and existing water safety practices. All hardware specifications, firmware framework, and deployment protocols are released under CC0 1.0 Universal to maximise humanitarian and educational deployment freedom. This work is intended as platform substrate for community-deployable water quality monitoring infrastructure, not as a complete contaminant identification solution. For everybody · Always · Riverrun.