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Battery-Powered Resistive Water Leak Detector with Remote Notifications

A battery-powered prototype for detecting water leaks using resistive sensing with remote notification capabilities.

Beginner Project — The project uses a standard dev board and a simple analog sensor with widely available libraries for WiFi notifications.
Assumptions:
  • The user needs a battery-operated device for placement under sinks or appliances.
  • Remote notification (WiFi or LoRa) is required for a practical leak detector.
  • A simple resistive or capacitive probe will be used for detection.

Bill of Materials

Microcontroller
Top Pick ESP32-DEVKITC-32E Espressif Systems From our database
The ESP32-DEVKITC-32E is the best choice because a leak detector is only useful if it can alert the user remotely. It provides built-in WiFi to send email or push notifications without needing extra modules.
Digikey $10.00 (908 in stock) Mouser $10.00 (1,045 in stock)
NUCLEO-L053R8 STMicroelectronics From our database
Ultra-low-power Cortex-M0+ ideal for long-term battery monitoring; excellent ADC for precise resistive probe measurements.
ARDUINO NANO EVERY Arduino
Simple 5V logic which can simplify resistive divider circuits; very high community support for beginners.
Leak Detection Sensor
Top Pick 2450 Adafruit
Top pick: 2450 (Adafruit). Stainless steel contact floor sensor; very durable for long-term placement in damp environments.
611 Adafruit
Non-contact capacitive liquid level sensor; can detect water through plastic containers or pipes without corrosion risks.
Power Supply
Top Pick MCP1700-3302E/TO Microchip From our database
The MCP1700-3302E/TO is the superior choice for a battery-powered sensor because its extremely low quiescent current prevents the battery from draining while the MCU is in deep sleep.
Digikey $0.50 (4,392 in stock) Mouser $0.50 (3,829 in stock)
R-78E3.3-0.5 RECOM From our database
High efficiency switching regulator; better if using a higher voltage battery pack (e.g. 9V or 12V) to avoid heat.
AZ1117CH-3.3TRG1 Diodes Incorporated From our database
High current capability (1A); useful if the prototype includes a loud alarm or multiple connectivity modules.
Connectivity
Top Pick RFM95W-868S2 RF Solutions From our database
Top pick: RFM95W-868S2 (RF Solutions). LoRa technology allows for massive range (kilometers) and penetration through concrete floors/basements where WiFi might fail.

Compatibility Notes

  • The ESP32 operates at 3.3V logic; ensure the leak sensor is powered from the 3.3V rail to protect ADC pins.
  • The MCP1700 LDO has a maximum input voltage of 6V; it is compatible with 3xAA batteries or a single LiPo, but not a 9V battery.

You'll Also Need

  • 3xAA Battery Holder or LiPo Battery
  • Hookup wire for the probe (recommend 22 AWG stranded)
  • Breadboard or Perforated Board for assembly
  • 10k Ohm pull-up/down resistors for the sensor circuit
  • Enclosure to protect the electronics from the leak it is detecting
Estimated BOM Cost: $25-30 (based on live distributor pricing)
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Design Considerations

Power Budget Analysis
A leak detector should last 1-2 years on 3xAA batteries. Use the ESP32 deep sleep mode with an external interrupt or RTC timer to wake every hour for a 'heartbeat' check, keeping average current draw below 50uA.
Probe Corrosion
Resistive probes suffer from electrolysis if DC current is applied constantly. Only power the sensor pin immediately before taking a reading and use a GPIO to turn off the sensor power entirely during sleep periods.
False Positive Mitigation
High humidity can trigger sensitive resistive sensors. Implement a software threshold in the ADC readings and require multiple consecutive readings above the threshold before triggering an alarm to filter out transient noise or condensation.
Communication Reliability
Leak detectors are often placed in RF-dead zones like under metal sinks. Implement a 'heartbeat' signal once per day; if the server doesn't receive the heartbeat, it should alert the user that the sensor is offline.
Environmental Protection
The electronics must be housed in a water-resistant enclosure (IP65 rated) while the probe remains exposed. Use a cable gland for the sensor wire to prevent moisture from wicking into the main housing and damaging the MCU.

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