water-leak-sms-alarm

A small battery-powered device that detects water leakage and sends an SMS alert.
 

Features

• Completely off until water (or anything conductive) closes the circuit between two of its legs,
  thereby latching on the "soft latching power circuit".
  Which can later be turned off again by the microcontroller.

• Latches on by either water detection or by pressing the test button.

• Sends an SMS alert if water is detected.

• Sends SMS diagnostics if the test button is pressed.

• Built with an ESP32 and PlatformIO, in C++.

 

Schematic and PCB

KiCad files can be found here: 📂 _KiCad/
More images in: 📂 _images/

Parts used

• ESP32 D1 Mini Node MCU
• SIM800L module with external antenna
• 3.3V LDO: MCP1700-3302E (250mA)
• LED: WS2812B
• P-channel mos: NTR4101PT1G
• N-channel mos: PMV16XNR
• Cap 470uF: Electrolytic
• Cap 22uF: Electrolytic
• Cap 1uF: Ceramic
• Cap 100nF: Ceramic
• Switch: Momentary DPST
• Conductive legs in copper/brass

PCB

Uses mostly through-hole components for easier soldering.
ESP32 is mounted on the bottom side of the PCB.

 

Schematic

 

Hardware

This picture shows version 1.
Version 2 eliminates some of the large capacitors that occasionally made the unit bootloop.

 

SMS Example