Water Level Sensor Module for Arduino and ESP32

Wiring & getting started

Wiring diagramArduino Nano and ESP32

1. Find the pins

   Hold the board with the parts facing you and the stripes pointing left. The three pins are marked S, + and - from top to bottom. S is the signal, + is power and - is ground.

2. Wire it to an Arduino

   Connect S to A0, + to D7 and - to GND. Our female-to-male jumper wires push straight onto the pins. Powering + from pin D7 instead of the 5V pin lets the code switch the sensor off between readings.

3. On an ESP32 or Pico

   Connect S to an analogue input pin, + to a spare output pin and - to GND, then change the two pin numbers at the top of the code. These boards run at 3.3V, and a sensor powered from a 3.3V pin keeps its S output within what the input pin can take. On a 38-pin ESP32, GPIO34 for S and GPIO26 for + both work with WiFi on.

4. Load the test code

   Upload the code below and open the Serial Monitor at 9600 baud. A new reading appears every second.

   Example Arduino codeArduino C++

   // Water sensor test for an Arduino Uno or Nano.
   // Wiring: S to A0, + to D7, - to GND.
   // The sensor is only switched on while it takes a reading,
   // which slows the wear on the bare metal stripes in water.
   const int POWER_PIN = 7;
   const int SIGNAL_PIN = A0;
   
   void setup() {
     Serial.begin(9600);
     pinMode(POWER_PIN, OUTPUT);
     digitalWrite(POWER_PIN, LOW);    // sensor off
   }
   
   void loop() {
     digitalWrite(POWER_PIN, HIGH);   // sensor on
     delay(10);                       // let the reading settle
     int reading = analogRead(SIGNAL_PIN);
     digitalWrite(POWER_PIN, LOW);    // sensor off again
   
     Serial.print("Water reading: ");
     Serial.println(reading);
     delay(1000);                     // one reading a second
   }

5. Check it works

   With the sensor dry, the reading sits at or near 0. Dip the stripes into a glass of tap water and the number jumps, then climbs as you lower the board. Write down the dry number and the number with the stripes fully under your water, and use those two as your empty and full marks. If the reading stays at 0, check that + goes to D7. The Power light on the board should flicker once a second, each time the code switches the sensor on.

6. Keep the pin end dry

   Only the striped end goes in the water. Keep the end with the parts and the pins above the surface.