SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 - Water Sensor

This tutorial instructs you how to use ESP32 and water sensor to detect rainfall, water leakage, tank overflow, and measure the water level.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Water level sensor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.

Introduction to Water Level Sensor

Water Level Sensor Pinout

The water level sensor includes 3 pins:

S (Signal) pin: This pin outputs analog voltage that is in proportion to the water level. This pin should be connected to an analog input pin of ESP32.
+ (VCC) pin: connects this pin to 3.3V or 5V.
- (GND) pin: connects this pin to GND.

How Water Level Sensor Works

Simply, the more water the sensor is sank in, the higher the output voltage in the S pin is. By measuring the voltage, we can know the water level.

Wiring Diagram

In theory, we can provide power to the water sensor by connecting the sensor's VCC and GND pins to ESP32's 3.3V and GND pins, respectively.

However, that way is not recommended in practice. If we supply power to the water sensor constantly, the water sensor is electrochemically corroded faster by the moist environment ⇒ It is better to provide power to the water sensor only and only when reading the value from the sensor. To do so, We can connect the sensor's VCC pin to an ESP32's digital pin, and program the ESP32's pin to HIGH before reading and LOW after reading.

How to connect ESP32 and water sensor using breadboard

This image is created using Fritzing. Click to enlarge image

How to connect ESP32 and water sensor using screw terminal block breakout board (powered via USB cable)

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 Code - Reading Value from Water Sensor

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-water-sensor */ #define POWER_PIN 17 // ESP32 pin GPIO17 connected to sensor's VCC pin #define SIGNAL_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to sensor's signal pin int value = 0; // variable to store the sensor value void setup() { Serial.begin(9600); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); pinMode(POWER_PIN, OUTPUT); // configure pin as an OUTPUT digitalWrite(POWER_PIN, LOW); // turn the sensor OFF } void loop() { digitalWrite(POWER_PIN, HIGH); // turn the sensor ON delay(10); // wait 10 milliseconds value = analogRead(SIGNAL_PIN); // read the analog value from sensor digitalWrite(POWER_PIN, LOW); // turn the sensor OFF Serial.print("The water sensor value: "); Serial.println(value); delay(1000); }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Copy the above code and paste it to Arduino IDE.
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
Slowly dip the sensor into the water ( a glass of water).
See the result on Serial Monitor. It looks like the below:. The value 0 when the sensor is not touching anything.

COM6

Send

The water sensor value: 0 The water sensor value: 0 The water sensor value: 0 The water sensor value: 25 The water sensor value: 196 The water sensor value: 587 The water sensor value: 625 The water sensor value: 1434 The water sensor value: 1449 The water sensor value: 1454 The water sensor value: 1469 The water sensor value: 2525 The water sensor value: 2526 The water sensor value: 2558

Autoscroll Show timestamp

Clear output

9600 baud

Newline

※ NOTE THAT:

The water sensor is not designed to be completely sank, only the exposed traces on the PCB can embed into the water. Please be careful to install it.

How To Detect Water Leakage

To detect the water leakage, rainfall, and tank overflow, we just need to compare the sensor's value with a threshold. The threshold is determined in the calibration part of this tutorial.

Let's make ESP32 turns on an LED if the water leakage is detected.

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

ESP32 Code - Detecting Water Leakage

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-water-sensor */ #define LED_PIN 21 // ESP32 pin GPIO21 connected to LED pin #define POWER_PIN 17 // ESP32 pin GPIO17 connected to sensor's VCC pin #define SIGNAL_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to sensor's signal pin #define THRESHOLD 1000 int value = 0; // variable to store the sensor value void setup() { Serial.begin(9600); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); pinMode(LED_PIN, OUTPUT); // configure pin as an OUTPUT pinMode(POWER_PIN, OUTPUT); // configure pin as an OUTPUT digitalWrite(POWER_PIN, LOW); // turn the sensor OFF digitalWrite(LED_PIN, LOW); // turn LED OFF } void loop() { digitalWrite(POWER_PIN, HIGH); // turn the sensor ON delay(10); // wait 10 milliseconds value = analogRead(SIGNAL_PIN); // read the analog value from sensor digitalWrite(POWER_PIN, LOW); // turn the sensor OFF if (value > THRESHOLD) { Serial.print("The water is detected"); digitalWrite(LED_PIN, HIGH); // turn LED ON } else { digitalWrite(LED_PIN, LOW); // turn LED OFF } }

How To Measure The Water Level

The below code divides the water level into 4 levels.

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-water-sensor */ #define POWER_PIN 17 // ESP32 pin GPIO17 connected to sensor's VCC pin #define SIGNAL_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to sensor's signal pin #define SENSOR_MIN 0 #define SENSOR_MAX 521 int value = 0; // variable to store the sensor value int level = 0; // variable to store the water level void setup() { Serial.begin(9600); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); pinMode(POWER_PIN, OUTPUT); // configure D7 pin as an OUTPUT digitalWrite(POWER_PIN, LOW); // turn the sensor OFF } void loop() { digitalWrite(POWER_PIN, HIGH); // turn the sensor ON delay(10); // wait 10 milliseconds value = analogRead(SIGNAL_PIN); // read the analog value from sensor digitalWrite(POWER_PIN, LOW); // turn the sensor OFF level = map(value, SENSOR_MIN, SENSOR_MAX, 0, 4); // 4 levels Serial.print("Water level: "); Serial.println(level); delay(1000); }

※ NOTE THAT:

SENSOR_MIN and SENSOR_MAX is determined by the calibration process.
The above mapping method is not accurate. However, it is acceptable in many applications.

Water Level Sensor Calibration

See how to calibrate the water lever sensor

※ NOTE THAT:

This tutorial uses the analogRead() function to read values from an ADC (Analog-to-Digital Converter) connected to a water sensor. The ESP32 ADC is good for projects that do NOT need high accuracy. However, for projects that need precise measurements, please note:

The ESP32 ADC is not perfectly accurate and might need calibration for correct results. Each ESP32 board can be a bit different, so you need to calibrate the ADC for each individual board.
Calibration can be difficult, especially for beginners, and might not always give the exact results you want.

For projects that need high precision, consider using an external ADC (e.g ADS1115) with the ESP32 or using an Arduino, which has a more reliable ADC. If you still want to calibrate the ESP32 ADC, refer to ESP32 ADC Calibration Driver

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