Arduino Nano ESP32 - Soil Moisture Sensor Pump

In this tutorial, We are going to learn how to use the Arduino Nano ESP32 to control the pump according to the value read from the capacitive soil moisture sensor.

Hardware Preparation

1	×	Arduino Nano ESP32
1	×	USB Cable Type-C
1	×	Capacitive Soil Moisture Sensor
1	×	Relay
1	×	12V Pump
1	×	Vinyl Tube
1	×	12V Power Adapter
1	×	(Optional) DC Power Jack
1	×	Breadboard
1	×	Jumper Wires
1	×	(Recommended) Screw Terminal Expansion Board for Arduino Nano
1	×	(Recommended) Breakout Expansion Board for Arduino Nano
1	×	(Recommended) Power Splitter For Arduino Nano 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 the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables.

Overview of soil moisture sensor and Pump

If you do not know about pump and soil moisture sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:

Arduino Nano ESP32 - Soil Moisture Sensor tutorial
Arduino Nano ESP32 - Controls Pump tutorial

How It Works

Arduino Nano ESP32 periodically reads the value from the capacitive soil moisture sensor. Based on the soil moisture value, it will take the following actions:

If the soil moisture value is below a threshold, Arduino Nano ESP32 automatically activates a relay to turn a pump on.
Otherwise, Arduino Nano ESP32 automatically deactivates a relay to turn a pump off.

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Nano ESP32 Code

/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-soil-moisture-sensor-pump */ #define RELAY_PIN D2 // The Arduino Nano ESP32 pin that connects to relay #define SENSOR_PIN A2 // The Arduino Nano ESP32 pin that connects to AOUT pin of moisture sensor #define THRESHOLD 1500 // => CHANGE YOUR THRESHOLD HERE void setup() { Serial.begin(9600); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); pinMode(RELAY_PIN, OUTPUT); } void loop() { int value = analogRead(SENSOR_PIN); // read the analog value from soild moisture sensor if (value > THRESHOLD) { Serial.print("The soil moisture is DRY => activate pump"); digitalWrite(RELAY_PIN, HIGH); } else { Serial.print("The soil moisture is WET => deactivate the pump"); digitalWrite(RELAY_PIN, LOW); } Serial.print(" ("); Serial.print(value); Serial.println(")"); delay(1000); }

Detailed Instructions

If you are new to Arduino Nano ESP32, refer to the tutorial on how to set up the environment for Arduino Nano ESP32 in the Arduino IDE.
Do calibration to determine the wet-dry THRESHOLD, see Arduino Nano ESP32 - Calibrates Soil Moisture Sensor
Update the calibrated value to THRESHOLD in the code
Open Serial Monitor on Arduino IDE
Upload the code to Arduino Nano ESP32
Check out the result on Serial Monitor.

COM6

Send

The soil moisture is DRY => activate the pump The soil moisture is DRY => activate the pump The soil moisture is DRY => activate the pump The soil moisture is DRY => activate the pump The soil moisture is WET => deactivate the pump The soil moisture is WET => deactivate the pump The soil moisture is WET => deactivate the pump The soil moisture is WET => deactivate the pump

Autoscroll Show timestamp

Clear output

9600 baud

Newline

Code Explanation

Read the line-by-line explanation in the comment lines of the source code!

※ NOTE THAT:

This tutorial uses the analogRead() function to read values from an ADC (Analog-to-Digital Converter) connected to a sensor or component. The Arduino Nano ESP32's ADC is suitable for projects that do not require high accuracy. However, for projects needing precise measurements, keep the following in mind:

The Arduino Nano ESP32's ADC is not perfectly accurate and might require calibration for correct results. Each Arduino Nano ESP32 board can vary slightly, so calibration is necessary for each individual board.
Calibration can be challenging, especially for beginners, and might not always yield the exact results you want.

For projects requiring high precision, consider using an external ADC (e.g ADS1115) with the Arduino Nano ESP32 or using another Arduino, such as the Arduino Uno R4 WiFi, which has a more reliable ADC. If you still want to calibrate the Arduino Nano ESP32's ADC, refer to the ESP32 ADC Calibration Driver.

Video Tutorial

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