Internet of Things - Moisture Sensor with ESP8266


In this little project we will use a cheap soil moisture sensor to monitor when a plant requires more water. This sensor will be connected to an ESP8266 that will check the humidity periodically to alert us via email and blinking a led alarm. The sketch will have some configurable parameters over the Internet, like setting led alarm state (enable/disable, frequency), changing the hysteresis period, or checking the water state.

Required components

  • ESP8266. In this project it is used a NodeMCU, but any other network enabled device can be used by adapting the code a little.
  • Soil Moisture sensor. It is used a cheap one from AliExpress
  • One led for blinking when there is no water.
  • Arduino IDE with library installed and support for the ESP8266 board.

This is the moisture sensor used in the project. Is a cheap one from AliExpress.


The wiring for this project is so easy. The moisture sensor output (digital) is connected to D1 of the Node MCU board, while the alarm led is connected to D2.

Source Code

#include <SPI.h>
#include <ESP8266WiFi.h>
#include <ThingerWifi.h>

// config
#define USER_ID "your_user_id"
#define DEVICE_ID "your_device_id"
#define DEVICE_CREDENTIAL "your_device_credential"
#define ALARM_ENDPOINT "your_alarm_endpoint"

// wifi config
#define WIFI_SSID "your_wifi_ssid"
#define WIFI_WPA2_PASSWORD "your_wifi_password"

// sensor/led pins
#define SENSOR_PIN D1
#define LED_PIN D2


typedef enum WaterState{

WaterState waterState = WATER;          // current water state
bool showLedAlarm = true;               // control led alarm on/off
unsigned long ledAlarmInterval = 500;   // led alam blink frequency
unsigned long previousMillis = 0;       // util for hysteresis and blink
unsigned long timeWithoutWater = 0;     // for hysteresis time
unsigned long hysteresisTime = 60000;   // one minute
int ledState = LOW;                     // current led alarm state

void setup() {
  // set pinmode for led alarm and humidity reader
  pinMode(LED_PIN, OUTPUT);

  // add wifi connection
  thing.add_wifi(WIFI_SSID, WIFI_WPA2_PASSWORD);

  // allow reading plant water/humidity
  thing["water"] >> [](pson& out){ out = !digitalRead(SENSOR_PIN); };

  // allow activating and deactivating led alarm remotelly
  thing["led_alarm"]["show"] << [](pson& in){ 
    if(in.is_empty()) in = showLedAlarm;
    else showLedAlarm = in;

  // allow changing led alarm frequency
  thing["led_alarm"]["freq"] << [](pson& in){ 
    if(in.is_empty()) in = ledAlarmInterval;
    else ledAlarmInterval = in;

  // allow changing hysteresisTime remotelly
  thing["hysteresis"] << [](pson& in){ 
    if(in.is_empty()) in = hysteresisTime;
    else hysteresisTime = in;

void loop() {

  // read water value
  bool water = !digitalRead(SENSOR_PIN);
      digitalWrite(LED_PIN, LOW); // turn off led alarm
      waterState = WATER; // reset water state
     unsigned long currentMillis = millis();
        case WATER:
            timeWithoutWater = 0;
            previousMillis = currentMillis;
            waterState = START_DETECTING_NO_WATER;
          timeWithoutWater += (currentMillis - previousMillis);
          previousMillis = currentMillis;
          // only notify after a hysteresis time to prevent drifts in sensor reading
            waterState = NO_WATER;
        case NO_WATER:
          if(currentMillis - previousMillis > ledAlarmInterval) {
            previousMillis = currentMillis;   
            ledState = ledState == LOW ? HIGH & showLedAlarm : LOW;
            digitalWrite(LED_PIN, ledState);

Some Details

To be continued…


Can you explain EndPoints???
Thanks you very much!!


Yes! I am working on some documentation!! Hope to release it in a few days!


More than a very hot welcome, needed info !!! :smile:

And Thank you for the hard work


Thanks! I will publish some documentation tomorrow for the Arduino client library, which is the way the people is using thinger (it includes some information about how to call endpoints). The next one will be documentation for Linux Clients, server API, console, etc.


thank you very much!
I use Arduino


Here is some starting documentation! At this moment still needs to be completed, but the Arduino section is almost complete. Just require some examples. Let me know what do you think about the docs!


kindly update your page


What page? Thanks…


actually my device is not able to connect to your platform…is there any step that is missing ?


As soon as I remove al the code exept the thing.handle() from loop(); I am able to receive the resources. As soon I have any snipet inside with other code. It’ stops transmitting the resources.
Any idea?
Kind regards


Hello @alvarolb,
This is Devaraj From India, i need to discuss some topics about Can to please help me to interact with you when you getting Free for your daily routines.

Thank you sir,
With Regards
R&D Engineer


Greate idea, we are engaged with the building and decoration products and intend to make them more smarter


Hello everyone,
Can I get the code for Ethernet and moisture sensor?



Hi im using the same sensor has you.
But im using blynk…

Is there a way to read the values with a 8266 ESP01 ?

I can only get Up or Down meaning 0 or 1 , or open or closed if you prefere…
Do i need a l2C to read the values ?


It is not possible to read analog values with ESP01, due it has not an ADC on board, what you can do is to communicate to an ADC chip via I2C (for example) and get that values from another device, actually you are getting a 0 or 1 because the ESP01 is capable just to make digital reads.