6. Plant Monitor

The purpose of this project is to create a smart watering system that detects the current temperature, humidity, intensity of light, and soil moisture and displays them on Blynk.

As soon as you turn on the Switch toggle in Blynk Cloud, the pump will start working and the plants will be hydrated.

1. Build the Cirduit


The ESP8266 module requires a high current to provide a stable operating environment, so make sure the 9V battery is plugged in.


2. Edit Dashboard

  1. The data streams created in the previous projects need to be saved, and they will be used in this project as well.

  2. For recording soil moisture, create another Datastream of type Virtual Pin on the Datastream page. Set DATA TYPE to Integer and MIN and MAX to 0 and 1024.

  3. Now go to the Wed Dashboard page, drag 2 Label widgets and set their data streams to V4 and V5 respectively; drag 2 Gauge widgets and set their data streams to show V6 and V7 respectively; and finally drag a Switch widget and set its data stream to V0.


3. Run the Code

Open the 6.plant_monitoring.ino file under the path of 3in1-kit\iot_project\6.plant_monitoring, or copy this code into Arduino IDE.

  1. Replace the Template ID, Device Name, and Auth Token with your own. You also need to enter the ssid and password of the WiFi you are using. For detailed tutorials, please refer to 1.4 Connecting the R3 board to Blynk.

  2. After selecting the correct board and port, click the Upoad button.

  3. Open the Serial monitor(set baudrate to 115200) and wait for a prompt such as a successful connection to appear.



    If the message ESP is not responding appears when you connect, please follow these steps.

    • Make sure the 9V battery is plugged in.

    • Reset the ESP8266 module by connecting the pin RST to GND for 1 second, then unplug it.

    • Press the reset button on the R3 board.

    Sometimes, you may need to repeat the above operation 3-5 times, please be patient.

  4. Back to the Blynk, you will see the current temperature, humidity, light intensity, and soil moisture. You can let the pump water the plants if necessary by clicking the Button Control widget.

  5. If you want to use Blynk on mobile devices, please refer to How to use Blynk on mobile device?.


How it works?

This BLYNK_WRITE causes Blynk’s Switch widget to start the pump when it is ON and turn it off when it is OFF.


These three functions are used to get the current environment temperature, humidity, light intensity and soil moisture.

int readMoisture(){
    return analogRead(moisturePin);

int readLight(){
    return analogRead(lightPin);

bool readDHT() {
    int chk = DHT.read11(DHT11_PIN);
    switch (chk)
        case DHTLIB_OK:
            roomHumidity = DHT.humidity;
            roomTemperature = DHT.temperature;
            return true;
    return false;

With the Blynk Timer, the ambient temperature, humidity, light intensity and soil moisture are obtained every second and sent to the data stream on the Blynk Cloud, from which the widgets display the data.

void myTimerEvent()
    bool chk = readDHT();
    int light = readLight();
    int moisture = readMoisture();