IoT project tutorial: Smart plant system

This IoT project tutorial describes how to build an IoT project that monitors plant health status. As a result, we want to check some environment parameters like temperature, humidity and light intensity that have effects on the plant. In addition, we want to retrieve the soil moisture.

All this information is sent by Arduino to the cloud using Ubidots IoT cloud platform. In this blog, we talked already about IoT ecosystem and you know already what it means. You already know how to use IoT cloud platforms to store and retrieve data.


If you are new to Internet of things, it is useful to know more about id reading my article about What is Internet of things.
It is useful to recap briefly, Internet of things is defined as:

“The internet of things (IoT) is the network of physical objects—devices, vehicles, buildings and other items—embedded with electronics, software, sensors, and network connectivity that enables these objects to collect and exchange data. The IoT allows objects to be sensed and controlled remotely across existing network infrastructure”.

Especially relevant in an IoT project is the IoT cloud platforms that store data coming from dev boards like Arduino, Raspberry and so on. Using this data, IoT cloud platforms build charts and have a built-in system to create some business rules on this information.
Moreover, Ubidots is an IoT cloud platform that not only stores data but enables users to create a dashboard to represent graphically the stored data.
In the first part of this IoT project tutorial, we will explore how to use sensors to collect environment information using Arduino and how to send this information to the cloud.
In addition, in the second part of IoT project tutorial, we will explore how to enable triggers on the sensor values stored. Moreover, we will send alert to user smartphone when some parameter value is out of the range.

IoT project tutorial

Now it is time to describe the project in more details. The image below shows the project at work:

IoT project tutorial

This IoT project tutorial uses Arduino Uno as dev board and a set of sensors:

  • DHT11
  • YL-38 + YL-69
  • TEMT6000

DHT11: Temperature humidity sensor

DHT11 is a sensor to measure temperature and pressure. It is a cheap sensor and suitable for Arduino, you can use more accurate sensor but the way to use it is the same.

YL-38 + YL-69: Soil moisture sensor

YL-38 + YL-69 is a sensor to measure the soil moisture. It has to be inserted into the plant soil.

TEMT6000: Light intensity

TEMT6000 is a sensor to measure the light intensity so that we can know how light the plant is receiving.

Implement a smart plant system using IoT Click To Tweet

The wiring part is very simple as it is clear in the picture below:
IoT sensors with Arduino

Moreover, in the picture above, it is clear that Arduino uses an ethernet shield to connect to the network, you can use also a WIFI shield it is almost the same approach.

Read sensors with Arduino

Now that it is clear how to connect sensors to Arduino the next step, especially relevant, is reading the values to send them to the cloud.
The sketch is very simple:

void loop() {
  float soilHum = analogRead(moisturePin);
  soilHum = (1023 - soilHum) * 100 /1023;
  Serial.println("Soil Humidty: " + String(soilHum));

  // Read light 
  float volts = analogRead(lightPin) * 5.0 / 1024.0;
  float amps = volts /10000.0;
  float microamps = amps * 1000000;
  float lux = microamps * 2.0;

  Serial.println("Lux: " + String(lux));

  float h = dht.readHumidity();
  float temp = dht.readTemperature();

where the dht variable is defined as:

#define DHTTYPE DHT11
// DHTPIN is the pin number connected to DHT11 data output

As a result, if we load the sketch into Arduino and run it you will know the values read by sensors using the serial monitor.

Arduino and cloud data

Another step is sending the data read to the cloud. In this IoT project tutorial as IoT cloud platform we use Ubidots. If you are new to this platform and don’t know how to use it, I suggest you read this tutorial named “Internet of things project: Connect Arduino to Ubidots and Android“.
This project defines 4 variables holding values read from the sensor. Moreover, using this variable we create the dashboard.
Ubidots variables
Once the variables are configured in Ubidots, we have the variable id:
iot platform data

Implement Arduino sketch

It is time to modify the Arduino sketch so that it sends the values to the Ubidots and these values are stored in these variables:

#include <SPI.h>
#include <Ethernet.h&amp>
#include "DHT.h"

#define DHTPIN 2
#define DHTTYPE DHT11

String tempVarId = "575475df7625423fd9da9c36";
String humVarId = "575475f1762542406cb10c43";
String lightVarId = "575475fc762542410358a0c3";
String soilVarId = "5754760576254241593d4d47";
String token = "xxxxx";

byte mac[] = {  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

char server[]="";

EthernetClient client;
IPAddress ip(192, 168, 1, 40); // Arduino IP Add
IPAddress myDns(8,8,8,8);
IPAddress myGateway(192,168,1,1);

int moisturePin = 0;
int lightPin = 3;

void setup() {
  // Net connection...

void loop() {
  float soilHum = analogRead(moisturePin);
  soilHum = (1023 - soilHum) * 100 /1023;
  Serial.println("Soil Humidty: " + String(soilHum));

  // Read light 
  float volts = analogRead(lightPin) * 5.0 / 1024.0;
  float amps = volts /10000.0;
  float microamps = amps * 1000000;
  float lux = microamps * 2.0;

  Serial.println("Lux: " + String(lux));

  float h = dht.readHumidity();
  float temp = dht.readTemperature();

  Serial.println("Temp: " + String(temp,2));
  Serial.println("Hum: " + String(h,2));
  sendValue(temp, h, lux, soilHum);
  delay (60000);


void sendValue(float tempValue, float humValue, float lux, float soil)
  Serial.println("Sending data...");
  // if you get a connection, report back via serial:
  int bodySize = 0;
  // Post single value to single var
  // String varString = "{\"value\":"+ String(tempValue) + "}";
  String varString = "[{\"variable\": \"" + tempVarId + "\", \"value\":"
                     + String(tempValue) + "}";
  // Add other variables

  if (client.connect(server,80))
       client.println("POST /api/v1.6/collections/values HTTP/1.1");
       Serial.println("POST /api/v1.6/collections/values HTTP/1.1");
       client.println("Content-Type: application/json");
       Serial.println("Content-Type: application/json");
       client.println("Content-Length: "+String(bodySize));
       Serial.println("Content-Length: "+String(bodySize));
       client.println("X-Auth-Token: "+token);
       Serial.println("X-Auth-Token: "+token);
    // if you didn't get a connection to the server:
    Serial.println("connection failed");

  boolean sta = client.connected();
  Serial.println("Connection ["+String(sta)+"]");
  if (!client.connected())
  while (client.available())
    char c =;


In conclusion, running the sketch and accessing the Ubidots dashboard we have:
IoT cloud dashboard

Finally, at the end of this IoT project tutorial, you gained, hopefully, the knowledge about reading data sensors and sending the values to the cloud.

  • Azeo

    Looks good, I’ll have to try as an alternative to Xively!

    • Azeo
      • Thx looks great. If you like you can post here how to do it. It would be very interesting for this blog readers.

        • Azeo

          I would be happy to look at doing that, it would take some work and time to “massage” and tidy the code glued together to make things work into a more suitable result for “publication”, and gather some links and credits, but that would also be a very worthwhile exercise for me!
          Cheers and Kind Regards,

  • Xively is an interesting product. Let me know the link of your project when it is ready.

  • Bongjun Hur

    your work surprised me a lot always. If I do, If I can, I’d like to make some lecture note using YOUR AWESOME WORK to Korean users~~. good~ 😉

    • Of corse you can. If you can you could add a reference to this original post. Thank you very much. As you can notice the wiznet shield is always in my projects.

  • Very cool project and very useful for real life applications!

    Have you ever thought on using an ESP8266 instead of an Arduino? This way you can reduce even more the price of your design.