Published May 10, 2018 © MIT

Measuring Soil Moisture With The NodeMCU Amica (ESP8266)

Use a NodeMCU Amica (ESP8266) and a Funduino moisture sensor to build a Wia Flow that notifies you when your plant needs watering!

BeginnerFull instructions provided1 hour2,603

Measuring Soil Moisture With The NodeMCU Amica (ESP8266)

Things used in this project

Hardware components

NodeMCU ESP8266 Breakout Board

SparkFun Soil Moisture Sensor (with Screw Terminals)

We used a Funduino but a Sparkfun will work also

Software apps and online services

Wia

Story

In this tutorial, we'll use a NodeMCU Amica (ESP8266 based development board) and a Funduino moisture sensor to measure soil moisture, and build a Wia Flow that notifies you when your plants need watering.

If you haven't already, check out our tutorial on getting started with the ESP8266. It details setting up the correct environment and libraries to complete this tutorial.

Connecting the hardware

Use jumper wires to connect the moisture sensor to the board as follows:

Install the required libraries

In the Arduino IDE, Go to Sketch > Include Libraries > Manage Libraries. Install each of the following libraries by searching for their name in the search bar within the modal. A button will appear in the bottom right of the box that will allow you to install the library.

ArduinoJson

ESP8266WiFi

ArduinoHttpClient

The Code

In the Arduino IDE, copy and paste the code labeled Publish Event to Wia.

Replace the following values of the following variables (Place the correct value between the quotation marks right of the variable names in the code):

your-ssid - with your WiFi network name

your-password - with your WiFi network password

your-device-secret-key with your device secret key from the Wia Dashboard (the one that begins with d_sk)

Make sure the correct board is selected - go to tools > board and select NodeMCU 1.0 (ESP-12E Module).Make sure the correct port is selected - tools > port.Click Sketch > Upload in the menu.

Go to your Wia dashboard and view the Events as they come in via the Device debugger.

Notifying you when your plant needs watering

Next, we'll set up a Flow that will send a notification to your phone when the moisture level drops below a certain threshold. The Wia app is required to send a push notification to your phone, it can be installed here for Android and for iOS here.

Go to your Wia Dashboard and click Flows in the left hand side menu. Create a new Flow with any name you like.

In Flow Studio, drag an Event node from the triggers section and:

Enter moisture as the the Event name

Add the Device that matches the one you added to the code earlier

Drag a function node from the logic section and copy and paste the following code:

if
    if (input.body.data > 500) {        
        output.process = 0;      
    }
}
else
output.process = 0; 
}

The Output from the soil moisture sensor is a number between 0 and 1023 with 0 being completely dry and 1023 being completely wet. The code above sets to not process the output when there is no input or if the input is greater than 500 (i.e The doesn't plant need watering).

Finally, add a notification node and enter The plant needs watering in the text field so that Wia can send a notification to you when your plant needs watering.

Completed Wia Flow

Taking it One Step Further

Here's just one way you could take this project to the next level: we're going to feed our moisture data into two Widgets on the Wia Dashboard, in addition to sending the notification.

First, add another function node from the logic section, and connect it to the same event. In this node, paste the following code:

// Check moisture levels
if
    // Plant is thirsty	
        output.body.data = "Thirsty";
} 
  // Plant is ok
	output.body.data = "Ok";
}

This code outputs 'Thirsty' if the plant needs watering, and 'Ok' otherwise. We're now going to connect the output of this function node to a new event action node. Drag one over from the 'actions' section (not 'triggers'). This will create a new event. Give the event a name (such as status), and connect the function node to it.

Next, head over to your Device's 'Overview' tab. Click 'Add a Widget'. Give the Widget a name ('Status'), choose Widget type 'text', and enter the name of the Event that you created in your Flow (status).

Create another Widget of type 'text', give it a name ('Moisture') and enter the name of your original Event trigger (moisture).

Now, when your events are published, the Widgets on your Device overview page will update in real time!

Widgets

Publish an Event to Wia

#include <ArduinoJson.h>
#include <ESP8266WiFi.h>
#include <ArduinoHttpClient.h>
#include <Arduino.h>

const char* ssid     = "your-ssid"; // Your WiFi ssid
const char* password = "your-password"; //Your Wifi password

// Get this secret key from the wia dashboard. It should start with `d_sk`
const char* device_secret_key = "your-device-secret-key";

// Wia API parameters
char server[] = "api.wia.io";
char path[] = "/v1/events";
int port = 80;

WiFiClient client;
int status = WL_IDLE_STATUS;

StaticJsonBuffer<200> jsonBuffer;
HttpClient httpClient = HttpClient(client, server, port);
JsonObject& root = jsonBuffer.createObject();

const int ANALOG_PIN = 0;

void setup() {
  
  // initialize serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }
  WiFi.begin(ssid, password);
  Serial.print("Attempting to connect to SSID: ");
  Serial.print(ssid);
  // attempt to connect to WiFi network:
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    // Connect to WPA/WPA2 network. Change this line if using open or WEP  network:
    // wait 5 seconds for connection:
    delay(5000);
  }

  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  Serial.println("connecting...");
}

// Thing function runs continiously
void loop() {
  
  root["name"] = "moisture";
  root["data"] =  analogRead (ANALOG_PIN);

  // if you get a connection, report back via serial:
  if (client.connect(server, port)) {

    sendToWia(root);

  } else {
    // if you didn't get a connection to the server:
    Serial.println("connection failed");
  }
  delay(1000*15*60); // Wait for 15 minutes to post again
}

// Adds the correct headers for HTTP and sends Data to Wia
void sendToWia(JsonObject& data) {
  size_t len = data.measureLength();
  size_t size = len + 1;
  char json[size];
  httpClient.beginRequest();
  httpClient.post(path);
  httpClient.sendHeader("Content-Type", "application/json");
  httpClient.sendHeader("Content-Length", data.measureLength());
  httpClient.sendHeader("Authorization", "Bearer " + String(device_secret_key));
  httpClient.beginBody();
  data.printTo(httpClient);
  Serial.print("Posting ");
  data.printTo(Serial);
  Serial.println(" to Wia");
  httpClient.endRequest();
}