Project tutorial
IoT Pressure Sensor: MKR GSM + Arduino Cloud + Google Sheets

IoT Pressure Sensor: MKR GSM + Arduino Cloud + Google Sheets © CC BY-NC-SA

IoT device to remotely monitor pressure (0-150 psi) using cellular data. Get notifications for pressures above/below high/low set-points.

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Components and supplies

Apps and online services

About this project


The objective of this project was to create a prototype for a low-cost device to monitor pressure on industrial equipment in remote locations using cellular data.

Project Walkthrough

The following is a a step by step walkthrough of the project following the flow of data from the pressure transducer to the email notification generated by the script attached to the Google Sheet.

Step 1: Pressure Transducer to Uno

The pressure transducer converts pressure to an analog electrical signal.

The Arduino Uno converts the analog signal from the pressure transducer into pressure (psi).

Step 2: Uno to MKR GSM 1400 via Serial

When communicating between two Arduino devices via Serial:

  • Connect RX on Device #1 to TX on Device #2
  • Connect TX on Device #1 to RX on Device #2
  • The devices must have a common ground

Data Transmission Frequency (Uno to MKR GSM 1400)

  • NORMAL: Every 30 minutes (transmitFrequency) the Uno will serial.print data to the MKR GSM 1400 which will transmit the data to the cloud.
  • HIGH/LOW TRIGGER: If the pressure goes above 40 psi (highTrigger) or below 20 psi (lowTrigger) and stays there for greater than 2 minutes (dtLastTriggerLimit) the Uno will serial.print data to the MKR GSM 1400 which will transmit the data to the cloud.
  • DEMAND POLL: If pin A1 on the Uno is pushed high it will serial.print data to the MKR GSM 1400 which will transmit the data to the cloud. Note: pin A1 is named "buttonPin" in the sketch for the Uno. There are 2 ways that pin A1 on the Uno can get pushed high. (1) There is a push button on the breadboard. (2) If pin A3 on the MKR GSM 1400 is high it will push pin A1 high. Since pin A3 is controlled by an input in the Arduino Cloud, the current pressure can be obtained remotely at any time without having to wait for a regularly scheduled data transmission.


  • The sketch for the Uno could be modified so that multiple inputs like temperature, humidity, battery voltage, etc. could be monitored with high and low setpoints in addition to pressure in the current version.

The code used for the Arduino Uno in this project is attached with comments explaining key information.

File Name: "InstrumentReader"

Step 3: MKR GSM 1400 to Arduino Cloud via Cellular

The MKR GSM 1400 processes serial data from the Arduino Uno and transmits the data to the Arduino Cloud using cellular data.

It is worth noting that in the code for the MKR GSM 1400 you'll see as opposed to The reference material on the Arduino website gives a good explanation. The table in the image below shows that the TX/RX pins on MKR boards are accessed via Serial1.

Arduino Cloud

This project is setup with 2 variables in the Arduino Cloud. The image below shows how these variables are displayed in the dashboard on the Arduino Cloud.

The first variable named "dataStringCloud" is effectively a package of all the data from the device. This approach was taken as opposed to one variable for each value to simplify processing the data in Google Sheets. With individual variable names, it was difficult to tell the difference between a value staying the same and a value that did not get updated. The data from this package is parsed in Google Sheets.

The second variable named "pinCloud" is used to control the MKR GSM 1400 from the Arduino Cloud. There is a switch function in the sketch that controls the action based on the value of pinCloud. When pinCloud = 1, pin A1 is pushed high causing an LED on the board to light up. When pinCloud = 2, pin A3 is pushed high which leads to the Arduino Uno sending the current data as described above.

The code used for the Arduino MKR GSM 1400 in this project is attached with comments explaining key information.

File Name: "CommunicationsDevice"

Step 4: Arduino Cloud to Google Sheets via Webhook

Data is transferred from the Arduino Cloud to Google Sheets using a webhook.

The core of the webhook is the doPost function written in the script of a Google Sheets file.

Here is a quick summary of how to set-up the webhook. Note that the process starts in Google Sheets. You don't get to the Arduino Cloud until the end. To get from A to B, start at B.

  • Create a New Google Sheets file
  • Click "Tools" on the toolbar & select "Script editor" in the dropdown
  • Write code with a doPost function (refer to GoogleSheetsScript.js attached to this project)
  • Click "Publish" on the toolbar & select "Deploy as web app..." in the dropdown
  • A dialog box will come up with 3 fields.
  • (1) Project Version: Always use the dropdown to select "New". After the first update it will default to the # of the current version; if you don't use the dropdown to select "New", the changes will not go into effect.
  • (2) Execute the App as: "me ("
  • (3) Who has access to the app: "Anyone, even anonymous"
  • Press deploy after verifying the values in the 3 fields
  • A second dialog box will appear with the "Current web app URL". This is the URL that you will copy & paste into the webhook tab on the Arduino Cloud. Worth noting, this URL stays the same regardless of the project version.
  • Click ok, and you are done!

A good portion of the JavaScript code used in this project is modeled after the code used in another project named "Arduino IoT Cloud Google Sheets Integration". The link to the project is below. I'd recommend checking it out.

Step 5: Use Google Sheets to Parse Data

Use Google Sheets to parse the individual values from dataStringCloud and display the unique records transferred from the Arduino Cloud

The link below is to the Google Sheets file used for a recent test of the device. The cells in this file are colored based on how they were populated as indicated in the legend on each sheet.

Step 6: Use Google Sheets to Send Notifications

You may have noticed that there are two functions in the JavaScript file for this project (GoogleSheetsScript.js) referenced above in step 4.

  • doPost function - Transmits data from the Arduino Cloud Webhook. It runs when there is new data on the Arduino Cloud.
  • sendEmail function - Sends emails based on values extracted from the sheet named "Data" in the Google Sheets file for the project. It runs once every minute based on the settings in the trigger setup.

Steps to Setup a Trigger for the sendEmail function

  • Open Google Sheets file
  • Click on "Tools" in the toolbar
  • Select "Script Editor" in the dropdown
  • From the Script editor window proceed to:
  • Click on "Edit" in the toolbar
  • Select "Current project's triggers" in the dropdown
  • From the G Suite Developer Hub window proceed to:
  • Select "Add Trigger" in the bottom right corner of the window
  • In the dialog box that comes up make selections to run the sendEmail function.
  • Note: running the trigger on a Time-Driven basis makes it possible to generate email notifications when the device stops updating.

Battery Life

~24 hours

This could be optimized by turning off or removing the displays. Another option would be to remove non-essential sensors like the DHT22 and the DS3231.

Data Usage

~0.7 megabytes/day

This could be optimized by reducing the size or frequency of data transmissions. For example: To reduce reduce size, only send pressure as opposed to pressure, temperature, humidity, and time. To reduce frequency, only hourly updates as opposed to every 30 minutes.

Project Cost

Total = $241

  • Arduino MKR GSM 1400 ($70)
  • Arduino Uno ($22)
  • 2 x 3.7V LiPo Batteries ($30)
  • 2 x LED Displays ($29)
  • Weather Resistant Plastic Box ($22)
  • Pressure Sensor ($19)
  • Temperature / Humidity Sensor - DHT22 ($10)
  • RTC Module - DS3231 ($5)
  • Voltage Step-up Converter ($5)
  • Logic Level Converter ($4)
  • Miscellaneous - LEDs, Resistors, Wiring, etc. ($25)

Hardware / Tools

All of the hardware and tools used for this project were purchased from the following:

  • Harbor Freight
  • Home Depot

In Conclusion...

Thanks for taking the time to review this project.

Any and all questions / feedback / comments / suggestions are welcome / appreciated.


InstrumentReader - Sketch for Arduino UnoArduino
// Sketch 1 of 2
// Arduino Uno
  // Data is collected by this device and transmitted to the MKR 1400 via serial

// The DHT22 Sensor Requires 2 libraries, but only one is called in the code.  
//     (1): DHT Sensor Library: 
//     (2): Adafruit Unified Sensor Lib: 

#include <SPI.h>
#include <Wire.h>
#include <DS3231.h>   // RTC module
#include <DHT.h>      // DHT22
#include "U8glib.h"   // Velleman 128 x 64 OLED SPI Display 
                      // Note: Another standard U8glib library did not work when I attempted to use it for this display. It did work when I used the library recommended by the manufacturer. 
                      // Library: 
                      // Syntax: &
//#include <SD.h>     // Option to save to SD card in Ethernet Shield for Arduino Uno


#define DHTPIN 11     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321

U8GLIB_SH1106_128X64 u8g(3, 4, 6, 7); // (CLK/SCK: 3, MOSI: 4, CS: 6, DC(A0): 7) // u8g(sck, mosi, cs, a0 [, reset]) 

int y_pos = 0;  // global variable

//const int chipSelect = 10; // Option to save to SD card in Ethernet Shield for Arduino Uno
//float fileSizeSD = 0.0;    // Option to save to SD card in Ethernet Shield for Arduino Uno

int i = 0; // Count # of readings taken by the Uno (same as # loops in program) 

const int ledPin = 9;     // transmit indicator (flashes when a data transmission occurs)
const int ledPin2 = 8;    // push transmit indicator (pushed high by manual button on breadboard or output from MKR 1400 activated from the cloud)
const int buttonPin = A1;

int buttonState = 0;

int transmitFrequency = 30;  // Frequency of Serial Print dataString for sending data to the second device (minutes)
String pTransmitDateTime = "";
int transmitCounter = 0;
int pTransmitMinute = 0;
int ptriggerTransmitAlertIndicator;

float cRuntimeAtTriggerStart = 0.0;
float dtLastTrigger = 0.0;
int triggerCounter = 0.0;
int triggerTransmitAlertCounter = 0;

// Input Variables to Control Trigger
float lowTrigger = 20.0;
float highTrigger = 40.0;
float dtLastTriggerLimit = 2.0; // If the condition is met for this length of time, an alert will be generated

void setup (void) {
    pinMode(ledPin, OUTPUT);
    pinMode(ledPin2, OUTPUT);
    pinMode(buttonPin, INPUT);
    u8g.setRot180();  // flip screen, if required (add/remove comments on this line to rotate)

    // Option to save to SD card in Ethernet Shield for Arduino Uno
        //    Serial.print("Initializing SD card...");
        //    if (!SD.begin(chipSelect))     // see if the card is present and can be initialized
        //    {
        //      Serial.println("Card failed, or not present");
        //      while (1);     // don't do anything more
        //    }
        //    Serial.println("card initialized.");

void loop (void) {
    DateTime now =;
    float cRuntime = millis()/60000;
    float p = getPressure();
//    Serial.println(p);

    buttonState = digitalRead(buttonPin);
//    Serial.print("Button: ");
//    Serial.println(buttonState);
    if(buttonState == 1)
      digitalWrite(ledPin2, HIGH);
      delay(30000); // delay to allow MKR1400 to get ready to recieve data if Uno:buttonPin is pushed HIGH by MKR1400:pingPin
      digitalWrite(ledPin2, LOW);
    float h = dht.readHumidity();
    float t = dht.readTemperature(true);  // t = dht.readTemperature(true) --> temp if degrees F & t = dht.readTemperature() --> temp if degrees C 
    int transmitIndicator = 0;
    if(now.minute() % transmitFrequency == 0 && now.minute() != pTransmitMinute)
      transmitIndicator = 1;
      pTransmitMinute = now.minute();
      pTransmitDateTime = String(now.hour())+String(":")+String(now.minute())+String(":")+String(now.second());

    int triggerStatus = 0;
    if(p <= lowTrigger || p >= highTrigger)  
 // Note: the variable referenced in the condition for this if statement is evaulated against high & low setpoints
 //    It is quick to change which variable is evaluated - this is the only location where the variable is specified

      triggerStatus = 1;
      triggerCounter = 0;
    if(triggerStatus == 1 && triggerCounter == 1)
      cRuntimeAtTriggerStart = cRuntime;
    dtLastTrigger = cRuntime - cRuntimeAtTriggerStart;
    int triggerTransmitAlertIndicator = 0;
    if((dtLastTrigger > dtLastTriggerLimit) && triggerStatus == 1)
      triggerTransmitAlertIndicator = 1;
      triggerTransmitAlertCounter = 0;

    if(triggerTransmitAlertCounter > 0 && triggerTransmitAlertCounter % 10 == 0)

    int triggerPushTransmitAlertIndicator = 0;
    if((triggerTransmitAlertIndicator == 1 && triggerTransmitAlertCounter == 1) || ptriggerTransmitAlertIndicator != triggerTransmitAlertIndicator) 
    // if(TriggerStatus existed for min specified time for Alert & Count = 1 meaining that this is the first loop where the time exceeded the min specified time 
    //       OR the triggerAlert status changes -- this will generate a push Alert if the TriggerStatus goes back to 0 meaning the Trigger conditions are no longer met.)
      triggerPushTransmitAlertIndicator = 1;

    ptriggerTransmitAlertIndicator = triggerTransmitAlertIndicator; // current indicator stored to previous indicator. On the next loop the value transferred here will be compared to the value generated based on new values.

    // Create strings
    String dataString = "";
    String cDateTime = "";
    String cHumTemp = "";
    String cP = "";
    dataString += "<"+String(i)+","+String(triggerTransmitAlertIndicator)+","+String(dtLastTrigger,0)+","+String(buttonState)+", "+String(now.month())+","+String(","+String(now.year())+", "+String(now.hour())+","+String(now.minute())+","+String(now.second())+", "+String(h)+","+String(t)+","+String(p)+">";
    cDateTime += String(now.month())+"/"+String("/"+String(now.year())+" "+String(now.hour())+":"+String(now.minute())+":"+String(now.second());
    cHumTemp += "H:"+String(h)+"% T:"+String(t)+"degF";
    cP += "P:"+String(p)+"psi";

    if(transmitIndicator == 1 || triggerPushTransmitAlertIndicator == 1 || buttonState == 1)
      char dataArray[100];
      dataString.toCharArray(dataArray, 100);
//    Serial.print("T:");
//    Serial.println(triggerStatus);
    delay(100);     // wait a bit for the entire message to arrive
    // picture loop
    draw(cDateTime,cHumTemp, cP,i,transmitCounter,now.minute(),transmitFrequency,pTransmitMinute);
    // writeToSD(dataString);  // Option to save to SD card in Ethernet Shield for Arduino Uno   

void draw(String DcDateTime,String DcHumTemp, String DcP, int Di, int DtransmitCounter,int DnowMinute,int DtransmitFrequency, int DpTransmitMinute) 
    u8g.setFont(u8g_font_5x7);  //u8g_font_micro //u8g_font_5x7  //u8g_font_5x8  //u8g_font_6x10
    u8g.print("3 #:");
    u8g.print("4 #t:");
    u8g.print("tFreq: ");
    u8g.print(DnowMinute % DtransmitFrequency);

float getPressure()
  int sensorVal=analogRead(A2);
//    Serial.print("Sensor Value: ");
//    Serial.print(sensorVal);
  float voltage = (sensorVal*5.0)/1023.0;
//    Serial.print(" Volts: "); 
//    Serial.print(voltage);
  // When Pressure = 0, Analog Input = 100
  // Conversion of Analog Input to Voltage: Analog Input = 100 -> Voltage = 100*(5/1023) = 0.4889
  float m = ((150-0)/(4.5-0.4889));
  float b = 150 - (m*4.5);
//    Serial.print(" m = ");
//    Serial.print(m);
//    Serial.print(" b = ");
//    Serial.print(b);
  float pressure_psi = ((m*voltage)+ b);
//    Serial.print(" Pressure = ");
//    Serial.print(pressure_psi);
//    Serial.println(" psi");    
//    delay(200);
  return pressure_psi;

void flashLED(int num, int t)
  for (int z = 1; z <= num; z++)
      digitalWrite(ledPin, HIGH);
      digitalWrite(ledPin, LOW);

// Option to save to SD card in Ethernet Shield for Arduino Uno   
    //void writeToSD(String dataToWrite)
    //    // open the file. note that only one file can be open at a time,
    //    // so you have to close this one before opening another.
    //    File dataFile ="datalog4.txt", FILE_WRITE);
    //    fileSizeSD = dataFile.size();  // Reurns file size in bytes
    //    fileSizeSD = fileSizeSD / 1000000 ;  // Converts bytes to MB. 1 MB = 1e6 bytes
    //    // if the file is available, write to it:
    //    if (dataFile) 
    //    {
    //      dataFile.println(dataToWrite);
    //      dataFile.close();
    //      // print to the serial port too:
    //      // Serial.println(dataToWrite);
    //    }
    //    // if the file isn't open, pop up an error:
    //    else 
    //    {
    //      Serial.println("error opening datalog1.txt");
    //    }   
// There are 2 functions in this code
// doPost function - Transmits data from the Arduino Cloud Webhook. It runs when there is new data on the Arduino Cloud.
// sendEmail function - Sends emails based on values extracted from the sheet named "Data" in the Google Sheets file for the project. It runs once every minute based on the settings in the trigger setup. For instructions, refer to the sendEmail function portion of the project hub post.

// The majority of this code (aside from the sendEmail function) is modeled after the following project on the Arduino Project Hub

// This a link to a GitHub repository with the Google Script used for the above mentioned project on the Project Hub. 
// This link was copied from the desription of the project on the Project Hub.

// get active spreasheet
var ss = SpreadsheetApp.getActiveSpreadsheet();

// get sheet named RawData
var sheet = ss.getSheetByName("RawData");
var sd = ss.getSheetByName("Data");
var sref =  ss.getSheetByName("References");

var MAX_ROWS = 1440;     // max number of data rows to display
// 3600s / cloud_int(30s) * num_ore(12h) = (60*60*12)/30 = (3600*12)/30 = 1440 readings in 12 hours at 30 second update interval
// (60*24)/15 = 96 readings in a 24 hour period at 15 minute update interval
// 15 days * 96 readings/day = 1440 readings
// 90 days * 96 readings/day = 8640 readings
// 365 days * 96 readings/day = 35040 readings
var HEADER_ROW = 1;     // row index of header
var TIMESTAMP_COL = 1;  // column index of the timestamp column

function doPost(e) {  
  var cloudData = JSON.parse(e.postData.contents); // this is a json object containing all info coming from IoT Cloud
  //var webhook_id = cloudData.webhook_id; // really not using these three
  //var device_id = cloudData.device_id;
  //var thing_id = cloudData.thing_id;
  var values = cloudData.values; // this is an array of json objects
  // Store names and values from the values array
  // Each incoming property has a: 
  //      name which will become the column names
  //      value which will be written into the rows below the column header 
  var incLength = values.length;
  var incNames = [];
  var incValues = [];
  for (var i = 0; i < incLength; i++) {
    incNames[i] = values[i].name;
    incValues[i] = values[i].value;
  // read timestamp of incoming message
  var timestamp = values[0].updated_at;          // format: yyyy-MM-ddTHH:mm:ss.mmmZ
  var date = new Date(Date.parse(timestamp)); 
  This if statement is due to the fact that duplicate messages arrive from the cloud!
  If that occurs, the timestamp is not read correctly and date variable gets compromised.
  Hence, execute the rest of the script if the year of the date is well defined and it is greater
  then 2018 (or any other year before)
  if (date.getYear() > 2018) {
    // discard all messages that arrive 'late'
    if (sheet.getRange(HEADER_ROW+1, 1).getValue() != '') { 
      // HEADER_ROW + 1 = Row #2 & Column #1 --> this is the location of the most recent timestamp in the sheet
      // If the most recent timestamp is not blank = (''), then compare the current time to the timestamp of the incoming data
      // If the most recent timestamp is blank, it is most likely the first time the script is run.
      //      In this case skip this if statement and proceed to write in the column headers and data. 
      //      It doesnt matter if the data is arriving late (current time vs timestamp of incoming data).
      var now = new Date(); // now
      var COMM_TIME = 120; // Note: changed to 120 to allow more messages to come through, previously set at 5 seconds & worked ok // rough overestimate of communication time between cloud and app
      if (now.getTime() - date.getTime() > COMM_TIME * 1000) {
        // If the difference between the current time and the timestamp is greater than 5 seconds, discard the data. 
        // When the condition in this If statement evaluates true, the funtion will stop due to the return statement.
        return; // "The return statement stops the execution of a function and returns a value from that function."
    // This section writes values to the header row based on the names of the incoming properties
    //      In other words, this section creates the column names
    // Assign a name to the cell that is in the header row & in the first column = timestamp
    sheet.getRange(HEADER_ROW, 1).setValue('timestamp');
    for (var i = 0; i < incLength; i++) {
      var lastCol = sheet.getLastColumn(); // at the very beginning this should return 1 // second cycle -> it is 2
      // column 1 is the timestamp column. 
      if (lastCol == 1) {
        // write the column names beginning with the column after lastCol == 1 which is the timestamp column
        // incNames is an array containing the names of all of the incoming properties
        // If lastCol == 1, write the value from 'i'th location in the incNames array to the header row in column #2 = lastCol + 1 
        sheet.getRange(HEADER_ROW, lastCol + 1).setValue(incNames[i]);
      } else {
        // evaluated if the lastCol != 1
        // check if the name is already in header
        var found = 0;
        for (var col = 2; col <= lastCol; col++) {
          // starting with column 2, iterate through all of the columns up to the lastCol evaluating the if statement enclosed
          if (sheet.getRange(HEADER_ROW, col).getValue() == incNames[i]) {
            // the condition of this If statement compares the value in the header row & column # = col to the 'i'th value in the array of incoming property names
            // This if statement is evaulated for each iteration of the for loop that it is enclosed in. 
            //     The condition is evaluated for all of the columns from column #2 to the last column. 
            //     It is checking to see if the 'i'th value in the incNames array exists in any of the columns in the header row.
            //     If the 'i'th value in the incNames array finds a match to any of the values in the header row, set found = 1 & exit the for loop with the break statment. 
            found = 1;
            break; // "The break statement breaks the loop and continues executing the code after the loop"
          } // close if statement evaluated for each iteration of the for loop that it is enclosed in.
        } // close for loop to check the 'i'th value in the incNames array to the values in the header row. 
        if (found == 0) {
          // This If statemnt will be evaluated after the preceeding for loop has completed. 
          //       If found == 0 it means that the 'i'th value in the incNames array did not match any of the existing values in the header row. 
          //       If found == 0, write the 'i'th value in the incNames array to the column after the last column.
          //       If new properties are added to the incoming data over time, the existing columns will not be impacted. The new property will be added to the column after the last column.
          sheet.getRange(HEADER_ROW, lastCol+1).setValue(incNames[i]);
        } // close if statement
      } // close else, since this is the end of the code block inside the main for loop, the next i will be evaluated up to i = incLength
      // The block of code inside this for loop is evaluated for each value at location i in the incNames array. 
      //     The values of i range from 0 to incLength (the number of values in the names array)
      //     In JavaScript the index in arrays starts at 0. In other words, the 1st value in the array is at location = 0.
    } // close main for loop used to write column names (assigning values from names array to header row)
    // redefine last coloumn and last row since new names could have been added
    var lastCol = sheet.getLastColumn();
    var lastRow = sheet.getLastRow();
    // delete last row to maintain constant the total number of rows
    if (lastRow > MAX_ROWS + HEADER_ROW - 1) { 
    // insert new row after deleting the last one
    // reset style of the new row, otherwise it will inherit the style of the header row
    var range = sheet.getRange('A2:Z2');
    // write the timestamp
    sheet.getRange(HEADER_ROW+1, TIMESTAMP_COL).setValue(date).setNumberFormat("yyyy-MM-dd HH:mm:ss");
    // write values in the respective columns
    for (var col = 1+TIMESTAMP_COL; col <= lastCol; col++) {
      // for loop to assign the value from incValues to the approrpriate column 
      // This block of code was replaced by an if statement checking for blank values after the incoming data is populated.
      //      Copy previous values 
      //      This is to avoid empty cells if not all properties are updated at the same time
      //      sheet.getRange(HEADER_ROW+1, col).setValue(sheet.getRange(HEADER_ROW+2, col).getValue());
      for (var i = 0; i < incLength; i++) {
        // for loop to identify the appropriate column to assign the value 
        // get the value in the header row in column = col
        var currentName = sheet.getRange(HEADER_ROW, col).getValue(); 
        if (currentName == incNames[i]) {
          // When the condition of this If statement evaluates as true, the 'i'th value in the incValues array will be assigned to row #2 (HEADER_ROW + 1) in column = col
          // turn boolean values into 0/1, otherwise google sheets interprets them as labels in the graph
          if (incValues[i] == true) {
            incValues[i] = 1;
          } else if (incValues[i] == false) {
            incValues[i] = 0;
          } // close else if to convert boolean values to 0/1
          sheet.getRange(HEADER_ROW+1, col).setValue(incValues[i]);
        } // close if checking for a match of the value in the header row for column = col to the 'i'th value in the incNames array 
      } // close for loop run for each value in the incNames array
      if(sheet.getRange(HEADER_ROW+1, col).getValue() == ''){
        // If statement to check for blank values.
        // If the condition is true the previous value will be copied.
        //    Option 1: copy the previous value if the incoming value is blank. This typicaly works, but sometimes the change in the value will not be captured in the transfer due to filtering of incoming messages to avoid duplicates. This can result in an old value getting carried forward
        //      sheet.getRange(HEADER_ROW+1, col).setValue(sheet.getRange(HEADER_ROW+2, col).getValue());
        //    Option 2: Insert a dash if the incoming value is blank.
        sheet.getRange(HEADER_ROW+1, col).setValue("-");
      } // close If statment used to copy the previous value if the value is blank. Since the values are only sent when they change, this carries forward the values that didn't change.
    } // close for loop run for each column from col #2 (TIMESTAMP_COL + 1) to the lastCol
  } // close if statment with the condtion (date.getYear() > 2018), used to eliminate dupicate messages from the Arduino Cloud
} // close doPost function

function sendEmail (){
  var emailAddress = sd.getRange("V3").getValue();

  var lastPressure = sd.getRange("K3").getValue(); // pressure at last update
  var lastUpdate = sd.getRange("A3").getValue(); // datetime of last update
  var ssLink = ""; 
  var triggerAlertCount = sd.getRange("L6").getValue();
  var triggerMonitor = sd.getRange("M3").getValue();
  var dtLastStatusChange = sd.getRange("P3").getValue();

  var dtLastDeviceUpdate1 = sd.getRange("S3").getValue();
  var dtLastDeviceUpdate2 = sd.getRange("S4").getValue();
  var emailSentNoUpdate = sd.getRange("T3").getValue();
  var emailSentStartedReading = sd.getRange("U3").getValue();
  var message = "Last Device Update: " + "\n" + lastUpdate + "\n\n" + " Last Pressure: " + "\n\t" + lastPressure.toFixed(2) + " psi" + "\n\n" + " Link to Spreadsheet: " + "\n\t" + ssLink;
  if(triggerMonitor == 0){
  if(triggerMonitor == -1 && triggerAlertCount <= 4){
    sd.getRange("L3").setValue(lastUpdate); // emailSent
    sd.getRange("L6").setValue(triggerAlertCount + 1);
    var subject = "Status Change Alert - Outside Setpoints";
    MailApp.sendEmail(emailAddress, subject, message);
  if(triggerMonitor == 1 && triggerAlertCount <= 4){
    sd.getRange("L3").setValue(lastUpdate); // emailSent
    sd.getRange("L6").setValue(triggerAlertCount + 1);
    var subject = "Status Change Alert - Normal";
    MailApp.sendEmail(emailAddress, subject, message);
  if(emailSentNoUpdate == 0 && dtLastDeviceUpdate1 > 60 && dtLastDeviceUpdate2 > 60){
    sd.getRange("T3").setValue(1); // emailSentNoUpdate
    sd.getRange("U3").setValue(0); // emailSentStartedReading
    sd.getRange("T4").setValue(now.getTime()); // emailSentNoUpdate
    var subject = "Alert - Over 60 minutes Since Last Device Update";
    MailApp.sendEmail(emailAddress, subject, message);
  if(emailSentNoUpdate == 1 && dtLastDeviceUpdate1 < 60){  // removed the following from the condition: && dtLastDeviceUpdate2 > 60
    sd.getRange("T3").setValue(0); // emailSentNoUpdate
    sd.getRange("U3").setValue(1); // emailSentStartedReading
    sd.getRange("U4").setValue(now.getTime()); // emailSentStartedReading
    var subject = "Alert - Device Started Updating";
    MailApp.sendEmail(emailAddress, subject, message);

CommunicationsDevice - Sketch for MKR 1400


Iot pressure sensor   final schematic f6x6u4r1pe


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