Introduction: Smart Personal Thermometer With Arduino

This instructable is prepared as a part of our assignment for TfCD (Technology for Concept Design) Course at TU Delft. The following instructable is prepared by:

Bo Koperdraat : 4209567
Karthik Mahadevan : 4501578

In this instructable you will learn how to quickly build a thermometer which can be used to measure body temperature. This example uses a thermistor to measure temperature, but greater accuracy of the reading can be achieved by using a different sensor. This setup can also be made to charge with a battery and concealed in an object like a soft toy to get children to take their temperature readings willingly.

Step 1: Collect the Thing and Make the Setup

The following components are required to make this setup:

- Breadboard
- Arduino (An Uno is used in my examples, but any model should do)
- SparkFun WiFi Shield ESP8266
- 10K Ohm Thermistor
- 10K Ohm Resistor (Brown, Black, Orange)
- Hookup Wires
- Computer with Arduino IDE installed (installing and using the IDE are not covered in this tutorial)
- USB Cable (to connect Arduino and PC)

Make the setup according to the schematic shown and hook it to your computer.

Step 2: Put the Code In

The code you see does the following things:

- Connects to a WiFi network
- Gets an IP address
- Connect over TCP to a server (as a client)
- Set up a TCP server of our own.
- Read and display the temperature reading from your sensor.
- Read and display the current time.
- Push the temperature reading to the server.
- Display the IP Address of the server.

Put the following code in your IDE, compile and upload it to your arduino.

SparkFun ESP8266 AT library - Demo
Jim Lindblom @ SparkFun Electronics
Original Creation Date: July 16, 2015
<a href="" rel="nofollow">></p><p>This example demonstrates the basics of the SparkFun ESP8266
AT library. It'll show you how to connect to a WiFi network,
get an IP address, connect over TCP to a server (as a client),
and set up a TCP server of our own.</p><p>Development environment specifics:
  IDE: Arduino 1.6.5
  Hardware Platform: Arduino Uno
  ESP8266 WiFi Shield Version: 1.0</p><p>This code is released under the MIT license.</p><p>Distributed as-is; no warranty is given.
// Library Includes //
// SoftwareSerial is required (even you don't intend on
// using it).
#include </p><p>//////////////////////////////
// WiFi Network Definitions //
// Replace these two character strings with the name and
// password of your WiFi network.
const char mySSID[] = "*****";    /Enter your SSID
const char myPSK[] = "*****";</p><p> /Enter your Password

// ESP8266Server definition //
// server object used towards the end of the demo.
// (This is only global because it's called in both setup()
// and loop()).
ESP8266Server server = ESP8266Server(80);</p><p>//////////////////
// HTTP Strings //
const char destServer[] = "";
const String htmlHeader = "HTTP/1.1 200 OK\r\n"
                          "Content-Type: text/html\r\n"
                          "Connection: close\r\n\r\n"
\r\n";</p><p>const String httpRequest = "GET <a href="" rel="nofollow"> <a href="" rel="nofollow"> </a> </a> HTTP/1.1\n"
                           "Connection: close\n\n";</p><p>// All functions called from setup() are defined below the
// loop() function. They modularized to make it easier to
// copy/paste into sketches of your own.
void setup() 
  // Serial Monitor is used to control the demo and view
  // debug information.
  }</p><p>  serialTrigger(F("Press any key to begin."));</p><p>  // initializeESP8266() verifies communication with the WiFi
  // shield, and sets it up.
  initializeESP8266();</p><p>  // connectESP8266() connects to the defined WiFi network.
  connectESP8266();</p><p>  // displayConnectInfo prints the Shield's local IP
  // and the network it's connected to.
  displayConnectInfo();</p><p>  serialTrigger(F("Press any key to connect client."));
  serialTrigger(F("Press any key to test server."));
}</p><p>double Thermister(int RawADC) 
{  //Function to perform the fancy math of the Steinhart-Hart equation
 double Temp;
 Temp = log(((10240000/RawADC) - 10000));
 Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );
 Temp = Temp - 273.15;              // Convert Kelvin to Celsius
 return Temp;
}</p><p>void loop() 
  int hours; // you must add these variables
int minutes; // to store the time</p><p>{
 // Show it on the serial monitor.
 Serial.print("Server Time is: ");
 Serial.println(minutes);</p><p> delay(5000); // delay - don't oveload my server...
  int val;                //Create an integer variable
  val=analogRead(0);      //Read the analog port 0 and store the value in val
  double temp;
  temp=Thermister(val); ;
  Serial.println("And the temperature is: ");
  Serial.println(temp);    //Print the value to the serial port
  Serial.println( "degrees Celsius");
  delay(1000);            //Wait one second before we do it again
}</p><p>void initializeESP8266()
  // esp8266.begin() verifies that the ESP8266 is operational
  // and sets it up for the rest of the sketch.
  // It returns either true or false -- indicating whether
  // communication was successul or not.
  // true
  int test = esp8266.begin();
  if (test != true)
    Serial.println(F("Error talking to ESP8266."));
  Serial.println(F("ESP8266 Shield Present"));
}</p><p>void connectESP8266()
  // The ESP8266 can be set to one of three modes:
  //  1 - ESP8266_MODE_STA - Station only
  //  2 - ESP8266_MODE_AP - Access point only
  //  3 - ESP8266_MODE_STAAP - Station/AP combo
  // Use esp8266.getMode() to check which mode it's in:
  int retVal = esp8266.getMode();
  if (retVal != ESP8266_MODE_STA)
  { // If it's not in station mode.
    // Use esp8266.setMode([mode]) to set it to a specified
    // mode.
    retVal = esp8266.setMode(ESP8266_MODE_STA);
    if (retVal < 0)
      Serial.println(F("Error setting mode."));
  Serial.println(F("Mode set to station"));</p><p>  // esp8266.status() indicates the ESP8266's WiFi connect
  // status.
  // A return value of 1 indicates the device is already
  // connected. 0 indicates disconnected. (Negative values
  // equate to communication errors.)
  retVal = esp8266.status();
  if (retVal <= 0)
    Serial.print(F("Connecting to "));
    // esp8266.connect([ssid], [psk]) connects the ESP8266
    // to a network.
    // On success the connect function returns a value >0
    // On fail, the function will either return:
    //  -1: TIMEOUT - The library has a set 30s timeout
    //  -3: FAIL - Couldn't connect to network.
    retVal = esp8266.connect(mySSID, myPSK);
    if (retVal < 0)
      Serial.println(F("Error connecting"));
}</p><p>void displayConnectInfo()
  char connectedSSID[24];
  memset(connectedSSID, 0, 24);
  // esp8266.getAP() can be used to check which AP the
  // ESP8266 is connected to. It returns an error code.
  // The connected AP is returned by reference as a parameter.
  int retVal = esp8266.getAP(connectedSSID);
  if (retVal > 0)
    Serial.print(F("Connected to: "));
  }</p><p>  // esp8266.localIP returns an IPAddress variable with the
  // ESP8266's current local IP address.
  IPAddress myIP = esp8266.localIP();
  Serial.print(F("My IP: ")); Serial.println(myIP);
}</p><p>void clientDemo()
  // To use the ESP8266 as a TCP client, use the 
  // ESP8266Client class. First, create an object:
  ESP8266Client client;</p><p>  // ESP8266Client connect([server], [port]) is used to 
  // connect to a server (const char * or IPAddress) on
  // a specified port.
  // Returns: 1 on success, 2 on already connected,
  // negative on fail (-1=TIMEOUT, -3=FAIL).
  int retVal = client.connect(destServer, 80);
  if (retVal <= 0)
    Serial.println(F("Failed to connect to server."));
  }</p><p>  // print and write can be used to send data to a connected
  // client connection.
  client.print(httpRequest);</p><p>  // available() will return the number of characters
  // currently in the receive buffer.
  while (client.available())
    Serial.write(; // read() gets the FIFO char
  // connected() is a boolean return value - 1 if the 
  // connection is active, 0 if it's closed.
  if (client.connected())
    client.stop(); // stop() closes a TCP connection.
}</p><p>void serverSetup()
  // begin initializes a ESP8266Server object. It will
  // start a server on the port specified in the object's
  // constructor (in global area)
  Serial.print(F("Server started! Go to "));
}</p><p>void serverDemo()
  // available() is an ESP8266Server function which will
  // return an ESP8266Client object for printing and reading.
  // available() has one parameter -- a timeout value. This
  // is the number of milliseconds the function waits,
  // checking for a connection.
  ESP8266Client client = server.available(500);
  if (client) 
    Serial.println(F("Client Connected!"));
    // an http request ends with a blank line
    boolean currentLineIsBlank = true;
    while (client.connected()) 
      if (client.available()) 
        char c =;
        // if you've gotten to the end of the line (received a newline
        // character) and the line is blank, the http request has ended,
        // so you can send a reply
        if (c == '\n' && currentLineIsBlank) 
          Serial.println(F("Sending HTML page"));
          // send a standard http response header:
          String htmlBody;
          // output the value of each analog input pin
          for (int a = 0; a < 1; a++)
            htmlBody += "A";
            htmlBody += String(a);
            htmlBody += ": ";
            htmlBody += String(Thermister(analogRead(a)));</p><p>            //htmlBody += Serial.println(temp);
            htmlBody += "<br>\n";
          htmlBody += "</p><p>\n";
        if (c == '\n') 
          // you're starting a new line
          currentLineIsBlank = true;
        else if (c != '\r') 
          // you've gotten a character on the current line
          currentLineIsBlank = false;
    // give the web browser time to receive the data
    // close the connection:
    Serial.println(F("Client disconnected"));
}</p><p>// errorLoop prints an error code, then loops forever.
void errorLoop(int error)
  Serial.print(F("Error: ")); Serial.println(error);
  Serial.println(F("Looping forever."));
  for (;;)
}</p><p>// serialTrigger prints a message, then waits for something
// to come in from the serial port.
void serialTrigger(String message)
  while (!Serial.available())
  while (Serial.available());

Step 3: Monitor the Values on Your Phone

Once the code is uploaded to your Arduino, test run it once in your serial monitor. This would display the IP address of your network. Copy and paste this in your web browser to see the output of your temperature. This would display the room temperature. If you touch the thermistor for 5 seconds and refresh the page, it will display your body temperature.

Now to check the values on your phone you need to enter the IP address into the browser on your smartphone. You can get easier access and make it feel like an app by saving the webpage on your home screen. You can do that on iOS devices by tapping the share button below and choosing add to homescreen.

Once added, the webpage will appear as an icon on your homescreen, which you can then access as an app to check your or your room's temperature anytime.