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LED Real Time Clock Temperature Sensor Shield for Arduino

Tutorial – LED Real Time Clock Temperature Sensor Shield for Arduino

In this tutorial we look at how to use the neat LED Real Time Clock Temperature Sensor Shield for Arduino from PMD Way. That’s a bit of a mouthful, however the shield does offer the following:

  • four digit, seven-segment LED display
  • DS1307 real-time clock IC
  • three buttons
  • four LEDs
  • a active buzzer
  • a light-dependent resistor (LDR)
  • and a thermistor for measuring ambient temperature

led-real-time-clock-temperature-sensor-shield-arduino-pmdway-1

The shield also arrives fully-assembled , so you can just plug it into your Arduino Uno or compatible board. Neat, beginners will love that. So let’s get started, by showing how each function can be used – then some example projects. In no particular order…

The buzzer

A high-pitched active buzzer is connected to digital pin D6 – which can be turned on and off with a simple digitalWrite() function. So let’s do that now, for example:

void setup() {
  // buzzer on digital pin 6
  pinMode(6, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(6, HIGH);   // turn the buzzer on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(6, LOW);    // turn the buzzer off by making the voltage LOW
  delay(1000);                       // wait for a second
}

If there is a white sticker over your buzzer, remove it before uploading the sketch. Now for a quick video demonstration. Turn down your volume before playback.

The LEDs

Our shield has four LEDs, as shown below:

led-real-time-clock-temperature-sensor-shield-arduino-pmdway-LEDs

They’re labelled D1 through to D4, with D1 on the right-hand side. They are wired to digital outputs D2, D3, D4 and D5 respectively. Again, they can be used with digitalWrite() – so let’s do that now with a quick demonstration of some blinky goodness. Our sketch turns the LEDs on and off in sequential order. You can change the delay by altering the variable x:

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(2, OUTPUT); // LED 1
  pinMode(3, OUTPUT); // LED 2
  pinMode(4, OUTPUT); // LED 3
  pinMode(5, OUTPUT); // LED 4
}

int x = 200;

void loop() {
  digitalWrite(2, HIGH);    // turn on LED1
  delay(x);
  digitalWrite(2, LOW);    // turn off LED1. Process repeats for the other three LEDs
  digitalWrite(3, HIGH);
  delay(x);
  digitalWrite(3, LOW);
  digitalWrite(4, HIGH);
  delay(x);
  digitalWrite(4, LOW);
  digitalWrite(5, HIGH);
  delay(x);
  digitalWrite(5, LOW);
}

And in action:

The Buttons

It is now time to pay attention to the three large buttons on the bottom-left of the shield. They look imposing however are just normal buttons, and from right-to-left are connected to digital pins D9, D10 and D11:

LED Real Time Clock Temperature Sensor Shield for Arduino from PMD Way

They are, however, wired without external pull-up or pull-down resistors so when initialising them in your Arduino sketch you need to activate the digital input’s internal pull-up resistor inside the microcontroller using:

pinMode(pin, INPUT_PULLUP);

Due to this, buttons are by default HIGH when not pressed. So when you press a button, they return LOW. The following sketch demonstrates the use of the buttons by lighting LEDs when pressed:

void setup() {
  // initalise digital pins for LEDs as outputs
  pinMode(2, OUTPUT); // LED 1
  pinMode(3, OUTPUT); // LED 2
  pinMode(4, OUTPUT); // LED 3

  // initalise digital pins for buttons as inputs
  // and initialise internal pullups
  pinMode(9, INPUT_PULLUP); // button K1
  pinMode(10, INPUT_PULLUP); // button K2
  pinMode(11, INPUT_PULLUP); // button K3
}

void loop()
{
  if (digitalRead(9) == LOW)
  {
    digitalWrite(2, HIGH);
    delay(10);
    digitalWrite(2, LOW);
  }

  if (digitalRead(10) == LOW)
  {
    digitalWrite(3, HIGH);
    delay(10);
    digitalWrite(3, LOW);
  }

  if (digitalRead(11) == LOW)
  {
    digitalWrite(4, HIGH);
    delay(10);
    digitalWrite(4, LOW);
  }
}

You can see these in action via the following video:

The Numerical LED Display

Our shield has a nice red four-digit, seven-segment LED clock display. We call it a clock display as there are colon LEDs between the second and third digit, just as a digital clock would usually have:

LED Real Time Clock Temperature Sensor Shield for Arduino from PMD Way with free delivery worldwide

The display is controlled by a special IC, the Titan Micro TM1636:

TM1636 Numerical LED Display Driver IC from PMD Way with free delivery worldwide

The TM1636 itself is an interesting part, so we’ll explain that in a separate tutorial in the near future. For now, back to the shield.

To control the LED display we need to install an Arduino library. In fact the shield needs four, so you can install them all at once now. Download the .zip file from here. Then expand that into your local download directory – it contains four library folders. You can then install them one at a time using the Arduino IDE’s Sketch > Include library > Add .zip library… command:

LED Real Time Clock Temperature Sensor Shield for Arduino from PMD Way with free delivery worldwide

The supplied library offers five functions used to control the display.

.num(x);

…this displays a positive integer (whole number) between 0 and 9999.

.display(p,d);

… this shows a digit d in location p (locations from left to right are 3, 2, 1, 0)

.time(h,m)

… this is used to display time data (hours, minutes) easily. h is hours, m is minutes

.pointOn();
.pointOff();

… these turn the colon on … and off. And finally:

.clear();

… which clears the display to all off. At the start of the sketch, we need to use the library and initiate the instance of the display by inserting the following lines:

#include <TTSDisplay.h>
TTSDisplay rtcshield;

Don’t panic – the following sketch demonstrates the five functions described above:

#include <TTSDisplay.h>
TTSDisplay rtcshield;

int a = 0;
int b = 0;

void setup() {}

void loop()
{
  // display some numbers
  for (a = 4921; a < 5101; a++)
  {
    rtcshield.num(a);
    delay(10);
  }

  // clear display
  rtcshield.clear();

  // display individual digits
  for (a = 3; a >= 0; --a)
  {
    rtcshield.display(a, a);
    delay(1000);
    rtcshield.clear();
  }
  for (a = 3; a >= 0; --a)
  {
    rtcshield.display(a, a);
    delay(1000);
    rtcshield.clear();
  }

  // turn the colon and off
  for (a = 0; a < 5; a++)
  {
    rtcshield.pointOn();
    delay(500);
    rtcshield.pointOff();
    delay(500);
  }

  // demo the time display function
  rtcshield.pointOn();
  rtcshield.time(11, 57);
  delay(1000);
  rtcshield.time(11, 58);
  delay(1000);
  rtcshield.time(11, 59);
  delay(1000);
  rtcshield.time(12, 00);
  delay(1000);
}

And you can see it in action through the video below:

The LDR (Light Dependent Resistor)

LDRs are useful for giving basic light level measurements, and our shield has one connected to analog input pin A1. It’s the two-legged item with the squiggle on top as shown below:

led-real-time-clock-temperature-sensor-shield-arduino-pmdway-LDR

The resistance of LDRs change with light levels – the greater the light, the less the resistance. Thus by measuring the voltage of a current through the LDR with an analog input pin – you can get a numerical value proportional to the ambient light level. And that’s just what the following sketch does:

#include <TTSDisplay.h>
TTSDisplay rtcshield;

int a = 0;

void setup() {}
void loop()
{
  // read value of analog input
  a = analogRead(A1);
  // show value on display
  rtcshield.num(a);
  delay(100);
}

The Thermistor

A thermistor is a resistor whose resistance is relative to the ambient temperature. As the temperature increases, their resistance decreases. It’s the black part to the left of the LDR in the image below:

led-real-time-clock-temperature-sensor-shield-arduino-pmdway-LDR

We can use this relationship between temperature and resistance to determine the ambient temperature. To keep things simple we won’t go into the theory – instead, just show you how to get a reading.

The thermistor circuit on our shield has the output connected to analog input zero, and we can use the library installed earlier to take care of the mathematics. Which just leaves us with the functions.

At the start of the sketch, we need to use the library and initiate the instance of the thermistor by inserting the following lines:

#include <TTSTemp.h>
TTSTemp temp;

… then use the following which returns a positive integer containing the temperature (so no freezing cold environments):

.get();

For our example, we’ll get the temperature and show it on the numerical display:

#include <TTSDisplay.h>
#include <TTSTemp.h>

TTSTemp temp;
TTSDisplay rtcshield;

int a = 0;

void setup() {}

void loop() {

  a = temp.get();
  rtcshield.num(a);
  delay(500);
}

And our thermometer in action. No video this time… a nice 24 degrees C in the office:

led-real-time-clock-temperature-sensor-shield-arduino-pmdway-thermometer

The Real-Time Clock 

Our shield is fitted with a DS1307 real-time clock IC circuit and backup battery holder. If you insert a CR1220 battery, the RTC will remember the settings even if you remove the shield from the Arduino or if there’s a power blackout, board reset etc:

LED Real Time Clock Temperature Sensor Shield for Arduino from PMD Way with free delivery worldwide

The DS1307 is incredibly popular and used in many projects and found on many inexpensive breakout boards. We have a separate tutorial on how to use the DS1307, so instead of repeating ourselves – please visit our specific DS1307 Arduino tutorial, then return when finished.

Where to from here? 

We can image there are many practical uses for this shield, which will not only improve your Arduino coding skills but also have some useful applications. An example is given below, that you can use for learning or fun.

Temperature Alarm

This projects turns the shield into a temperature monitor – you can select a lower and upper temperature, and if the temperature goes outside that range the buzzer can sound until you press it.

Here’s the sketch:

#include <TTSDisplay.h>
#include <TTSTemp.h>

TTSTemp temp;
TTSDisplay rtcshield;

boolean alarmOnOff = false;
int highTemp = 40;
int lowTemp = 10;
int currentTemp;

void LEDsoff()
{
  // function to turn all alarm high/low LEDs off
  digitalWrite(2, LOW);
  digitalWrite(4, LOW);
}

void setup() {
  // initalise digital pins for LEDs and buzzer as outputs
  pinMode(2, OUTPUT); // LED 1
  pinMode(3, OUTPUT); // LED 2
  pinMode(4, OUTPUT); // LED 3
  pinMode(5, OUTPUT); // LED 4
  pinMode(6, OUTPUT); // buzzer

  // initalise digital pins for buttons as inputs
  // and initialise internal pullups
  pinMode(9, INPUT_PULLUP); // button K1
  pinMode(10, INPUT_PULLUP); // button K2
  pinMode(11, INPUT_PULLUP); // button K3
}

void loop()
{
  // get current temperature
  currentTemp = temp.get();

  // if current temperature is within set limts
  // show temperature on display

  if (currentTemp >= lowTemp || currentTemp <= highTemp)
    // if ambient temperature is less than high boundary
    // OR if ambient temperature is grater than low boundary
    // all is well
  {
    LEDsoff(); // turn off LEDs
    rtcshield.num(currentTemp);
  }

  // if current temperature is above set high bounday, show red LED and
  // show temperature on display
  // turn on buzzer if alarm is set to on (button K3)

  if (currentTemp > highTemp)
  {
    LEDsoff(); // turn off LEDs
    digitalWrite(4, HIGH); // turn on red LED
    rtcshield.num(currentTemp);
    if (alarmOnOff == true) {
      digitalWrite(6, HIGH); // buzzer on }
    }
  }

  // if current temperature is below set lower boundary, show blue LED and
  // show temperature on display
  // turn on buzzer if alarm is set to on (button K3)

  if (currentTemp < lowTemp)
  {
    LEDsoff(); // turn off LEDs
    digitalWrite(2, HIGH); // turn on blue LED
    rtcshield.num(currentTemp);
    if (alarmOnOff == true)
    {
      digitalWrite(6, HIGH); // buzzer on }
    }
  }
  // --------turn alarm on or off-----------------------------------------------------
  if (digitalRead(11) == LOW) // turn alarm on or off
  {
    alarmOnOff = !alarmOnOff;
    if (alarmOnOff == 0) {
      digitalWrite(6, LOW); // turn off buzzer
      digitalWrite(5, LOW); // turn off alarm on LED
    }
    // if alarm is set to on, turn LED on to indicate this
    if (alarmOnOff == 1)
    {
      digitalWrite(5, HIGH);
    }
    delay(300); // software debounce
  }
  // --------set low temperature------------------------------------------------------
  if (digitalRead(10) == LOW) // set low temperature. If temp falls below this value, activate alarm
  {
    // clear display and turn on blue LED to indicate user is setting lower boundary
    rtcshield.clear();
    digitalWrite(2, HIGH); // turn on blue LED
    rtcshield.num(lowTemp);

    // user can press buttons K2 and K1 to decrease/increase lower boundary.
    // once user presses button K3, lower boundary is locked in and unit goes
    // back to normal state

    while (digitalRead(11) != LOW)
      // repeat the following code until the user presses button K3
    {
      if (digitalRead(10) == LOW) // if button K2 pressed
      {
        --lowTemp; // subtract one from lower boundary
        // display new value. If this falls below zero, won't display. You can add checks for this yourself :)
        rtcshield.num(lowTemp);
      }
      if (digitalRead(9) == LOW) // if button K3 pressed
      {
        lowTemp++; // add one to lower boundary
        // display new value. If this exceeds 9999, won't display. You can add checks for this yourself :)
        rtcshield.num(lowTemp);
      }
      delay(300); // for switch debounce
    }
    digitalWrite(2, LOW); // turn off blue LED
  }
  // --------set high temperature-----------------------------------------------------
  if (digitalRead(9) == LOW) // set high temperature. If temp exceeds this value, activate alarm
  {

    // clear display and turn on red LED to indicate user is setting lower boundary
    rtcshield.clear();
    digitalWrite(4, HIGH); // turn on red LED
    rtcshield.num(highTemp);

    // user can press buttons K2 and K1 to decrease/increase upper boundary.
    // once user presses button K3, upper boundary is locked in and unit goes
    // back to normal state

    while (digitalRead(11) != LOW)
      // repeat the following code until the user presses button K3
    {
      if (digitalRead(10) == LOW) // if button K2 pressed
      {
        --highTemp; // subtract one from upper boundary
        // display new value. If this falls below zero, won't display. You can add checks for this yourself :)
        rtcshield.num(highTemp);
      }
      if (digitalRead(9) == LOW) // if button K3 pressed
      {
        highTemp++; // add one to upper boundary
        // display new value. If this exceeds 9999, won't display. You can add checks for this yourself :)
        rtcshield.num(highTemp);
      }
      delay(300); // for switch debounce
    }
    digitalWrite(4, LOW); // turn off red LED
  }
}

Operating instructions:

  • To set lower temperature, – press button K2. Blue LED turns on. Use buttons K2 and K1 to select temperature, then press K3 to lock it in. Blue LED turns off.
  • To set upper temperature – press button K1. Red LED turns on. Use buttons K2 and K1 to select temperature, then press K3 to lock it in. Red LED turns off.
  • If temperature drops below lower or exceeds upper temperature, the blue or red LED will come on.
  • You can have the buzzer sound when the alarm activates – to do this, press K3. When the buzzer mode is on, LED D4 will be on. You can turn buzzer off after it activates by pressing K3.
  • Display will show ambient temperature during normal operation.

You can see this in action via the video below:

Conclusion

This is a fun and useful shield – especially for beginners. It offers a lot of fun and options without any difficult coding or soldering – it’s easy to find success with the shield and increase your motivation to learn more and make more.

You can be serious with a clock, or annoy people with the buzzer. And at the time of writing you can have one for US$14.95, delivered. So go forth and create something.

A little research has shown that this shield was based from a product by Seeed, who discontinued it from sale. I’d like to thank them for the library.

This post brought to you by pmdway.com – everything for makers and electronics enthusiasts, with free delivery worldwide.

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Arduino Tutorials – Chapter 16 – Ethernet

In this chapter we will introduce and examine the use of Ethernet networking with Arduino over local networks and the greater Internet.

It will be assumed that you have a basic understanding of computer networking, such as the knowledge of how to connect computers to a hub/router with RJ45 cables, what an IP and MAC address is, and so on. Furthermore, here is a good quick rundown about Ethernet.

Getting Started

You will need an Arduino Uno or compatible board with an Ethernet shield that uses the W5100 Ethernet controller IC (pretty much all of them):

W5100 Ethernet shield for Arduino from PMD Way

Furthermore you will need to power the board via the external DC socket – the W5100 IC uses more current than the USB power can supply. A 9V 1.5A plug pack/wall wart will suffice.

Finally it does get hot – so be careful not to touch the W5100 after extended use. In case you’re not sure – this is the W5100 IC:

W5100 Ethernet shield for Arduino from PMD Way

Once you have your Ethernet-enabled Arduino, and have the external power connected – it’s a good idea to check it all works. Open the Arduino IDE and select File > Examples > Ethernet > Webserver. This loads a simple sketch which will display data gathered from the analogue inputs on a web browser. However don’t upload it yet, it needs a slight modification.

You need to specify the IP address of the Ethernet shield – which is done inside the sketch. This is simple, go to the line:

IPAddress ip(192,168,1, 177);

And alter it to match your own setup. For example, in my home the router’s IP address is 10.1.1.1, the printer is 10.1.1.50 and all PCs are below …50. So I will set my shield IP to 10.1.1.77 by altering the line to:

IPAddress ip(10,1,1,77);

You also have the opportunity to change your MAC address. Each piece of networking equipment has a unique serial number to identify itself over a network, and this is normall hard-programmed into the equipments’ firmware. However with Arduino we can define the MAC address ourselves.

If you are running more than one Ethernet shield on your network, ensure they have different MAC addresses by altering the hexadecimal values in the line:

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

However if you only have one shield just leave it be. There may be the very, very, statistically rare chance of having a MAC address the same as your existing hardware, so that would be another time to change it.

Once you have made your alterations, save and upload the sketch. Now open a web browser and navigate to the IP address you entered in the sketch, and you should be presented with something similar to the following:

Arduino-webserver-example-sketch

What’s happening? The Arduino has been programmed to offer a simple web page with the values measured by the analogue inputs. You can refresh the browser to get updated values.

At this point – please note that the Ethernet shields use digital pins 10~13, so you can’t use those for anything else. Some Arduino Ethernet shields may also have a microSD card socket, which also uses another digital pin – so check with the documentation to find out which one.

Nevertheless, now that we can see the Ethernet shield is working we can move on to something more useful. Let’s dissect the previous example in a simple way, and see how we can distribute and display more interesting data over the network. For reference, all of the Ethernet-related functions are handled by the Ethernet Arduino library. If you examine the previous sketch we just used, the section that will be of interest is:

 for (int analogChannel = 0; analogChannel < 6; analogChannel++) 
          {
            int sensorReading = analogRead(analogChannel);
            client.print("analog input ");
            client.print(analogChannel);
            client.print(" is ");
            client.print(sensorReading);
            client.println("<br />");       
          }
          client.println("</html>");

Hopefully this section of the sketch should be familiar – remember how we have used serial.print(); in the past when sending data to the serial monitor box? Well now we can do the same thing, but sending data from our Ethernet shield back to a web browser – on other words, a very basic type of web page.

However there is something you may or may not want to  learn in order to format the output in a readable format – HTML code. I am not a website developer (!) so will not delve into HTML too much.

However if you wish to serve up nicely formatted web pages with your Arduino and so on, here would be a good start. In the interests of simplicity, the following two functions will be the most useful:

client.print(" is ");

Client.print (); allows us to send text or data back to the web page. It works in the same way as serial.print(), so nothing new there. You can also specify the data type in the same way as with serial.print(). Naturally you can also use it to send data back as well. The other useful line is:

client.println("<br />");

which sends the HTML code back to the web browser telling it to start a new line. The part that actually causes the carriage return/new line is the <br /> which is an HTML code (or “tag”) for a new line. So if you are creating more elaborate web page displays, you can just insert other HTML tags in the client.print(); statement.

If you want to learn more about HTML commands, here’s a good tutorial site. Finally – note that the sketch will only send the data when it has been requested, that is when it has received a request from the web browser.

Accessing your Arduino over the Internet

So far – so good. But what if you want to access your Arduino from outside the local network?

You will need a static IP address – that is, the IP address your internet service provider assigns to your connection needs to stay the same. If you don’t have a static IP, as long as you leave your modem/router permanently swiched on your IP shouldn’t change. However that isn’t an optimal solution.

If your ISP cannot offer you a static IP at all, you can still move forward with the project by using an organisation that offers a Dynamic DNS. These organisations offer you your own static IP host name (e.g. mojo.monkeynuts.com) instead of a number, keep track of your changing IP address and linking it to the new host name. From what I can gather, your modem needs to support (have an in-built client for…) these DDNS services. As an example, two companies are No-IP andDynDNS.com. Please note that I haven’t used those two, they are just offered as examples.

Now, to find your IP address… usually this can be found by logging into your router’s administration page – it is usually 192.168.0.1 but could be different. Check with your supplier or ISP if they supplied the hardware. For this example, if I enter 10.1.1.1 in a web browser, and after entering my modem administration password, the following screen is presented:

WAN-IP-address-router

What you are looking for is your WAN IP address, as you can see in the image above. To keep the pranksters away, I have blacked out some of my address.

The next thing to do is turn on port-forwarding. This tells the router where to redirect incoming requests from the outside world. When the modem receives such a request, we want to send that request to the port number of our Ethernet shield. Using the:

EthernetServer server(125);

function in our sketch has set the port number to 125. Each modem’s configuration screen will look different, but as an example here is one:

Arduino-router-port-forwarding

So you can see from the line number one in the image above, the inbound port numbers have been set to 125, and the IP address of the Ethernet shield has been set to 10.1.1.77 – the same as in the sketch.

After saving the settings, we’re all set. The external address of my Ethernet shield will be the WAN:125, so to access the Arduino I will type my WAN address with :125 at the end into the browser of the remote web device, which will contact the lonely Ethernet hardware back home.

Furthermore, you may need to alter your modem’s firewall settings, to allow the port 125 to be “open” to incoming requests. Please check your modem documentation for more information on how to do this.

Now from basically any Internet connected device in the free world, I can enter my WAN and port number into the URL field and receive the results. For example, from a phone when it is connected to the Internet via LTE mobile data:

Arduino-webserver-example-cellular

So at this stage you can now display data on a simple web page created by your Arduino and access it from anywhere with unrestricted Internet access. With your previous Arduino knowledge you can now use data from sensors or other parts of a sketch and display it for retrieval.

Displaying sensor data on a web page

As an example of displaying sensor data on a web page, let’s use an inexpensive and popular temperature and humidity sensor – the DHT22. You will need to install the DHT22 Arduino library which can be found on this page. If this is your first time with the DHT22, experiment with the example sketch that’s included with the library so you understand how it works.

Connect the DHT22 with the data pin to Arduino D2, Vin to the 5V pin and GND to … GND.

Now for our sketch – to display the temperature and humidity on a web page. If you’re not up on HTML you can use online services such as this to generate the code, which you can then modify to use in the sketch.

In the example below, the temperature and humidity data from the DHT22 is served in a simple web page:

#include <SPI.h>
#include <Ethernet.h>

// for DHT22 sensor
#include "DHT.h"
#define DHTPIN 2
#define DHTTYPE DHT22

// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = {   0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(10,1,1,77);

// Initialize the Ethernet server library
// with the IP address and port you want to use 
// (port 80 is default for HTTP):
EthernetServer server(125);
DHT dht(DHTPIN, DHTTYPE);

void setup() 
{
  dht.begin();
 // Open serial communications and wait for port to open:
  Serial.begin(9600);
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }
  // start the Ethernet connection and the server:
  Ethernet.begin(mac, ip);
  server.begin();
  Serial.print("server is at ");
  Serial.println(Ethernet.localIP());
}

void loop() 
{
  // listen for incoming clients
  EthernetClient client = server.available();
  if (client) {
    Serial.println("new client");
    // an http request ends with a blank line
    boolean currentLineIsBlank = true;
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();
        Serial.write(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) 
        {
          // send a standard http response header
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println("Connection: close");  // the connection will be closed after completion of the response
	  client.println("Refresh: 30");  // refresh the page automatically every 30 sec
          client.println();
          client.println("<!DOCTYPE HTML>");
          client.println("<html>");

          // get data from DHT22 sensor
          float h = dht.readHumidity();
          float t = dht.readTemperature();
          Serial.println(t);
          Serial.println(h);

          // from here we can enter our own HTML code to create the web page
          client.print("<head><title>Office Weather</title></head><body><h1>Office Temperature</h1><p>Temperature - ");
          client.print(t);
          client.print(" degrees Celsius</p>");
          client.print("<p>Humidity - ");
          client.print(h);
          client.print(" percent</p>");
          client.print("<p><em>Page refreshes every 30 seconds.</em></p></body></html>");
          break;
        }
        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
    delay(1);
    // close the connection:
    client.stop();
    Serial.println("client disonnected");
  }
}

It is a modification of the IDE’s webserver example sketch that we used previously – with a few modifications. First, the webpage will automatically refresh every 30 seconds – this parameter is set in the line:

client.println("Refresh: 30");  // refresh the page automatically every 30 sec

… and the custom HTML for our web page starts below the line:

// from here we can enter our own HTML code to create the web page

You can then simply insert the required HTML inside client.print() functions to create the layout you need.

Finally – here’s an example screen shot of the example sketch at work:

arduino-ethernet-pmdway-dht22-humid-cellular

You now have the framework to create your own web pages that can display various data processed with your Arduino.

Remote control your Arduino from afar

We have a separate tutorial on this topic, that uses the teleduino system.

Conclusion

So there you have it, another useful way to have your Arduino interact with the outside world.

This post is brought to you by pmdway.com – everything for makers and electronics enthusiasts, with free delivery worldwide.

To keep up to date with new posts at tronixstuff.com, please subscribe to the mailing list in the box on the right, or follow us on twitter @tronixstuff.

Arduino Tutorials – Chapter 30 – twitter

In this article you will learn how to send messages from an Ethernet-enabled Arduino to twitter. For the uninitiated who may be thinking “what is all this twitter nonsense about?”, twitter is a form of microblogging. 

You can create a message with a maximum length of 140 characters, and broadcast this on the twitter service. For people to receive your messages (or tweets) they also need to be a member of twitter and choose to subscribe to your tweets.

The neat thing about twitter on a mobile device is that if your username is mentioned in a tweet, you will be notified pretty well immediately as long as you have mobile data access. More on that later. In some areas, you can set twitter to send tweets from a certain user to your mobile phone via SMS – however if doing so be careful to confirm possible charges to your mobile phone account.

Finally, if you are worried about privacy with regards to your tweets, you can set your account to private and only allow certain people to follow your tweets.

So let’s get started.

First of all – you will need a twitter account. If you do not have one, you can sign up for one here. If you already have a twitter account, you can always open more for other uses – such as an Arduino.

For example, our twitter account is @tronixstuff, but the demonstration machine twitter account is @tronixstuff2. Then we have set the primary account to follow my machine’s twitter account.

Now log into twitter with using the account you will have for your Arduino and visit this page and get yourself a token by following the Step One link. The process will take you through authorising the “tweet library” page to login to your twitter account – this is ok. It will then present you with a long text called a “token”, for example:

twitter_token

Save your token somewhere safe, as you will need to insert it into your Arduino sketch. Finally, don’t give it to others as then they will be able to post onto twitter using your account. Next, follow step two from the same page – which involves download and installation of the required Arduino library.

Now for the hardware.

You will need an Arduino Uno or compatible board with an Ethernet shield that uses the W5100 Ethernet controller IC (pretty much all of them).

Furthermore you will need to power the board via the external DC socket – the W5100 IC uses more current than the USB power can supply. A 9V 1.5A plug pack/wall wart will suffice.

From this point it would be a good idea to check your hardware is working. To do so, please run the webserver example sketch as explained in chapter sixteen (Ethernet). While you do that, we’ll have a break…

lopburi-0606

Sending your first tweet

If you want your Arduino to send a simple tweet consider the following sketch. We have a simple function tweet() which simply sends a line of text (which has a maximum length of 140 characters). Don’t forget to update your IP address, MAC address and token:

// Simple twitter interface

#include <SPI.h>
#include <Ethernet.h>
#include <Twitter.h>

// Alter IP address to suit your own network!
byte mac[] = {   0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; // create MAC address for ethernet shield
byte ip[] = {   192, 168, 0, 99}; // choose your own IP for ethernet shield
Twitter twitter("aaaaaaa"); // replace aaaaaaa with your token

void setup()
{
  delay(5000);
  Ethernet.begin(mac, ip);
  Serial.begin(9600);
}

void tweet(char msg[])
{
  Serial.println("connecting ...");
  if (twitter.post(msg))
  {
    // Specify &Serial to output received response to Serial.
    // If no output is required, you can just omit the argument, e.g.
    // int status = twitter.wait();
    int status = twitter.wait(&Serial);
    if (status == 200)
    {
      Serial.println("OK.");
    } 
    else
    {
      Serial.print("failed : code ");
      Serial.println(status);
    }
  } 
  else
  {
    Serial.println("connection failed.");
  }
}

void loop()
{
  delay(1000);
  tweet("Purple monkey dishwasher");
  do{} while(1>0); // endless loop
}

You can check the status of the tweeting via the serial monitor. For example, if the tweet was successful you will see:

arduino-twitter-success-2014

However if you try to send the same tweet more than once in a short period of time, or another error takes place – twitter will return an error message, for example:

arduino-twitter-duplicate

And finally if it works, the tweet will appear:

Arduino-twitter-works-2014

Previously we mentioned that you can be alerted to a tweet by your mobile device. This can be done by putting your own twitter account name in the contents of the tweet.

For example – our normal twitter account is @tronixstuff. If we put the text “@tronixstuff” in the text tweeted by the Arduino’s twitter account – the twitter app on our smartphone will let us know we have been mentioned – as shown in the following video:

You may have noticed in the video that a text message arrived as well – that service is a function of our cellular carrier (Telstra) and may not be available to others. Nevertheless this is a neat way of getting important messages from your Arduino to a smart phone or other connected device.

Sending data in a tweet

So what if you have  a sensor or other device whose data you want to know about via twitter? You can send data generated from an Arduino sketch over twitter without too much effort.

In the following example we’ll send the value from analogue pin zero (A0) in the contents of a tweet. And by adding your twitter @username you will be notified by your other twitter-capable devices:

// Simple twitter interface

#include <SPI.h>
#include <Ethernet.h>
#include <Twitter.h>

// Alter IP address to suit your own network!
byte mac[] = {   0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; // create MAC address for ethernet shield
byte ip[] = {   192, 168, 0, 99}; // choose your own IP for ethernet shield
Twitter twitter("aaaaaaa"); // replace aaaaaaa with your token

int analogZero;
char tweetText[140];

void setup()
{
  delay(5000);
  Ethernet.begin(mac, ip);
  Serial.begin(9600);
}

void tweet(char msg[])
{
  Serial.println("connecting ...");
  if (twitter.post(msg))
  {
    // Specify &Serial to output received response to Serial.
    // If no output is required, you can just omit the argument, e.g.
    // int status = twitter.wait();
    int status = twitter.wait(&Serial);
    if (status == 200)
    {
      Serial.println("OK.");
    } 
    else
    {
      Serial.print("failed : code ");
      Serial.println(status);
    }
  } 
  else
  {
    Serial.println("connection failed.");
  }
}

void loop()
{
  // get some data from A0. 
  analogZero=analogRead(0);

  // assemble message to send. This inserts the value of "analogZero" into the variable "tweetText" at point %d
  sprintf(tweetText, "Pin analogue zero reads: %d. @username.", analogZero); // change @username to your twitter account name

  delay(1000);
  tweet(tweetText);
  do{ } 
  while(1>0); // endless loop
}

You may have noticed a sneaky sprintf function in void loop(). This is used to insert the integer analogZero into the character array tweetText that we send with the tweet() function. And the results of the example:

Arduino-Twitter-Tutorial-success

So you can use the previous sketch as a framework to create your own Arduino-powered data twittering machine. Send temperature alerts, tank water levels, messages from an alarm system, or just random tweets to your loved one.

Conclusion

So there you have it, another useful way to send information from your Arduino to the outside world.

This post is brought to you by pmdway.com – everything for makers and electronics enthusiasts, with free delivery worldwide.

To keep up to date with new posts at tronixstuff.com, please subscribe to the mailing list in the box on the right, or follow us on twitter @tronixstuff.