Getting data from the sensor to the internet

• these pages describe how to get data from the sensor to the internet where you can watch it on some site with a normal browser
• you can even add a warning function sending you an SMS
• the hardware is based on an arduino running on a normal computer with internet access, the software is based on the arduino programming environment, python with serpy and pdata and google drive
• here is a little sketch of what we are building
  

Part I: Setting up the arduino as a analog to digital converter

• get an arduino and a USB cable for it
• download the arduino programming environment from:
  http://arduino.cc/en/Main/Software and follow the installation instructions for your OS, especially read the instructions on how to install the arduino driver, this sometimes it tricky
• start the arduino software; go to Tools - Board on the menu and click on the type of arduino you want to use (I use an uno)
• open Tools - Serial Port, you will see some serial ports that are available, if you now plug in your arduino and open once more Tools - Serial Port, you will see which serial port your arduino occupies
  
• you will now need to put code on the arduino that reads a sensor and transmits the data to your computer:
  
  const int sensorPin = 0;    // select the input pin for the sensor
  const int ledPin = 13; // the pin with the LED built in
  int incomingByte;      // a variable to read incoming serial data into
  int sensorValue;
  
  void setup() {
    // initialize serial communication:
    Serial.begin(9600);
    // initialize the LED pin as an output:
    pinMode(ledPin, OUTPUT);
  }
  
  void loop() {
    // see if there's incoming serial data:
    if (Serial.available() > 0) {
      // read the oldest byte in the serial buffer:
      incomingByte = Serial.read();
      // if it's a capital H (ASCII 72), turn LED on and measure:
      if (incomingByte == 'H') {
        digitalWrite(ledPin, HIGH);//turn LED on
        sensorValue = analogRead(sensorPin);
        Serial.println(sensorValue,DEC); //format in DEC -
        digitalWrite(ledPin, LOW);//turn LED off!
      }
    
     
    }
  } 
• compile the code first, then upload it on the arduino
•  now start the serial monitor - press H and enter in the monitor interface:
• I connected the input port A0 with the ground or the 5V to get a reading of 0 or 1023 respectively - see this photo:
• 
• now the arduino is ready to talk to your computer - you just implemented and tested a little serial inferface; the computer sends an 'H' and the arduino will respond with a number between 0 and 1023, which is the value of 0 to 5V at the input port A0 digitized with 10bit

Part II: Getting python up and reading the data from the arduino

• you will need to download python - for this tutorial I will rely on a python 2.7 distribution, which you can download here (python 3 will show you some errors that you can however fix)
• download python  http://www.python.org/download/releases/2.7.3/
• we need the pyserial module to talk to the arduino via the serial interface (its USB cable)
• the pyserial documentation, installation instructions and download is at: http://pyserial.sourceforge.net/, for windows you can directly download a prepackaged .exe (http://sourceforge.net/projects/pyserial/files/pyserial/2.4/)
• now you can do a first test  - see if you get some data from the arduino
• python comes with IDLE, usually if you want to open a file with the extension .py, you will get the option to open it with idle
• so - save the following text snippet as test.py:
  from __future__ import print_function
  import serial
  import time
  
  upperVoltage=5.0 # this is the upper volate of the arduino - corresponding to 5V
  voltageStep=upperVoltage/1023 #voltage step in 10 bit AD conv
  ser=serial.Serial('COM13',9600, timeout=1) # your com port goes here
  dummy=1;
  
  while dummy==1: #this means the while loop runs forwever
     a=time.localtime()
     while a.tm_sec!=0: #check if the seconds of your time are zero (every minute)
         a=time.localtime()#unless the minute has passed
  
  
     print(ser.write("H"))#send an H to the arduino
     time.sleep(1.5) #wait some time...
     msg=ser.readline()#read the serial input - its a string
     msg=msg.strip('\r\n')#get signs off the string
     print(msg) #print into terminal
     msgInt=int(msg) #convert str to integer
     #roound(x,1) means ronding on the first digit after decimal dot
     msgVolt=msgInt*voltageStep # the voltage of the arduino reader
     msgStr=str(msgVolt)#convert float to str
     data=open("test.txt", "a") #open text file in append mode
     print(a.tm_mon, a.tm_mday, a.tm_hour, a.tm_min, msgStr, file=data)
     #write into file
     data.close() #close file
     print(msgStr)#print the value written into the file
     print('done')
  ser.close()# just to show you how to close the port - the while runs forever
• open the file with IDLE (in win klick on it and choose open with idle)
• test the script - if it runs all right, you should get a terminal output that looks like this (although maybe with other numbers):
  
• most likely its not gonna work the first time - type the parts of your code line for line into the python shell and check what step is wrong...don't give up!
• so, that was ok, right? you should have also a file in the directory of your .py program, which is called test.txt- it will show some output like this:
  1 22 17 56 3.28445747801
  1 22 17 57 3.28445747801
  1 22 17 58 5.0
  1 22 17 59 5.0
  1 22 18 0 5.0
  1 22 18 1 5.0
  1 22 18 2 5.0
  1 22 18 3 5.0
  1 22 18 4 5.0
  1 22 18 5 4.99511241447
   
• the format is month, day, hour, minute, then the value of your sensor in volts

Part III: get a google account and let them work for you

• sounds good, right? google has some pretty nice features and interfaces easily with python
• get a gmail account, if you don't already have one
• go on google drive and create a new spreadsheet
• the URL in your browser contains the unique key of the spreadsheet, it goes from key= to #:
  https://docs.google.com/spreadsheet/ccc?key=0AhU9bTOO3AfDdF9MQYRTOEKSNWncxcHplbGRFdEE#gid=0
• this one has the key 0AhU9bTOO3AfDdF9MQYRTOEKSNWncxcHplbGRFdEE
• now name the first two columns of your spreadsheet: - first time, second voltage
  
• you are ready for some new python stuff, download the gdata from google:
  http://code.google.com/p/gdata-python-client/downloads/list
• after installing it (see instructions in the zip file) you should be able to type "import gdata" into the python shell without error message
• we now extend your old python code that was writing into a file to write into the google spreadsheet that you just created
• 
  from __future__ import print_function
  import serial
  import time
  import gdata.spreadsheet.service
  
  
  upperVoltage=5.0 # this is the upper volate of the arduino - corresponding to 5V
  voltageStep=upperVoltage/1023 #voltage step in 10 bit AD conv
  ser=serial.Serial('COM13',9600, timeout=1)#your com port needs to go here
  dummy=1;
  
  while dummy==1: #this means the while loop runs forwever
     a=time.localtime()
     while a.tm_sec!=0: #check if the seconds of your time are zero (every minute)
         a=time.localtime()#unless the minute has passed
  
  
     print(ser.write("H"))#send an H to the arduino
     time.sleep(1.5) #wait some time...
     msg=ser.readline()#read the serial input - its a string
     msg=msg.strip('\r\n')#get signs off the string
     print(msg) #print into terminal
     msgInt=int(msg) #convert str to integer
     #roound(x,1) means ronding on the first digit after decimal dot
     msgVolt=msgInt*voltageStep # the voltage of the arduino reader
     msgStr=str(msgVolt)#convert float to str
     data=open("test.txt", "a") #open text file in append mode
     print(a.tm_mon, a.tm_mday, a.tm_hour, a.tm_min, msgStr, file=data)
     #write into file
     data.close() #close file
     print(msgStr)#print the value written into the file
     print('done')
  
     #the next section of the code will write into your google spreadsheet
     #make sure gdata is imported (see top)
    
     email = 'you@gmail.com'
     password = 'yourpasswd'
     # Find this value in the url after 'key=' before '#'
     spreadsheet_key = 'yourkey'
     # All spreadsheets have worksheets. I think worksheet #1 by default always
     # has a value of 'od6'
     worksheet_id = 'od6'
  
     spr_client = gdata.spreadsheet.service.SpreadsheetsService()
     spr_client.email = email
     spr_client.password = password
     spr_client.source = 'test'
     spr_client.ProgrammaticLogin()
  
     # Prepare a python dictionary to write
     dict = {}
     dict['time'] =time.strftime('%m/%d/%Y %H:%M:%S')# time needs to be in the
     #spreadsheet
     dict['voltage'] = msgStr #voltage needs to be in the spreadsheet
     print (dict)
  
     entry = spr_client.InsertRow(dict, spreadsheet_key, worksheet_id)
     if isinstance(entry, gdata.spreadsheet.SpreadsheetsList):
       print ("Insert row succeeded.")
     else:
       print ("Insert row failed.")
    
  ser.close()# just to show you how to close the port - the while runs forever
•  special thanks to Matt for showing how to put python and google together
  http://www.mattcutts.com/blog/write-google-spreadsheet-from-python/
• the spreadsheet now looks like this:
   
• the first row contains the date and time, the second the voltage you read from the arduino
• in the menu you will find Insert and then chart - use this to make your chart:
  
• the chart looks like this:
  
• the chart has a menu with the item publish chart. you will get text that you can copy paste into any html website and have your chart available to the public (if you want)
• of course you can also do this on google site (has a insert chart menu point) - but you cannot do it in blogger....:(