This is the same exercise that we did in Chapter 7, Internet of Things with BeagleBone. The Python package flask-mail can be used to create a local mail server inside BeagleBone to send e-mails. But to match the same example we did in Chapter 5, Reading from Analog Sensors we will use Gmail. An Internet connection is essential for this exercise. It is recommended to create a new temporary Gmail account for this exercise. You will have to visit the webpage https://myaccount.google.com/security and turn on Allow less secure apps. If you have enabled two-factor authentication, you will have to generate an app password from the same webpage. An in-depth explanation about this is covered in Chapter 7 for the same over-temperature exercise.

Create a circuit setup the same as we did for temperature sensing using TMP36 in Chapter 5, Reading from Analog Sensors. Open Cloud9. Write the following program. Change the e-mail addresses and password at the beginning of the program. Then save it as emailAlert.py and run it. Touch TMP36 with semi-hot metal and you should hit the 50 degree Celsius threshold. Then check if you got an e-mail at the e-mail address you specified in variable emailTo. If you are using an e-mail provider other than Gmail, you will have to change the variables emailServer and emailServerPort accordingly. The code for emailAlert.py is as follows:

#!/usr/bin/python

import Adafruit_BBIO.ADC as ADC
import smtplib
from email.MIMEText import MIMEText
import time

tmp36 = "P9_40"
check_interval = 4
threshold = 50
emailFrom = "[email protected]"  ##gmail address
emailPasswd = 'yyyyyy'  ##gmail {app} password
emailTo = "[email protected]"  ## email address where emails will be sent
emailServer = 'smtp.gmail.com'
emailServerPort = 587

ADC.setup()

while True:
    time.sleep(check_interval)   ## wait 4 seconds to measure again
    volts = ADC.read(tmp36)* 1.8
    temperature = (volts * 100) - 50
    print " Current Temperature is " + str(temperature)
    if (temperature>threshold):
        msg = MIMEText("Current temperature is " + str(temperature)) ##email body
        msg['From'] = emailFrom
        msg['To'] = emailTo
        #msg['Reply-to'] = emailFrom
        msg['Subject'] = "Overtemperature Alert!!!"
        server = smtplib.SMTP(emailServer,emailServerPort)
        server.ehlo()
        server.starttls()
        server.ehlo()
        server.login(emailFrom,emailPasswd)
        server.sendmail(emailFrom,emailTo,str(msg))
        server.close()
        print 'Email sent'
        time.sleep(3600)  ##wait 1 hour if email is sent