IoT as a Diagnostic Tool (Part 3): The Code
Program the Raspberry Pi to get sensor input
1. Python program to get the current temperature:
- On the Raspberry Pi open a terminal window and create a new Python file named “getTemperature” with the following code:
nano getTemperature.py
- In that new file enter the following code:
import os import glob import subprocess import calendar import time os.system('modprobe w1-gpio') os.system('modprobe w1-therm') # set up temperature sensor base_dir = '/sys/bus/w1/devices/' device_folder = glob.glob(base_dir + '28*')[0] device_file = device_folder + '/w1_slave' def read_temp_raw(): catdata = subprocess.Popen(['cat',device_file], stdout=subprocess.PIPE, stderr=subprocess.PIPE) out,err = catdata.communicate() out_decode = out.decode('utf-8') lines = out_decode.split('\n') return lines # read temperature and return in Fahrenheit def read_temp(): lines = read_temp_raw() while lines[0].strip()[-3:] != 'YES': time.sleep(0.2) lines = read_temp_raw() equals_pos = lines[1].find('t=') if equals_pos != -1: temp_string = lines[1][equals_pos+2:] temp_c = float(temp_string) / 1000.0 temp_f = temp_c * 9.0 / 5.0 + 32.0 return temp_f - Ctrl-X to exit the file. “Y” to save.
2. Python program to get door status
- On the Raspberry Pi open a terminal window and create a new Python file named “door” with the following code:
nano door.py
- In that new file enter the following code:
import RPi.GPIO as io io.setmode(io.BCM) door_pin = 23 io.setup(door_pin, io.IN, pull_up_down=io.PUD_UP) # check door def check_door(): if io.input(door_pin): return ("OPEN") else: return ("CLOSED") - Ctrl-X to exit the file. “Y” to save.
3. Python program to check temp and write record to database
- On the Raspberry Pi open a terminal window and create a new Python file named “temperatureLog” with the following code:
nano temperatureLog.py
- In that new file enter the following code:
import calendar import time import requests import json import getTemperature import door #get temperature temperature = getTemperature.read_temp() #get door status door = door.check_door() # change the following to the url that I called out in the Firebase setup step 1.5: url = 'https://FreezerTempAndDoor.firebaseio.com/' tableName = 'temperatureLog.json' finalUrl = url + tableName postdata = { 'date': str(calendar.timegm(time.gmtime())), 'temp': str(temperature), 'door': door } data = json.dumps(postdata) response = requests.patch(finalUrl, data) - Ctrl-X to exit the file. “Y” to save.
4. Python program to check temp and write record to database if temperature exceeds 10 degrees F
- On the Raspberry Pi open a terminal window and create a new Python file named “temperatureAlarm” with the following code:
nano temperatureAlarm.py
- In that new file enter the following code:
import calendar import time import requests import json import getTemperature import door #get temperature temperature = getTemperature.read_temp() if temperature > 10.0: #get door status door = door.check_door() # change the following to the url that I called out in the Firebase setup step 1.5: url = 'https://FreezerTempAndDoor.firebaseio.com/' tableName = 'temperatureAlarm.json' finalUrl = url + tableName postdata = { 'date': str(calendar.timegm(time.gmtime())), 'temp': str(temperature), 'door': door } data = json.dumps(postdata) response = requests.patch(finalUrl, data) - Ctrl-X to exit the file. “Y” to save.
5. Use CRON to run our programs at scheduled intervals
- In a Raspberry Pi terminal window open the crontab file with the following code:
crontab -e
- Scroll to the bottom of that file and enter the following code:
# write temp/door to log database every hour 0 * * * * /usr/bin/python /home/pi/temperatureLog.py # check for alarm status (temp is over 10 degrees F) every minute * * * * * /usr/bin/python /home/pi/temperatureAlarm.py
And that’s it! Your Raspberry Pi should be sending data to Firebase. If you’d like to see it appear in the database more often while testing, warm up the temp sensor or set the temperatureLog program to run more than once an hour.
Here is some of the data that I recorded in the temperatureLog table:
I was able to learn about the freezer’s cycles and diagnose the issue just by watching the log and alarm tables in the database. If you wanted it to alert you could have it email you by following this great article.
During this series of articles I’ve shown you how I was able to solve a church mystery and save them from having to buy a new freezer. I learned quite a bit and had fun tinkering in the process. Would you have approached the problem in a different manner? Please let me know what you would have done in the comments.
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