Superset - Temperature Monitoring with Sensor (DS18B20) & TimeScaleDB

• The goal of this IoT Project - Get DS18B20 Temperature Data to Timescale & Superset
  • The Python Script - Pushing DS18B20 Sensor Data from Python to TimeScaleDB
  • Setup TimeScaleDB
  • Configure Apache Superset for Visualization

The Sensor: DS18B20

The DS18B20 can detect: -55C to 125 Celsius

• Connection:
  • Black cable - gnd
  • Red - 3.3 to 5v
  • Yellow - data –> to pin 7
  • It needs a resistor. A 4.7K Ohm Resistor (Colour Code: Yellow Purple Red Gold)
    • or 4.7k/10k resistor between data and 3.3v

The RPi4 with the DS18B20 sensor will look like:

DS18B20 temperature sensor connection to a Raspberry Pi 4

• These videos were of great help to me:

  • https://www.youtube.com/watch?v=wDdJ6stXQi0&t=10s
  • https://bigl.es/ds18b20-temperature-sensor-with-python-raspberry-pi/

1-wire must be enabled so that the RPi can read this sensor’s data.

connect the wiring and go to /sys/bus/w1/devices and find the folder with the serial number, then select the w1_slave file

The file should contain a YES in the first line.

Also, the video from ReefSpy helped me a lot with the initial setup plus the general idea of the Python code that can be used.

The Base Code: Python

Find the related project code here

Reading DS18B20 with Python

Create this Python script on your RPi.

import os 
import glob
import time

os.system('modprobe w1-gpio') 
os.system('modprobe w1-therm')

base_dir = '/sys/bus/w1/devices/' 
device_folder = glob.glob(base_dir + '28*')[0] 
device_file = device_folder + '/w1_slave'

def read_temp_raw():
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines
 

def read_temp(scale):
     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 
          if scale == "F":
               return "{:.1f}".format(temp_f)
          if scale =="C":
               return "{:.1f}".format(temp_c)     
          else:
               return temp_c, temp_f

while True:
     print(read_temp("C"))
     time.sleep(1)

Execute it with:

python3 dsb.py

Pushing Data from Python to Timescale

We have 3 mandatory components for this to work:

• The adjusted Python code that pushed data: https://github.com/JAlcocerT/RPi/Z_IoT/DS18B20-to-TimeScaleDB/Python2TimeScale.py
• https://github.com/JAlcocerT/RPi/Z_IoT/DS18B20-to-TimeScaleDB/Python2TimeScale-Stack.yml
• The docker image that isolates all of this and allow us to deploy easier: https://hub.docker.com/r/fossengineer/iot/tags
  • The tag is: ds18b20_sensor_to_timescale

And another one if you want to replicate the docker build process:

• The https://github.com/JAlcocerT/RPi/Z_IoT/DS18B20-to-TimeScaleDB/Dockerfile>

---

FAQ

How can I query TimeScaleDB?

You will have to login to the container:

docker run -it --rm --network=dsbtimescale_dsb_network postgres psql -h timescaledb_dsb_container -U myuser -d mydb --username=myuser

Then execute:

psql -U myuser -d mydb

And then qrite your SQL Queries:

SELECT * FROM ds18b20_sensor;
SELECT MAX(temperature) FROM ds18b20_sensor;
SELECT * FROM ds18b20_sensor ORDER BY time DESC LIMIT 1;

How to Setup Superset

Use this docker compose to setup Superset.

Thanks to:

• https://www.timescale.com/blog/data-visualization-in-postgresql-with-apache-superset/
• https://www.attilatoth.dev/speaking/timescaledb-superset/