Raspberry Pi based Gas Sensor & Weather Station Readout

Description

MOX Gas sensor and weather station WH2600 readout on Raspberry Pi Zero 2 in Python.

Hardware

The Pi is connected via I2C to a ENS160 MOX gas sensor and a ENS210 temperature and humidity sensor. The pinout of the Pi header is described here. The ENS160 and the ENS210 sensor are supplied with 3.3.V. The wiring of the sensors is shown in Fig. 1.

Description	Pin #	Color
3.3V	1	red
SDA	2	green
SCL/CLK	3	yellow
GND	6	orange

The wheat

Fig. 1 Pi Zero and ENS Sensor wiring.

I2C interface

The I2C interface must be enabled manually via the raspi-config

sudo raspi-config

The I2C address of a connected I2C device can be checked with

sudo apt-get install i2c-tools
sudo i2cdetect -y 1

where 1 corresponds the the I2C interface 1

Docker

Build the Python environment using

docker build -t measure_app . --platform=linux/arm/v7

InfluxDB v1.x Handling

https://darkwolfcave.de/raspberry-pi-influxdb-backup-ganz-einfach-sichern/

• Load an influxdb database with name db_name using a time step formatting according to '2016-07-31T20:07:00Z'

  influx -precision rfc3339 -database db_name
  

• List all measurements and field keys in the database with

  show measurements 
  show field keys
  

• Use a Query to extract data form the database, e.g.,

  SELECT key from measurement
  

• Delete a measurement from the DB with

  drop MEASUREMENT measurement
  

• Use the WHERE statement in the query for filtering

  SELECT key from measurement WHERE time >= now() -1m
  SELECT R0 from ENS160 WHERE time >= now() -2m AND time <= now() -1m
  

• Export a database to a csv file with

  influx -database 'db_name' -execute "query" -format 'csv' > filename.csv
  

  where the query is given in quotes

• Check size of database (sensornode) via disk usage

  sudo du -sh influxdb/data/sensornode
  

SSH Time Synchronization

ssh -i ~/.ssh/key user@hostname "sudo date -s '$(date)'"