Sniffy Monitor v1

Solent Air Watch is a community project run solely by volenteers with day jobs. Please help support us by suggesting improvements to our code or documentation. Build plans for the sniffy air quality monitor will be available soon at www.solentairwatch.co.uk

Sniffy is an air quality monitor based on the raspberry pi. It is designed to accept a number of different air quality sensors. We currently use the plantower PMS5003 to estimate concentrations of PM1, PM2.5 and PM10. We use Alphasense's range of gas sensors to measure NO2.

Our current efforts are in developing the monitor to work reliably on public and private wifi and we're looking at extending to long range wireless networks (GSM, LTE, LoRaWAN and sigfox). The Sniffy communicates via MQTT to opensensors.io. This gives free opensource access to a ready made API. Our current priority is to implement a more scaleable backend to the sniffy monitor.

The scripts in this repository have been tested using Raspberry Pi 3 and Raspberry Pi Zero W with Rasbian Jessie Lite. This can be downloaded at https://www.raspberrypi.org/downloads/raspbian/.

Currently only Python 2.7 is supported until the bitwise operations are updated to python 3.

The following instructions assume you have a fresh install of raspbian Lite and are not familiar with the Raspbery Pi.

The easy way to enable ssh and setup wireless on the Raspberry Pi

The boot partition is readable using a card reader with any opertating system. Create the file /boot/wpa_supplicant.conf. Add your wifi settings as follows:

network={
    ssid="YOUR_SSID"
    psk="YOUR_PASSWORD"
    key_mgmt=WPA-PSK
}

On the first boot raspbian will copy the file to the normal location (/etc/wpa_supplicant/wpa_supplicant.conf). To enable SSH on the raspberry pi, copy an empty file named shh to the boot partition.

Installing monitor software to Raspbery Pi

Find the IP address of your Pi. The easiest way is through your home router. Then login using ssh. The default password is raspberry.

shh pi@<your ip address>

Firstly change the default password by typing

passwd

The PM sensor uses the serial port, the environmental sensor uses I2C and the ADC uses SPI. THese interfaces should be turned on using by running

sudo raspi-config

Go to /Interfacing Options/Serial answer no to a login shell and yes to the serial port being enabled. Also turn on SPI and I2C. You will be prompted to reboot when you exit.

The monitor is in the early stages of development, this means things can change.

sudo apt-get update
sudo apt-get install -y python-pip git build-essential python-dev python-smbus

To install the Sniffy monitor scripts clone the Sniffy repositary and run

cd
git clone https://github.com/solentairwatch/sniffy
./sniffy/install.sh

This includes the scipts for the analogue gas sensors which interface via the MCP3008 ADC chip on the SPI bus.

The monitor currently runs seperate scripts for each sensor.

To start the monitor when the pi boots

sudo crontab -e

then add the following line (currently starts PM monitor only) NB script assumes that your not using virtualenv.

@reboot sh /home/pi/sniffy/sniffy.sh >/home/pi/logs/cronlog 2>&1

Important scripts

• pmsx003.py this sends PMS5003 and BME280 data to opensensors.io via MQTT
• standalonePMS.py as above but logs to SD instead of MQTT for offline use