pi-light

Raspberry Pi Light Sensor

This example will read data from a light sensor (wired to a Raspberry Pi device) and send that data to a TimescaleDB instance (hosted by Timescale Cloud).

Contents

A brief overview of the files in this directory and how they're used:

• photoresistor.py: Python script to read sensor values and insert them into TimescaleDB.
• pi-schema.sql: data definition (DDL) to create the necessary hypertables.
• grafana.json: Grafana dashboard configuration.
• pi_photoresistor.service: systemd service definition to ensure the sensor is restarted on reboot.

The Cloud (Timescale Cloud)

Prepare TimescaleDB instance by creating the pi schema

psql postgres://USERNAME:PASSWORD@HOST:PORT/defaultdb?sslmode=require -f ./pi-schema.sql

Prepare Grafana instance by creating a datasource

Login to Grafana > Configuration > Data Sources > Add data source > PostgreSQL

Create Grafana dashboard

Login to Grafana > Dashboard > Import > ./grafana.json

The Edge (Raspberry Pi)

On device, install PostgreSQL Database Adapter for python

sudo apt-get install libpq-dev
pip3 install psycopg2

On device, install CircuitPython libraries

pip3 install adafruit-blinka

Copy python script to device

scp ./photoresistor.py [email protected]:/home/pi

The photoresistor.py script assumes that you're implementing a pull-down resistor on GPIO pin 23. You'll need to modify this depending on the specifics of your own sensor configuration.

Copy systemd started setup in place

scp ./pi_photoresistor.service /etc/systemd/system

Be sure to set the TIMESCALEDB_CONNECTION string to your Service URI "postgres://..." for your TimescaleDB instance.

On device, start the service

sudo systemctl start pi_photoresistor.service