Python to MQTT for an Opto Isolator attached to a 240v PIR sensor. This is an updated version of the previous PowerShell version that achieved the same thing but this version instead publishes MQTT messages to a broker.

The opto isolator, isolates the mains/line voltage from the Raspberry Pi and is the safest way to detect AC voltage using a Raspberry Pi since the Pi is never in contact with the high AC voltage.

The opto-isolator circuit used was purchased from eBay and is described as:

240V 220V AC Mains Sensor opto-isolator optoisolator optocoupler 5V 3.3V Arduino

The opto-isolator is connected to the Raspberry Pi as follows:

Go to https://get.docker.com/

or

curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh

sudo apt-get install git

git clone https://github.com/lwsrbrts/Py-Opto-Docker.git ~/Py-Opto-Docker/

cd ~/Py-Opto-Docker/

docker build --tag py-opto:1.0 .

Builds the image locally and tags it as py-opto:1.0

These environment variables must be passed to the container (PowerShell script ultimately).

• CLIENT_NAME - The name of the MQTT topic.
• ROOT_TOPIC - The name of the MQTT root topic. Topic becomes eg. "{ROOT_TOPIC}/{CLIENT_NAME}"
• MQTT_BROKER - The IP address or host name of hte MQTT broker.
• MQTT_USER - The username to be used to connect to the MQTT broker
• MQTT_PASS - The password for the MQTT_USER.
• OPTO_PIN - The broadcom GPIO pin number the opto-isolator OUT is connected to.
• PYTHONUNBUFFERED - Required to ensure that python doesn't buffer stdout so you can see docker logs.

This is an example docker run command which assumes the image has been built and called py-opto:1.0.

docker run -d --privileged --name py-opto \
              --restart=unless-stopped \
              -h FRONT \
              -e ROOT_TOPIC=garage \
              -e CLIENT_NAME=FRONT \
              -e MQTT_BROKER=192.168.1.100 \
              -e OPTO_PIN=4 \
              -e MQTT_USER=my-mqtt-user \
              -e MQTT_PASS='Thepassword' \
              -e PYTHONUNBUFFERED=1 \
              py-opto:1.0

• -h will set the hostname. This isn't used in the script.
• --privileged is used to ensure the docker container can access the GPIO pins.

Tail the docker container's logs to see what's going on.

docker container logs -f py-opto

Execute /bin/bash inside the container interactively.

docker exec -it py-opto /bin/bash

Basically pull the Dockerfile and script from the GitHub repo and build it again then run once a new image is built.

docker container stop py-opto

docker container rm py-opto

cd ~/Py-Opto-Docker/

git pull

docker build --tag py-opto:1.0 .