Python daemon listening for MQTT updates and controlling the motion of a Weasley Clock.
This is part of my larger project to create a fully working Weasley Clock like in Harry Potter.
This daemon runs on a raspberry pi, subscribes to MQTT messages on the topic weaseleyclock/#, and updates the hand positions of the Weasley Clock. Hand position is controlled using HS-785HB servos controlled by a Servo Hat.
Updates for hand positions are received via MQTT messages. I use Home Assistant to determine the location of each person and update the state. Home Assistant sends a MQTT message on the weasleyclock topic for each person. The weasleyclockd sends a update request message when it connects to Home Assistant using a weasleyclock/UPDATE request.
I have three different ways of positioning the hand withing the designated sector on the clock face. For states that have a variable distance component like Lost or In Transit I use a log scale to pick where within the sector. As the person move closer to Home their clock hand moves ever so slightly closer to the Home sector on the clock face.
For sectors that have a fixed distance from Home like School or Work, I divide the sector into four sub-positions, one for each hand. So that even if the whole family is at School all the hands won't be stacked up on top of each other. This makes them more readable.
The last way is to just place the hand in the middle of the sector. This method is not currently used, I wrote this one first for testing.
The daemon is started on boot by systemd service.
pip3 install -r requirements.txt
mkdir /home/pi/weasleyclockd/
cp weasleyclockd.py weasleyclockd.json /home/pi/weasleyclockd/
sudo cp weasleyclockd.service /lib/systemd/system/
sudo chmod 644 /lib/systemd/system/weasleyclockd.service
sudo systemctl daemon-reload
sudo systemctl enable weasleyclockd.service
sudo systemctl start weasleyclockd.service
tail -f /home/pi/weasleyclockd/weasleyclock.logFollow these instructions to setup your servo HAT and install the necessary software. https://learn.adafruit.com/adafruit-16-channel-pwm-servo-hat-for-raspberry-pi
I wrote a python program to control HS-785HB servos with the Servo HAT. hs785hb_servo.py This was useful for calibrating the servos and mapping the pulse range for the servos to the servo's physical range.