Liquid2MQTT

What is it?

A simple Python script that leverages a JSN-SRO4T 2.0 waterproof ultrasonic sensor module, connected to a Raspberry Pi, which broadcasts the results of the measurements using an MQTT broker.

The measurements do need to take place in an enclosed container (cubic or cylindrical) containing a certain liquid. The sensor is mounted at the top of the container and is measuring the distance between the sensor and surface of the liquid at a specified interval. Based upon the measured distance (expressed in centimeters) and the container inner dimensions, the volume (expressed in liters) is also calculated.

What is needed?

• Raspberry Pi, with GPIO 14 & 15 pins available.
• JSN-SR04T sensor module, version 2.0 supports a voltage range between 3.3 - 5V.
  • TX is connected to GPIO 14 (pin 8).
  • RX is connected to GPIO 15 (pin 10).
  • GND is connected to GND (pin 6).
  • 5V is connected to 3.3V (pin 1).
• Existing & running MQTT broker.

Good to know...

Connection schema & code is based upon the following StackExchange question/answers: https://raspberrypi.stackexchange.com/a/81793

Config

Configuration is managed using settings.ini file. Each option is listed below with additional comments explaining the example values.

[DEFAULT]
VERBOSE = True                  # wether additional output should be visible in the console
INTERVAL = 5                    # time in seconds between each measurement

[CONTAINER]
LENGTH =                        # the inner length in centimeters of the container, if not set width is assumed to be the diagonal for a cylindric container
WIDTH = 236                     # the inner width or diagonal (when length value is not set) in centimeters of the container
HEIGHT = 228                    # the inner height in centimeters of the container

[SENSOR]
OFFSET = 40                     # distance in centimeters between sensor and maximum surface level
GPIO_TRIGGER = 15               # trigger GPIO pin
GPIO_ECHO = 14                  # echo GPIO pin
TRIGGER_TIME = 0.00001          # duration time in seconds for sensor trigger
MAX_TIME = 0.004                # max time in seconds waiting for response

[MQTT]
HOST = 192.168.0.229            # MQTT broker host
PORT = 1883                     # MQTT broker port
USER =                          # MQTT broker username or blank if not needed
PASS =                          # MQTT broker password or blank if not needed
TLS = False                     # MQTT broker TLS encryption
CERT_PATH =                     # MQTT broker path to encryption certificate
TOPIC = rainwater/status        # MQTT topic to which results are published

Script execution

The script will run until manually interrupted, using the following command. Additional flags for --config and/or --verbose option overrides can be passed along.

python3 liquid2MQTT.py