Run this once instead of a loop, do I need the 'calibration' steps?

[duckredbeard]

I am running this code to measure the weight of a water jug. All is working but I expect that I might have issues if the internet is interrupted when it tries to send the requests.post. Is there a way I can run the calibration part (lines 21-26) one time (saving anything important) and then just run it on a cronjob or SSH command?

Here is the whole thing...

import time
import sys
import RPi.GPIO as GPIO
from hx711 import HX711
import requests
from ShaneKeys import ARKEY1
from gpiozero import LED


LED2 = LED(12) # Red LED to indicate low level.
LED1 = LED(16) # Green LED to indicate high level.

def cleanAndExit():
    print("Cleaning...")        
    print("Bye!")
    sys.exit()
    
LED1.on() # Indication that the program has started and that LED indications are functional.
LED2.on() # Indication that the program has started and that LED indications are functional.

hx = HX711(20, 21)
hx.set_reading_format("MSB", "MSB")
referenceUnit = 114
hx.set_reference_unit(referenceUnit)
hx.reset()
hx.tare()

LED2.off() # Indication that reset and tare functions are complete.
time.sleep(5) # Take a moment to reflect. 
LED1.off() # Indication that reset and tare functions are complete.

print("Scale has been set to zero, add weight now...")  # This is when I know that the "zero" or "calibration" is done.  If not using VNC, I use the LEDs to tell me when to load the load.

while True:
    try:
        val = hx.get_weight(5)
        wholeval = (val * -1)  # For some reason the "val" was reporting a negative value.  This makes it positive.
        newval = wholeval / 100  # This makes the value in a unit of whole pounds (2154 becomes 21.54 pounds).
        roundedval = round(newval, 2)  # This ensures that the pound value is limited to two decimal places.
        print(roundedval)  # This displays the measured weight in pounds.
        weight = str(roundedval)
        if roundedval > 10:  # If the volume is greater than 25%, then power on the green LED on GPIO16.
            LED2.off()
            LED1.on()
        else:  # If the volume is less than 25%, then power the red LED on GPIO12.
            LED2.on()
            LED1.off()
        r = requests.post(ARKEY1 + "|water|" + str(roundedval)) #This is where the script sends the weight to my phone - the variable "roundedval" is the weight of the keg in pounds.
        hx.power_down()
        hx.power_up()
        time.sleep(1800) #Sleep for 30 minutes then recheck the weight of the water.

    except (KeyboardInterrupt, SystemExit):
        cleanAndExit()

[from1991]

Here I have created two scripts: one for calibration and another for regular measurements.

calibrate.py:

import RPi.GPIO as GPIO
from hx711 import HX711
import json
from gpiozero import LED

LED2 = LED(12)  # Red LED to indicate low level.
LED1 = LED(16)  # Green LED to indicate high level.

def calibrate():
    LED1.on()  # Indication that the program has started and that LED indications are functional.
    LED2.on()  # Indication that the program has started and that LED indications are functional.

    hx = HX711(20, 21)
    hx.set_reading_format("MSB", "MSB")
    referenceUnit = 114
    hx.set_reference_unit(referenceUnit)
    hx.reset()
    hx.tare()

    LED2.off()  # Indication that reset and tare functions are complete.
    LED1.off()  # Indication that reset and tare functions are complete.

    print("Calibration complete. Saving calibration data...")

    # Save calibration data
    calibration_data = {
        "referenceUnit": referenceUnit,
        "offset": hx.get_offset()
    }

    with open('calibration_data.json', 'w') as f:
        json.dump(calibration_data, f)

    print("Calibration data saved. You can now run the measurement script.")

if __name__ == "__main__":
    try:
        calibrate()
    except (KeyboardInterrupt, SystemExit):
        print("Calibration interrupted.")
    finally:
        GPIO.cleanup()

measure_weight.py:

import time
import sys
import RPi.GPIO as GPIO
from hx711 import HX711
import requests
from ShaneKeys import ARKEY1
from gpiozero import LED
import json

LED2 = LED(12)  # Red LED to indicate low level.
LED1 = LED(16)  # Green LED to indicate high level.

def cleanAndExit():
    print("Cleaning...")
    GPIO.cleanup()
    print("Bye!")
    sys.exit()

def load_calibration_data():
    with open('calibration_data.json', 'r') as f:
        return json.load(f)

def measure_weight():
    calibration_data = load_calibration_data()

    hx = HX711(20, 21)
    hx.set_reading_format("MSB", "MSB")
    hx.set_reference_unit(calibration_data['referenceUnit'])
    hx.set_offset(calibration_data['offset'])

    while True:
        try:
            val = hx.get_weight(5)
            wholeval = (val * -1)
            newval = wholeval / 100
            roundedval = round(newval, 2)
            print(roundedval)
            weight = str(roundedval)
            if roundedval > 10:
                LED2.off()
                LED1.on()
            else:
                LED2.on()
                LED1.off()
            
            try:
                r = requests.post(ARKEY1 + "|water|" + str(roundedval))
            except requests.exceptions.RequestException as e:
                print(f"Failed to send data: {e}")
                # You might want to implement a retry mechanism here

            hx.power_down()
            hx.power_up()
            time.sleep(1800)  # Sleep for 30 minutes then recheck the weight of the water.

        except (KeyboardInterrupt, SystemExit):
            cleanAndExit()

if __name__ == "__main__":
    measure_weight()

Let me know if you face any issue while running these scripts

[duckredbeard]

I will certainly try this today. I was just messing with it remotely and accidentally stopped my looping script. The only way to get it going is to be there, remove the weight, restart the existing script, then restore the weight.

It is killing me that I no longer get updates on the quantity of the water jug in the water cooler in my den. Perhaps I should leave work early!

All jokes aside, I see plenty of uses for this script. Under the big bin of dog food to alert me to go get them food. Under their gravity fed) water dispenser so I will know they need water. Under the shelf of my beer fridge to know if my kids are getting into my beer.

I like to create problems just to see if they can be solved with a Raspberry Pi or the Tasker (Android) app.