Normalizing a value from HX711 - Printable Version +- Python Forum (https://python-forum.io) +-- Forum: Python Coding (https://python-forum.io/forum-7.html) +--- Forum: General Coding Help (https://python-forum.io/forum-8.html) +--- Thread: Normalizing a value from HX711 (/thread-29549.html) |
Normalizing a value from HX711 - duckredbeard - Sep-09-2020 I have a scale project that is used to determine the quantity of beer in a keg. Since not all beers weigh the same, the full weight of the keg is inconsistent. I'd like to find a way to "normalize" the range of variables used for the varied weights. When I run the following code, it starts out with getting a "zero" reference then I place the full keg on. With a full keg, I get values between 500000 and 515000. How do I convert the larger number to a simple "100" so that I could use percentage of range (0-100) instead of 0-inconsistent number. # Scale project that uses a scale to determine the volume of beer in the keg. # A row of LEDs indicates the state of the program and the volume of the keg. # A requests post initiates a push notification to my phone when the weight of the keg changes. import time import sys import requests from gpiozero import LED #Define LED indicators - these are GPIO numbers LED1 = LED(21) #Blue LED2 = LED(26) #Red LED3 = LED(20) #Amber LED4 = LED(19) #Green LED5 = LED(16) #Green LED6 = LED(13) #Green LED7 = LED(6) #Green LED8 = LED(12) #Green LED9 = LED(5) #Pink EMULATE_HX711=False referenceUnit = 1 if not EMULATE_HX711: import RPi.GPIO as GPIO from hx711 import HX711 else: from emulated_hx711 import HX711 def moving_average(prev_average, new_value, num_steps = 5.0): return (prev_average * (num_steps - 1) + new_value) / num_steps average = weight = 400000 #just a value close to what a newly deployed keg would be w_threshold = 2000 #approximate value of 3-4 fluid ounces of the beer def cleanandexit(): print("Cleaning...") if not EMULATE_HX711: GPIO.cleanup() print("Bye!") sys.exit() hx = HX711(27, 22) hx.set_reading_format("MSB", "MSB") hx.set_reference_unit(1) hx.reset() hx.tare() print("The scale is ready") print("put the keg on...") LED9.blink(.2,3) # indication that the scale is running - not blinking means program crash start = time.time() while True: try: keg1 = hx.get_weight(5) weight = keg1 keg1 = round(keg1,3) start_weight = keg1 print(keg1, average) if time.time() - start > 5: weight = keg1 lost_weight = average - keg1 lost_weight = round(lost_weight,3) if lost_weight > w_threshold: #r = requests.post("https://bit.ly/editedforprivacy") #Join URL that triggers push notification to my phone print("You got served") average = keg1 #resets average to new keg1 value for faster recovery print(lost_weight) #visual indication of how much was poured - one pint is about 8400 average = moving_average(average, weight) average = round(average,3) start = time.time() if 8000 >= keg1 <= 507001: #keg is outside of usable range - flashes when keg is missing (indicating tare is complete at startup) LED1.blink(.2,.2) else: LED1.off() if 109800 >= keg1 >= 80000: #Red less than 5% - DANGER LED2.blink(.5,.5) else: LED2.off() if 130600 >= keg1 >= 109799: #Amber less than 10% - Warning LED3.on() else: LED3.off() if 507000 >= keg1 >= 130599: # Green 10-20% - Caution LED4.on() else: LED4.off() if 507000 >= keg1 >= 172199: #Green2 20-40% LED5.on() else: LED5.off() if 507000 >= keg1 >= 255400: #Green3 40-60% LED6.on() else: LED6.off() if 507000 >= keg1 >= 338600: #Green4 60-80% LED7.on() else: LED7.off() if 507000 >= keg1 >= 421800: #Green5 80-100% LED8.on() else: LED8.off() hx.power_down() hx.power_up() time.sleep(1) except (KeyboardInterrupt, SystemExit): cleanandexit()Keep in mind that this code's values are based on a full keg being about 507000 and an empty keg being about 89000. This works out to a net weight of about 418000, which is the weight of the beer. I have found that I can get inconsistent "full" values using the same keg. Running this 4 times this morning, I got the following values for full: 507000, 511000, 509000, and 516000. RE: Normalizing a value from HX711 - deanhystad - Sep-09-2020 scale = 100 / (full - empty) percent_full = (weight - empty) * scale Empty is the weight of an empty keg. Hopefully this is consistent enough to be a constant. full is the weight of a full keg and would be taken just before entering the loop. It will be different for each keg. RE: Normalizing a value from HX711 - duckredbeard - Sep-09-2020 That seems easy enough. So what I need to do now is to tell the program when to capture the "full" value. Plobby do that with a button push, kind of like a reset function. I will see what I can do with this. Thanks for the idea. RE: Normalizing a value from HX711 - duckredbeard - Sep-09-2020 So I added a few things, haven't been able to test it yet. Let me know if this is what you were talking about. I only changed the part where these maths control the lights, not much else. I also added the reset button on GPIO4, expecting a push of that button will reset the "full" value to the currently observed "keg1" value that the HX711 is reporting. On paper, this looks like what I am after. Behold the code: # Scale project that uses a scale to determine the volume of beer in the keg. # A row of LEDs indicates the state of the program and the volume of the keg. # A requests post initiates a push notification to my phone when the weight of the keg changes. import time import sys import requests from gpiozero import LED #Define LED indicators - these are GPIO numbers LED1 = LED(21) #Blue LED2 = LED(26) #Red LED3 = LED(20) #Amber LED4 = LED(19) #Green LED5 = LED(16) #Green LED6 = LED(13) #Green LED7 = LED(6) #Green LED8 = LED(12) #Green LED9 = LED(5) #Pink Reset = Button(4) #Button to reset the variable "full" to the current scale value EMULATE_HX711=False referenceUnit = 1 if not EMULATE_HX711: import RPi.GPIO as GPIO from hx711 import HX711 else: from emulated_hx711 import HX711 def moving_average(prev_average, new_value, num_steps = 5.0): return (prev_average * (num_steps - 1) + new_value) / num_steps def reset_full(): full = keg1 average = weight = 400000 #just a value close to what a newly deployed keg would be w_threshold = 2000 #approximate value of 3-4 fluid ounces of the beer def cleanandexit(): print("Cleaning...") if not EMULATE_HX711: GPIO.cleanup() print("Bye!") sys.exit() hx = HX711(27, 22) hx.set_reading_format("MSB", "MSB") hx.set_reference_unit(1) hx.reset() hx.tare() print("The scale is ready") print("put the keg on...") LED9.blink(.2,3) # indication that the scale is running - not blinking means program crash start = time.time() while True: try: keg1 = hx.get_weight(5) weight = keg1 keg1 = round(keg1,3) start_weight = keg1 print(keg1, average) if time.time() - start > 5: weight = keg1 lost_weight = average - keg1 lost_weight = round(lost_weight,3) if lost_weight > w_threshold: #r = requests.post("https://bit.ly/editedforprivacy") #Join URL that triggers push notification to my phone print("You got served") average = keg1 #resets average to new keg1 value for faster recovery print(lost_weight) #visual indication of how much was poured - one pint is about 8400 average = moving_average(average, weight) average = round(average,3) start = time.time() Reset.when_pressed = reset_full full = keg1 empty = 89000 scale = 100 / (full - empty) percent_full = (weight - empty) * scale if 1 >= percent_full <= 102: #keg is outside of usable range - flashes when keg is missing (indicating tare is complete at startup) LED1.blink(.2,.2) else: LED1.off() if 1.1 >= percent_full >= 5: #Red less than 5% - DANGER LED2.blink(.5,.5) else: LED2.off() if 100 >= percent_full >= 10: #Amber less than 10% - Warning LED3.on() else: LED3.off() if 100 >= percent_full >= 20: # Green 10-20% - Caution LED4.on() else: LED4.off() if 100 >= percent_full >= 40: #Green2 20-40% LED5.on() else: LED5.off() if 100 >= percent_full >= 60: #Green3 40-60% LED6.on() else: LED6.off() if 100 >= percent_full >= 80: #Green4 60-80% LED7.on() else: LED7.off() if 100 >= keg1 >= 80.1: #Green5 80-100% LED8.on() else: LED8.off() hx.power_down() hx.power_up() time.sleep(1) except (KeyboardInterrupt, SystemExit): cleanandexit() RE: Normalizing a value from HX711 - deanhystad - Sep-10-2020 The percent_full equation converts the keg weight to a number in the range 0 to 100. This is the number you should use for calculating average and turning LED's on and off. It should be calculated each time you weigh the keg. |