Ever felt like wasting too much time feeding your pet? Ever had to call someone to feed your pets while you were on a holiday? I have tried to fix both these issues with my current school project: Petfeed!

Supplies

Raspberry Pi 3b

Bar Load Cell (10kg)

HX711 Load Cell Amplifier

Waterlevel Sensor (https://www.dfrobot.com/product-1493.html)

Ultrasonic Proximity Sensor

LCD 16-pins

2x stepper motor 28byj-48

2x stepper motor driver ULN2003

Step 1: Wiring

lots of cabling here. Get out your jumper cables and start pinning!

Step 2: Make Your Load Cell Usable

to use the load cell, we first need to attach it to two plates: a bottom plate, and a plate on which we will weigh our food.

The screws you need are a pair of M4 screws with matching bolts and a pair of M5 screws with matching bolts. I used a small drill to make the holes.

(pic: https://tutorials-raspberrypi.com/digital-raspberry-pi-scale-weight-sensor-hx711/)

Step 3: Normalised Database

data from our sensors has to be saved in a database. For the python files to connect to the database: see below.

then you also need a config file:

[connector_python]<br>user = *yourusername*
host = 127.0.0.1 #if local
port = 3306
password = *yourpassword*
database = *yourdb*

[application_config]
driver = 'SQL Server'

Step 4: Coding the Load Cell

import RPi.GPIO as GPIO<br>import threading
import time

from hx711 import HX711
from helpers.stepperFood import StepperFood
from helpers.LCDWrite import LCDWrite
from repositories.DataRepository import DataRepository <br>

After importing all of our libraries (note, we're using the HX711 Library to drive the load cell) we can start writing our actual code

TARRA_CONSTANT = 80600
GRAM_CONSTANT = 101

For finding out our constants, first set TARRA_CONSTANT = 0 and GRAM_CONSTANT = 1.

Next we need to find out the value our load cell reads when theres nothing being weighed. This value will be TARRA_CONSTANT.

As for GRAM_CONSTANT, simply take an object you know the weight of (i used a pack of spaghetti's), weigh it and divide the load cell readout with the actual weight of the object. For me this was 101.

class LoadCell(threading.Thread):
    def __init__(self, socket, lcd):
        threading.Thread.__init__(self)
        self.hx711 = HX711(
            dout_pin=5,
            pd_sck_pin=6,
            channel='A',
            gain=64
        )
        self.socket = socket
        self.lcd = lcd

here we initialize the LoadCell class and map the pins.

    def run(self):
        try:
            while True:
                self.hx711.reset()   # Before we start, reset the HX711 (not obligate)
                measures_avg = sum(self.hx711.get_raw_data()) / 5
                weight = round(
                    (measures_avg - TARRA_CONSTANT) / GRAM_CONSTANT, 0)
                print("weight: {0}".format(weight))
                DataRepository.insert_weight(weight)
                data_weight = DataRepository.get_data_sensor(3)
                historyId = data_weight["SensorsHistory"]
                db_weight = data_weight["value"]
                actionTime = data_weight["actionTime"]
                self.socket.emit('data_weight', {
                    "id": historyId, "Weight": db_weight, "Time": DataRepository.serializeDateTime(actionTime)})
                print("zou moeten emitten")
                writeWeight = "weight: " + str(db_weight)
                msg = "PETFEED"
                LCDWrite.message()
                if int(db_weight[:-2]) <= 100:
                    StepperFood.run()
		time.sleep(20)


        except Exception as e:
            print("Error with weighing" + str(e))

Step 5: Coding the Water Sensor

import time<br>import threading
from repositories.DataRepository import DataRepository
from RPi import GPIOGPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

GPIO_Water = 18
GPIO.setup(GPIO_Water, GPIO.IN)

class WaterSensor(threading.Thread):
    def __init__(self, socket):
        threading.Thread.__init__(self)
        self.socket = socket
        self.vorige_status = 0

def run(self):
        try:
            while True:
                water = self.is_water()
                print(water)
                status = water["status"]
                action = water["action"]
                DataRepository.insert_water(str(status), action)
                data_water = DataRepository.get_data_sensor(2)
                historyId = data_water["SensorsHistory"]
                value = data_water["value"]
                if value == "0":
                    value = "te weinig water"
                else:
                    value = "genoeg water"
                actionTime = data_water["actionTime"]
                self.socket.emit('data_water', {
                    "id": historyId, "value": value, "Time": DataRepository.serializeDateTime(actionTime), "action": action})
                time.sleep(5)        

	except Exception as ex:
            print(ex)
            print('error bij watersensor')

    def is_water(self):
        status = GPIO.input(GPIO_Water)


        if self.vorige_status == 0 and status == 1:
            print('water gedetecteerd')
            sensorData = {"status": status, "action": "water gedetecteerd"}
            self.vorige_status = status
            status = GPIO.input(GPIO_Water)

        if self.vorige_status == 1 and status == 1:
            print('water aanwezig')
            sensorData = {"status": status, "action": "water aanwezig"}
            status = GPIO.input(GPIO_Water)

        if self.vorige_status == 1 and status == 0:
            print('water weg')
            sensorData = {"status": status, "action": "water weg"}
            self.vorige_status = status
            status = GPIO.input(GPIO_Water)

        if self.vorige_status == 0 and status == 0:
            print('startpositie')
            status = GPIO.input(GPIO_Water)
            sensorData = {"status": status, "action": "startpositie"}
        return sensorData

Step 6: Coding the Proximity Sensor

import time<br>import threading
from repositories.DataRepository import DataRepository
from RPi import GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

GPIO_Trig = 4
GPIO_Echo = 17

GPIO.setup(GPIO_Trig, GPIO.OUT)
GPIO.setup(GPIO_Echo, GPIO.IN)

def current_milli_time(): return int(round(time.time() * 1000))

class UltrasonicSensor(threading.Thread):
    def __init__(self, socket):
        threading.Thread.__init__(self)
        self.socket = socket

    def run(self):
        try:
            last_reading = 0
            interval = 5000
            while True:
                if current_milli_time() > last_reading + interval:
                    dist = self.distance()
                    print("Measured Distance = %.1f cm" % dist)
                    DataRepository.insert_proximity(dist)
                    data_prox = DataRepository.get_data_sensor(1)
                    historyId = data_prox["SensorsHistory"]
                    prox = data_prox["value"]
                    actionTime = data_prox["actionTime"]
                    self.socket.emit('data_proximity', {
                        "id": historyId, "Proximity": prox, "Time": DataRepository.serializeDateTime(actionTime)})
                    last_reading = current_milli_time()

        except Exception as ex:
            print(ex)

    def distance(self):
        # set Trigger to HIGH
        GPIO.output(GPIO_Trig, True)

        # set Trigger after 0.01ms to LOW
        time.sleep(0.00001)
        GPIO.output(GPIO_Trig, False)

        StartTime = time.time()
        StopTime = time.time()

        # save StartTime
        while GPIO.input(GPIO_Echo) == 0:
            StartTime = time.time()

        # save time of arrival
        while GPIO.input(GPIO_Echo) == 1:
            StopTime = time.time()

        # time difference between start and arrival
        TimeElapsed = StopTime - StartTime
        # multiply with the sonic speed (34300 cm/s)
        # and divide by 2, because there and back
        distance = (TimeElapsed * 34300) / 2

        return distance

Step 7: Coding the Stepper Motors

import RPi.GPIO as GPIO<br>import time
import threading

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

control_pins = [12, 16, 20, 21]

for pin in control_pins:
    GPIO.setup(pin, GPIO.OUT)
    GPIO.output(pin, 0)

halfstep_seq = [
    [1, 0, 0, 0],
    [1, 1, 0, 0],
    [0, 1, 0, 0],
    [0, 1, 1, 0],
    [0, 0, 1, 0],
    [0, 0, 1, 1],
    [0, 0, 0, 1],
    [1, 0, 0, 1]
]

class StepperFood:
    # 512 is 1 keer rond

    def run():
        for i in range(512):
            for halfstep in range(8):
                for pin in range(4):
                    GPIO.output(control_pins[pin], halfstep_seq[halfstep][pin])
                time.sleep(0.001)

        for pin in range(4):
            GPIO.output(control_pins[pin], 0)

This code is reusable for the other stepper motor, just set the control pin numbers to their repective pins and rename the class to StepperWater:

Step 8: Coding the LCD

Lots of code, but we're almost done.

The LCD class is included as file LCD.py

from helpers.LCD import LCD

E = 26
RS = 25

D0 = 19
D1 = 13
D2 = 24
D3 = 22
D4 = 23
D5 = 8
D6 = 7
D7 = 10

lcd = LCD(E, RS, [D0, D1, D2, D3, D4, D5, D6, D7])

class LCDWrite:

    def message(msg):
        try:
            print("try")
            lcd.init_LCD()
            lcd.send_instruction(12)
            lcd.clear_display()
            lcd.write_message(msg, '1')
        except:
            print("error LCDWrite")