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4.1.2 Counting Device

Introduction

Here we will make a number-displaying counter system, consisting of a PIR sensor and a 4-digit segment display. When the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1. You can use this counter to count the number of people walking through the passageway.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Raphael Kit	337	Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
GPIO Extension Board	BUY
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
4-Digit 7-Segment Display	-
74HC595	BUY
PIR Motion Sensor Module	-

Schematic Diagram

T-Board Name	physical	wiringPi	BCM
GPIO17	Pin 11	0	17
GPIO27	Pin 13	2	27
GPIO22	Pin 15	3	22
SPIMOSI	Pin 19	12	10
GPIO18	Pin 12	1	18
GPIO23	Pin 16	4	23
GPIO24	Pin 18	5	24
GPIO26	Pin 37	25	26

Experimental Procedures

Step 1: Build the circuit.

Step 2: Go to the folder of the code.

cd ~/raphael-kit/python-pi5

Step 3: Run the executable file.

sudo python3 4.1.7_CountingDevice_zero.py

After the code runs, when the PIR detects that someone is passing by, the number on the 4-digit segment display will add 1.

There are two potentiometers on the PIR module: one is to adjust sensitivity and the other is to adjust the detection distance. To make the PIR module work better, you You need to turn both of them counterclockwise to the end.

Code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python-pi5. After modifying the code, you can run it directly to see the effect.

#!/usr/bin/env python3
from gpiozero import OutputDevice, MotionSensor

# Initialize PIR motion sensor on GPIO 26
pir = MotionSensor(26)

# Initialize shift register pins
SDI = OutputDevice(24)    # Serial Data Input
RCLK = OutputDevice(23)   # Register Clock Input
SRCLK = OutputDevice(18)  # Shift Register Clock Input

# Initialize 7-segment display pins
placePin = [OutputDevice(pin) for pin in (10, 22, 27, 17)]

# Define digit codes for 7-segment display
number = (0xc0, 0xf9, 0xa4, 0xb0, 0x99, 0x92, 0x82, 0xf8, 0x80, 0x90)

# Counter for the displayed number
counter = 0

def clearDisplay():
    # Clears the display by setting all segments off
    for _ in range(8):
        SDI.on()
        SRCLK.on()
        SRCLK.off()
    RCLK.on()
    RCLK.off()

def hc595_shift(data):
    # Shifts data into the 74HC595 shift register
    for i in range(8):
        SDI.value = 0x80 & (data << i)
        SRCLK.on()
        SRCLK.off()
    RCLK.on()
    RCLK.off()

def pickDigit(digit):
    # Activates a specific digit of the 7-segment display
    for pin in placePin:
        pin.off()
    placePin[digit].on()

def display():
    # Updates the display with the current counter value
    global counter
    clearDisplay()
    pickDigit(0)
    hc595_shift(number[counter % 10])

    clearDisplay()
    pickDigit(1)
    hc595_shift(number[counter % 100//10])

    clearDisplay()
    pickDigit(2)
    hc595_shift(number[counter % 1000//100])

    clearDisplay()
    pickDigit(3)
    hc595_shift(number[counter % 10000//1000])

def loop():
    # Main loop to update display and check for motion
    global counter
    currentState = 0
    lastState = 0
    while True:
        display()
        currentState = 1 if pir.motion_detected else 0
        if currentState == 1 and lastState == 0:
            counter += 1
        lastState = currentState

try:
    loop()
except KeyboardInterrupt:
    # Turn off all pins when the script is interrupted
    SDI.off()
    SRCLK.off()
    RCLK.off()
    pass

Code Explanation

1. This line imports the OutputDevice and MotionSensor classes from the gpiozero library. OutputDevice can be an LED, motor, or any device that you want to control as an output. The MotionSensor is typically a PIR (Passive Infrared) sensor used to detect motion.

   #!/usr/bin/env python3
   from gpiozero import OutputDevice, MotionSensor
   

2. Initializes the PIR motion sensor connected to GPIO pin 26.

   # Initialize PIR motion sensor on GPIO 26
   pir = MotionSensor(26)
   

3. Initializes GPIO pins connected to the shift register’s Serial Data Input (SDI), Register Clock Input (RCLK), and Shift Register Clock Input (SRCLK).

   # Initialize shift register pins
   SDI = OutputDevice(24)    # Serial Data Input
   RCLK = OutputDevice(23)   # Register Clock Input
   SRCLK = OutputDevice(18)  # Shift Register Clock Input
   

4. Initializes the pins for each digit of the 7-segment display and defines the binary codes for displaying numbers 0-9.

   # Initialize 7-segment display pins
   placePin = [OutputDevice(pin) for pin in (10, 22, 27, 17)]
   
   # Define digit codes for 7-segment display
   number = (0xc0, 0xf9, 0xa4, 0xb0, 0x99, 0x92, 0x82, 0xf8, 0x80, 0x90)
   

5. Clears the 7-segment display by setting all segments off before displaying the next digit.

   def clearDisplay():
       # Clears the display by setting all segments off
       for _ in range(8):
           SDI.on()
           SRCLK.on()
           SRCLK.off()
       RCLK.on()
       RCLK.off()
   

6. Shifts a byte of data into the 74HC595 shift register, controlling the display segments.

   def hc595_shift(data):
       # Shifts data into the 74HC595 shift register
       for i in range(8):
           SDI.value = 0x80 & (data << i)
           SRCLK.on()
           SRCLK.off()
       RCLK.on()
       RCLK.off()
   

7. Selects which digit of the 7-segment display to activate. Each digit is controlled by a separate GPIO pin.

   def pickDigit(digit):
       # Activates a specific digit of the 7-segment display
       for pin in placePin:
           pin.off()
       placePin[digit].on()
   

8. Initiate the display for the unit digit first, followed by activating the display for the tens digit. Subsequently, engage the displays for the hundreds and thousands digits in order. This rapid succession of activations creates the illusion of a continuous four-digit display.

   def display():
       # Updates the display with the current counter value
       global counter
       clearDisplay()
       pickDigit(0)
       hc595_shift(number[counter % 10])
   
       clearDisplay()
       pickDigit(1)
       hc595_shift(number[counter % 100//10])
   
       clearDisplay()
       pickDigit(2)
       hc595_shift(number[counter % 1000//100])
   
       clearDisplay()
       pickDigit(3)
       hc595_shift(number[counter % 10000//1000])
   

9. Defines the main loop where the display is continuously updated, and the PIR sensor’s state is checked. If motion is detected, the counter is incremented.

   def loop():
       # Main loop to update display and check for motion
       global counter
       currentState = 0
       lastState = 0
       while True:
           display()
           currentState = 1 if pir.motion_detected else 0
           if currentState == 1 and lastState == 0:
               counter += 1
           lastState = currentState
   

10. Runs the main loop and ensures that the script can be interrupted with a keyboard command (Ctrl+C), turning off all pins for a clean exit.

    try:
        loop()
    except KeyboardInterrupt:
        # Turn off all pins when the script is interrupted
        SDI.off()
        SRCLK.off()
        RCLK.off()
        pass