.. note:: Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts. **Why Join?** - **Expert Support**: Solve post-sale issues and technical challenges with help from our community and team. - **Learn & Share**: Exchange tips and tutorials to enhance your skills. - **Exclusive Previews**: Get early access to new product announcements and sneak peeks. - **Special Discounts**: Enjoy exclusive discounts on our newest products. - **Festive Promotions and Giveaways**: Take part in giveaways and holiday promotions. 👉 Ready to explore and create with us? Click [|link_sf_facebook|] and join today! .. _py_traffic_light: 7.6 Traffic Light ================================= `Traffic Light `_ is a signal device located at roadway intersections, crosswalks and other locations to control the flow of traffic. Traffic signals are standardized by the `Vienna Convention on Road Signs and Signals `_. Provides users with the right-of-way by alternating LEDs in three standard colors. * **Red light**: Traffic should stop if it sees a flashing red light, equivalent to a stop sign. * **Yellow light**: A warning signal is about to turn red. Yellow lights are interpreted differently in different countries (regions). * **Green light**: Allows traffic to move in the indicated direction. In this project, we will use three colors of LEDs to implement traffic light changes and a 4-digit 7-segment display to show the time of each traffic state. **Required Components** In this project, we need the following components. It's definitely convenient to buy a whole kit, here's the link: .. list-table:: :widths: 20 20 20 :header-rows: 1 * - Name - ITEMS IN THIS KIT - LINK * - Kepler Kit - 450+ - |link_kepler_kit| You can also buy them separately from the links below. .. list-table:: :widths: 5 20 5 20 :header-rows: 1 * - SN - COMPONENT - QUANTITY - LINK * - 1 - :ref:`cpn_pico_w` - 1 - |link_picow_buy| * - 2 - Micro USB Cable - 1 - * - 3 - :ref:`cpn_breadboard` - 1 - |link_breadboard_buy| * - 4 - :ref:`cpn_wire` - Several - |link_wires_buy| * - 5 - :ref:`cpn_resistor` - 7(220Ω) - |link_resistor_buy| * - 6 - :ref:`cpn_4_dit_7_segment` - 1 - * - 7 - :ref:`cpn_74hc595` - 1 - |link_74hc595_buy| * - 8 - :ref:`cpn_led` - 3 - |link_led_buy| **Schematic** |sch_traffic_light| * This circuit is based on the :ref:`py_74hc_4dig` with the addition of 3 LEDs. * The 3 red, yellow and green LEDs are connected to GP7~GP9 respectively. **Wiring** |wiring_traffic_light| **Code** .. note:: * Open the ``7.6_traffic_light.py`` file under the path of ``kepler-kit-main/micropython`` or copy this code into Thonny, then click "Run Current Script" or simply press F5 to run it. * Don't forget to click on the "MicroPython (Raspberry Pi Pico)" interpreter in the bottom right corner. * For detailed tutorials, please refer to :ref:`open_run_code_py`. .. code-block:: python import machine import time from machine import Timer # Define the duration for each traffic light color in seconds [Green, Yellow, Red] lightTime = [30, 5, 30] # 7-segment display codes for digits 0-9, using hexadecimal to represent LED segments SEGCODE = [0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, 0x7f, 0x6f] # Initialize pins for shift register communication (74HC595) sdi = machine.Pin(18, machine.Pin.OUT) # Serial Data Input rclk = machine.Pin(19, machine.Pin.OUT) # Register Clock (Latch) srclk = machine.Pin(20, machine.Pin.OUT) # Shift Register Clock # Initialize list to store 4 digit control pins for the 7-segment display placePin = [] pin = [10, 13, 12, 11] # Pin numbers for the 4-digit display for i in range(4): placePin.append(None) # Reserve space in list placePin[i] = machine.Pin(pin[i], machine.Pin.OUT) # Initialize pins as output # Function to select which digit (0-3) to display by controlling the common anode pins def pickDigit(digit): for i in range(4): placePin[i].value(1) # Turn off all digits placePin[digit].value(0) # Turn on the selected digit # Function to clear the display by sending '0x00' to the shift register def clearDisplay(): hc595_shift(0x00) # Function to send data to the shift register (74HC595) def hc595_shift(dat): rclk.low() # Pull latch low to prepare for data shifting time.sleep_us(200) # Small delay for timing stability for bit in range(7, -1, -1): # Loop through each bit (MSB first) srclk.low() # Prepare to send the next bit time.sleep_us(200) value = 1 & (dat >> bit) # Extract the current bit from the data sdi.value(value) # Set the data line to the current bit value time.sleep_us(200) srclk.high() # Pulse the shift clock to store the bit in the register time.sleep_us(200) time.sleep_us(200) rclk.high() # Pulse the register clock to move the data to the output # Function to display a number on the 7-segment display # This function breaks down the number into its individual digits and displays them def display(num): pickDigit(0) # Select the units place hc595_shift(SEGCODE[num % 10]) # Display units pickDigit(1) # Select the tens place hc595_shift(SEGCODE[num % 100 // 10]) # Display tens pickDigit(2) # Select the hundreds place hc595_shift(SEGCODE[num % 1000 // 100]) # Display hundreds pickDigit(3) # Select the thousands place hc595_shift(SEGCODE[num % 10000 // 1000]) # Display thousands # Setup for traffic light LEDs (Red, Yellow, Green) # LEDs are connected to pins 9 (Green), 8 (Yellow), and 7 (Red) pin = [7, 8, 9] # LED pin numbers led = [] for i in range(3): led.append(None) # Reserve space in list led[i] = machine.Pin(pin[i], machine.Pin.OUT) # Initialize each pin as output for LEDs # Function to turn on the correct LED based on the current state # 0 = Green, 1 = Yellow, 2 = Red def lightup(state): for i in range(3): led[i].value(0) # Turn off all LEDs led[state].value(1) # Turn on the selected LED (Green, Yellow, or Red) # Timer-related variables counter = 0 # Counter for the remaining time color_state = 0 # Current state of the traffic light (0 = Green, 1 = Yellow, 2 = Red) # Timer interrupt callback to update the traffic light state and counter def time_count(ev): global counter, color_state counter -= 1 # Decrease the counter by 1 second if counter <= 0: # If the counter reaches zero, switch to the next light color color_state = (color_state + 1) % 3 # Cycle through Green, Yellow, and Red counter = lightTime[color_state] # Reset counter based on the new color's duration # Initialize a timer to call the time_count function every 1 second (1000ms) tim = Timer(period=1000, mode=Timer.PERIODIC, callback=time_count) # Main loop to update the 7-segment display and traffic light LEDs while True: display(counter) # Update the display with the remaining time lightup(color_state) # Update the traffic light LEDs based on the current color When the code runs, the green LED stays on for 30 seconds, the yellow LED stays on for 5 seconds, and the green LED stays on for 30 seconds.