.. 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_alarm_lamp: 7.3 Building an Alarm Siren Lamp ======================================================= In this project, we'll create an **Alarm Siren Lamp** using the Raspberry Pi Pico 2. This device simulates the flashing lights and siren sound of a police car or emergency vehicle. It's a fun way to learn about PWM (Pulse Width Modulation), interrupts, and controlling multiple components like LEDs and buzzers. **What You'll Need** 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 * - Newton Lab Kit - 450+ - |link_newton_lab_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_2` - 1 - |link_pico2_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_led` - 1 - |link_led_buy| * - 6 - :ref:`cpn_transistor` - 1(S8050) - |link_transistor_buy| * - 7 - :ref:`cpn_resistor` - 3(1KΩ, 220Ω, 10KΩ) - |link_resistor_buy| * - 8 - Passive :ref:`cpn_buzzer` - 1 - |link_passive_buzzer_buy| * - 9 - :ref:`cpn_capacitor` - 1(104) - |link_capacitor_buy| * - 10 - :ref:`cpn_slide_switch` - 1 - **Understanding the Components** * **Passive Buzzer**: Requires an external signal to produce sound. We'll use PWM to generate varying frequencies, creating a siren effect. * **LED**: Will simulate the flashing light of a siren by changing brightness. * **Slide Switch**: Acts as an on/off switch to control the alarm. * **NPN Transistor (S8050)**: Used to drive the buzzer, as the Pico's GPIO pins cannot supply enough current directly. * **Resistor and Capacitor**: Used to debounce the slide switch, ensuring stable readings. **Circuit Diagram** |sch_alarm_siren_lamp| * GP17 is connected to the middle pin of the slider, along with a 10K resistor and a capacitor (filter) in parallel to GND, which allows the slider to output a steady high or low level when toggled to the left or right. * As soon as GP15 is high, the NPN transistor conducts, causing the passive buzzer to start sounding. This passive buzzer is programmed to gradually increase in frequency to produce a siren sound. * An LED is connected to GP16 and is programmed to periodically change its brightness in order to simulate a siren. **Wiring Diagram** |wiring_alarm_siren_lamp| **Writing the Code** We'll write a MicroPython script to control the buzzer and LED based on the position of the slide switch. .. note:: * Open the ``7.3_alarm_siren_lamp.py`` from ``newton-lab-kit/micropython`` or copy the code into Thonny, then click "Run" or press F5. * Ensure the correct interpreter is selected: MicroPython (Raspberry Pi Pico).COMxx. .. code-block:: python import machine import utime # Initialize PWM for buzzer and LED buzzer = machine.PWM(machine.Pin(15)) led = machine.PWM(machine.Pin(16)) led.freq(1000) # Set LED PWM frequency # Initialize the slide switch switch = machine.Pin(17, machine.Pin.IN, machine.Pin.PULL_DOWN) # Function to map values from one range to another def interval_mapping(x, in_min, in_max, out_min, out_max): # Ensure in_min != in_max to avoid division by zero if in_max - in_min == 0: return out_min return int((x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min) # Main loop try: while True: if switch.value() == 1: # Alarm is ON # Increase frequency and brightness for i in range(0, 100, 2): # Map 'i' to LED brightness and buzzer frequency brightness = interval_mapping(i, 0, 100, 0, 65535) frequency = interval_mapping(i, 0, 100, 500, 2000) # Set LED brightness led.duty_u16(brightness) # Set buzzer frequency and duty cycle buzzer.freq(frequency) buzzer.duty_u16(32768) # 50% duty cycle utime.sleep(0.01) # Decrease frequency and brightness for i in range(100, 0, -2): brightness = interval_mapping(i, 0, 100, 0, 65535) frequency = interval_mapping(i, 0, 100, 500, 2000) led.duty_u16(brightness) buzzer.freq(frequency) buzzer.duty_u16(32768) utime.sleep(0.01) else: # Alarm is OFF # Turn off LED and buzzer led.duty_u16(0) buzzer.duty_u16(0) utime.sleep(0.1) except KeyboardInterrupt: # Clean up buzzer.deinit() led.deinit() print("Program stopped.") Once the code is running, toggle the slide switch to the ON position. The buzzer should emit a siren sound, and the LED should flash accordingly. Toggle the switch to OFF to stop the alarm. **Understanding the Code** #. Initialization: * **buzzer**: PWM object on GP15. * **led**: PWM object on GP16, frequency set to 1kHz for smooth brightness control. * **switch**: Input pin on GP17 with an internal pull-down resistor. #. Interval Mapping Function: Maps a value from one range to another, useful for scaling the loop variable to desired frequency and brightness ranges. .. code-block:: python # Function to map values from one range to another def interval_mapping(x, in_min, in_max, out_min, out_max): # Ensure in_min != in_max to avoid division by zero if in_max - in_min == 0: return out_min return int((x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min) #. Main Loop: * Checks the state of the switch. * If the switch is ON (``switch.value() == 1``): * Runs two loops to simulate the siren effect: * Increasing frequency and brightness. * Decreasing frequency and brightness. * The buzzer frequency varies between 500 Hz and 2000 Hz. * The LED brightness varies from off to full brightness and back. .. code-block:: python if switch.value() == 1: # Alarm is ON # Increase frequency and brightness for i in range(0, 100, 2): # Map 'i' to LED brightness and buzzer frequency brightness = interval_mapping(i, 0, 100, 0, 65535) ... utime.sleep(0.01) * If the switch is OFF: Turns off the LED and buzzer. .. code-block:: python else: # Alarm is OFF # Turn off LED and buzzer led.duty_u16(0) buzzer.duty_u16(0) utime.sleep(0.1) * Exception Handling: Captures a keyboard interrupt (Ctrl+C) to cleanly deinitialize the PWM objects. .. code-block:: python except KeyboardInterrupt: # Clean up buzzer.deinit() led.deinit() print("Program stopped.") **Experimenting Further** * Adjusting the Siren Effect: * Modify the frequency range in the ``interval_mapping`` function to change the pitch. * Adjust the delay in the loops (``utime.sleep(0.01)``) to speed up or slow down the siren cycle. * Add More LEDs: * Incorporate additional LEDs of different colors to create a more dynamic light show. * Use multiple GPIO pins and PWM channels. * Motion Activation: Replace the slide switch with a motion sensor (e.g., PIR sensor) to trigger the alarm when movement is detected. * Remote Control: Integrate an IR receiver to control the alarm using a remote control. **Conclusion** You've successfully built an Alarm Siren Lamp using the Raspberry Pi Pico 2! This project demonstrates how to control multiple components and create interactive effects. It's a great foundation for more complex projects like security systems, emergency signals, or creative art installations.