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7.10 Building a Reversing Aid

In this project, we’ll create a Reversing Aid System using the Raspberry Pi Pico 2, an ultrasonic sensor, an LED, and a buzzer. This system simulates how real-world parking sensors work by detecting the distance to an obstacle and providing audio and visual feedback that changes based on proximity. You can attach this setup to a remote-controlled car to mimic the experience of reversing into a garage.

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:

Name

ITEMS IN THIS KIT

LINK

Newton Lab Kit

450+

Newton Lab Kit

You can also buy them separately from the links below.

SN

COMPONENT

QUANTITY

LINK

1

Raspberry Pi Pico 2

1

BUY

2

Micro USB Cable

1

3

Breadboard

1

BUY

4

Jumper Wires

Several

BUY

5

Transistor

1(S8050)

BUY

6

Resistor

2(1KΩ, 220Ω)

BUY

7

Active Buzzer

1

8

LED

1

BUY

9

Ultrasonic Module

1

BUY

Understanding the Components

  • Ultrasonic Sensor (HC-SR04): Measures the distance to an object by sending out ultrasonic waves and measuring the time it takes for the echo to return.

  • Buzzer: Provides audio feedback; beeps more frequently as the object gets closer.

  • LED: Provides visual feedback; blinks more rapidly as the object gets closer.

Circuit Diagram

sch_reversing_aid

Wiring Diagram

wiring_reversing_aid

Writing the Code

We’ll write a MicroPython script that:

  • Measures the distance using the ultrasonic sensor.

  • Adjusts the beep frequency of the buzzer and the blink rate of the LED based on the distance.

  • Provides continuous feedback as the object moves closer or further away.

Note

  • Open the 7.10_reversing_aid.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.

import machine
import utime

# Set up pins
trigger = machine.Pin(17, machine.Pin.OUT)
echo = machine.Pin(16, machine.Pin.IN)
buzzer = machine.Pin(15, machine.Pin.OUT)
led = machine.Pin(14, machine.Pin.OUT)

# Function to measure distance
def measure_distance():
    # Ensure trigger is low
    trigger.low()
    utime.sleep_us(2)
    # Send 10us pulse to trigger
    trigger.high()
    utime.sleep_us(10)
    trigger.low()

    # Measure the duration of the echo pulse
    while echo.value() == 0:
        signaloff = utime.ticks_us()
    while echo.value() == 1:
        signalon = utime.ticks_us()

    timepassed = utime.ticks_diff(signalon, signaloff)
    distance = (timepassed * 0.0343) / 2  # Convert to cm
    return distance

# Function to control buzzer and LED
def alert(interval):
    buzzer.high()
    led.high()
    utime.sleep(0.1)
    buzzer.low()
    led.low()
    utime.sleep(interval)

# Main loop
try:
    while True:
        dist = measure_distance()
        print("Distance: {:.2f} cm".format(dist))
        if dist < 0:
            print("Out of range")
            utime.sleep(1)
        elif dist <= 10:
            alert(0.2)  # Very close, alert rapidly
        elif dist <= 20:
            alert(0.5)  # Close, alert moderately
        elif dist <= 50:
            alert(1)    # Not too close, alert slowly
        else:
            alert(2)    # Far away, alert infrequently
except KeyboardInterrupt:
    print("Measurement stopped by User")

Once the code is running, place an object at varying distances from the ultrasonic sensor. Observe the changes in the beep frequency and LED blink rate. The console will display the measured distance.

Understanding the Code

  1. Distance Measurement:

    • The measure_distance() function sends a 10-microsecond pulse to the TRIG pin.

    • It then measures the time until the ECHO pin goes high and then back low.

    • Calculates the distance based on the time it takes for the ultrasonic pulse to return.

    def measure_distance():
    # Ensure trigger is low
    trigger.low()
    utime.sleep_us(2)
    # Send 10us pulse to trigger
    trigger.high()
    utime.sleep_us(10)
    trigger.low()

    # Measure the duration of the echo pulse
    while echo.value() == 0:
        signaloff = utime.ticks_us()
    while echo.value() == 1:
        signalon = utime.ticks_us()

    timepassed = utime.ticks_diff(signalon, signaloff)
    distance = (timepassed * 0.0343) / 2  # Convert to cm
    return distance

  2. Alert Function:

    • The alert(interval) function turns the buzzer and LED on for 0.1 seconds and then off.

    • The interval parameter adjusts the pause between alerts based on the distance.

    def measure_distance():
    # Ensure trigger is low
    trigger.low()
    utime.sleep_us(2)
    # Send 10us pulse to trigger
    trigger.high()
    utime.sleep_us(10)
    trigger.low()

    # Measure the duration of the echo pulse
    while echo.value() == 0:
        signaloff = utime.ticks_us()
    while echo.value() == 1:
        signalon = utime.ticks_us()

    timepassed = utime.ticks_diff(signalon, signaloff)
    distance = (timepassed * 0.0343) / 2  # Convert to cm
    return distance

  3. Main Loop:

    • Continuously measures the distance.

    • Adjusts the alert frequency according to predefined distance thresholds.

    try:
    while True:
        dist = measure_distance()
        print("Distance: {:.2f} cm".format(dist))
        if dist < 0:
            print("Out of range")
            utime.sleep(1)
        elif dist <= 10:
            alert(0.2)  # Very close, alert rapidly
        elif dist <= 20:
            alert(0.5)  # Close, alert moderately
        elif dist <= 50:
            alert(1)    # Not too close, alert slowly
        else:
            alert(2)    # Far away, alert infrequently
except KeyboardInterrupt:
    print("Measurement stopped by User")

Safety Considerations

  • Voltage Levels:

    • Be cautious with the ECHO pin voltage from the ultrasonic sensor if using 5V.

    • Use a voltage divider or level shifter to protect the Pico’s GPIO pins.

  • Power Supply:

    Ensure the power supply can handle the current requirements of all components.

Experimenting Further

  • Visual Display:

    Add an LCD or OLED display to show the distance visually.

  • Multiple Sensors:

    Use additional ultrasonic sensors to cover more directions.

  • Advanced Alerts:

    Implement different tones or patterns on the buzzer for different distances.

Conclusion

You’ve successfully built a Reversing Aid System using the Raspberry Pi Pico 2! This project demonstrates how sensors can be used to provide real-time feedback, a fundamental concept in robotics and automation.