💡 Level 1 – Fundamentals

Project 1.12: "Total Integration N1"

 

🚀 Project 1.12 – Obstacle Avoidance

🎯 What You’ll Learn

  • ✅ Goal 1: Detect obstacles using sensors.
  • ✅ Goal 2: Stop or turn when obstacle detected.
  • ✅ Goal 3: Combine logic for continuous navigation.

Key Ideas

  • Digital input: Sensor readings.
  • Logic: If/else for obstacle detection.
  • Motor control: Forward, stop, turn.
  • Loops: Continuous monitoring.

🧱 Blocks Glossary (used in this project)

  • pinX = machine.Pin(X, machine.Pin.OUT) → Motor direction.
  • pwmX = machine.PWM(machine.Pin(X)) → Motor speed control.
  • pwmX.freq(2000) → Set PWM frequency.
  • pwmX.duty(value) → Set duty cycle (0–1023).
  • sonar.Sonar(trigger, echo).checkdist() → Distance measurement.
  • while True: → Infinite loop.
  • time.sleep() → Delay.

🧰 What You Need

Part How many? Pin connection
D1 R32 1 USB cable
L298N Driver 1 IN1=Pin 2, IN2=Pin 4, ENA=Pin 5; IN3=Pin 12, IN4=Pin 13, ENB=Pin 14
Motors 2 Connected to L298N outputs
Ultrasonic Sensor 1 Trigger=Pin 26, Echo=Pin 5

✅ Before You Start

  • USB cable connected
  • Motors and sensor wired correctly
  • Test print shows:
print("Ready!")  # Confirm serial is working

🎮 Microprojects (5 Mini Missions)

🎮 Microproject 1.12.1 – Read distance

Blocks used: External sensor (sonar), Serial print
Block sequence:

  1. Setup sonar sensor
  2. Read distance
  3. Print value

MicroPython Code:

import machine, time, sonar                   # Import modules
sensor = sonar.Sonar(26, 5)                   # Trigger pin 26, Echo pin 5
while True:                                   # Infinite loop
    dist = sensor.checkdist()                 # Read distance
    print("Distance:", dist, "cm")            # Serial log
    time.sleep(0.5)                           # Delay

Reflection: Sensor reads distance continuously.
Challenge: Try faster refresh (0.2s).

🎮 Microproject 1.12.2 – Stop at obstacle

Blocks used: External sensor, Motor control, Logic
Block sequence:

  1. Setup motors forward
  2. If distance < 20 cm → stop

MicroPython Code:

import machine, time, sonar                   # Import modules
# Motor A setup
pin2 = machine.Pin(2, machine.Pin.OUT)        # Motor A IN1
pin4 = machine.Pin(4, machine.Pin.OUT)        # Motor A IN2
pwm5 = machine.PWM(machine.Pin(5))            # Motor A ENA PWM
# Motor B setup
pin12 = machine.Pin(12, machine.Pin.OUT)      # Motor B IN3
pin13 = machine.Pin(13, machine.Pin.OUT)      # Motor B IN4
pwm14 = machine.PWM(machine.Pin(14))          # Motor B ENB PWM
# Sensor setup
sensor = sonar.Sonar(26, 5)                   # Trigger pin 26, Echo pin 5
pwm5.freq(2000); pwm14.freq(2000)             # Set frequencies
pwm5.duty(512); pwm14.duty(512)               # Set speeds
while True:                                   # Infinite loop
    dist = sensor.checkdist()                 # Read distance
    print("Distance:", dist, "cm")            # Serial log
    if dist < 20:                             # If obstacle closer than 20 cm
        pwm5.duty(0); pwm14.duty(0)           # Stop motors
        print("Obstacle detected: STOP")      # Serial log
    else:                                     # If safe distance
        pin2.value(1); pin4.value(0)          # Motor A forward
        pin12.value(1); pin13.value(0)        # Motor B forward
        pwm5.duty(512); pwm14.duty(512)       # Motors ON
        print("Path clear: GO")               # Serial log
    time.sleep(0.2)                           # Delay

Reflection: Robot stops when obstacle detected.
Challenge: Try different threshold (30 cm).

🎮 Microproject 1.12.3 – Turn at obstacle

Blocks used: External sensor, Motor control, Logic
Block sequence:

  1. Setup motors forward
  2. If distance < 20 cm → turn left

MicroPython Code:

import machine, time, sonar                   # Import modules
# Motor setup
pin2 = machine.Pin(2, machine.Pin.OUT)
pin4 = machine.Pin(4, machine.Pin.OUT)
pwm5 = machine.PWM(machine.Pin(5))
pin12 = machine.Pin(12, machine.Pin.OUT)
pin13 = machine.Pin(13, machine.Pin.OUT)
pwm14 = machine.PWM(machine.Pin(14))
sensor = sonar.Sonar(26, 5)                   # Sensor setup
pwm5.freq(2000); pwm14.freq(2000)
pwm5.duty(512); pwm14.duty(512)
while True:
    dist = sensor.checkdist()                 # Read distance
    print("Distance:", dist, "cm")
    if dist < 20:                             # Obstacle detected
        pwm5.duty(0)                          # Stop motor A
        pwm14.duty(512)                       # Motor B forward
        print("Obstacle: TURN LEFT")          # Serial log
        time.sleep(1)                         # Turn left
    else:                                     # Path clear
        pin2.value(1); pin4.value(0)
        pin12.value(1); pin13.value(0)
        pwm5.duty(512); pwm14.duty(512)
        print("Path clear: GO")
    time.sleep(0.2)

Reflection: Robot turns left when obstacle detected.
Challenge: Try right turn instead.

🎮 Microproject 1.12.4 – Continuous navigation

Blocks used: External sensor, Motor control, Loop
Block sequence:

  1. Forward until obstacle
  2. Turn left
  3. Continue

MicroPython Code:

import machine, time, sonar                   # Import modules
pin2 = machine.Pin(2, machine.Pin.OUT)
pin4 = machine.Pin(4, machine.Pin.OUT)
pwm5 = machine.PWM(machine.Pin(5))
pin12 = machine.Pin(12, machine.Pin.OUT)
pin13 = machine.Pin(13, machine.Pin.OUT)
pwm14 = machine.PWM(machine.Pin(14))
sensor = sonar.Sonar(26, 5)
pwm5.freq(2000); pwm14.freq(2000)
while True:
    dist = sensor.checkdist()
    print("Distance:", dist, "cm")
    if dist < 20:
        pwm5.duty(0)
        pwm14.duty(512)
        print("TURN LEFT")
        time.sleep(1)
    else:
        pin2.value(1); pin4.value(0)
        pin12.value(1); pin13.value(0)
        pwm5.duty(512); pwm14.duty(512)
        print("GO")
    time.sleep(0.2)

Reflection: Robot navigates continuously avoiding obstacles.
Challenge: Add random turns for variety.

 

🎮 Microproject 1.12.5 – Smart avoidance

Blocks used: External sensor, Logic, Motor control
Block sequence:

  1. If distance < 10 cm → stop
  2. If distance < 20 cm → turn left
  3. Else → go forward

MicroPython Code:

import machine, time, sonar                   # Import modules
# Motor A setup
pin2 = machine.Pin(2, machine.Pin.OUT)        # Motor A IN1
pin4 = machine.Pin(4, machine.Pin.OUT)        # Motor A IN2
pwm5 = machine.PWM(machine.Pin(5))            # Motor A ENA PWM
# Motor B setup
pin12 = machine.Pin(12, machine.Pin.OUT)      # Motor B IN3
pin13 = machine.Pin(13, machine.Pin.OUT)      # Motor B IN4
pwm14 = machine.PWM(machine.Pin(14))          # Motor B ENB PWM
# Sensor setup
sensor = sonar.Sonar(26, 5)                   # Trigger pin 26, Echo pin 5
# Configure PWM frequency
pwm5.freq(2000)                               # Motor A frequency
pwm14.freq(2000)                              # Motor B frequency
while True:                                   # Infinite loop
    dist = sensor.checkdist()                 # Read distance
    print("Distance:", dist, "cm")            # Serial log
    if dist < 10:                             # If obstacle very close
        pwm5.duty(0)                          # Stop motor A
        pwm14.duty(0)                         # Stop motor B
        print("STOP: Obstacle too close")     # Serial log
    elif dist < 20:                           # If obstacle moderately close
        pwm5.duty(0)                          # Stop motor A
        pwm14.duty(512)                       # Motor B forward
        print("TURN LEFT: Obstacle detected") # Serial log
        time.sleep(1)                         # Turn left
    else:                                     # If path clear
        pin2.value(1); pin4.value(0)          # Motor A forward
        pin12.value(1); pin13.value(0)        # Motor B forward
        pwm5.duty(512); pwm14.duty(512)       # Motors ON
        print("GO: Path clear")               # Serial log
    time.sleep(0.2)                           # Delay for stability

Reflection: Robot stops if obstacle is too close, turns if moderately close, and moves forward otherwise.
Challenge: Add right turn option for variety.

✨ Main Project – Obstacle Avoidance

🔧 Blocks Steps (with glossary)

  • External sensor: Detect distance.
  • Logic: Decide stop, turn, or go.
  • Motor control: Execute movement.
  • Loop: Continuous navigation.

Block sequence:

  1. Setup motors and sensor.
  2. Read distance.
  3. Stop if too close.
  4. Turn if moderately close.
  5. Move forward if clear.

📖 External Explanation

This project shows how robots avoid obstacles using sensors.

  • Ultrasonic sensor measures distance.
  • Logic decides whether to stop, turn, or go.
  • Motors execute the decision.
    This is the foundation of autonomous navigation.

✨ Story Time

Imagine your robot as an explorer 🛤️. It moves forward until it sees a wall. If the wall is too close, it stops. If it’s near but not too close, it turns left to find a new path. If the way is clear, it continues its journey.

🕵️ Debugging (2 Common Problems)

🐞 Debugging 1.12.A – Sensor always reads 0

Problem: Distance always 0 cm.
Clues: Echo pin not connected.
Broken code/wiring:

sensor = sonar.Sonar(26, 0)   # Wrong echo pin

Fixed code:

sensor = sonar.Sonar(26, 5)   # Correct echo pin

Why it works: Correct wiring ensures sensor reads properly.

🐞 Debugging 1.12.B – Robot spins endlessly

Problem: Motors keep turning even when path is clear.
Clues: Duty cycle not reset.
Broken code:

elif dist < 20:
    pwm5.duty(0)
    pwm14.duty(512)
# Missing reset after turn

Fixed code:

elif dist < 20:
    pwm5.duty(0)
    pwm14.duty(512)
    time.sleep(1)
    pwm5.duty(512); pwm14.duty(512)   # Reset speeds

Why it works: Resetting duty cycles restores forward motion.

✅ Final Checklist

  • Sensor reads distance.
  • Robot stops at close obstacles.
  • Robot turns at moderate obstacles.
  • Robot moves forward when clear.
  • Continuous navigation works.

📚 Extras

  • 🧠 Student tip: Try different thresholds (10 cm, 30 cm).
  • 🧑‍🏫 Instructor tip: Show how sensor readings change with hand movement.
  • 📖 Glossary: Sonar, trigger, echo, threshold.
  • 💡 Mini tip: Always test sensor separately before combining with motors.
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