💡 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:

Setup sonar sensor
Read distance
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:

Setup motors forward
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:

Setup motors forward
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:

Forward until obstacle
Turn left
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:

If distance < 10 cm → stop
If distance < 20 cm → turn left
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:

Setup motors and sensor.
Read distance.
Stop if too close.
Turn if moderately close.
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.