💡 Level 1 – Fundamentals
Project 1.9: "Speed Control"
🚀 Project 1.9 – Speed Control
🎯 What You’ll Learn
- ✅ Goal 1: Control motor speed gradually.
- ✅ Goal 2: Create smooth acceleration and variable speed curves.
- ✅ Goal 3: Simulate terrain changes with automatic speed adjustment.
Key Ideas
- PWM duty cycle: Controls motor speed.
- Loops: Change speed step by step.
- Logic: Adjust speed based on conditions.
🧱 Blocks Glossary (used in this project)
pwmX = machine.PWM(machine.Pin(X))→ Motor speed control.pwmX.freq(2000)→ Set PWM frequency.pwmX.duty(value)→ Set duty cycle (0–1023).pinX = machine.Pin(X, machine.Pin.OUT)→ Motor direction.pinX.value(1)→ Forward.pinX.value(0)→ Backward.time.sleep()→ Delay.for i in range(...)→ Loop for gradual changes.
🧰 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 |
🔌 Wiring tip: Motor A = pins 2/4/5, Motor B = pins 12/13/14.
✅ Before You Start
- USB cable connected
- Motors wired correctly
- Test print shows:
print("Ready!") # Confirm serial is working
🎮 Microprojects (5 Mini Missions)
🎮 Microproject 1.9.1 – Gradual speed
Blocks used: PWM, Loop, Delay
Block sequence:
- Setup motor PWM
- Increase duty cycle step by step
- Observe gradual speed
MicroPython Code:
import machine, time # Import modules
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
pwm5.freq(2000) # Set PWM frequency to 2 kHz
pin2.value(1) # Motor A forward IN1 HIGH
pin4.value(0) # Motor A forward IN2 LOW
for duty in range(0, 1024, 128): # Loop from 0 to 1023 step 128
pwm5.duty(duty) # Set duty cycle
print("Motor speed duty:", duty) # Serial log
time.sleep(0.5) # Delay for observation
Reflection: Motor speed increases gradually.
Challenge: Try smaller steps (64) for smoother acceleration.
🎮 Microproject 1.9.2 – Smooth acceleration
Blocks used: PWM, Loop, Delay
Block sequence:
- Setup motor PWM
- Increase duty cycle slowly
- Create smooth acceleration
MicroPython Code:
import machine, time # Import modules
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
pwm14.freq(2000) # Set PWM frequency to 2 kHz
pin12.value(1) # Motor B forward IN3 HIGH
pin13.value(0) # Motor B forward IN4 LOW
for duty in range(0, 1024, 64): # Loop from 0 to 1023 step 64
pwm14.duty(duty) # Set duty cycle
print("Motor B speed duty:", duty) # Serial log
time.sleep(0.3) # Delay for smoother acceleration
Reflection: Motor accelerates smoothly.
Challenge: Try decreasing duty for smooth deceleration.
🎮 Microproject 1.9.3 – Variable speed curves
Blocks used: PWM, Loop, Delay
Block sequence:
- Setup motor PWM
- Alternate duty cycles
- Create speed curve pattern
MicroPython Code:
import machine, time # Import modules
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
pwm5.freq(2000) # Set PWM frequency
pin2.value(1) # Motor A forward
pin4.value(0) # Motor A forward
curve = [256, 512, 768, 1023, 512, 256] # Speed curve values
for duty in curve: # Loop through curve
pwm5.duty(duty) # Set duty cycle
print("Curve duty:", duty) # Serial log
time.sleep(0.5) # Delay
Reflection: Motor follows variable speed curve.
Challenge: Try designing your own curve.
🎮 Microproject 1.9.4 – Simulated distance control
Blocks used: PWM, Loop, Delay
Block sequence:
- Setup motor PWM
- Run at different speeds for “distance”
- Stop after loop
MicroPython Code:
import machine, time # Import modules
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
pwm14.freq(2000) # Set PWM frequency
pin12.value(1) # Motor B forward
pin13.value(0) # Motor B forward
for duty in [256, 512, 768]: # Different speeds
pwm14.duty(duty) # Set duty cycle
print("Motor B duty:", duty) # Serial log
time.sleep(2) # Run for 2 seconds
pwm14.duty(0) # Stop motor
print("Motor stopped") # Serial log
Reflection: Motor simulates distance with speed changes.
Challenge: Try longer times for each speed.
🎮 Microproject 1.9.5 – Automatic speed by “terrain”
Blocks used: PWM, Logic, Delay
Block sequence:
- Setup motor PWM
- If terrain = flat → medium speed
- If terrain = hill → high speed
MicroPython Code:
import machine, time # Import modules
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
pwm5.freq(2000) # Set PWM frequency
pin2.value(1) # Motor A forward
pin4.value(0) # Motor A forward
terrain = "hill" # Simulated terrain
if terrain == "flat": # If terrain is flat
pwm5.duty(512) # Medium speed
print("Flat terrain: duty 512") # Serial log
elif terrain == "hill": # If terrain is hill
pwm5.duty(768) # Higher speed
print("Hill terrain: duty 768") # Serial log
time.sleep(3) # Run for 3 seconds
pwm5.duty(0) # Stop motor
print("Motor stopped") # Serial log
Reflection: Motor speed changes with terrain condition.
Challenge: Add more terrain types.
✨ Main Project – Speed Control
🔧 Blocks Steps (with glossary)
- PWM: Control motor speed.
- Loops: Gradual changes.
- Logic: Adjust speed by conditions.
Block sequence:
- Setup motors with PWM.
- Gradually increase speed.
- Smooth acceleration.
- Variable curves.
- Terrain simulation.
🐍 MicroPython Code (mirroring blocks)
# Project 1.9 – Speed Control
import machine, time # Import required 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
# Configure PWM frequency
pwm5.freq(2000) # Set PWM frequency for motor A
print("Motor A PWM freq: 2000 Hz") # Serial log
pwm14.freq(2000) # Set PWM frequency for motor B
print("Motor B PWM freq: 2000 Hz") # Serial log
# Forward direction for both motors
pin2.value(1) # Motor A forward
pin4.value(0) # Motor A forward
pin12.value(1) # Motor B forward
pin13.value(0) # Motor B forward
print("Motors set to forward") # Serial log
# Gradual speed increase
for duty in range(0, 1024, 128): # Loop from 0 to 1023 step 128
pwm5.duty(duty) # Motor A duty cycle
pwm14.duty(duty) # Motor B duty cycle
print("Duty cycle:", duty) # Serial log
time.sleep(0.5) # Delay
# Smooth acceleration
for duty in range(0, 1024, 64): # Smaller steps for smoothness
pwm5.duty(duty) # Motor A duty cycle
pwm14.duty(duty) # Motor B duty cycle
print("Smooth duty:", duty) # Serial log
time.sleep(0.3) # Delay
# Variable speed curve
curve = [256, 512, 768, 1023, 512, 256] # Curve values
for duty in curve: # Loop through curve
pwm5.duty(duty) # Motor A duty cycle
pwm14.duty(duty) # Motor B duty cycle
print("Curve duty:", duty) # Serial log
time.sleep(0.5) # Delay
# Terrain simulation
terrain = "hill" # Simulated terrain
if terrain == "flat": # If terrain is flat
pwm5.duty(512) # Medium speed
pwm14.duty(512) # Medium speed
print("Flat terrain: duty 512") # Serial log
elif terrain == "hill": # If terrain is hill
pwm5.duty(768) # Higher speed
pwm14.duty(768) # Higher speed
print("Hill terrain: duty 768") # Serial log
time.sleep(3) # Run for 3 seconds
pwm5.duty(0) # Stop motor A
pwm14.duty(0) # Stop motor B
print("Motors stopped") # Serial log
📖 External Explanation
This project shows how PWM controls motor speed.
- Gradual increase teaches duty cycle basics.
- Smooth acceleration uses smaller steps.
- Curves simulate speed profiles.
- Terrain logic shows conditional control.
✨ Story Time
Imagine your robot as a car 🚗. On a flat road, it cruises at medium speed. On a hill, it accelerates harder. By programming speed curves, you choreograph how your robot “feels” the terrain.
🕵️ Debugging (2 Common Problems)
🐞 Debugging 1.9.A – Speed does not change
Problem: Motor runs at same speed.
Clues: Duty cycle not updated.
Broken code:
pwm5.duty(512) # Always same duty
Fixed code:
for duty in range(0, 1024, 128):
pwm5.duty(duty)
Why it works: Loop updates duty cycle step by step.
Avoid next time: Always use loops for gradual changes.
🐞 Debugging 1.9.B – Sudden movement
Problem: Motor jumps to high speed.
Clues: Duty cycle set too high at once.
Broken code:
pwm14.duty(1023) # Max speed instantly
Fixed code:
for duty in range(0, 1024, 64):
pwm14.duty(duty)
Why it works: Smaller increments create smooth acceleration.
Avoid next time: Use gradual loops instead of single max duty.
✅ Final Checklist
- Gradual speed increase works.
- Smooth acceleration implemented.
- Variable speed curves tested.
- Terrain simulation logic applied.
- Motors stop correctly.
📚 Extras
- 🧠 Student tip: Try designing your own speed curve.
- 🧑🏫 Instructor tip: Show how duty cycle values map to speed.
- 📖 Glossary: PWM, duty cycle, acceleration, terrain simulation.
- 💡 Mini tip: Always test with small duty values before max speed.