Lesson 5: Conditionals (Teacher Notes)

This is the teacher guide for Lesson 5.
It includes lesson flow, strategies, and example logic using if / else statements.

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Learning Objectives

• Students understand how conditionals (if / else) work
• Students can use comparison operators such as >, <, and =
• Students can change behavior based on input (buttons)
• Students can change behavior based on movement (acceleration speed)

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Suggested Lesson Flow

1. Introduction (5 mins)

• Ask: “How does a computer make a decision?” (e.g., traffic lights, video games, speed cameras)
• Explain that an if / else statement helps the Micro:bit decide what to do
• Introduce the term condition (a question with a true/false answer)

Examples:

• IF it is raining → take an umbrella
• IF speed > limit → show warning

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2. Demonstration (5–7 mins)

On the board or projector, demonstrate:

• Where to find if / else in the Logic toolbox
• Where to find acceleration (strength) in the Input toolbox
• Creating this condition:

acceleration (strength) > 800

Inside the condition:

• IF true → show Sad icon 😞
• ELSE → show Happy icon 🙂

Explain:

• The Micro:bit constantly measures how fast it is moving
• It checks the condition and chooses what to do

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3. Student Activity (15–20 mins)

Students must:

1. Add on shake block
2. Put an if / else inside
3. Use this condition:

acceleration (strength) > 800

1. Add icons:
   • IF → Sad face
   • ELSE → Happy face

Then add a second conditional:

• On button A pressed → check speed
• IF → show “FAST”
• ELSE → show “SLOW”

Encourage students to test:

• Gentle movement
• Strong shaking
• Completely still

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4. Extension / Fast Finishers

Challenge students to:

• Change the threshold number
• Add Button B to do the opposite
• Play a warning sound if speed is too high
• Use a double condition:

if speed > 800 AND button B is pressed

Optional real-world links:

• Car speed warning systems
• Automatic doors
• Alarm systems

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Common Issues & Fixes

Problem	Fix
Icons don’t change	Make sure the if / else is inside on shake or on button A
Always shows same icon	Student may have used < instead of > or wrong number
Nothing happens	Check they used acceleration (strength) not direction
Too sensitive / not sensitive	Adjust number to 400 / 1200

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Example Code (JavaScript)

input.onGesture(Gesture.Shake, function () {
    if (input.acceleration(Dimension.Strength) > 800) {
        basic.showIcon(IconNames.Sad)
    } else {
        basic.showIcon(IconNames.Happy)
    }
})

input.onButtonPressed(Button.A, function () {
    if (input.acceleration(Dimension.Strength) > 800) {
        basic.showString("FAST")
    } else {
        basic.showString("SLOW")
    }
})

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Reflection (Teacher Prompts)

• Where do we use conditionals in everyday life?
• Why is decision-making important in programming?
• How could this be used in a safety system or a game?