Micro:bit Stopwatch

Overview

Students build and test a simple stopwatch on a micro:bit that counts up each time button A is pressed. The lesson emphasizes clear writing and organized thinking about variables, inputs, outputs, and how the program logic works.

Learning intentions

Students will be able to:

• write an organized explanation of a micro:bit stopwatch (topic sentences, categories, and clear formatting).
• represent the stopwatch time relationship using an equation with variables.
• evaluate expressions to predict stopwatch behavior at specific counts.
• use a simple program structure: start/stop logic driven by button presses.

Success criteria

Students can:

• produce a short, structured “How it works” writing piece with headings and a simple table.
• define variables (such as t for time) and write an equation using at least one operation.
• compute the expected time for given button-press counts using evaluation.
• demonstrate the stopwatch by pressing button A to start counting up correctly.

Curriculum links

• Writing — WHST.6-8.2a: Introduce a topic, preview what follows, organize ideas, and include formatting/graphics to aid comprehension.
• Math — 6.EE.C.9: Use variables for changing quantities in a real-world problem; write an equation and relate it to graphs/tables.
• Math — 6.NS.A.1: Interpret and compute quotients in fraction word problems (used here as an optional “time per tick” check if using fractional timing).
• Math — 6.EE.A.2a and 6.EE.A.2c: Write expressions with letters and evaluate expressions at specific values (used to predict counts/ticks).

Lesson structure ({total minutes})

1. 0–5 min · Hook & goal check. Teacher displays the micro:bit stopwatch concept (start counting on button A) and asks, “What does the program do step-by-step when you press A?” Students do a quick think-pair-share and jot two predictions.

2. 5–12 min · Mini direct teach: variables + logic. Teacher introduces t (elapsed time in seconds) and n (number of increments/ticks) and shows how a counting program increases a value over time; teacher models writing an equation like t = k·n (where k is seconds per tick). Students copy the variables and complete a one-sentence logic summary: “When A is pressed, the program starts increasing ___.”

3. 12–25 min · Build time: program stopwatch. Teacher demonstrates the blocks/program structure: initialize a counter, on button A press start/continue counting up, and show the number on the micro:bit display (or via a variable displayed/output). Students build their own stopwatch in pairs, using a “Stopwatch Checklist” visible to the class: correct start, counting up, clear reset behavior (students decide a reset action such as pressing A again or using button B depending on teacher’s chosen setup).

4. 25–33 min · Math check: predict using equations. Teacher gives a short worksheet prompt: if each tick is k = 0.5 seconds and a student expects n = 6 increments, ask for t = k·n. Students evaluate expressions at given variable values, then add the results to a small table titled “Counts vs. Time.”

5. 33–40 min · Writing workshop: “How it works.” Teacher models the writing plan using headings: “Goal,” “Input,” “Process,” “Output,” plus a small table or graphic. Students draft their explanation using sentence starters provided (topic sentence + organized categories). Teacher circulates, checking that students include formatting and preview what they will explain.

6. 40–45 min · Share-out & exit ticket. Teacher selects 2–3 pairs to demonstrate their stopwatch while a partner reads the “Output” paragraph aloud. Students complete a quick exit ticket: “Write the equation you used (or the one you would use) and evaluate it for one value.” Collect for next-day grouping.

Resources

• micro:bit devices (1 per student pair) with battery/USB access
• micro:bit computers/tablets for programming
• prepared starter project files (stopwatch template) or block screenshots
• “Stopwatch Checklist” handout
• “Counts vs. Time” table worksheet
• “How it works” writing organizer with headings
• timer/stopwatch reference demo video (optional, played offline)
• student notebooks or lab sheets

Assessment

• During building: teacher observes whether button A triggers counting up and whether the counter displays/upgrades correctly.
• During math check: collect the table/equation responses to confirm correct variable use and evaluation.
• During writing: use a quick rubric (topic sentence, organized headings/categories, includes a table/graphic, clear process description).
• Exit ticket: verify equation + one evaluated prediction.

Differentiation

• Support: provide sentence starters for writing (“The purpose of my program is…”, “When button A is pressed…”, “The output shows…”); provide a partially filled variable/equation example.
• Support: offer two “reset options” (press A again to stop or press B to reset) so students choose what fits their understanding.
• Extension: students who finish early add a second behavior (button B to reset to 0, or button A to toggle start/stop) and include a second equation for the reset state (e.g., t = 0 after reset).
• EAL/SEN: allow oral rehearsal of the writing sections with a partner before drafting; allow word bank use (start, count up, display, reset, variable).