Arduino Learning Studiorobotics pathway

R11-U4 · usually age 11 · Robot Explorers

Robot Trail Mission

Can our rover handle an unfamiliar path?

Pilot unit plan · 5 sessions · not yet classroom-validated

Build: Line-following rescue rover

A rescue trail the team has never seen: the rover must follow an unfamiliar multi-turn course to a rescue point. Learners work in teams of four (two pairs, one rover) with roles (driver, safety lead, recorder, troubleshooter), practise on their own course, hunt planted faults one check at a time, and document every trial so that another team could follow it.

  • Sense
  • Decide
  • Act
  • Test and debug

Who it is for

Age is a starting point, never a limit. A learner who can show what this unit starts from can begin here at any age.

How they learn
By arranging instruction cards or blocks, predicting what happens, and testing on a kit. Short sentences, with words and pictures together.
The adult's role
An adult oversees circuits, batteries and motors.
Session
60–75 minutes
Hardware
micro:bit with MakeCode, or a similar child-friendly board. Start in the board's own simulator. A micro:bit is 3.3 V: never connect a 5 V signal straight to it.

Starts from

Builds, and what it is the input for

In the studio today

No studio lab or activity for this unit yet.

Sessions

  1. Session 1 · 60 min

    How will our team take on a course we have never seen?

    The mission: The mission course is unfamiliar: the adult lays it on new paper, with at least three turns both ways, and keeps it covered until session 4. It is never the training mat or a course the team practised on. The team plans how to meet it: roles that take turns, a troubleshooting sheet that checks one thing at a time, and a trial log that someone else could follow. Integration is a need: the sensors, the steering and the stops already work together.

    The adult says first: “A new course, never seen. Plan your roles. Plan your records.”

    Learner card

    1. Pick your first role.
    2. Roles swap every trial.
    3. Check one thing at a time.
    4. Write so others can follow.
    5. The course stays covered.

    Key words (show each with a picture): mission · role · document

    Timing (10 of 60 min at the screen)

    1. 10 minAway from the screen: The mission and the covered course; share out the role cards.
    2. 15 minAway from the screen: Write the troubleshooting sheet: one check at a time.
    3. 10 minAway from the screen: Draw a trial log another team could follow.
    4. 10 minAt the screen: Read the blocks aloud in the simulator; what does each one do?
    5. 15 minAway from the screen: Fill in the table; say how the team will document its trials.

    In the studio

    No studio lab or activity.

    Outside the studio: MakeCode editor and its micro:bit simulator (makecode.microbit.org)

    Hands-on

    Nothing is powered: this session uses role cards, paper and the simulator only. First, away from the screen, the adult reads the mission and shows the rule: the course stays covered. The team shares out four role cards: driver (predicts each trial and, at the adult's word, presses A; never places, lifts or touches a switched-on rover, and never presses B), safety lead (runs the safety checks and calls “Stop!”), recorder (writes the trial log) and troubleshooter (keeps the troubleshooting sheet); the roles swap each trial. The team writes its troubleshooting sheet: for each symptom, the checks in order, one at a time (the sign, the stand check, the sensor numbers, the threshold, the speed, the detector's height, the wires with the power off, the cells). It draws a trial log another team could follow. In MakeCode next, the learner reads their blocks aloud to the team, from “on start” down. In the simulator, each sensor pin the blocks read shows a number from 0 to 1023 that starts at 0; drag the pin up for a bigger number. It is a stand-in you set: the simulator cannot see a mat or a line. The team agrees what each block does.

    Starting blocks: The learner's own blocks from R11-U3, with the better setting.

    Evidence to collect

    A prediction for each role's hardest moment, the learner's own short test table (Role | My guess | What I check) for the four roles, and the learner's spoken explanation of how the team will document trials so another team can follow them.

    Test table columns: Role | My guess | What I check

    Predict
    For each role, the learner guesses the hardest moment, and what they will check then.
    Debug
    If the team cannot agree on a check, write both and test them one at a time later.
    Reflect
    Why does a trial log need to make sense to someone who was not there?

    Works towards: Documenting

  2. Session 2 · 75 min

    Can our records tell someone else what we did?

    Documented practice: on a practice course the team lays itself (three turns, one each way at least), every trial is logged with what changed, the guess and what happened. One change between trials, and the reason written down. This course is the team's own, not the mission course.

    The adult says first: “Every trial goes in the log. Someone else must be able to follow it.”

    Learner card

    1. Lay three turns or more.
    2. One change between trials.
    3. Write the reason down.
    4. Swap roles each trial.
    5. Can another team follow it?

    Key words (show each with a picture): log · trial · change

    Timing (10 of 75 min at the screen)

    1. 15 minAway from the screen: Lay the practice course: a start box, three turns, an end.
    2. 5 minAt the screen: The R11-U3 blocks in the simulator; download.
    3. 15 minAway from the screen: First turns, one team at a time (about 6 minutes each, three trials): documented, roles swapping.
    4. 5 minAt the screen: At most one change, with its reason; the simulator, then download.
    5. 15 minAway from the screen: Second turns (about 5 minutes each, two trials): documented, roles swapping.
    6. 20 minAway from the screen: Another team reads the log: what could it repeat?

    In the studio

    No studio lab or activity.

    Outside the studio: MakeCode editor and its micro:bit simulator (makecode.microbit.org)

    Hands-on

    First, away from the screen, the team lays its practice course on paper with black tape 10 to 20 mm wide: a start box, three turns and an end, with no loops, junctions or crossings. In the simulator next, the learner checks the R11-U3 blocks; then the learner downloads them (the board switched off, the micro:bit out of the board, USB in; USB out once the light on the back stops flashing, the micro:bit back in). The safety lead runs the checks. At each turn, the stop drill; with the rover on its stand the adult switches on and checks the sign (the No icon: the line program). The stand check: at the adult's word the learner presses A and steps back, and the adult slides the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait, or the rover stays on the stand and the adult switches off to check the middle sensor. With the program waiting for A, the adult carries the rover by its chassis from the stand to the start box and sets it down. Five trials over two turns, roles swapping each trial: at the adult's word the driver presses A and steps back outside the tape; only the adult presses B; the recorder logs the change made, the guess and what happened, and the troubleshooter writes any check made. First turn: three trials. Between the turns, at most one change, tried in the simulator and downloaded the same way, with its reason written. Second turn: two trials. Last, another team reads the log aloud and says what it could repeat.

    Starting blocks: The learner's own blocks from R11-U3, with the better setting.

    Pins

    P0
    left line sensor
    P1
    middle line sensor
    P2
    right line sensor

    Evidence to collect

    A prediction for each trial, the learner's own short test table (Trial | Change made | My guess | What happened) for five trials, and the learner's spoken or written explanation of what another team could and could not repeat from their log.

    Test table columns: Trial | Change made | My guess | What happened

    Predict
    Before each trial, the driver says pass or fail and where it may struggle.
    Debug
    If the log cannot say why a trial changed, add a column or a sentence: what changed, and why.
    Reflect
    What did the other team need from your log that was missing?

    ⚠ Adult checks before power-on: Nothing metal touches the micro:bit, its gold pins or the board, and nothing metal lies under it. Before the adult switches on: the micro:bit is firmly in the board, display facing the Link header, its own battery pack and USB unplugged; both switches were off while anything was plugged in or moved. The board's battery is the motor battery: it reaches the motors only through the holder's switch, the board's on/off switch (the power-off switch) and its Motor 1 and Motor 2 terminals. The power-off switch is the board's on/off switch: it cuts the battery to the board, the micro:bit and every motor and servo. Anyone may switch it off at any time; only the adult switches it on. The battery holder rides on the rover, tied down: only the adult opens it, fits cells or works its switch. Safe start: the motors never run just because the board was switched on. “on start” turns them off; only A starts them, after a 3-second wait, and B stops them: a B during the wait clears armed, which A checks after the wait, so the drive never starts. Lift first: the board is switched on only with the rover on its stand, wheels in the air, because a mistake in the blocks could start a wheel at once. On the stand, the board's switch faces the adult, who stands at it; learners stay outside a zone taped 30 cm round the stand. Buttons on a switched-on rover: a learner presses only A, only at the adult's word and only while every wheel is still, with one hand on the micro:bit, nowhere near a wheel, and is back outside the taped edge before the 3-second wait ends. B, the switch, and lifting, carrying or placing a switched-on rover are the adult's: on the floor only the adult presses B. Every program shows its own sign at start, and the adult checks it on the stand before the rover leaves it: the drive program (R11-U1) a Heart, the reading program a sensor number, the line program the No icon. A rover showing the wrong sign does not go on the floor. Fingers, hair, sleeves and cords stay away from the wheels while the board is on; long hair is tied back. The rover is lifted only by its chassis. Floor speed limit: the rover's speed numbers are never above 40 (of 100), a planning choice. Practise the stop before every switch-on: the adult is the stopper. On “Stop!”, the adult switches the board off (on the floor, lifting the rover by its chassis first); learners call “Stop!” from outside the taped zone and never reach for the rover. Rewire only when unpowered: the board and the holder are switched off before any wire, motor, servo or sensor is plugged in, moved or taken out. Never leave a lead loose while the board is on: switch off first; a lead taken out is capped and taped away from the board. The line sensor is a Kitronik Clippable Detector Board, rated 2 V to 5.5 V and powered only from the Link header's 3V pin, so its outputs come from 3.3 V; never from 5 V. Kitronik gives the detector's current as 54 mA at 3 V. At the header's 3.3 V it will draw a little more (about 60 mA if it rises in step with the voltage, an estimate), still under the header's 90 mA. The detector's leads, checked before every switch-on: its 3V lead goes to the Link header's 3V pin, never to a servo header's V pin. The board marks each servo header ‘GND V SIG’, and its V pin carries the battery's voltage (the datasheet: the servo outputs ‘Provide supply voltage to servos’), above the detector's 5.5 V and far above the micro:bit's 3.6 V. All five leads are tied down to the chassis and each one given a gentle tug. No music blocks in these units: MakeCode plays music through pin P0, where the left line sensor is. Before every floor turn, on the stand: A, then the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait. If it does not, the rover stays on the stand and the adult switches off to check the middle sensor and its wire. The lost-line stop: if the middle sensor sees no line for 20 passes of the loop in a row (each pass waits 100 ms, so about 2 seconds), the rover stops by itself. B stops the motors too. The run time-out: a second counter, passes, that A sets to 0 and every pass of the loop adds 1 to; at 300 passes (about 30 seconds, a little more in practice) the rover stops by itself wherever it is, even if a sensor has failed and reads dark all the time. 300 is a planning choice, sized to the plans' courses, where a good run at 30 takes under 20 seconds. Every course ends: the line stops at an end, with no loops, junctions or crossings, so a rover that keeps finding a line cannot circle for ever. The adult times a good run on each new course: if it takes 20 seconds or more, the course is made shorter. A switched-on rover that is not showing the No icon is live: it may be driving or about to drive. Hands off; the adult stays beside its switch. Stall or runaway: if a wheel is blocked, the rover pushes against anything, a motor hums without turning or the rover leaves the mat, call “Stop!” at once. Floor runs happen only in a cleared area with adults present: at least 1 m clear round the mat, learners outside its taped edge, one rover at a time per adult, who walks beside it.

    Works towards: Documenting

  3. Session 3 · 75 min

    Can we find a fault one check at a time?

    Troubleshooting: the adult plants one fault in each rover, with everything switched off, and the team finds it with its sheet, one check at a time, documenting each check and its result. Finding faults is a need: the new part is writing the hunt down so another team could follow it.

    The adult says first: “Something is wrong on purpose. Find it, one check at a time.”

    Learner card

    1. Write what you see.
    2. Read the next check.
    3. Guess, then check.
    4. Wires only with power off.
    5. Log every check.

    Key words (show each with a picture): symptom · check · fault

    Timing (10 of 75 min at the screen)

    1. 10 minAway from the screen: Read the troubleshooting sheet; guess which check finds most faults.
    2. 15 minAway from the screen: Round 1, one team at a time (about 7 minutes each, one trial): the stand check, one run, one check at a time.
    3. 5 minAt the screen: Any fix in the blocks: the simulator, then download.
    4. 15 minAway from the screen: Round 2, roles swapped (about 7 minutes each, one trial).
    5. 5 minAt the screen: Any fix in the blocks: the simulator, then download.
    6. 15 minAway from the screen: Round 3, roles swapped (about 7 minutes each, one trial).
    7. 10 minAway from the screen: Fill in the table; improve the sheet.

    In the studio

    No studio lab or activity.

    Outside the studio: MakeCode editor and its micro:bit simulator (makecode.microbit.org)

    Hands-on

    Before each round, with the board and the holder switched off, the adult plants one fault: the P0 and P2 wires swapped on the header; a wrong threshold in the blocks; one speed number set to 0; the detector moved from the height written on the chassis. None of them is unsafe. At each turn, the stop drill; with the rover on its stand the adult switches on and checks the sign (the No icon: the line program). The stand check: at the adult's word the learner presses A and steps back, and the adult slides the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait, or the rover stays on the stand and the adult switches off to check the middle sensor. With the program waiting for A, the adult carries the rover by its chassis from the stand to the start box and sets it down. If the stand check fails, that is the symptom, and the rover stays on the stand. Otherwise the team watches one run on the practice course: at the adult's word the driver presses A and steps back outside the tape; only the adult presses B. The recorder writes the symptom; the troubleshooter reads the next check on the sheet; each check is predicted, made and logged (a check of wires or the detector only with the board switched off). In the simulator, any fix in the blocks is checked first, then downloaded (the board switched off, the micro:bit out of the board, USB in; USB out once the light on the back stops flashing, the micro:bit back in). Three rounds, roles swapping.

    Starting blocks: The learner's own blocks from session 2, with any planted fault the adult put in.

    Pins

    P0
    left line sensor
    P1
    middle line sensor
    P2
    right line sensor

    Evidence to collect

    A prediction for each check, the learner's own short test table (Symptom | Check made | My guess | Found?) for three planted faults, and the learner's spoken or written explanation of how the sheet led them to each fault, one check at a time.

    Test table columns: Symptom | Check made | My guess | Found?

    Predict
    Before each check, the troubleshooter says what the check will show if it is the fault.
    Debug
    If two checks changed at once, put both back and make them again one at a time: otherwise the log cannot say which one fixed it.
    Reflect
    Which check on your sheet should come first next time, and why?

    ⚠ Adult checks before power-on: Nothing metal touches the micro:bit, its gold pins or the board, and nothing metal lies under it. Before the adult switches on: the micro:bit is firmly in the board, display facing the Link header, its own battery pack and USB unplugged; both switches were off while anything was plugged in or moved. The board's battery is the motor battery: it reaches the motors only through the holder's switch, the board's on/off switch (the power-off switch) and its Motor 1 and Motor 2 terminals. The power-off switch is the board's on/off switch: it cuts the battery to the board, the micro:bit and every motor and servo. Anyone may switch it off at any time; only the adult switches it on. The battery holder rides on the rover, tied down: only the adult opens it, fits cells or works its switch. Safe start: the motors never run just because the board was switched on. “on start” turns them off; only A starts them, after a 3-second wait, and B stops them: a B during the wait clears armed, which A checks after the wait, so the drive never starts. Lift first: the board is switched on only with the rover on its stand, wheels in the air, because a mistake in the blocks could start a wheel at once. On the stand, the board's switch faces the adult, who stands at it; learners stay outside a zone taped 30 cm round the stand. Buttons on a switched-on rover: a learner presses only A, only at the adult's word and only while every wheel is still, with one hand on the micro:bit, nowhere near a wheel, and is back outside the taped edge before the 3-second wait ends. B, the switch, and lifting, carrying or placing a switched-on rover are the adult's: on the floor only the adult presses B. Every program shows its own sign at start, and the adult checks it on the stand before the rover leaves it: the drive program (R11-U1) a Heart, the reading program a sensor number, the line program the No icon. A rover showing the wrong sign does not go on the floor. Fingers, hair, sleeves and cords stay away from the wheels while the board is on; long hair is tied back. The rover is lifted only by its chassis. Floor speed limit: the rover's speed numbers are never above 40 (of 100), a planning choice. Practise the stop before every switch-on: the adult is the stopper. On “Stop!”, the adult switches the board off (on the floor, lifting the rover by its chassis first); learners call “Stop!” from outside the taped zone and never reach for the rover. Rewire only when unpowered: the board and the holder are switched off before any wire, motor, servo or sensor is plugged in, moved or taken out. Never leave a lead loose while the board is on: switch off first; a lead taken out is capped and taped away from the board. The line sensor is a Kitronik Clippable Detector Board, rated 2 V to 5.5 V and powered only from the Link header's 3V pin, so its outputs come from 3.3 V; never from 5 V. Kitronik gives the detector's current as 54 mA at 3 V. At the header's 3.3 V it will draw a little more (about 60 mA if it rises in step with the voltage, an estimate), still under the header's 90 mA. The detector's leads, checked before every switch-on: its 3V lead goes to the Link header's 3V pin, never to a servo header's V pin. The board marks each servo header ‘GND V SIG’, and its V pin carries the battery's voltage (the datasheet: the servo outputs ‘Provide supply voltage to servos’), above the detector's 5.5 V and far above the micro:bit's 3.6 V. All five leads are tied down to the chassis and each one given a gentle tug. No music blocks in these units: MakeCode plays music through pin P0, where the left line sensor is. Before every floor turn, on the stand: A, then the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait. If it does not, the rover stays on the stand and the adult switches off to check the middle sensor and its wire. The lost-line stop: if the middle sensor sees no line for 20 passes of the loop in a row (each pass waits 100 ms, so about 2 seconds), the rover stops by itself. B stops the motors too. The run time-out: a second counter, passes, that A sets to 0 and every pass of the loop adds 1 to; at 300 passes (about 30 seconds, a little more in practice) the rover stops by itself wherever it is, even if a sensor has failed and reads dark all the time. 300 is a planning choice, sized to the plans' courses, where a good run at 30 takes under 20 seconds. Every course ends: the line stops at an end, with no loops, junctions or crossings, so a rover that keeps finding a line cannot circle for ever. The adult times a good run on each new course: if it takes 20 seconds or more, the course is made shorter. A switched-on rover that is not showing the No icon is live: it may be driving or about to drive. Hands off; the adult stays beside its switch. Stall or runaway: if a wheel is blocked, the rover pushes against anything, a motor hums without turning or the rover leaves the mat, call “Stop!” at once. Floor runs happen only in a cleared area with adults present: at least 1 m clear round the mat, learners outside its taped edge, one rover at a time per adult, who walks beside it.

    Works towards: Documenting

  4. Session 4 · 75 min

    What happens on a course we have never seen?

    The mission course, uncovered: The mission course is unfamiliar: the adult lays it on new paper, with at least three turns both ways, and keeps it covered until session 4. It is never the training mat or a course the team practised on. The team walks it first, predicts where the rover will struggle, then runs documented trials, with at most one change between trials, each change and its reason logged.

    The adult says first: “Here is the course you have never seen. Walk it. Then run it.”

    Learner card

    1. Walk beside the course first.
    2. Mark where it is hard.
    3. Guess how far it gets.
    4. One change between trials.
    5. Every trial counts.

    Key words (show each with a picture): unfamiliar · course · trial

    Timing (10 of 75 min at the screen)

    1. 15 minAway from the screen: Uncover the course: walk it, draw it, mark where it is hard.
    2. 5 minAt the screen: Check the blocks in the simulator; download.
    3. 15 minAway from the screen: First turns, one team at a time (about 6 minutes each, two trials): documented, roles swapping.
    4. 5 minAt the screen: One change from the evidence; the simulator, then download.
    5. 15 minAway from the screen: Second turns (about 6 minutes each, two trials): documented, roles swapping.
    6. 20 minAway from the screen: Say where the course was hardest, and what each change did.

    In the studio

    No studio lab or activity.

    Outside the studio: MakeCode editor and its micro:bit simulator (makecode.microbit.org)

    Hands-on

    First, away from the screen, the adult uncovers the mission course; the team walks beside it, draws it, marks the turns and writes where the rover may struggle and why. In the simulator next, the learner checks the blocks, then downloads them (the board switched off, the micro:bit out of the board, USB in; USB out once the light on the back stops flashing, the micro:bit back in). The safety lead runs the checks. At each turn, the stop drill; with the rover on its stand the adult switches on and checks the sign (the No icon: the line program). The stand check: at the adult's word the learner presses A and steps back, and the adult slides the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait, or the rover stays on the stand and the adult switches off to check the middle sensor. With the program waiting for A, the adult carries the rover by its chassis from the stand to the start box and sets it down. Four trials over two turns, roles swapping each trial: at the adult's word the driver presses A and steps back outside the tape; only the adult presses B; the recorder logs the change made, the guess and what happened. First turn: two trials. Between the turns, at most one change, from the evidence, tried in the simulator and downloaded the same way. Second turn: two trials. Every trial counts.

    Starting blocks: The learner's own blocks from session 3, with every planted fault taken out.

    Pins

    P0
    left line sensor
    P1
    middle line sensor
    P2
    right line sensor

    Evidence to collect

    A prediction for each trial, the learner's own short test table (Trial | Change made | My guess | What happened) for every trial on the unfamiliar course, and the learner's spoken or written explanation of where the course was hardest and what each change did.

    Test table columns: Trial | Change made | My guess | What happened

    Predict
    Before each trial, the driver says how far along the course the rover will get.
    Debug
    If the rover fails at a new kind of turn, use the sheet: the sensor numbers on this paper first, then the speed.
    Reflect
    What did the unfamiliar course show that your own course never did?

    ⚠ Adult checks before power-on: Nothing metal touches the micro:bit, its gold pins or the board, and nothing metal lies under it. Before the adult switches on: the micro:bit is firmly in the board, display facing the Link header, its own battery pack and USB unplugged; both switches were off while anything was plugged in or moved. The board's battery is the motor battery: it reaches the motors only through the holder's switch, the board's on/off switch (the power-off switch) and its Motor 1 and Motor 2 terminals. The power-off switch is the board's on/off switch: it cuts the battery to the board, the micro:bit and every motor and servo. Anyone may switch it off at any time; only the adult switches it on. The battery holder rides on the rover, tied down: only the adult opens it, fits cells or works its switch. Safe start: the motors never run just because the board was switched on. “on start” turns them off; only A starts them, after a 3-second wait, and B stops them: a B during the wait clears armed, which A checks after the wait, so the drive never starts. Lift first: the board is switched on only with the rover on its stand, wheels in the air, because a mistake in the blocks could start a wheel at once. On the stand, the board's switch faces the adult, who stands at it; learners stay outside a zone taped 30 cm round the stand. Buttons on a switched-on rover: a learner presses only A, only at the adult's word and only while every wheel is still, with one hand on the micro:bit, nowhere near a wheel, and is back outside the taped edge before the 3-second wait ends. B, the switch, and lifting, carrying or placing a switched-on rover are the adult's: on the floor only the adult presses B. Every program shows its own sign at start, and the adult checks it on the stand before the rover leaves it: the drive program (R11-U1) a Heart, the reading program a sensor number, the line program the No icon. A rover showing the wrong sign does not go on the floor. Fingers, hair, sleeves and cords stay away from the wheels while the board is on; long hair is tied back. The rover is lifted only by its chassis. Floor speed limit: the rover's speed numbers are never above 40 (of 100), a planning choice. Practise the stop before every switch-on: the adult is the stopper. On “Stop!”, the adult switches the board off (on the floor, lifting the rover by its chassis first); learners call “Stop!” from outside the taped zone and never reach for the rover. Rewire only when unpowered: the board and the holder are switched off before any wire, motor, servo or sensor is plugged in, moved or taken out. Never leave a lead loose while the board is on: switch off first; a lead taken out is capped and taped away from the board. The line sensor is a Kitronik Clippable Detector Board, rated 2 V to 5.5 V and powered only from the Link header's 3V pin, so its outputs come from 3.3 V; never from 5 V. Kitronik gives the detector's current as 54 mA at 3 V. At the header's 3.3 V it will draw a little more (about 60 mA if it rises in step with the voltage, an estimate), still under the header's 90 mA. The detector's leads, checked before every switch-on: its 3V lead goes to the Link header's 3V pin, never to a servo header's V pin. The board marks each servo header ‘GND V SIG’, and its V pin carries the battery's voltage (the datasheet: the servo outputs ‘Provide supply voltage to servos’), above the detector's 5.5 V and far above the micro:bit's 3.6 V. All five leads are tied down to the chassis and each one given a gentle tug. No music blocks in these units: MakeCode plays music through pin P0, where the left line sensor is. Before every floor turn, on the stand: A, then the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait. If it does not, the rover stays on the stand and the adult switches off to check the middle sensor and its wire. The lost-line stop: if the middle sensor sees no line for 20 passes of the loop in a row (each pass waits 100 ms, so about 2 seconds), the rover stops by itself. B stops the motors too. The run time-out: a second counter, passes, that A sets to 0 and every pass of the loop adds 1 to; at 300 passes (about 30 seconds, a little more in practice) the rover stops by itself wherever it is, even if a sensor has failed and reads dark all the time. 300 is a planning choice, sized to the plans' courses, where a good run at 30 takes under 20 seconds. Every course ends: the line stops at an end, with no loops, junctions or crossings, so a rover that keeps finding a line cannot circle for ever. The adult times a good run on each new course: if it takes 20 seconds or more, the course is made shorter. A switched-on rover that is not showing the No icon is live: it may be driving or about to drive. Hands off; the adult stays beside its switch. Stall or runaway: if a wheel is blocked, the rover pushes against anything, a motor hums without turning or the rover leaves the mat, call “Stop!” at once. Floor runs happen only in a cleared area with adults present: at least 1 m clear round the mat, learners outside its taped edge, one rover at a time per adult, who walks beside it.

    Works towards: Documenting

  5. Session 5 · 75 min

    Can our rover complete the trail, and can others follow our records?

    The prototype, a line-following rescue rover, on the unfamiliar mission course: three final trials from the start box to the rescue point, each documented. A run passes when the rover follows the line from the start box to the end of the line without help, and the lost-line stop then stops it by itself. Then another team reads the log and repeats one trial from it: documentation works when someone else can follow it.

    The adult says first: “Three final trials. Then another team follows your log.”

    Learner card

    1. Guess each trial first.
    2. Swap roles each trial.
    3. Every result counts.
    4. Hand the log to another team.
    5. Could they follow it?

    Key words (show each with a picture): complete · documented · rescue

    Timing (5 of 75 min at the screen)

    1. 15 minAway from the screen: Read the log; choose the final setting; a guess for each trial.
    2. 5 minAt the screen: The final blocks in the simulator; download.
    3. 20 minAway from the screen: Final turns, one team at a time (about 7 minutes each, three trials): every result counts.
    4. 15 minAway from the screen: Repeat turns (about 5 minutes each, one trial): another team follows the log.
    5. 20 minAway from the screen: Explain the trail and the documents to the adult.

    In the studio

    No studio lab or activity.

    Outside the studio: MakeCode editor and its micro:bit simulator (makecode.microbit.org)

    Hands-on

    First, away from the screen, the team reads its log from session 4, chooses its final setting and writes a guess for each of three trials. In the simulator next, the learner checks the final blocks, then downloads them (the board switched off, the micro:bit out of the board, USB in; USB out once the light on the back stops flashing, the micro:bit back in). The safety lead runs the checks. At each turn, the stop drill; with the rover on its stand the adult switches on and checks the sign (the No icon: the line program). The stand check: at the adult's word the learner presses A and steps back, and the adult slides the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait, or the rover stays on the stand and the adult switches off to check the middle sensor. With the program waiting for A, the adult carries the rover by its chassis from the stand to the start box and sets it down. Three final trials on the mission course, roles swapping: at the adult's word the driver presses A and steps back outside the tape; only the adult presses B; the recorder logs each trial, and every result counts. Then another team takes the log and repeats one trial from it on this team's rover, from the stop drill and the stand check onwards, with the adult switching on and carrying as before, and says whether the log was enough. Last, the team explains its trail to the adult.

    Starting blocks: The learner's own blocks from session 4, with the final setting.

    Pins

    P0
    left line sensor
    P1
    middle line sensor
    P2
    right line sensor

    Evidence to collect

    The unit's evidence: the rover tries to complete a multi-turn course with documented trials: a prediction for each, the learner's own short test table (Trial | Change made | My guess | What happened) for three final trials on the unfamiliar course, another team's repeat of one trial from the log, and the learner's spoken or written explanation of what the documents show.

    Test table columns: Trial | Change made | My guess | What happened

    Predict
    Before each trial, the driver says pass or fail and where it may struggle.
    Debug
    If the other team cannot repeat a trial, find the missing detail in the log: the start, the setting, or the change.
    Reflect
    If a rescue team took your rover tomorrow, what would they need to read first?

    ⚠ Adult checks before power-on: Nothing metal touches the micro:bit, its gold pins or the board, and nothing metal lies under it. Before the adult switches on: the micro:bit is firmly in the board, display facing the Link header, its own battery pack and USB unplugged; both switches were off while anything was plugged in or moved. The board's battery is the motor battery: it reaches the motors only through the holder's switch, the board's on/off switch (the power-off switch) and its Motor 1 and Motor 2 terminals. The power-off switch is the board's on/off switch: it cuts the battery to the board, the micro:bit and every motor and servo. Anyone may switch it off at any time; only the adult switches it on. The battery holder rides on the rover, tied down: only the adult opens it, fits cells or works its switch. Safe start: the motors never run just because the board was switched on. “on start” turns them off; only A starts them, after a 3-second wait, and B stops them: a B during the wait clears armed, which A checks after the wait, so the drive never starts. Lift first: the board is switched on only with the rover on its stand, wheels in the air, because a mistake in the blocks could start a wheel at once. On the stand, the board's switch faces the adult, who stands at it; learners stay outside a zone taped 30 cm round the stand. Buttons on a switched-on rover: a learner presses only A, only at the adult's word and only while every wheel is still, with one hand on the micro:bit, nowhere near a wheel, and is back outside the taped edge before the 3-second wait ends. B, the switch, and lifting, carrying or placing a switched-on rover are the adult's: on the floor only the adult presses B. Every program shows its own sign at start, and the adult checks it on the stand before the rover leaves it: the drive program (R11-U1) a Heart, the reading program a sensor number, the line program the No icon. A rover showing the wrong sign does not go on the floor. Fingers, hair, sleeves and cords stay away from the wheels while the board is on; long hair is tied back. The rover is lifted only by its chassis. Floor speed limit: the rover's speed numbers are never above 40 (of 100), a planning choice. Practise the stop before every switch-on: the adult is the stopper. On “Stop!”, the adult switches the board off (on the floor, lifting the rover by its chassis first); learners call “Stop!” from outside the taped zone and never reach for the rover. Rewire only when unpowered: the board and the holder are switched off before any wire, motor, servo or sensor is plugged in, moved or taken out. Never leave a lead loose while the board is on: switch off first; a lead taken out is capped and taped away from the board. The line sensor is a Kitronik Clippable Detector Board, rated 2 V to 5.5 V and powered only from the Link header's 3V pin, so its outputs come from 3.3 V; never from 5 V. Kitronik gives the detector's current as 54 mA at 3 V. At the header's 3.3 V it will draw a little more (about 60 mA if it rises in step with the voltage, an estimate), still under the header's 90 mA. The detector's leads, checked before every switch-on: its 3V lead goes to the Link header's 3V pin, never to a servo header's V pin. The board marks each servo header ‘GND V SIG’, and its V pin carries the battery's voltage (the datasheet: the servo outputs ‘Provide supply voltage to servos’), above the detector's 5.5 V and far above the micro:bit's 3.6 V. All five leads are tied down to the chassis and each one given a gentle tug. No music blocks in these units: MakeCode plays music through pin P0, where the left line sensor is. Before every floor turn, on the stand: A, then the white end of the test card under the sensors; the No icon must come back about 2 seconds after the 3-second wait. If it does not, the rover stays on the stand and the adult switches off to check the middle sensor and its wire. The lost-line stop: if the middle sensor sees no line for 20 passes of the loop in a row (each pass waits 100 ms, so about 2 seconds), the rover stops by itself. B stops the motors too. The run time-out: a second counter, passes, that A sets to 0 and every pass of the loop adds 1 to; at 300 passes (about 30 seconds, a little more in practice) the rover stops by itself wherever it is, even if a sensor has failed and reads dark all the time. 300 is a planning choice, sized to the plans' courses, where a good run at 30 takes under 20 seconds. Every course ends: the line stops at an end, with no loops, junctions or crossings, so a rover that keeps finding a line cannot circle for ever. The adult times a good run on each new course: if it takes 20 seconds or more, the course is made shorter. A switched-on rover that is not showing the No icon is live: it may be driving or about to drive. Hands off; the adult stays beside its switch. Stall or runaway: if a wheel is blocked, the rover pushes against anything, a motor hums without turning or the rover leaves the mat, call “Stop!” at once. Floor runs happen only in a cleared area with adults present: at least 1 m clear round the mat, learners outside its taped edge, one rover at a time per adult, who walks beside it.

    Works towards: Documenting

Materials

  • Per pair: a BBC micro:bit and its USB cable (USB micro-B at the micro:bit end)
  • A computer with a web browser for MakeCode (makecode.microbit.org); no installs needed
  • Per pair: a Kitronik Compact All-In-One Robotics Board for BBC micro:bit (stock code 5693), its Link header fitted with a 2.54 mm pin header by the adult (soldering is adult-only)
  • Kept by the adult: 4 × AA alkaline cells (1.5 V each, 6 V nominal) in a holder with a screwed-shut cover and its own on/off switch, wired by the adult to the board's power terminal block; no rechargeable cells, Li-ion, LiPo, RC or coin-cell packs
  • Pencils and paper for the test tables
  • Per rover: two right-angle geared TT motors with yellow wheels (Kitronik stock code 25100), leads soldered on by the adult
  • Per rover: a flat chassis about 20 cm by 12 cm (stiff corrugated plastic or thick card), a smooth plastic ball caster with spacers to level the deck, cable ties, M3 nuts and bolts, and a stand (a box that holds the wheels in the air)
  • Per rover: a Kitronik Clippable Detector Board (stock code 5678), five wires each with a ring end for a pad bolt and a female jumper socket, M3 nuts, bolts and spacers for its stand-offs, and a ruler
  • The mission course, made by the adult on new paper (at least three turns both ways, a start box and a rescue point where the line ends; no loops, junctions or crossings), kept covered until session 4
  • Paper and black tape 10 to 20 mm wide for each team's practice course, role cards, masking tape and a stopwatch

⚠ Safety before any session

  • Batteries: only AA alkaline cells in the board's closed holder, and USB from a computer for downloads; no rechargeable cells, power banks, Li-ion, LiPo, RC packs or coin cells.
  • Cells: the adult fits four new alkaline cells of one type, the right way round, never mixes new and used cells, takes spent cells out and screws the cover shut.
  • The power-off switch is the board's on/off switch: it cuts the battery to the board, the micro:bit and every motor and servo. Anyone may switch it off at any time; only the adult switches it on.
  • The board's battery is the motor battery: it reaches the motors only through the holder's switch, the board's on/off switch (the power-off switch) and its Motor 1 and Motor 2 terminals.
  • A motor never runs from a micro:bit pin: it runs only from the board's motor terminals, powered by the board's battery.
  • Lift first: the board is switched on only with the rover on its stand, wheels in the air, because a mistake in the blocks could start a wheel at once.
  • Fingers, hair, sleeves and cords stay away from the wheels while the board is on; long hair is tied back. The rover is lifted only by its chassis.
  • Floor speed limit: the rover's speed numbers are never above 40 (of 100), a planning choice.
  • Floor runs happen only in a cleared area with adults present: at least 1 m clear round the mat, learners outside its taped edge, one rover at a time per adult, who walks beside it.
  • Stall or runaway: if a wheel is blocked, the rover pushes against anything, a motor hums without turning or the rover leaves the mat, call “Stop!” at once.
  • Rewire only when unpowered: the board and the holder are switched off before any wire, motor, servo or sensor is plugged in, moved or taken out.
  • Never leave a lead loose while the board is on: switch off first; a lead taken out is capped and taped away from the board.
  • The battery holder rides on the rover, tied down: only the adult opens it, fits cells or works its switch.
  • Learners press only A, at the adult's word, with every wheel still and one hand on the micro:bit only. B, the switch and moving a switched-on rover are the adult's.
  • Only the parts the plan names connect to the micro:bit, through the board's Link header. Never connect a 5 V signal or supply to a micro:bit's pins or battery socket: it runs at 3.6 V at most.
  • If the board, a motor, the holder or a wire gets warm: switch the board off, don't touch it, tell the adult.
  • The line sensor is a Kitronik Clippable Detector Board, rated 2 V to 5.5 V and powered only from the Link header's 3V pin, so its outputs come from 3.3 V; never from 5 V.
  • The detector's 3V lead goes only to the Link header's 3V pin, never a servo header's V pin (battery voltage); its five leads are tied down and tug-tested.
  • No music blocks in these units: MakeCode plays music through pin P0, where the left line sensor is.
  • The lost-line stop: if the middle sensor sees no line for 20 passes of the loop in a row (each pass waits 100 ms, so about 2 seconds), the rover stops by itself. B stops the motors too.
  • Every line run ends by itself: the lost-line stop after about 2 seconds without a line, and the run time-out after 300 passes (about 30 seconds), even if a sensor fails.
  • Every course ends: no loops, junctions or crossings, and a good run takes under 20 seconds.
  • A switched-on rover that is not showing the No icon is live: it may be driving or about to drive. Hands off; the adult stays beside its switch.
Safety for every band
  • Low voltage only: battery packs or USB. Never mains electricity.
  • Never connect a motor straight to a controller pin: use a driver and a separate supply.
  • Every moving robot has a power-off switch within reach that cuts the motor battery (or all power). A software stop button is extra, never a replacement.
  • No coin or button cells and no loose small magnets; battery compartments screwed shut.
  • Guard wheels and moving parts against pinched fingers; keep robots slow and indoors.
  • No exposed lithium cells, improvised chargers or lasers.
  • No Li-ion, LiPo or RC packs: AA alkaline or NiMH cells in a closed holder with a switch, or USB.
  • Check polarity and voltage before power-on; a 3.3 V board must not receive 5 V signals.

Notes for the adult

  • Read each step aloud first: your words come before the learner's card. The card uses short sentences; show each key word with a picture.
  • These plans assume one adult for up to four pairs. Learners plug the USB cable into their own computer, gripping the plug, while the adult watches; only the adult handles cells and battery packs. With more pairs, add an adult or bring fewer pairs to the real board at once.
  • Each session's timing keeps screen time to short bursts (15 minutes at most), with building, acting or testing away from the screen between them.
  • Before the first session on the real board, set up each computer and test a download: either pair each micro:bit once with WebUSB (then MakeCode's Download button sends the program straight to it), or download the .hex file and drag it onto the MICROBIT drive. The light on the back flashes while the program copies: unplug only after it stops.
  • To download, the board is switched off and the adult takes the micro:bit out of it (or the learner does, with the adult watching), holding it by its edges and pulling it straight out; the learner plugs in USB, downloads and unplugs USB once the light on the back stops flashing; the micro:bit goes back in the same way, straight and firmly, display facing the Link header, before the adult switches on. Every swap wears the edge connector a little: swap only to download or at a pair's turn, and never rock the micro:bit out.
  • Powered work rotates: one rover at a time per adult, each pair (or team) taking its turn while the others work away from the screen. Planning figures: a turn takes about 3 minutes to set up (the stand, the sign, the stop drill, the stand check) and about a minute a run, so each session's timing gives every turn its minutes.
  • The pack is 6 V nominal (4 × 1.5 V), at the edge of all three ranges: the bottom of Kitronik's recommended 6.0–10.8 V for the board, and the top of the TT motor's 3–6 V and the servo's 4.8–6 V. Expect it to vary: new cells can read above 1.5 V each with nothing running (Energizer's handbook works an example with an open circuit voltage of 1.6 V), and the pack sags under load, because each fresh cell has 150 to 300 milliohms of internal resistance (Energizer E91). Kitronik's board page lists under Requires a Power Supply that links to its 3 × AA holder; these plans use 4 × AA instead, because 3 × AA is 4.5 V nominal, below the board's recommended 6.0 V and the servo's 4.8 V.
  • Kitronik labels the board Age 11+ and tags it Designed for_Engineers. These plans are adult-led for that reason: the adult builds, wires, powers and switches every rig and keeps the battery holder; the learner changes numbers in blocks, presses the micro:bit's buttons when the adult says, and watches from outside the safe zone or the gate's path.
  • Before the first session, add the extensions on each computer: in MakeCode's Extensions, search for Kitronik and pick the Kitronik robotics Board; for the line sensor, search for Kitronik clip detector.
  • The MakeCode simulator prepares the work. Only the real board, seen working by the adult, counts as evidence: a simulator run is never physical success.
  • Learners already make their own test tables (R09-U3): give the columns, and the learner draws and fills in the table.
  • The studio's Arduino labs are written for ages 12 and up and are not used in this unit, not even its motor or steering labs: they wire a 5 V Uno, never a micro:bit.
  • Carried over from age 10: the same board, battery and power-off switch; the same motor blocks with a speed from 0 to 100; the power path from R10-U1 (battery, board, motor, back), now through two motor drivers; and the safe stop rule from R10-U3 (when unsure, the safe choice), now: stop when the line is lost. The servo socket stays empty at age 11.
  • Motor 1 drives the left wheel and Motor 2 the right; the left line sensor is on P0, the middle one on P1 and the right one on P2.
  • An engineering note, not a maker's quote: the board's driver chip keeps the last speeds it was sent. If the program halts (it crashes, or the micro:bit is pulled out), a wheel that was turning can keep turning; after a reset, “on start” turns the motors off only once the program runs again. Only the switch is sure to stop the motors.
  • If both wheels stall, the pack's voltage can sag far enough to reset the micro:bit. The safe start then keeps the motors off until A, so the rover sits still showing its sign: treat it as live and switch off.
  • Planning choices, not sourced figures: the speeds 30 and 25, the floor limit of 40 of 100, the 3000 ms drive limit, the 3-second wait after A, the lost-line stop's 20 passes of 100 ms, the run time-out of 300 passes, the detector's starting height of 10 mm, the 1 m clearance and the 30 cm zone.
  • Kitronik gives the detector's current as 54 mA at 3 V. At the header's 3.3 V it will draw a little more (about 60 mA if it rises in step with the voltage, an estimate), still under the header's 90 mA.
  • The detector hangs under the front on stand-offs (bolts with nuts and spacers) that set one height above the floor: start at about 10 mm (a planning choice: Kitronik gives no height), measured with a ruler and written on the chassis. Keep it fixed: every reading and threshold holds only at that height.
  • Which side P0 is on depends on how the detector is bolted on, so check it: with the line under the left sensor only, does P0 drop? If P2 drops instead, the adult switches off and swaps the P0 and P2 wires at the header.
  • If a sensor's white and black numbers overlap (its lowest white is not above its highest black), no threshold works: switch off and change one thing at a time, the detector's height on its stand-offs, the light on the mat (no sunlight or lamp on it) or the mat itself (matt white paper, a darker line), then read again.
  • A substitute line sensor must have, on its own datasheet: a supply rating that includes 3.3 V (as the Kitronik board's 2–5.5 V does), analogue outputs, and a total current under 90 mA at 3.3 V (the Link header's limit). The adult checks all three before buying.
  • The mission course is unfamiliar: the adult lays it on new paper, with at least three turns both ways, and keeps it covered until session 4. It is never the training mat or a course the team practised on.
  • A run passes when the rover follows the line from the start box to the end of the line without help, and the lost-line stop then stops it by itself.
  • Teams of four: two pairs share one rover, so each adult has at most two teams, and two rovers taking turns, on the floor.
  • The safety lead's job is the checks and the call; the adult still carries, places and lifts the switched-on rover, presses B and works the switch. The driver presses only A, at the adult's word.
  • Planted faults are made only with the board and the holder switched off, and none of them is unsafe: no fault puts anything on a pin that the plan does not name.
  • The final trials are run once each: a failed trial counts and is never rerun to make a streak.
  • Readiness decides, not age: a learner who already documents trials another team can follow, and troubleshoots one check at a time, can move on to the next band's work.

Planned studio features

Not built yet. The unit runs without them.

  • A line-following simulator in the studio with printable unfamiliar courses, the sensor numbers labelled as simulated inputs and every setting labelled as a code setting.
  • Printable picture cards for each session's key words, role cards and printable learner cards.
  • A printable troubleshooting sheet and a documented trial log.

Sources

The facts this plan relies on, in each source's own words.