--- title: "One robot, many jobs" subtitle: "Robotics challenges · Modes · Lesson 6" --- # One robot, many jobs **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** A robot lawn mower has modes: mow, go home, pause. You press one button and it keeps doing that job until you choose another. :::teacher-note **In one sentence:** Students use a mode variable to give one robot several jobs (go, follow, stop); buttons change the mode and forever does the job, then they add explore and guard modes. **Students should be able to say:** I can use a variable to remember which job (mode) the robot is doing. I can change the mode with buttons, and make forever do the job for the current mode. I can add a new mode to a program. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/4d1bd8397ecb.png?v=f5f8fe0f3af2e31f) :::keep-together **The robot is on the line. You press B, wait, then press A+B. What happens?** ☐ Nothing: buttons cannot change what forever does ☐ It follows the line only while you hold B ☐ It moves a little when you press B, then stops by itself ☐ It follows the line, then stops when you press A+B My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** It follows the line until you press A+B. B sets mode to follow, and forever keeps following while mode stays follow. A+B sets mode to stop. ::: ## Run Run the program in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Investigate ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/4d1bd8397ecb.png?v=f5f8fe0f3af2e31f) :::keep-together ### Still following **You pressed B a while ago and let go. Why does the robot keep following the line?** ☐ mode still says follow, and forever checks it again every time round ☐ followLine runs forever by itself ☐ The robot remembers the line ☐ The button is still pressed inside the micro:bit ::: :::teacher-note **Answer:** mode still says follow, and forever checks it again every time round Pressing B ran one block: set mode to follow. The variable keeps that value, so every time forever checks, it finds follow and calls followLine. ::: :::keep-together ### Ruby's robot Ruby's program: ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/0c635b01a591.png?v=24e98be13021427a) **Ruby's robot never moves, even when she presses A. Which part is wrong?** ☐ She needs else if ☐ Her A button sets the wrong mode ☐ forever sets mode to stop every time round, wiping out the A press straight away ☐ robot motor tank needs a time ::: :::teacher-note **Answer:** forever sets mode to stop every time round, wiping out the A press straight away Setting mode to stop belongs in on start, once. Inside forever, it runs again every time round, so mode is stop again before the robot can move. ::: :::typical ## Modify **Which mode?.** A person needs to know which job the robot is doing. Show a **different picture** on the micro:bit for each mode, when its button is pressed. **Explore mode.** Add a fourth job: **explore**, chosen by touching the **logo**. In explore mode the robot drives and turns away from boxes, like lesson 4. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. **Which mode?:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/11a6ffb610e2.png?v=1c0622cf55fb1d98) **Explore mode:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/b396869083a4.png?v=069db6ea850ca11a) ::: ::: ## Make Add a **guard** mode, like a security robot watching a doorway: - shake the micro:bit to choose guard - in guard mode the robot stays **still** - when something comes closer than **20 cm**, it shows **red** lights and **beeps**; otherwise its lights are off Drag a box towards the robot to test it. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/f9136e5c5823.png?v=b5c11fc0408251a2) ::: :::wider ## On a real robot The same program runs on a real robot. Things to notice: - A real robot moves as soon as you press a button, so put it on the floor first, or press A+B before you pick it up. - Pressing A and B together needs both at once; real buttons make it easy to press one a moment early. That is a reason real robots often use one button to **cycle** through modes instead. ::: ## Exit ticket :::keep-together **Why does the robot keep following the line after you let go of B?** {{lines-3}} ::: :::teacher-note **Answer:** B set the mode variable to follow. The variable keeps that value, and forever checks it every time round, so it keeps calling followLine. :::