An Introduction to Programming using the NXT Robot:

Transcription

1 An Introduction to Programming using the NXT Robot: exploring the LEGO MINDSTORMS Common palette. Student Workbook for independent learners and small groups The following tasks have been completed by: Task 1 Measuring the Move boxes pages 4, 5 Task 2 Distance Challenge page 5 Task 3 Distance Questions page 7 Task 4 Turns boxes page 8, 9, 10 Task 5 Robot Walk Loop page 11 Task 6 Little Red Riding Robot Challenge page 12 Task 7 Clap and Go Challenge page 14 Task 8 Tiger Robot Challenge page 16 Task 9 Round the Garage Challenge page 17 Task 10 Runaway Robot Challenge page 18 Task 11 Racing Robot page 19 Task 12 Yo-yo Robot page 21 Task 13 Line Follower Challenge page 22 Task 14 Blocked Up Challenge page 24 written by Sandy Garner

2 Getting started: If you see a screen like this: type a name for your program in the Start New Program box, and press the Go button otherwise: choose New Program from the MINDSTORMS Toolbar The program will now have a name but it still isn't saved on the computer. 1. Choose Save Program, and you will see a Save As window. Type the name for your program in the File Name box if it isn't there already. Keep.rbt at the end of the name, because that's how the computer knows that this is a MINDSTORMS NXT program. 2. Press the Save button to save your program with the name you have chosen. The exercises in this book expect an NXT robot built with motor outputs on ports B and C, a touch sensor behind, a light sensor pointing down, an ultrasonic sensor pointing forward and a sound sensor somewhere. The standard setup as in the building guide that comes with the educational set is ideal. An Introduction to Programming using the NXT Robot 2 Exploring the LEGO MINDSTORMS Common Palette

3 You should now be able to see something like the picture below. This is the space where you write your robot program. The program starts on the left, where it says Start, and is built up to the right by connecting blocks together in a line. The blocks you can use are chosen from the left hand side. These blocks are from the Common Palette. Any changes you make to your program won't be saved on the computer unless you select Save Program. It is a good idea to save your program often. Move The robot can move forward and backward (reverse). It has one motor for each wheel. The motors are connected to the B and C ports of the robot by cables. 1. Drag a Move block (cog) to the position outlined around the word Start. The Move block lets you control how far your robot will move but it doesn t use metres or centimetres, and you might start to see why soon. When the Move block is highlighted (you will see a pale blue line around the outside) some choices about Move appear in the gray box underneath your program space. This gray box is called the Configuration Panel. If you don't change anything, the robot is set to move the B motor and the C motor for 1 rotation. Rotations A rotation is a turn. One rotation is one whole turn of the wheel. Let's find out how far the robot will move with one rotation. You will need to download the program you have written on the computer (the Move block) to the robot. Download means to copy the program from your computer to the robot. 2. Download your program to the robot using the Download arrow. The USB cable needs to be connected to the robot's USB port while the computer is downloading. The robot needs to be turned on. Press the orange button on the robot if your robot isn't turned on. The robot will beep when the downloading is finished. After the beep, you may pull out the USB cable. 3. Run your program on the robot. An Introduction to Programming using the NXT Robot 3 Exploring the LEGO MINDSTORMS Common Palette

4 Watch the robot's screen while you push the robot's orange button 4 times. It should show My Files then Software files then your file's name, then Run. Run the program again. 4. Stick a marker (e.g. chalk, blue tack) on the side of a wheel. Watch how far the wheel moves when your program is run. Task 1. Fill in the 10 Boxes about Measuring the Move 5. Measure how far your robot moves with 1 rotation. 6. Calculate how far your robot will move with 2 rotations. Try it, and measure it Question: Does doubling the rotations double the distance travelled? 1.3 Seconds You can choose how long the robot's axle turns for in seconds. You will have to experiment with how far the robot travels. 1. Change Rotations to Seconds. Make your robot move for 1 second on half power (50). Download and run. Measure how far it goes Make your robot move for 1 second on full power (100). Download and run. Measure how far it goes. Compare the distance with step 1 above. 1.5 Question: Does doubling the power double the distance travelled exactly? Make your robot move for 2 seconds on half power (50). Download and run. Measure how far it goes. 1.7 Question: Does doubling the time double the distance travelled exactly? 1.8 An Introduction to Programming using the NXT Robot 4 Exploring the LEGO MINDSTORMS Common Palette

5 Degrees You can measure how far the wheel will go round using a measure called degrees. All the way round a circle (or a wheel) is 360 degrees, which is written 360 o. If you choose either 1 rotation or 360 degrees, your robot should do exactly the same thing - turn the wheel 1 complete circle. 1. Change your Move block's Duration to 360 Degrees. If you download and run your program now, the wheel should go round exactly once. Can you work out how many degrees would make the wheel turn half way round? 1.9 Can you work out how many degrees would make the wheel turn a quarter of the way round? 1.10 Degrees are really useful if you want the wheel to turn just a little. Task 2. Distance Challenge 1. Make your robot travel exactly 8 cm. See if you can get it right first time, using the measurements you have already made to calculate the settings required. 2. Make your robot travel exactly 1 metre. Once again, work it out first. An Introduction to Programming using the NXT Robot 5 Exploring the LEGO MINDSTORMS Common Palette

6 Building programs. Now that you are an expert on using the Move block, you can start to build longer programs. 1. Drag another Move block to your program space and connect it to the right of the one you already have. 2. Move your mouse over the Wait (hour glass) block, then click on the Time (clock) block. An orange Time block will be created. 3. Drag the orange Time block so it pushes between your two green Move blocks. The program pictured above will make your robot perform three tasks, one after the other, from left to right. They are connected by what MINDSTORMS calls the sequence beam. (A sequence is an ordered list. A beam is a long thin shape.) Now that you have more than one block, to change the settings on any one block, click on it once to highlight it then make the change in its Configuration Panel. 4. Change the settings on all 3 blocks in your program to make your robot move forward 1 rotation stop and wait for 2 seconds move backwards (reverse) for 1 rotation. 5. Download and run. Have you noticed the little changes to the pictures on the block when you change the settings? When you write longer programs these pictures will help remind you which block is doing what. An Introduction to Programming using the NXT Robot 6 Exploring the LEGO MINDSTORMS Common Palette

7 Task 3. Move Questions 3.1 Are you more likely to make the robot travel an exact distance using seconds or rotations? 3.2 If you want the wheel to turn just a little, should you use seconds, rotations or degrees? 3.3 What do you think would happen if you put smaller wheels on the robot then ran your exactly 2 metre program again? 3.4 What do you think would happen to your robot if one wheel was bigger than the other when you ran your exactly 2 metre program? Why? 3.5 Why do you think the MINDSTORMS program doesn t just let you tell the robot how many centimetres or metres you want it to go? 3.6 When you make a change to your program and download it to the robot, what has happened to the old version of your program on the robot? 3.7 What do you think would happen if you put the brake on one wheel and turned the other wheel? An Introduction to Programming using the NXT Robot 7 Exploring the LEGO MINDSTORMS Common Palette

8 Turning Task 4. Fill in the 11 Boxes about Turns How can your robot turn when it doesn't have a steering wheel? The picture shows a robot moving in a circle. It shows 2 wheels which we can call the inside wheel and the outside wheel. The inside wheel makes the small circle and the outside wheel makes the big circle as the robot goes around. Which wheel moves the furthest? 4.1 Which wheel turns the fastest? 4.2 Curve Turn 1. Delete all blocks in your program except one Move block. 2. Look at the Curve Turn picture below, and make your Steering match. Make your robot do the turn for 1 Rotation. Download and run. Curve Turn 3. Put a marker on the side of each wheel. Watch each wheel in turn as the program runs. Do they both do one whole rotation? 4.3 If not, describe what happens Change the Duration to 10 rotations. Download and run. Can you see the circle the robot is trying to travel around? An Introduction to Programming using the NXT Robot 8 Exploring the LEGO MINDSTORMS Common Palette

9 Point Turn 1. Make your robot do an all-the-way turn for 1 rotation. Download and run. Point Turn Watch each wheel in turn as the program runs. Do they both do one whole rotation? Did you notice anything else? Change the Duration to Degrees. Without changing the steering, try different numbers in the degrees box until you get the robot to make a quarter turn. How many degrees will give you a quarter turn? 4.7 Wheel Turn 1 1. This time, take the slider back one position towards the centre. Set the Duration to 1 rotation or 360 degrees. Download and run. Watch each wheel in turn as the program runs. Describe what you see. Wheel Turn Try different numbers in the Degrees box until you get the robot to make a quarter turn. How many degrees will give you a quarter turn? 4.9 An Introduction to Programming using the NXT Robot 9 Exploring the LEGO MINDSTORMS Common Palette

10 Wheel Turn 2 1. Try one more way of making a turn. Turn the C motor off. Download and run. Wheel Turn 2 Watch each wheel in turn as the program runs. Describe what you see Try different numbers in the Degrees box until you get the robot to make a quarter turn. How many degrees will give you a quarter turn? 4.11 The numbers you have written down will be very useful for the Little Red Riding Robot challenge, and other challenges ahead. Turn summary: These are the three different types of turn your robot can make. 1. The curve turn - the robot will move in a circle. This turn is made by turning the robot's wheels at different speeds. The further the slider is from the centre position, the smaller the circle will be. 2. The point turn - the robot spins around a point under its middle. This turn is made by turning the robot's wheels in different directions, one forward, the other backwards. 3. The wheel turn - the robot spins around one wheel. This turn is made by one wheel staying where it is and the other wheel turning. An Introduction to Programming using the NXT Robot 10 Exploring the LEGO MINDSTORMS Common Palette

11 Task 5. Robot Walk Loop The task is to make your robot look as much as it can like it is walking by moving one wheel just a little, then the other. 1. Program the robot's first two 'steps'. 2. Drag a Wait for Time block after each 'step'. How long should your robot wait between 'steps'? Loops Loops are very useful for saving boring repetition. All the other robot steps will just be the same as these two. Rather than drag more and more Move and Wait blocks down, you can make the program repeat these steps over and over by putting them in a loop. 3. Drag a Loop block to the first position of your program space. 4. Change the Loop control from Forever to Count. Type 4 in the Count box. 5. Drag your program blocks, keeping them in the same order, inside the Loop block. 6. Download and run. Did your robot stop after 8 (4 pairs of) steps? 7. Save your program using File > Save As because you will want to use it again later. Call it Walk.rbt. An Introduction to Programming using the NXT Robot 11 Exploring the LEGO MINDSTORMS Common Palette

12 Task 6. Little Red Riding Robot Challenge Your Little Red Riding Robot has been to visit Grandma and it is time to go home. The map shows you the shape of the turns she has to make. Make sure she stops and waits to look for cars at the end of Grandma's driveway before turning into the main road. She always reverses into her garage, because she likes to come out facing forwards. Program your robot to make the journey home. Use the table to help with your planning. If you have been careful filling in the boxes so far you might be able to make the journey correctly on the first attempt. Now there's a challenge! List of journey actions, in order Measured distance or turn Block used Block Setting (degrees, rotations, seconds, power, B/C...) An Introduction to Programming using the NXT Robot 12 Exploring the LEGO MINDSTORMS Common Palette

13 Sound Sensor The robot can detect (sense) noises that are made around it. It can be made to wait until it detects a loud noise before it carries on with its program. The program you are about to write will make the robot wait for a sound, like a clap, before it starts to move. 1. Start a New Program. Drag a Wait for Sound block to the Start position. 2. The Configuration Panel lets you pick how loud a sound to wait for. Choose Sound > (greater than) Drag a Move block to your program. Download and run. Your program will do nothing until... a clap, a sneeze, a door slam, a shout... then off it goes. Reading the sound level on the computer. The robot can help you choose a number for the sound level by showing you number readings for sounds. Readings can be shown on the computer or on the robot screen. The following steps will show you how to get a reading on the computer. 4. Connect the USB (download) cable to the robot, and select (click on) the orange Sound block in your program. 5. Select the NXT window - it is above the Download button. 6. Connect and Close the window that pops up. An Introduction to Programming using the NXT Robot 13 Exploring the LEGO MINDSTORMS Common Palette

14 7. Look under the Hourglass at the bottom left corner of the Configuration Panel. There is a box with a number in it. This is the feedback box. Now that you have connected your robot to the computer, the feedback box is showing how loud the noises around the robot are right now. Watch it quietly for a minute and write down the highest number you see Make a noise and watch the number in the feedback box change. If your noise is finished very quickly, like a clap, it may not show unless you make a few of them one after the other. A continuous noise should give you a steady reading. Try humming. Task 7. Clap and Go Challenge Make your robot move in a square. It doesn't start to move until you clap. Each time you clap it moves 1 rotation along one side, turns a 90 o (square) corner and waits for the next clap. Use a loop. It stops after 4 sides. clap clap clap clap An Introduction to Programming using the NXT Robot 14 Exploring the LEGO MINDSTORMS Common Palette

15 Light Sensor Your robot can detect when it comes to a dark line on a light coloured floor. 1. Start a new program. Drag a Move block to the Start position and set it to Unlimited. 2. Drag a Wait for Light block to the program. 3. In the Light Sensor Configuration Panel, set the Until box to Light < Make sure the Generate light box has a tick in it. 5. Drag another Move block to the end of the program, and set it's Direction to Stop. 6. Download and run. Set your robot off towards a black stripe. Does it stop when it reaches the stripe? 8.1 What happens if you start it on black? 8.2 What happens if you take the last Move block (Stop) away? 8.3 The light sensor is sending a light out and measuring how much light is reflected back. Different colours will reflect different amounts of light. Other things will also change the reading. If the sun comes out, a light in the room is turned on or somebody makes a shadow, the reading will change. An Introduction to Programming using the NXT Robot 15 Exploring the LEGO MINDSTORMS Common Palette

16 It is useful to know what readings the light sensor makes for the black line and the white background. You could use the feedback box as you did for the Sound sensor, but probably your USB cable won't reach far enough. There is another way to get a reading that doesn't need the computer to be attached to the robot. Reading the light level on the NXT using View. 1. Get My Files showing on the robot's screen. If you have just run a program, press the darker gray button 3 times so you see My Files. If you have just turned the robot on, My Files will be showing. 2. Find View by pressing the grey right-arrow button 2 or 3 times. NXT Program, then View OR NXT Program, then NXT Datalog, then View 3. With View showing, press the orange button to select it. 4. Now you may choose which sensor reading you wish to view. Press the right-arrow button twice to find Reflected Light. Press the orange button to select it. 5. You are asked to choose which port this sensor is plugged in to. Use the arrows to select Port 3 (or whichever port your light sensor is in). 6. If you have pressed the orange button, you should see a little box with a number in it on the robot's screen. This is the Light Sensor reading. Put your robot's light sensor over the black line and write down the reading. Black 8.4 Put your robot's light sensor over the white background and write down the reading. White It is important to know these numbers so that you can make good choices about the numbers to use in your program. 8.5 Task 8. Tiger Robot Challenge First, work through pages 15 and 16 and fill in boxes Write a program to keep your tiger robot pacing in its cage. Make your robot move in a straight line across its square black tiger cage. It turns when it meets the edge of its cage then keeps on in a straight line until it meets another edge. Repeat this for ever. You will need to use a loop, but this time set it to Unlimited rather than a Count. An Introduction to Programming using the NXT Robot 16 Exploring the LEGO MINDSTORMS Common Palette

17 Touch Sensor The back of your robot has a touch sensor, which will be pressed when it bumps in to something. 1. Start a New Program. Drag a Move block to the Start position and set it to move an Unlimited distance in reverse direction. 2. Drag a Wait for Touch block to your program. 3. Drag a green Sound block to your program. 4. Change the sound file it will play from Good Job to Ouch Drag another Move block to finish your program. This time move the robot forwards for 2 rotations. Download and run. The robot is going to reverse until it bumps something, so put it near a wall or hold a book up for it to bump into. Task 9. Round the Garage Challenge Get your robot to move backwards until it bumps into a box or pile of books on the floor. When it has bumped, get it to move forward (not more than 40cm) turn a little go back on this new angle (not more than10cm) straighten up go backwards again until it bumps It repeats these five steps forever. It will eventually work its way around the box. An Introduction to Programming using the NXT Robot 17 Exploring the LEGO MINDSTORMS Common Palette

18 Ultrasonic Sensor The 'eyes' on your robot can detect objects as far as two and a half metres away. It uses an ultrasonic sensor, like a bat or a radar. A signal is sent out, and if an object is in front, the signal bounces back. The time taken for the signal to come back is a measure of the distance between the object and the robot. 1. Start a New Program. Drag a Move block to the Start position and set it to move an Unlimited distance forwards. 2. Drag a Wait for Distance block to your program. 3. Set it to Distance < 30 cm. 4. Drag a Move block and set it to Stop. Download, point your robot towards a wall, and run. You will have to be careful not to let the robot 'see' your hands when you press the run button. The robot may also see its own cables if they are in front of its 'eyes'. Measure how far away your robot stops from the object it has detected Where should you measure from on the robot? 10.2 Large sized objects with hard surfaces return the best readings. Objects made of soft fabric or that are curved [like a ball] or are very thin or small can be difficult for the sensor to detect. Two or more Ultrasonic Sensors operating in the same room may interrupt each other s readings. Source: Task 10. Runaway Robot Challenge Make your robot move forward slowly. When you move in front of it, it should turn a half turn away from you and keep moving forward (away from you). Repeat these actions for 10 seconds. An Introduction to Programming using the NXT Robot 18 Exploring the LEGO MINDSTORMS Common Palette

19 Loops and Switches You have already used loops that never finish, loops that repeat a certain number of times, and loops that repeat for a number of seconds. Loops are a very useful way of repeating a code pattern. Usually a 'stop condition' will stop the loop when something has been achieved (a length of time, a number of times, a sensor reading...) Let's get some more practice with loops. Task 11. Racing Robot Racing Robot needs to: walk to the starting line (a black stripe) steps 1 & 2 below wait for the orange Enter button to be pressed step 3 below race off to the finish line (another black stripe) step 4 below beep and stop. step 5 below 1. Start by writing a robot walk program or opening the one you made from page 11. Don't make the steps too big you'll see why shortly. Try 80 degrees. 2. If you haven't already, put the steps in a Loop. The robot needs to walk until it senses the start line, so make the Loop control Sensor > Light Sensor. Set the Loop to finish when the light sensor sees black. The robot will now walk to the Start line. 3. Put another loop after the walk loop. Control this loop by Sensor > NXT button. Choose the Enter button. You don't need to put anything inside this loop. The robot will just wait for the button press. The next action the program needs is to race to the finish line. 4. Add another Loop to your program. Put an unlimited Move block inside the loop, and finish the loop when the robot sees black. This is a race, so set the Power to Finish the program with a Beep and stop the wheels. This program looks like it should do the job, but it has at least one and probably two serious problems. Before you read on, run the program and see if you can work out what the problems are. An Introduction to Programming using the NXT Robot 19 Exploring the LEGO MINDSTORMS Common Palette

20 Fixing problem 1 6. Put another Loop in your program after the NXT button Loop. Control this loop with Time and give the robot long enough to get past the start line before it starts checking for black again. A setting of 0.5 seconds is plenty. There is still nothing inside the loop which will actually move the robot past the start line. 7. Put a Move block inside the loop and set it to Unlimited. Fixing problem 2 8. Drag a Switch block and put it between the robot's 2 steps. A Switch gives the program a choice of 2 paths to follow. 9. Set this Switch block to be controlled by the Light Sensor. Make it switch for a light level of < 35 (or whatever you setting you need to be sure of it being on black). The top path (sequence beam) is for the comparison being true (light level < 35), so the top path is for what you want to happen if the robot is on black after the first step in its loop. (Nothing. It has found the start line and is ready to race.) The bottom path is for a robot which is still on white after its first step. You want it to take the second step in the loop. 10. Drag the second step blocks to the bottom path of the Switch. The robot is less likely to miss seeing (sensing) the start line now. 11. Finish the Racing Robot challenge by making sure your robot takes steps small enough that it NEVER misses the start line putting a message on the screen saying Enter to start so that other people will know what the robot is waiting for on the starting line. take this message off the screen when the race has started. You could replace it with one which says Racing now Extra challenges if you are keen: The NXT stops well after the finish line because it makes the beep before it puts the brake on. One way you can make these things happen at the same time is by splitting the sequence beam into two paths which will be followed at the same time. Drag the Move block down first, then hold the shift key down and draw the extra beam. Make the NXT say Three Two One ( one number each second ) before it waits for the Enter button to be pushed. Should the numbers be in the loop or before it? An Introduction to Programming using the NXT Robot 20 Exploring the LEGO MINDSTORMS Common Palette

21 Task 12. Yo-yo robot This program moves the robot forward a little if there is nothing in front of it, and backwards if there is something in front of it. 1. Drag a Switch block to a new program. 2. It will be showing a Touch sensor. Change this to the Ultrasonic (distance) sensor. 3. In the Configuration Panel, set the Ultrasonic sensor to Distance less than 30cm. You will see there are 2 paths (MINDSTORMS calls them sequence beams) in the Switch block. Your program will choose which one to follow depending on the Distance setting on the Switch block and the information received by the sensor. In this case, if the robot is less than 30cm from an object, it will follow the top sequence beam. Otherwise it will follow the lower sequence beam. 4. Drag a Move block into the top sequence beam. Set it to move backwards 3 rotations. (If the robot is closer than 30cm to an object, it will move backwards.) 5. Drag a Move block into the lower sequence beam. Set it to move forward 1 rotation. (If the robot is further than 30 cm away from an object, it will move forward 1 rotation.) There is one further step needed. The ultrasonic sensor is likely to see your hand as a close object when you push the run button. 6. Drag a Wait for Time block to the beginning of your program (before the Switch block). Set the time for long enough to get your hand away. Download. Put the robot near (and pointing towards) a wall and run the program. If your robot is very close to the wall, it should move backwards. Otherwise it will move forward. Shift the robot and run the program again, and again, and again... The Switch block can be thought of as an 'if ' then an 'else' : If the robot is closer than 30 cm it will go back, or else it will go forwards. 7. Put this program in a loop so that the robot moves backwards and forwards forever. An Introduction to Programming using the NXT Robot 21 Exploring the LEGO MINDSTORMS Common Palette

22 Task 13. Line Follower Challenge You can use the Switch block in a loop to make a your robot follow a black line. The process can be described in word like this: Do this forever: If the sensor is on black, turn to the right. If the sensor is on white, turn to the left. Write a program which uses a Switch block to make the robot follow a black line. The following tips may be helpful. The safest way is to just use one wheel when making each turn. You will need to stop the other wheel first or it will keep on moving. Lower power settings will give you a more reliable line follower. Fast robots make mistakes by overshooting the line, especially on curves. Try Power of 60. Question: Is the robot following the middle of the line or the edge? 13.1 Display The Display block lets you display images or text on the Robot's screen. 1. Drag a Display block to your program. Look at the Configuration Panel. If you don't change anything, it will choose a Smiley Face (which is saved in a file called Smile 01), and will draw it with its bottom left corner at position X=12, Y=8 on the robot's screen. You may change the position by dragging the smiley face around or typing new numbers for X and Y. If you increase the X value, the picture will move to the right on the screen. The maximum X value is 99. If you increase the Y value, the picture will move up on the screen. The maximum Y value is 63. You can also display Text (words) or a Drawing. If you want to put both text and an image on the screen, you can do this by using a second Display block with its Clear field unchecked. Y X How MINDSTORMS uses these words: Image - what you might think of as a picture or a photograph Text - letters, words, numbers, symbols e.g. was 23 % Drawing - dots (points), lines and shapes e.g. circles, ovals, squares Graphic - the Image files An Introduction to Programming using the NXT Robot 22 Exploring the LEGO MINDSTORMS Common Palette

23 Blocks When you have a piece of program working, you can save it in a Block so that you can use it again. 1. Open your walking robot program (Walk.rbt from page 11) or write another one. It should look something like this: 2. Drag your cursor over a rectangle which contains the whole program (see the Start and Finish positions in the picture below). 3. Select the Create My Block button from the Toolbar at the top of the program space. A new window will appear. 4. Type a name for your block e.g. Walker. 5. Type a description of what your block does e.g. walks 8 steps. 6. Click on Next and choose a picture for your block. 7. Click on Finish. Your code sequence is now tidied away neatly into a block. You can use this block as often as you like and in as many programs as you like. 1. Open a New Program. 2. Click on the Custom Palette button. 3. Click on My Blocks. An Introduction to Programming using the NXT Robot 23 Exploring the LEGO MINDSTORMS Common Palette

24 4. Choose your block and drag it to your program. You could put this block in a loop, or put 2 of them side by side... If you want to make changes to your block, doubleclick on it to open it. If it is already open, just click on its name tab above the program space. You must save any changes for them to have an effect. Make sure you download your program, not your block - click on the program's tab before you download. You can add and delete My Blocks from the Custom Palette by selecting the Manage Custom Palette command in the Edit menu. Task 14. Blocked Up Challenge Make the blocks inside the loop of your line follower program into a block. Using your line follower block and the walker block from the previous exercise, write a new program which follows the line for 3 seconds then walks for 8 steps, then follows the line again. Use only blocks and loops. * * * * * If you have worked through this book and completed all the tasks, well done! I hope you have enjoyed your introduction to programming and robotics. What you do now is only limited by your imagination. Go and play! Sandy Garner Department of Computer Science University of Otago Dunedin New Zealand An Introduction to Programming using the NXT Robot 24 Exploring the LEGO MINDSTORMS Common Palette