Lego’s are a big attraction to many young children. FIRST (For Inspiration and Recognition of Science and Technology) has created a program for young children who can create robots out of Legos using a kit. As a team, kids create a robot out of this kit to perform a simple daily task. In this tutorial I will teach you how to build a robot out of the NXT Mindstorm kit. I will teach you how to write and run a program on how to move the bot forward and backward.

 

Cost:

NXT Lego Robot Kit             depending on the kit  >$100

Time:

Depending on how steady you hands are and you easily frustrated you get:  :30 – 1:30

*Caution: Lego pieces are small and children may swallow*

Paso 1: The Kit

After obtaining a NXT Lego robotics kit, lay out all of the pieces in the kit. The supplies should contain all that is in the above photo

Paso 2: The Arm

Take one of the arm pieces, two of the smaller gray couplings, and four of the large black couplings as shown in the top half of the photo.  Place the two gray pieces into the last two holes of the arm piece on the long side of the arm.  The gray pieces should have an even amount on either side of the hole. Place the four black couplings over the ends of the gray couplings with the crown side closest to the arm.  A finished product will look like the bottom half of the photo.

Paso 3: The Chassis Part 1

Take the two NXT axles, the big gray coupling and two of the black couplings. The correct parts are shown in the top photo.  Connect the two black couplings to the end of the gray piece. This is shown in the top half of the second photo. The ends of the black crowns should be placed through the middle hole of the group of three holes on the axle next to the orange circle. The completed product for step three will look like product in the bottom half of the second photo.

Paso 4: The Chassis Part 2

Take the completed products from steps two and three. Flip the product from step three over so that the piece that you inserted will be on the bottom and the empty holes next to the larger circle are on the top. The black crowns will go in the back two holes of the group of three. Perform this for both sides of the product from step two. The finished product will look like the photo above.

Paso 5: The Wheel Axle Part 1

Take two of the L-shaped pieces with five holes and the longest dark gray pieces with the bridge as shown in the top half of the photo. Place the longer side of the dark gray piece through the first hole on the shorter side of the bend. This will look like the bottom half of the photo. Push the dark gray piece all the way to the bridge.

Paso 6: The Wheel Axle Part 2

        Take the finished product from Step 5 as well as the large gray gears shown in the top half of the photo. Stick the long end of the large dark gray piece through the center cross hole in the gear. The gear should be on the same side of the bridge as the L-shaped piece. The Final product of this step should look like the bottom half of the photo.

Paso 7: Fitting the Axle to the Tire Part 1

        Take the finished products from step 6 and the tires. Insert the finished piece from step 6 into the center cross hole in the tire. The tire should be on the same side as the gear and L-shaped piece. The finished  product should look like the photo above.

Paso 8: Fitting the Wheel Axle to the Tire Part 2

Take either the gray hub caps or the yellow hub caps. These are interchangeable. Insert them over the end of the dark gray piece that is sticking out through the cross hole in the tire from step 7. The finished product will look like the right half of the photo.

Paso 9:

Take the finished chassis product for step 4. Take the small blue pieces that were in the photo from step 1. Place the two blue pieces in the third hole of the group of three next to the orange circle on the chassis. In this group of three, the blue pieces will go in the hole furthest from the orange circle. One blue piece on each side of the chassis. The final product will look like the photo.

Paso 10: Building the Axle

Take the small gray gear, the small black couplings, and the finished product from step 9 as shown in the top half of the photo above. Insert the black couplings through one end of the small gray gear. Take these two pieces and insert the other end of the black coupling into one of the cross holes in the orange circles on the chassis. Repeat this with the other coupling. The finished product is shown in bottom half of the photo.

Paso 11: Connecting the Wheels

      Take the finished products from steps 10 and 8. Take one of the wheels connected to  the L-shaped piece. Connect the longer side of the L-shaped piece to the blue and black couplings from the product of step 10. The blue piece will connect to the cross hole on the L-shaped piece and the black coupling will go through the hole next to the cross. The finished product will look like the photo. Repeat this for the other wheel. The small gear connected to the orange circle will connect with the large gear connected to the wheel. After finishing with this step, the body of the robot is now complete.

Paso 12: Prepping the NXT Brick

Take the NXT brick and four small black couplings. Put the brick on its side like what is shown on the left side of the photo. Take the black couplings and place them in the first and third holes that are in a horizontal line to you as the brick is place like it is in left side of the picture. The finished product should look like the right side of the picture.

Paso 13: Prepping the bot for the Brick

        Take the finished problem from step 11. Take four of the small black couplings. Let’s say that the arm is on the front of the bot and the wheels are on the back of the bot. Find the group of three holes in the front of the bot. They are located in the top half of the photo. Place two of the four black couplings into the back two outside holes of the group of three holes. The finished product will look like the bottom half of the picture.

Paso 14: Connecting the Brick to the bot Part 1

Take the NXT Brick, the remaining two arms, and the finished product from step 13. Place the brick on top of the bot. Make sure the black couplings are on the same half of the bot. This set up should look like the top half of the picture. Take one of the arms and connect the shorter side of the arm to the chassis of the bot and the longer side of the arm to the NXT brick. On the shorter side of the arm, the bot couplings should go through the two holes that don’t have a cross hole. On the longer side, the couplings should be placed in the third and fifth hole down from the cross hole at the top. The finished product should look like the bottom half of the photo.

Paso 15: Connecting the Brick to the bot Part 2

In order for the bot to move from a program, it must be connected to the command Brick. Flip the bot on its side so that it sits on it back end with the front end up in the air. This should look like the left side of the photo. Take notice of the ports that are on the side of the Brick. These are where the cables will be connected to the bot. Take one of the cables and place one of the connectors in the port labeled “A”. Connect the other end of the cable into the port on the right side of the front of the bot. Take the other cable. Place one of the connectors into the port labeled “C”. Connect the other end of the cable into the port on the left side of the front of the bot. The finished product will look like the right side of the photo.

Paso 16: Bricx Command Center

The bot is now ready to be programmed. The NXT Brick uses a computer program called Bricx Command Center. If the program is not already on your computer, go to bricxcc.sourceforge.net. If the program is already on the computer that you are using, continue on to step 17. On the left hand column, there are multiple different utilities that the company can program for. Click on the NXT link. Click on the link that says “latest version”. This will bring you to the download screen. Click on the link that says “download” and follow instructions to finish the download and installation of Bricx Command Center. Once Bricx Command Center is installed on your computer, you are able to create programs that will be used by the robot.

Paso 17: Open a new program

First open up BricxCC. BricxCC will ask you to connect to the robot. Take the USB cord that came in the kit and connect one end to a USB port on your computer and the other end to the side of the Brick. Turn on the robot by pressing the orange button on the Brick and press OK on the computer screen. BricxCC should connect to the robot automatically. To start a new program select “New File” on the main screen.

Paso 18: Naming the program

There are various things that you can program the robot to do. We will just cover the basics of making the robot move forward and backward. To program for a NXT Lego robot we will have to program in Next Byte Codes (NBC).  This program that you write will be changed from NBC to binary code by BricxCC which the robot will then be able to read. Begin with a name for the code. In mine, I chose to name it “task main()”. Next we will need to open the program for coding. to do this we enter { below the name of the program.

Paso 19: Moving the bot forwards

19) First we will start with getting the robot to move forward. BricxCC has some already written programs that will help us here. OnFwd(x,y) is an already written program that will move the wheel forward. Notice that after the command, there are two inputs. The x refers to the motor that the command will be sent to. For motor A, x would be OUT_A; For motor C, x would be OUT_C. The y refers to the percentage that you want the motor to move at. I chose 100% for this, so y would be 100. The next line will be for how long you want the robot to move for in milliseconds. The command for this is Wait(z). So if we want the robot to move for 5 seconds, we would input 5000. We will then turn the motors off. This command is Off(x). Write this code twice for both motors on separate lines. After turning off the motors, typing Continue(z) will shut them off for a certain amount of time before the Brick reads the next line of code. For the program to output this code, place a ; after each line of code. If the ; is not there the program will not run properly and the Brick will be overloaded.

Paso 20: Moving the bot backwards.

Next we will move the robot backwards. For the bot to go backwards the command is OnRev(x,y) the inputs are the same as in the previous step. To make it easier on us, we can start both motors at the same time. In step 18, we created two separate steps to turn the motors on. To turn both motors on at the same time, we would instead write OUT_AC in the x input location. For the power input, we will leave it at 100% so y will still be 100. The next line of code will have the time commitment. We will again leave it a 5 seconds. The command is the same as previously stated. Wait(5000) for the motors to move the wheels for 5 seconds. When the robot is done moving, we want to turn the motors off. We can combine the multiple steps that were used in step 18 to turn the motors off into one step by using the same shortcut we used earlier in this step. Off(OUT_AC). This turns both motors off at the same time.

Paso 21: Closing out the program

To finish the program, we need to close it out. To do this all we do is hit “enter” or “return” a couple of lines to show that there is no more code and enter the } key. The finished code will look similar to the figure above. The figure has comments as to what the robot will do during each section of code. We did not talk about how to do that in these instructions.

Paso 22: Running the program

We have now built the robot. We have created a program that will make the robot move. Now all we have to do is get the robot to move. First we need to compile the program so that it can be read by the Brick. On the main screen of BricxCC there is a group of four buttons and a drop down menu. It will look like the figure below. The farthest left button will compile the program, the second to the left will download and rewrite into binary for the Brick, the drop down menu should show the name of your program, the second from the right is the run button, the farthest right is the stop button. Assuming there were no errors in the program click the second to the left button. This will download the program to the Brick. If there are errors, you will be notified of them. After the download is complete, click the second from the right or the “run” button. This will run the program from the Brick.

Paso 23: Conclusion

Congratulations, were finished! Did the robot do what we wanted? If not make sure to check the wiring to make sure the cables are connected to the correct ports. If there were errors in the program, check what you have written with mine from step 21. If everything went to plan, you have built a NXT Lego robot. You have written the program that will move the bot. If the code was written correctly, the bot would have moved forward for five seconds, then waited another five seconds before going backwards for five seconds. If the timing needs to be changed, more or less time can be added. If the direction needs to be changed to go right or left, only one of the motors needs to be turned on for a certain amount of time. Now you know how to change up the code for changing direction as well as timing. 
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    Mar 10, 2013

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