Introduction: Guard Tower Versus Bugs

We are first-year students from The UM-SJTU Joint Institute, which is located in Ming Hang campus of Shanghai Jiaotong University, Shanghai, China.

We’re here to form the Group 13 for the VG100 Introduction to Engineering course of the JI, and this project, which is called “GUARD TOWER VERSUS BUGS”, is a project of the course. The group members, from left to right, are:

Wang Shuhan, 王书涵;

Yu Siyuan, 余思远;

Gong Tianyu, 龚天宇;

Sun Bingqi, 孙秉琪;

Shen Zheyu, 沈哲宇.

By the time this manual is published, the final game results haven’t come out yet. Nevertheless, our bug is the FIRST bug to pass the bug test and excels in performance. In this manual, we’ll show how to build the bug and the tower.

In this competitive project, groups try to build “bugs”, which are essentially mini arduino-driven cars, that can be “killed” by laser, as well as towers that may kill others’ bugs with its laser. The rules of the game are roughly listed as follows:

  • 3 bugs approach and try to “pull down” the tower from 3 tracks out of 4 that lay around the tower. The tower needs to kill the bugs before it gets “pulled down”.
  • The bug must go along the path in 0.2~0.3m/s and stop as long as it’s irradiated by the laser; the execptions are that it can’t be killed when it’s in the shelter or stopping on the white line.

The constraints on our design can be summarized as the following items:

  • Bug design
    • Move between 0.2 m/s to 0.3 m/s.
    • Immune to the raking of laser.
    • Able to go straight ahead along the track.
    • Behave according to the requirements implied in the game rule.
  • Tower design
    • At least 60cm high.
    • Made out of 80g\m^2 A4 paper.
    • No stacking of more than 3 layers of A4 paper.
    • Electronic components (except sensors) placed only on the top of the tower.

The bug needs to pass the bug-test as early as possible and perform well on the game day; the tower’s performance relies on some other factors, including:

  • Weight. Lighter is better.
  • Speed, which includes:
    • Killing more bugs before being hit, preferably all of the 3;
    • Killing the bugs as early as possible, i.e. Kill them before they move much.

For the materials list, please refer to the following document:

Materials list for the tower: here

Materials list for the bug: here

Step 1: Circuit Diagrams of the Bug

A few quick notes:

  • The circuit diagrams are split into 4 different ones for a good visual, i.e. the arduino board and the breadboard are the same throughout the 4 diagrams.
  • “S.” stands for “Sensor”.
  • The line-tracking sensors may look slightly different from the ones in the material list in that they have potentiometers to adjust their sensitivity; this won't really affect the overall functionality of the bug.
  • The R1 potentiometer adjusts the backlight of the LCD.
  • The pins on the breadboard of the first two rows are equivalent within the row. If you see multiple wires connected to one pin, simply find another one.


All diagrams made with Fritzing @

Step 2: Circuit Diagram of the Tower

A few quick notes:

  • Since the servo motor is very power-hungry, a second Arduino board is used to provide proper regulated power supply to the motor.
  • Unplug the batteries when the tower should be idle. Servos drain them quickly.

Step 3: Bug Fabrication & Assembly: Preparing the Board

  1. Use a pencil to draw a rectangle (15cm×10cm).
  2. Draw another rectangle which is 15cm×30xm.
  3. Use a ceramic knife to slice both rectangles. We name the first as the Board 1, and the second one as Board 2.
  4. Polish the rectangle with a grater and make its size perfectly match the original size.

Step 4: Bug Fabrication & Assembly: Fixing Main Parts on the Board

    1. Label a tapping hole in the Arduino and mark it on board 2.
    2. Use the hole as the origin to establish a coordinate system.
    3. Measure every element components and locate them on the appropriate position on Board 2.
    4. Put the Arduino Uno, the drive board and the bread board onto Board 2, and use some screws to fix them on the board.
    5. Connect the three units with wires properly, according to the previous circuit diagrams Figure 1, Figure 2, Figure 3 and Figure 4 in Step 1.

          Step 5: Bug Fabrication & Assembly: Adding Tires and Wheels to the Car

          1. Connect the tires and motors with motor brackets and fix it at the back of the car. If you’ve done it properly, the back wheels should look parallel to each other.
          2. Use a universal wheel and add a few nuts at the front of the car, so that the car can be more balanced.
          3. Fix the line tracking sensor on the car with screws and nuts. In order that the sensor can work properly, put some nuts between the sensor and Board 2 to make it closer to the ground.
          4. Fix Board 1 vertically on Board 2 with L shaped brackets, screws and nuts.
          5. Punch 4 holes parallel to the ground, on the midperpendicular of the longer sides of Board 2 and 5cm away from the ground.

          6. Fix the photosensor on Board 2 with screws and nuts, and keep it parallel to the ground. Check Figure 3 of this step before installing to make sure that the photosensor’s orientation is correct.

          Step 6: Bug Fabrication & Assembly: Adding Other Parts of the Car & Partial Overview

          • Stick the 11.1V lithium battery on the back of Board 2 and connect it to the drive with wires.

          An overview of the finished bug can be seen above.

          Step 7: Tower Fabrication: the Four Pillars

          What you need for the tower:

          • A4 paper *11
          • White glue
          • An accurate ruler

          The four pillars:

          • Take 4 pieces of A4 paper. Slice each pieces of A4 paper into 3 pieces, each of which is 70mm in width and 297mm in length. (The more accurate the better)

          TIPS: Slice every piece of paper with paper knife patiently and carefully, so that the later steps will be easier.


          • Connect the quarter points on both shorter sides (70mm) by pencil.
          • Draw a line which is parallel to a shorter side and the distance should be 90mm.

          Step 8: Tower Fabrication: the Reinforcement Parts

          • Take 2 pieces of papers, slice them into equally six parts and the size should be 35mm*297mm and there should be 12 parts.
          • Using an accurate ruler to measure a length of 207mm on 8 parts and cut it to 35mm*207mm, these are Part C.
          • Similarly make 4 parts which these sizes are 35mm*117mm and here are the Part D.

          Step 9: Tower Fabrication: the Columns

          • Take two Part A and one Part B, then stick these like the following picture.
          • Wait for some moment than apply glue on the whole surface, after that roll it with great care and patience than we got a stick.

          TIPS: for the best effectiveness, please let the blue lines in the picture coincide.

          • Take two partC and one partD, place them in the same position like the picture, then use the glue to make these parts attach to the stick made in Figure 3.3.2.
          • After the white glue dry, one of the pillars is made and repeat it for three times to make four in all.

          Step 10: Tower Fabrication: the Connnection Parts

          • Take 5 pieces of paper, equally divided it into six parts, than fold it like a roll to make it 35mm*297mm in sizes and have a thickness of six pieces of paper than apply a slice of glue to stick it, after these parts dry cut them into half.
          • Draw the reference line like the following pictures make 2 partE and 8 partF, than cut off the shadow parts than extend the central part into a circle and the up and down side should be both three pieces of paper thickness.
          • Pay attention to the parts in circle and deal with them carefully to make them only one paper thickness.

          Step 11: Tower Assembly

          Assembling the pillars and the connection parts like the way in the following picture. Embrace the single-thick-paper around the pillar. Stick these with glue.

          TIPS: Clearly that the useful length of Part E and Part F are different, so Part E are used to connect between the diagonally ones while Part F are used to the neighbor ones.
          Use proper connection parts (Part E and Part F) to connect all the points marked in the picture.

          TIPS: If the tower has some problem in structure stability, try to make a hole at the center of the middle two connection parts and than use a thing stick to cross over it just like tenon-and-mortise work in ancient China.

          Step 12: Final System View & Troubleshooting

          This is what the final system looks like.

          Troubleshooting Section:

          • My bug isn’t going! What should I do?

          Make sure that the line-tracking sensors on the sides aren’t activated. Also, use IR controller to change the isRunning? Flag to “true” and the forceStop? Flag to “false”. (See 2.6.)

          • My bug is going off-track!

          Make sure that nothing gets in the way of the wheel, and the motors are properly fixed to their location. Also, you may fine-tune the speed of either wheel by adjusting the speed multiplier of the motors. (See 2.6.)

          • My tower is firing randomly!

          Fix the distance sensors in the correct position. Make sure that your body parts/your stuff/some furniture don’t get into their way, and nothing suddenly appears in front of them.

          • None of the above solves my problem!

          Press the Reset button on the Arduino board and pray for the best.