Vibrobots— Tiny Robots from Scratch

Background Information for Teachers

Have you ever noticed how your cell phone might move slightly if it vibrates while sitting on a hard surface? Inside the phone there is a tiny motor that causes the vibrations. The motor is powered by a battery, which stores electrical energy. The same type of motor is also used in video game controllers to make them vibrate.

In this project, your students will build a simple circuit by connecting a small battery to a vibration motor. They will attach their circuit to the body of a robot that they build from craft materials. The vibrating motor will make the robot buzz around like a bug. However, they have to be careful—all those vibrations can make the robot wobbly and prone to falling over, or even fall apart. They will use the engineering design process to build a sturdy robot that can move around without falling over. The engineering design process is iterative, meaning you might go through the steps more than once. Many times, students' robots will not work well on the first try. They will have to test, redesign, and retest them until they can get a working robot.

In order to help your class build their robots, it will help to understand some basic terms about electrical circuits. The battery and the motor each have two wires, as shown in Figure 1.

• When only one set of wires is connected as shown in the top of Figure 1, it is called an open circuit. There is no complete path for electricity to flow, so the motor will not vibrate.
• When both pairs of wires are connected as shown in the middle of Figure 1, it is called a closed circuit. Electricity can flow in a complete loop from the battery and through the motor, and the motor will vibrate.
• When the battery wires touch each other as shown in the bottom of Figure 1, it is called a short circuit. Short circuits are bad because they will drain the battery very quickly and even cause it to get hot.

Image Credit: Ben Finio, Science Buddies / Science Buddies

A battery must be correctly connected to a motor for both to function properly. In an open circuit there is no connection between the wires of a battery and motor so the motor receives no power. In a closed circuit the positive and negative leads are connected and the motor receives power. If the positive and negative leads between a battery and motor are crossed then a short circuit occurs and the motor receives no power.

Figure 1. Open, closed, and short circuits.

The battery in this project does not have an on/off switch. So, to turn the robots "off," you will need to disconnect one set of wires to make an open circuit. To turn the robots "on," you will need to reconnect the wires to form a closed circuit.

Additional Background Links

• Bristlebot: A tiny directional vibrobot, Evil Mad Scientist Laboratories
• Race Tiny RumbleBots with a Hand-Cranked Raceway, Doug Stith, Make Community
• The Engineering Design Process, Science Buddies

Prep Work (10 minutes)

Organize your materials in advance:

• One battery and one motor for each group.
• Put all the craft materials in a central location.
• Print out copies of the student worksheet.
• Optional: apply a dab of glue to the base of each wire on the motor. These wires are thin and can be easy to break if you aren't careful. Glue will help reinforce them and prevent your students from accidentally ripping them out.

Engage (5 minutes)

Has anyone ever seen a cell phone or video game controller vibrate? What makes them vibrate?

Cell phones and game controllers have tiny motors inside that make them vibrate (hold up a motor to show the class).

What happens to the cell phone or controller if it vibrates while sitting on a flat, hard surface?

The vibrations will cause the phone or controller to move around.

In this project, we will harness those vibrations to build a tiny robot that moves around. The vibrations can make the robot fall over or fall apart, so our goal will be to build sturdy robots that can move around without falling over.

Explore (45 minutes)

Assemble the Circuit

Walk the entire class through these steps to test their circuits (see Figure 2):

1. Pick up the yellow circle with red and black wires. This piece is the battery. Remove any loose bits of plastic from the ends of the wires.
2. Pick up the gray cylinder with red and blue wires. This piece is the motor. Remove any loose bits of plastic from the ends of the wires.
   Be gentle with the motor wires. They are thin and can rip if you are not careful. You can apply a dab of hot glue at the base of the wires to reinforce them.
3. Twist together the exposed metal parts of the red battery wire and the red motor wire. They should be twisted tightly enough that if you tug on them gently, they do not come apart.

   What happens?

   Nothing! We have only connected one set of wires, and so far we have an open circuit. There is no complete path for electricity to flow, so the motor does not vibrate.

4. Pinch together the exposed metal parts of the black battery wire and the blue motor wire.

   What happens?

   The motor should vibrate! Now we have a closed circuit, and there is a complete loop for electricity to flow from the battery and through the motor.

5. Briefly pinch together the red and black battery wires (while keeping the black battery wire and blue motor wire pinched together).

   What happens?

   The motor should stop vibrating. When the battery wires touch, they create a short circuit. Short circuits are bad because they drain the battery very quickly and can cause it to get hot. It is very important to make sure the battery wires do not touch each other.

6. Release the blue and black wires. The motor should stop vibrating. This will prevent the battery from draining while you build your robot.

Image Credit: Science Buddies
Figure 2. Battery (left) and motor (right) connected to form a closed circuit.

Build the Robot

Now, let each group design, build, and test their robots.

1. Show the students the materials you have available for them to build their robots' bodies. Let them use the student worksheet to brainstorm and sketch designs before they start building.
2. Let each group gather materials and start building their robots based on their design ideas.
3. After completing the body, attach the motor and battery.
   1. The motor has an adhesive coating on the bottom. Peel off the paper backing to expose the adhesive, and stick the motor to the robot's body.
   2. Use a piece of tape to attach the battery.
4. Twist together the black battery wire and blue motor wire (tightly enough that they do not come apart, but loosely enough that you will be able to undo them to turn the robot off). The robot should start vibrating.
5. Put the robot down on the desk and observe how it moves. Write down observations on the student worksheet.

   What happens?

   Results will vary depending on how students built their robots. Some robots might buzz around the desk randomly, kind of like bugs, especially if they are lightweight and sturdy. However, robots that are too heavy or too flexible might not move at all. Robots that are too tall might fall over. Robots that are not taped together well enough might fall apart.

6. Disconnect the black and blue wires to turn the robot off.
7. As time allows, ask each group to share their results with the rest of the class or nearby groups.

   Did we notice any common problems with the robots? How could we work to improve our designs?

   Answers will vary depending on how students built their robots. For example: Robots that fell over frequently could be made shorter or wider to make them more stable. Robots that fell apart or had the motor/battery fall off could be reinforced with more tape. Robots that were too heavy to move could be redesigned with fewer or lighter materials.

8. Allow students to iterate and continue redesigning and retesting their robots as time allows. Can each group build a robot that moves around without falling over or falling apart?
9. As time allows, ask each group to share their final design with the class or nearby groups. How different is it from their initial design?
10. Disconnect the blue and black wires to turn all the robots off when everyone is done testing.

Reflect (10 minutes)

Discuss the following questions as a class.

What kinds of problems did people run into when building their robots?

What changes did they make to their robots to overcome those problems?

How different are the designs different groups came up with? What types of shapes and materials did people use for their robots' bodies?

Did some designs work better than others? Why or why not?

Assess

You can use this quiz to assess student learning after the activity:

• Online quiz, assignable in any LMS
• Quiz (pdf) and answer key (PDF)

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Robotics Engineer

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Career Profile

Robotics engineers combine expertise from different areas, including electrical and mechanical engineering and computer science, to design the robots that you see in the real world. Robots do everything from building cars to vacuuming floors to disarming bombs and interacting with people. If you liked designing and building your own robot from scratch, you might want to be a robotics engineer! Read more

Mechanical Engineer

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Career Profile

Mechanical engineers design and build mechanical systems, like the bodies of robots or vehicles. They often work with motors and need to analyze the properties of different materials to determine the best way to build a structure. If you liked thinking about the different materials you could use to build your robot, how you could connect them, and analyzing how your robot moves, you might like being a mechanical engineer. Read more

Electrical & Electronics Engineer

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Career Profile

Electrical engineers deal with electrical circuit components like the motors, wires, and batteries in your robot. They also design and build the circuits that go inside electronic devices we use every day like cell phones, computers, and video game consoles. If you liked connecting the motor and battery wires to make a circuit and think learning more about circuits would be fun, then you should read more about electrical engineering. Read more

Lesson Plan Variations

• Challenge your students to build vibrobots that can go straight instead of moving randomly or spinning in circles (hint: they key is giving the robot slanted legs).
• Instead of craft materials, you can use toothbrush heads as bodies for the robots. Try experimenting with different types of toothbrushes (like straight vs. slanted bristles) to see how they affect the robots' motion. See the Build a Bristlebot activity and the Racing Bristlebots project for more information.
• Build jumbo versions of vibrobots using bigger motors and batteries. See the Building Junkbots—Robots from Recycled Materials lesson plan for more information.