PBL: How Can I Design a Robot That Moves Using Vibrations?

Project based learning often explores a question. One of the questions explored in this instructable is, "How Can I Design a Robot That Moves Using Vibrations?"

This Instructable shares step by step instructions for one possible design to build a robot that moves using vibrations. It also shares various lesson plan ideas so you can adapt this project to meet the needs of your students. In my experience, students will need at least 50 minutes to build the design shared here and at least 90 minutes to create an open-ended design.

I currently teach at a public middle school in North Carolina. I've done variations of this robot building lesson with middle and high school students. While many sumobot designs involve soldering and/or programming, this project requires neither.

A common introductory circuit lab involves lighting a bulb using a battery and wires. Similarly, this lab involves a battery and wires but instead of lighting a bulb, the goal of the circuit is to power a motor. If your focus for this lesson is circuit construction, here are some supporting teaching standards:

• North Carolina State Standards
• NC 7th Grade Science: 7.P.2.3 Recognize that energy can be transferred from one system to another when two objects push or pull on each other over a distance (work) and electrical circuits require a complete loop through which an electrical current can pass.
• NGSS Related Standards
• The explicit use of the word "circuits" is absent from NGSS, but an entire article explains how "NGSS says Yes! to teaching circuits". This article cites several standards, including:
• 4th Grade: 4-PS3-2. Make observations to provide evidence that energy can be transferred from place to place by sound, light, heat, and electric currents.
• High School: HS-PS2-5. Plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current.

Another variation of this lesson focuses on concepts related to friction and mass.

Supplies Needed for Each Individual Robot (Tip: This design works well for students to build in pairs.)

• 3 Paper Clips (preferably the larger, 2 inch vinyl coated ones)
• 2 Jumbo Craft Sticks (the 6 inch size)
• ≈24 Inches of Electrical Tape
• 1 Hobby Motor with Pre-soldered Wires (must run using 1.5 volts if only using one AA; otherwise your battery needs may differ - I bought my lot of hobby motors from Ebay)
• Pro Tip: Add drops of hot glue to where the wires connect to the hobby motors BEFORE being used by students. This will GREATLY reduce the number of wires that break off the motors. If you don't plan on having to solder wires back on to the motors, this is a must do step! Otherwise, you will also need wire-strippers, a soldering iron, and solder!
• 1 Offset Motor Weight (Built in Tinkercad and 3d printed, or another option shared in Step 4)
• 1 AA Battery (Apparently I've bought this same box 3 different times)
• Counterbalance Weight (A domino is pictured; however, any small, heavy object can work)

Tools Needed

• Pliers (for bending paper clips, but it is possible to also bend by hand)
• 3d Printer and Filament (if printing student designed offset motor weights)

Hold one wire to the positive end of the AA battery and the second wire to the negative end of the AA battery. If connected correctly, the motor spindle will spin. Note: I intentionally use a design that requires only one AA battery because this is a cost effective choice for the 110 students I have each semester. Batteries are expensive! I also often reuse the same batteries from class to class. Depending on the motor you have, it may require two AA batteries or even a 9 volt battery. Use the correct voltage required by your hobby motor.

Using your hands or pliers, bend each of the three paper clips around one of the craft sticks. Allow an equal amount of paper clip to be on both sets of the loop created by the craft stick. This will create three sets of legs. Similar to an insect, this robot will have 6 legs total. Note: Regular paper clips are pictured, but in my experience, vinyl coated paper clips are much easier to bend. Also, this step doesn't have to be done perfectly. The legs can be bent and tweaked at the end to best support the robot. When trying this design, my students managed to bend the paper clips without pliers. They were pretty grumbly over this step at first, but ultimately figured it out.

Space out the three sets of legs along the length of the first craft stick. Place the second craft stick directly above the first. Hold both craft sticks tightly, sandwiching the legs between the two craft sticks. Secure the two craft sticks and legs by wrapping electrical tape tightly around both craft sticks. The design should be secure so the vibrations from the motor will travel along the robot body to the tips of its toes. This particular design works best when the tape is wrapped around in four places - the top and bottom of the design and the two spaces between the sets of legs. Note: This step is easiest with the help of a partner. One person holds the craft sticks tightly while the other wraps around the tape.

Attach the offset motor weight to the spindle of the motor.

Here are some offset motor weight options for students:

• Design offset motor weights in Tinkercad and 3d print designs to test
• Use pre-built offset motor weights (Note: I bought the ones pictured from the UK. If anyone knows a US source, please share!)
• Hot glue object directly to the motor spindle like a coin in this Wigglebot design or a nut in this Speedy Vibrobot design. Note: This is a good time to remind everyone that safety glasses for eye protection are important!

Determine what will be the "front" of the robot. Tape the entire motor securely to the craft sticks at the front of the robot. Make sure the spindle and offset motor weight is hanging off the front of the robot so it will be able to spin freely. Note: This step is the most common source of troubleshooting for students. At the end they may find their design isn't working because the craft stick is in the way of allowing the motor to spin. It will spin once and get stuck. If this happens, they may be able to push their motor forward. Or, they may have to cut the motor off and re-tape it in a better position.

First find the perfect placement for the battery. This is where both wires from the motor can reach both ends of the AA battery. Once the perfect position is determined, tape the battery to the body of the robot. Next tape the metal end of one wire to one end of the battery. Make sure the metal on the end of the wire is in full contact with the end of the battery. Then, tape the second wire end to the other end of the battery. This should make the motor spin, so be ready! Last, un-tape one of the wires as shown in the picture. This tape/wire will be the on-off switch for the robot. Right now it is in the off position. Tape the wire back when you want to turn the robot back on.

If needed, add a counterbalance. If your motor wires were as short as mine, it is likely that your robot is front heavy and unbalanced. A variety of different objects can be taped to the back of the robot for balance. The robot design in the picture uses a domino. Brainstorm possible other counterbalance ideas. For example, you can fold an origami paper box to tape to the end and add coins. Or you can design a small box to 3d print. The easiest solution is to use materials you already own.

After adding a counterbalance, bend the legs as needed. Pliers can be very helpful during this step. You can bend the end of each paper clip to add a "foot". A couple of different student leg designs are shown in the second photo.

Create a defined battle ring on the floor or tabletop using electrical tape. Have students create rules for their SumoBot competition and play according to the rules they created. I like having my students create their own rules. If you want to provide rules, here are two simple rules created by my students that they refined after several rounds of battle:

1. If any part of the craft stick body touches the tape edge, that robot is out.
2. Any robot that doesn't move or stays in the same spot for 5 or more seconds is out.

Note: You may want to create multiple sumo rings and limit each ring to 10 students or less.

Everyone Builds the Same Thing vs. Everyone Builds Something Different

Project based learning puts students at the center of building solutions to problems.

If you use the robot build provided in this instructable, your students may be focusing on just one particular problem that best aligns with your objectives. For example, students might focus on:

• How can I create an on/off switch for a vibrational robot?
• How can I 3d design and print an offset motor weight?
• How can I design legs so a vibrational robot travels in a straight path?

Open Ended Challenge

Many times when I teach this lesson, I do not give students any models or examples at all. Their challenge is to create their own working circuit and robot using provided materials. When I use this approach, all the groups have different supplies from my "happy trash" stash. This is a great way to use up spare materials. Providing different materials is also handy when you do not have enough of the same material for all groups. Each partnership/group needs a base set of materials (motor with wires, offset weight or way to create offset weight, and battery). Beyond that, the materials can vary from group to group and/or class to class. You can approach this challenge all at one time, or approach it in stages by using the following outline:

• First Challenge: Build a Working Circuit
• Second Challenge: Create an on/off Switch
• Third Challenge: Design an Offset Motor Weight (or some other method to create vibrations for movement)
• Fourth Challenge: Design a Robot Body

Note: Seriously, do not give or show any examples. If I show my students even one example, I find all their designs resemble what I share. You can easily spot designs inspired by this resource. The only true help I give as needed is how to set up the basic circuit. From there I simply circulate and facilitate group collaboration.

Creativity Rubric for Student Assessment Criteria

The Buck Institute for Education (BIE) PBLWorks has a 2022 Creativity Rubric for Grades 6-12 that is useful to use with students or for students to use as part of self evaluation that is useful with this activity.

Other Teacher Tips

• Dollar store electrical tape is not always my favorite tape, but I find it works just fine for this project. Dollar store vinyl coated paper clips can be used as well.
• You can have students CAREFULLY cut apart their designs to reuse materials with other classes if supplies are limited. Take pictures of designs first so students see you have pride in their work.
• Follow student joy and enthusiasm. Do they want to create wings to see if it can fly? Try it! Do they want to forgo legs in favor of a caterpillar design? Go for it!
• Enlist student help always. I thought some of my very old hobby motors were broken. Shoutout to Riley who discovered that spinning the spindle to "get it going" fixed all my old motors.
• YOU CAN solder! This project does NOT require soldering, but as a teacher it is helpful to have this skill. If you currently cannot solder, you can easily learn how to solder! Being able to solder will save you money because you can fix your own hobby motors. When I need to solder, I like to enlist the help of a student because four hands are better than two. Teaching middle schoolers to solder is a special challenge all by itself, so sometimes a teacher/student soldering duo is the easiest and safest approach. Someone in your school or community may even have soldering supplies you can borrow.

Thank you for taking the time to read over my instructable. I'd love to hear other variations and tips you have for this project so please share in the comments. Happy teaching!