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Racing Bristlebots: On Your Mark. Get Set. Go!

Difficulty
Time Required Average (6-10 days)
Prerequisites None
Material Availability Motors and batteries to do this project are available in a kit from Science Buddies. The kit can also be used to do several other robotics projects. See the Materials and Equipment list for details. Estimated project time includes time to ship the kit.
Cost Low ($20 - $50)
Safety Adult supervision is required when cutting the head off a toothbrush.

Abstract

Have you ever wanted to build your very own robot from scratch? Bristlebots are a cheap, easy, and fun-to-build robot made from the head of a toothbrush, a battery, and a small motor. Once completed, they buzz along the top of a table like bugs. How can you make a bristlebot go faster? In this project, you will build bristlebots from two different types of toothbrushes, and race them against each other to find out.

Objective

Build one bristlebot with straight bristles and one with slanted bristles, and race them to see which is faster.

Credits

Ben Finio, PhD, Science Buddies

This project is based on the following post by Evil Mad Scientist Laboratories: http://www.evilmadscientist.com/2007/bristlebot-a-tiny-directional-vibrobot/

Cite This Page

MLA Style

Science Buddies Staff. "Racing Bristlebots: On Your Mark. Get Set. Go!" Science Buddies. Science Buddies, 17 Oct. 2014. Web. 30 Oct. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Robotics_p010.shtml>

APA Style

Science Buddies Staff. (2014, October 17). Racing Bristlebots: On Your Mark. Get Set. Go!. Retrieved October 30, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Robotics_p010.shtml

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Last edit date: 2014-10-17

Introduction

Have you ever wanted to build your own robot? What about tiny robots that you could race against each other? In this science project, you will build and race bristlebots, tiny robots built on the head of a toothbrush, like the ones shown in Figure 1, below.

bristlebots racing
Figure 1. Two bristlebots racing against each other.

The bristlebot uses a small electric motor to move. In order to power the motor, the robot also needs a battery. When you connect the battery to the motor, you complete an electrical circuit, and this allows the motor to spin.

The motor has an off-center weight attached to it, which causes the motor to vibrate when it spins. When the motor vibrates, it causes the robot to shake and buzz along the tabletop. This is the same technology that makes video game controllers and cell phones vibrate; on the inside, they have little spinning motors with weights attached.

In this science project, you will build two different bristlebots: one with slanted toothbrush bristles, and one with straight bristles. Then you will race them against each other to see which one is faster!

Terms and Concepts

  • Robot
  • Motor
  • Battery
  • Circuit
  • Vibrate
  • Short circuit

Questions

  • What makes the motor vibrate?
  • How can a vibrating motor make something move?
  • What do you think will go faster, a bristlebot with straight bristles, or one with slanted bristles?

Bibliography

This project is based on the following post by Evil Mad Scientist Laboratories:

If you want to learn more about some of the concepts in this project, like circuits and vibrational motion, check out these references:

Materials and Equipment Product Kit Available

These specialty items can be purchased from the Science Buddies Store:

  • Bristlebot kit (1). You will need these items from the kit:
    • Coin cell battery with leads (2)
    • Mini vibration motor with leads (2)
    • Note: The kit also contains enough electronics pieces to make two additional types of small robots. See the kit instructions page for details.

You will also need to gather the following materials, which are not included in the kit:

  • Toothbrushes (2), one with slanted bristles and one with straight bristles
  • Double-sided foam tape
  • Scissors
  • Piece of paper
  • Optional: Stopwatch
  • Lab notebook

Order Product Supplies

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Project Kit: $34.95

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Experimental Procedure

Building Your Bristlebots

  1. Have an adult help you cut the heads off two toothbrushes. Make sure one toothbrush has straight bristles and one has slanted bristles, like the ones shown in Figure 2, below.
    1. If you cannot cut all the way through the neck of the toothbrush with scissors, you can score it (cut into the surface as far as possible), then bend it back and forth several times to break the head off.
toothbrush heads for bristlebot
Figure 2. A toothbrush head with straight bristles (left) and one with slanted bristles (right).
  1. Cut a small piece of double-sided foam tape, about the size of one of your toothbrush heads.
  2. Place one piece of tape onto the back of a toothbrush head, and remove the tape's paper backing, as shown in Figure 3, below.
bristlebot double sided tape
Figure 3. Place double-sided tape on the back of one of the toothbrush heads.
  1. Firmly press a motor (the shiny metal cylinder) lengthwise onto the double-sided tape, so that the off-center weight is sticking off the short edge of the tape at the brush end, and the motor's wires are pointing toward the cut end of the toothbrush, as shown in Figure 4, below.
    1. It is important to make sure that the weight is free to rotate completely, and that it does not get stuck against the tape or the toothbrush.
bristlebot pager motor bristlebot pager motor
Figure 4. Attach the motor to the double-sided tape.
  1. Firmly press a coin-cell battery (the piece wrapped in yellow plastic) onto the double-sided tape, as shown in Figure 5, below. The battery's wires should be pointing toward the cut end of the toothbrush, in the same direction as the motor's wires.
    1. Note: do not remove the yellow plastic wrapper from the battery. It helps keep the wires attached to the battery.
bristlebot coin cell battery
Figure 5. Press the battery onto the double-sided tape.
  1. Twist the exposed metal parts of the battery's black wire and the motor's blue wire together, as shown in Figure 6, below.
    1. Note: your wires might have short sections of plastic insulation still stuck on the ends, covering the metal parts. You can gently tug on these sections to remove the insulation. Be careful not to pinch and pull too hard, as you might rip the entire wire off of the motor or battery.
twisting together bristlebot battery and motor leads
Figure 6. Twist together one set of wires from the motor and battery.
  1. Do not twist together the red wires yet. If you do this, your bristlebot will turn on! First, you need to build your second bristlebot and set up a race course.
  2. Repeat steps 2–6 to build your second bristlebot.

Racing Your Bristlebots

  1. One problem with bristlebots is that they tend to randomly buzz all over the place instead of going straight. This makes it rather difficult to race them against each other. To force them to go straight, cut and fold a piece of paper to make two side-by-side "chutes," like in Figure 7, below. Each chute should be wide enough that a bristlebot does not get stuck against the sides, but narrow enough that it cannot spin around completely. Be sure you have your finished chute on a flat surface.
bristlebot racing chute
Figure 7. Make a racing chute for your bristlebots from a piece of paper (top left: a view straight down the chutes, showing how the paper is folded).
  1. Now, get ready to race your bristlebots! For each bristlebot, twist together the exposed metal part of the red wires from the motor and battery, just like you did in Figure 6 (above) for the black wires. This will cause your bristlebots to start moving, so don't let them escape!
    1. Important: Make sure the exposed metal parts of the red and black wires from the battery do not touch each other. This will create a short circuit and cause the battery to overheat and die very quickly. It is okay for the insulated plastic parts of the wires to touch, just make sure the metal parts do not touch.
  2. Pick up your bristlebots and place them side by side in your racing chute, with the cut ends of the toothbrushes facing toward the far end of the chute, as shown in Figure 7, above.
  3. Let both bristlebots go at the same time. Watch closely to see which one makes it to the other end of the chute first.
  4. Record the winner of the race in your lab notebook.
  5. Repeat the race four more times, for a total of five trials. Make sure you record your results in your lab notebook.
  6. Optional: Use a stopwatch to record how long it takes each bristlebot to go down the chute. Have a volunteer help if it is too difficult to use a stopwatch and control both bristlebots at the same time.
  7. Analyze your results.
    1. Does one bristlebot consistently win the race?
    2. How do your results compare to your prediction about which type of bristlebot would be faster?

Troubleshooting

For troubleshooting tips, please read our FAQ: Racing Bristlebots: On Your Mark. Get Set. Go!.

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Variations

  • Try building more bristlebots with even more types of toothbrushes. Which toothbrush head works the best?
  • If you would like to build a larger robot that works on the same principle as the bristlebot (vibrational motion), check out the Science Buddies project Art Bot: Build a Wobbly Robot Friend That Creates Art. The electronic parts required to build an Art Bot are already included in your Basic Vibrobot kit from Science Buddies.
  • If you would like to try a more advanced project, you can build a light-following bristlebot in the Build a Light-Tracking Bristlebot project.
  • Instead of using a chute, make a circular "arena" for your bristlebots to let them move around freely. Set up a video camera directly above the arena, looking down, and use it to record the bristlebot's motion. Then, analyze the video with a computer and make plots of the path each bristlebot follows. Do the paths seem totally random, or can you identify any patterns? For example, do certain bristlebots tend to always turn in one direction?
  • Make a "maze" for your bristlebots and time how long it takes different designs to find their way out of the maze.

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Frequently Asked Questions (FAQ)

If you are having trouble with this project, please read the FAQ below. You may find the answer to your question.
Q: Why will my bristlebot not go straight?
A: A bristlebot's motion is random, meaning that it has no steering. It is very difficult to build a bristlebot that will go perfectly straight on its own. This is why the instructions recommend making a chute to guide the bristlebots on a straight path.
Q: Why does my bristlebot keep falling over?
A: If your bristlebot falls over, it is likely that your toothbrush head is too narrow. If the base of the robot (formed by the toothbrush bristles) is too narrow, it is easy for the robot to tip over. Try using a larger toothbrush head with more widely spaced bristles.

There is also a chance that you have the battery and/or motor placed too far off-center. Since the battery and motor are both heavy, they can cause the bristlebot to lean to one side. If you notice that your bristlebot always falls in one direction, try moving the battery or motor away from that side of the robot.

Q: Why does my bristlebot suddenly stop moving?
A: If your bristlebot abruptly stops moving, two of the wires you twisted together probably came loose. Constant vibrations can cause the wires to wiggle and gradually come apart. Check to make sure the wires from the motor and battery are tightly twisted together.
Q: Why can I not measure a speed difference between my two bristlebots?
A: Make sure you are using two completely different types of toothbrush heads, one with straight bristles and one with slanted bristles. If you are using two similar toothbrush heads, even if they are not identical, the bristlebots might move at about the same speed.
Q: How long will my bristlebots' batteries last?
A: Your bristlebots' motors use a lot of electricity. The tiny coin cell batteries that come with your bristlebots were not designed to supply a lot of electricity for long periods of time. You might notice your bristlebot starting to slow down after 5–10 minutes of continuous use. If this happens, disconnect the motor and battery wires to let the battery "rest."

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If you have purchased a kit for this project from Science Buddies, we are pleased to answer any question not addressed by the FAQ above.

In your email, please follow these instructions:
  1. What is your Science Buddies kit order number?
  2. Please describe how you need help as thoroughly as possible:

    Examples

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    Bad Question I don't understand the instructions. Help!
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