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

Difficulty
Time Required Average (6-10 days)
Prerequisites None
Material Availability You will need to order several parts from an online vendor or hobby store. See the Materials and Equipment list for details.
Cost Very Low (under $20)
Safety Adult assistance is required to snip off the head from a toothbrush using scissors or wire cutters.

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. In this project, you will build assorted BristleBots with different types of toothbrushes and race them against each other.

Objective

Build different versions of the BristleBot and see which type goes the fastest.

Credits

Ben Finio, Ph.D.,S cience Buddies

The BristleBot name and idea were originally posted online by Evil Mad Scientist Laboratories in 2007, at http://www.evilmadscientist.com/2007/bristlebot-a-tiny-directional-vibrobot/. This science project is an adaptation of their original directions.

Thanks to Michelle Maranowski of Science Buddies for help testing this project.

Cite This Page

MLA Style

Science Buddies Staff. "Racing BristleBots: On Your Mark. Get Set. Go!" Science Buddies. Science Buddies, 24 Jan. 2014. Web. 1 Aug. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Robotics_p010.shtml?from=Blog>

APA Style

Science Buddies Staff. (2014, January 24). Racing BristleBots: On Your Mark. Get Set. Go!. Retrieved August 1, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Robotics_p010.shtml?from=Blog

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Last edit date: 2014-01-24

Introduction

Have you ever wished that you could have your very own robot? The robots in this project might not be quite as cool as Pixar's WALL-E or Optimus Prime from the Transformers, but they are still a lot of fun — and easy to build!

A vibrobot is a robot powered by a vibrating motor, like the kind found in cell phones or video game controllers that make them vibrate. A popular version of the vibrobot is called a BristleBot — a tiny robot made from the head of a toothbrush, a watch battery, a vibrating motor, and some double-sided tape. The toothbrush head acts as the robot's "body". The motor and the battery form an electrical circuit when they are connected — the battery powers the motor to make it spin. The double-sided tape lets you attach this circuit to the top of the toothbrush head. When assembled, these parts make a little robot that buzzes along a flat surface, kind of like a bug! Even though it does not actually having moving legs, the spinning motion of the motor can make the BristleBot vibrate and move forward or spin in circles. For the same reason, you may have noticed a cell phone slide along a tabletop slightly when it rings in vibrate mode.

The BristleBot name was originally introduced by Evil Mad Scientist Laboratories, and their work has inspired several different books and toys based on the idea (unfortunately, not all of them give appropriate credit — you can read more about the origins of the idea in this article). Evil Mad Scientist Laboratories put their directions to build a BristleBot online with this video in 2007:

This video provides helpful, step-by-step directions for how to build a BristleBot. We highly recommend watching it before you continue with the project, but remember that our instructions have a few tweaks to help your BristleBot's performance. (Many thanks to Evil Mad Scientist Laboratories for making this video).

Watch this Bristlebot YouTube video http://www.youtube.com/watch?feature=player_embedded&amp;v=rUSTXUis_ys This video provides helpful, step-by-step directions for how to build your first BristleBot. We highly recommend watching it before you continue with the project. (Many thanks to Evil Mad Scientist Laboratories for making this video).

One important thing to remember about BristleBots is that they cannot steer or be steered remotely — they only have one motor that either turns on or off, depending on whether the circuit is open or closed. In a closed circuit, all the wires are connected, which means electricity flows from the battery to the motor, and the motor spins. In an open circuit, at least one wire is disconnected, so electricity cannot flow, and the motor will not spin. Since BristleBots only have one motor and no steering wheel, building a robot that goes perfectly straight can be very difficult. You can adjust the position of the battery and motor to affect how the robot moves, but in this project you will make a chute out of paper to help the robots move in a straight (or nearly straight) line.

The type of toothbrush bristles is one big factor that affects how your BristleBot performs. At supermarkets or drugstores, you will see many different types of toothbrushes — some with straight bristles, some slanted, some even pointing in multiple directions and with different lengths. The type of bristle will affect the speed of your BristleBot: Can you guess how? In this project, you will build at least two BristleBots with different types of toothbrushes, and then race them down a narrow chute (to keep them going in a straight line) and then see which is faster.

Terms and Concepts

  • Robot
  • Vibrobot
  • BristleBot
  • Battery
  • Motor
  • Circuit
  • Open circuit
  • Closed circuit
  • Average

Questions

  • What BristleBot do you think will go faster — one with straight bristles, or one with slanted bristles?
  • BristleBots are fun toys, but many other kinds of robots with real-life uses exist. Can you find at least three other types of robots and what they are used for?
  • What is the difference between an open circuit and a closed circuit?

Bibliography

Materials and Equipment

This list contains all the parts to build two BristleBots to race. If you want to build and compare more robots, you will need more parts.

  • Toothbrushes (2). One with straight bristles and one with slanted bristles. You can get more if you want to test additional kinds of bristles.
    • Important: Toothbrush heads that are too small or narrow may be too top-heavy when you add the motor and battery, and therefore tend to fall over. Larger toothbrushes will be more stable.
  • Strong scissors or wire cutters (to snip off the toothbrush heads)
  • Roll of double-sided foam tape (to mount the motor and battery to the toothbrush head) available from Amazon.com
  • Roll of electrical tape (to help attach the motor wires to the battery).
  • Small binder clips (optional) — if you are having trouble getting a good connection between your motor wires and the battery, these can be used to help "clip" the wires on.
  • CR1220 3-volt coin cell batteries (2), available from Amazon.com
  • Small vibrating motors (2), available from Amazon.com
  • Piece of printer or construction paper (to create the chute to race your robots), minimum size 8½" x 11" (larger is OK)
  • Stopwatch
  • Lab notebook

Note: Some online vendors sell BristleBot kits. If you chose to explore one of those remember you will need enough supplies to build at least two Bristlebots. Also, these kits typically only come with one type of toothbrush head, so you will still need to buy an extra toothbrush.

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Experimental Procedure

Building Your BristleBots

These directions show you how to build one robot. Repeat Steps 1-6 to build your second robot. We have rewritten our own directions here, but remember that Evil Mad Scientist laboratories also has a great video showing how to build a BristleBot if you need additional help. We have also added one more recommended step — using tape to attach the motor wires to the battery (otherwise it can be hard to get them to touch and make a good connection).

  1. Cutting off the toothbrush head — ask an adult to help you with this step! Use a strong pair of scissors or wire cutters to cut off the head of a toothbrush. If you cannot cut all the way through the plastic, it should be easy to snap the head off after you have cut into the surface. Figure 1 below shows several different toothbrush heads after they have been removed from the shaft of the toothbrush.
Robotics science project Different types of toothbrush heads for Bristlebots
Figure 1. Four types of toothbrush heads with different styles of bristles.
  1. Arrange the rest of the materials you need to build one BristleBot: a piece of foam tape, a battery, and a motor. These pieces are shown in Figure 2 below.
Robotics science project Bristlebot components – toothbrush, motor, battery and foam tape.
Figure 2. The four components needed to build one BristleBot: a toothbrush head, motor, battery, and foam tape.
  1. Peel the backing off the foam tape and attach it to the top surface of the toothbrush head. This step is shown in Figure 3 below.
Robotics science project Bristlebot construction step – attach foam tape.
Figure 3. The foam tape (white rectangle) is attached to the top surface of the toothbrush head.
  1. Using electrical tape, attach one of the motor wires to one side of the battery. Make sure the exposed metal part of the wire is touching the metal on the battery, as shown in Figure 4 below. Note: The images are taken with clear tape so that you can see the position of the wires more clearly. But, we recommend using electrical tape on your BristleBot instead as it will hold the wires together better than clear adhesive tape when the robot moves.
Robotics science project Bristlebot construction step – attach wire to battery with tape.
Figure 4. Use tape to attach one motor lead to one side of the battery. Note: We used clear adhesive tape for this picture because it is translucent, so you can see the position of the wire under the tape. However, we highly recommend using electrical tape for connecting the wire to the battery.
  1. Put the motor and battery on top of the piece of foam tape, with the taped-down motor lead side of the battery facing down, as shown in Figure 5 below. Important: Make sure that the motor's weight can spin freely and does not get stuck on the tape. Do this by putting the main body of the motor on the foam tape, letting the spinning weight hang slightly off the edge of the tape.
Robotics science project Bristlebot construction step – attach motor and battery to foam tape.
Figure 5. The motor and battery attached to the top of the toothbrush head.
  1. Attach the remaining motor wire to the top of the battery, as shown in Figure 6 below. With patience and a few tries, you should be able to bend the wire and press it against the side of the battery and it will stay there, but this can be hard to do. Getting a good connection to the battery with both of the motor wires is essential for your BristleBot to work properly. If one of the wires is not touching the battery, the circuit is still open, so the motor will not spin, and your BristleBot will not move. If you are having trouble getting a good connection, you can try a few things:
    1. Use electrical tape to attach the end of the remaining wire to the battery. This might make it easier for the wires to stick to the battery.
    2. Use a small binder clip to "pinch" the wires to the battery. Make sure to cover the wires with tape first if you are using metal binder clips (otherwise electricity will flow through the binder clip and not through the motor). This might make the connection better, but it also risks making your BristleBot top-heavy and more likely to fall over, depending on the size of your toothbrush head and the size of your binder clip.
    3. (Ask an adult to do this step). Using scissors, a sharp knife, or wire strippers if you have them available, try to remove some insulation from the ends of the motor wires, making the exposed metal part longer. This might make it easier to get a good connection.
Robotics science project Completed Bristlebot
Figure 6. A completed BristleBot with the second motor wire taped to the top of the battery. Remember that we used clear adhesive tape for these pictures (so you can see the wire through the tape), but for your project, we recommend using electrical tape.
  1. Repeat steps 1-6 to build your second BristleBot with a different type of toothbrush head. In the meantime, temporarily detach the top motor wire from the battery of your first BristleBot, so you do not drain the battery (and do it does not escape when you are not looking!).

Note: If you remove the motor and battery from the foam tape and put them back on several times, the tape might start to lose its stickiness. If this happens, simply use a new piece of tape from the roll you bought for this project.

Racing Your BristleBots

Once your BristleBots begin moving, you may have noticed that they do not travel in a very straight line. This will make racing them rather difficult. So you will create a chute to help the robots go straight so you can measure their speed accurately. Before you start, make a prediction — which of your BristleBots do you think will be the fastest? If you made more than two BristleBots, can you rank them from what you think will be fastest to slowest?

  1. Cut a long strip of paper about 1½ to 2 inches wide. Then fold up the long edges of the paper (about ¼ to ½ inch on each) side to form a long chute with side walls — make sure the chute is wide enough for the BristleBot to travel through without getting stuck, but not so wide that it can completely spin around. It should be able to move only in one direction. An example chute is shown in Figure 7 below.
Robotics science project Racing chute for Bristlebots
Figure 7. A strip of printer paper is folded to create a racing chute for the BristleBots.
  1. Using your stopwatch, time how long it takes one of your BristleBots to travel from one end of the chute to the other. Do at least three trials to make sure your times are accurate and scientific, and record those times in your lab notebook. If something goes wrong (for example, your BristleBot gets stuck or falls over), redo that trial.

    Note: if you find it difficult to operate your BristleBot and your stopwatch at the same time, get a volunteer to help. One person can operate the BristleBot on the chute, and the second person can operate the stopwatch and record times.

  2. Repeat step 2 for your other BristleBot. Do at least three trials, and record the times in your lab notebook.
  3. Compare the times it took your BristleBots to travel down the chute. If you know how to calculate an average (or have an adult that can show you how),average the race times for each BristleBot. Is one of them faster on average? If so, what type of bristles did the faster BristleBot have, and why do you think it was faster? Were your predictions correct?

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Variations

The BristleBot has many existing variations — you will see a lot of them if you search on YouTube for "bristlebot," "vibrobot," or "brushbot." Here are just a few of these ideas:

  • BristleBot steering: Sometimes you can adjust which way your BristleBot turns by changing the position of the motor and the battery. Can you fine-tune these adjustments to make your BristleBots go straight, even without a chute?
  • BristleBot maze: BristleBots can be excellent at wandering through mazes, because they have a tendency to bounce off walls and corners without getting stuck. Can you construct a maze for your BristleBots (from paper, cardboard, or toys like LEGOs®)? Even though the BristleBots cannot actually steer, do they eventually find their way out?
  • Jumbo BristleBot: You can make a much larger BristleBot using a scrub brush instead of a toothbrush head, but this will require bigger batteries and a bigger motor.

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