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How to Make a BristleBot
DIY Toothbrush Robots
In the last couple of years, kids have grown a love for hexbugs. They are little robotic bugs. You turn them on and they just go. But, before there were hexbugs, there were Bristlebots.
Bristlebots are made out of the end of a toothbrush with an attached vibration motor and battery to power it. It seems simple, but when you see your bristlebot bustling across the table, you can't help but grin.
BristleBots are, in my opinion, far more interesting and cool than hexbugs since they are a project you can do yourself and then improve upon. You can make a BristleBot for under $5, or much cheaper if you buy your materials in bulk.
The Evil Mad Scientist
The Evil Mad Scientist started the whole concept for the bristlebot, and coined the name.
The beauty of the BristleBot is that you have to make it work with your materials. Only you are using that toothbrush, cut in that spot, with that motor, and that battery. You might just have to use your noggin to make it work.
Keeping it light weight is crucial so you'll want a small battery (not AA). A round batter (like a coin or watch battery) will give enough power to run your bot.
How Cool Are Bristlebots?
- The head of a toothbrush, (preferably with angled bristles)
- A vibration motor, (aka pager motor)
- Copper Wire, (a few inches will do)
- A Battery, (alkaline or lithium coin cell or a watch battery - 1.5 V or 3 V)
- Double Sided Foam Tape
- First test your motor with your battery by connecting them with the copper wire. Once you know it will work, it's time to put the Bristlebot together.
- 1. Cut the head off of your toothbrush.
- 2. Use the double sided foam tape to attach the motor to the bristle head. Make sure the weight that spins is not obstructed (if your motor has it external).
- 3. Stick down the battery to the bot with the tape as well. Your battery may not fit well with the motor, so you may need to stand it up.
- 4. Connect your wires and watch it go!
The magic of a bristlebot comes from the vibration motor.
Vibration motors (aka pager motors) are called Eccentric Rotating Mass vibration motors, or ERMs.
ERMs have an asymmetric weight which is spun around causing an unbalance that makes the motor move. Here is a video showing a vibration motor in slow motion:
Slow Motion Capture of Multiple Vibration Modes
For more details on ERMs, visit: Understanding ERM Vibration Motor Characteristics
For a project like this one, which is creative, there is no real right or wrong one to choose. I actually recommend buying a couple and playing around with them. Having different models of motors will let you play with how the weight effects the bot, and how to mount it.
Because these little motors can be salvaged from many different products (pagers, cell phones, electric toothbrushes, toys, etc), there are often a good assortment available on ebay at very low prices. As I mentioned, it's nice to buy a handful of different ones so you can try out how they balance differently on your bot to work the best.
I also like to pick up cheap toys in yard sales and reuse the parts. Many yard sales have a box of fast food toys for ten cents each, and if you look at them as parts, that's a bargain!
You'll Need to Get A Toothbrush
It is a bristlebot, after all, so you're going to need some bristles. I highly recommend using a toothbrush that has at least some angled bristles so that your bot moves better in one direction. Some have a few little rubber bristles mixed in, and these are great, too.
Buy a new toothbrush or recycle an old one - just make sure you wash it first! (Ewwww.)
Because you want to keep your bristlebot light (and therefore fast) you will want to use a small battery - 1.5V - 3V. This should give enough power to run your tiny motor, and still keep it light weight. Plus, they will balance better on your toothbrush head.
If you look around online, you can find lots like this one with many batteries at a very low price. If you are using bristlebots as a project for your class, this can really bring down the price.
What to Do With Your Bristlebot
So, you made a bristlebot. Now what?
1. Hold a Bristlebot Race
Get together with your friends and their bristlebots and see who has the fastest vibrator of the bunch. Here is a race idea that keeps the bots going pretty straight and not interfering with each other. You can also try with an open area (all together) so it tests not just speed, but how straight it goes.
2. Make a Bristlebot Obstacle Course
Create a course for your bot to navigate through. Consider adding walls, curved walls, etc to your maze and time how long he takes to get through a few times. Maybe race another bot through the maze.
3. Give Your Bristlebot a Personality
4. Improve It
So, you figured out how to make it go, but how can you made it better? Can you make it faster or more stable? What variables could you change to effect this?
Get Creative. Try something different. Add another toothbrush head, or add something else - anything. Play with it and see what you can make.
Try your hand at a catamaran style like the one to the left, or maybe add a pencil and track your bots path.
Tricked Out BristleBots
Double sided foam tape will make it easy to mount the battery and motor to your brush. It's a lot cleaner than getting into gluing it, plus you can take off your materials and reuse them later. You could go with duct tape, but that's ugly and heavier.
If you are doing these with a class, you can buy longer rolls of this tape as well.
A Bristlebot is a Vibrobot - A Very Simple Robot
A Vibrobot is any robot that uses some power source and a vibration motor, often a called a pager motor, to jiggle it about. It is about the most basic form of robot that exists.
A Bristlebot uses the angled bristles of a toothbrush head to give direction to those jiggles and cause the bot to move in one direction. When it bumps into something, it corrects itself and moves in a different direction.
Here are a few other designs for vibrobots that don't involve toothbrushes:
This book comes with all you need to make a bristlebot. Personally, I think having it all there takes away the fun (and learning) involved with gathering the required items and making it work with what you've got. I recommend working it out for yourself with the materials you can get, but if you want to get it all packaged up for you, here it is.
20 Robotics Projects
This book is perfect for kids who love to tinker and build things. It's nice to give them something to make other than Lego sets!
This book not only covers the history of robotics, what constitutes a robot, and a lot of terminology, it's got 20 great projects that you can do at home.
One project included is a Drawing Vibrobot that you can make with the same vibration motor you used on your BristleBot.
See Some Other VibroBots
The fun is obvious, but where is the learning in making bristlebots?
How Bristlebots Relate to Science & How to Use them in Science Class
There is a ton a kid can learn from making bristlebots.
First off it's a lesson in following directions and problem solving. Given a basic set of instructions as to what to do, they will have to problems solve exactly how to mount their motor and their battery. If it's not centered, the bot will fall over and they'll have to problem solve how to correct that.
- Electronics - Making a bristlebot is a basic lesson in electronics. You have to get the wires just right to make it work. They will learn to understand the positive and negative sides of the battery to create the circuit - simple as it is.
- Robotics - A bristlebot is a robot - a simple robot, but a robot nonetheless. What does it take to be called a robot? Why does this qualify?
- Going Green - Making a bristlebot is a simple lesson in Reusing and Recycling. If you salvage your materials - used toothbrush, motors from cell phones (or old toys, battery operated toothbrushes), and wires from anything, you can show - not just tell, but show - how things people throw away still have value. Discuss how this can be done on a grander scale. If they could do this with just a broken electric toothbrush, what could they make with a broken boat? a broken car?
How you can add value to the lesson:
There a tons of things you can do - experiments you can perform - with your bristlebot.
I highly suggest downloading the worksheets found here: Bristlebot worksheets. Whether you use the sheets or not, it will give you a lot of ideas of how to use bristlebots to teach the electronics, scientific method, center of gravity, and even biology.
In my opinions, Scientific Method is the thing that this leans itself to best.
Once the bristlebot is made, ask a question like "What would happen if we added a weight to the top of your bristlebot?" Have them make their predictions and write them down. Take some starting information (control data) such as speed down an thin path. Then add a weight to the bristlebots - such as a coin taped to it. Record the speeds down the path with the weight. Let them compare the results and draw conclusions. Then discuss why they came up with these results.