Build a Bristle Bot

Motors turn electricity into movement. There are many different types of motors, but in this project we will be using a vibration motor. Vibration motors are inside of most cell phones, and they are the reason you hear a buzzing sound when the phone rings!

In this activity, we will be building a robot using a battery, a vibration motor, and a toothbrush. These Bristle Bots are really fun to build, decorate, and race around!

What you'll need:

  • Toothbrush with flat bristles (angles bristles will cause the robot to tip over)
  • 3V coin cell battery (like this, but you can usually find at the dollar store)
  • 3V vibration motor (like this - or purchase this kit)
  • Masking tape
  • Scissors
  • Shears (for cutting the head off of the toothbrush)
  • Stuff to decorate with (e.g. googly eyes, modelling clay, etc.)

First, an adult will need to cut the head off of the toothbrush using shears. Scissors usually won't be strong enough for this. Check the cut edges to make sure they aren't too sharp, and if needed smooth them with sandpaper.

Next, an adult will need to strip the plastic off of the ends of the wires attached to the motor. This can be done using wire strippers, or by gently scoring the plastic using scissors then pulling off the plastic. You will want about 1 cm of exposed metal wires. If you purchased the vibration motor from our store the wires will already be stripped.

Now it's time to assemble your Bristle Bot! Stick the vibration motor to the back end of the toothbrush, with the wires pointing toward the front. Tape the black (or blue) wire to the negative side of the battery (the side without any writing).

Then tape the battery to the toothbrush.

 

Next, tape the red wire to the positive side of the battery (the side with the + symbol). This will complete the electric circuit, allowing the electricity to flow from the battery and into the vibration motor.

At this point your motor should start vibrating. If it does not, check to make sure that the metal ends of the wires are touching the battery (red on the positive side, black on the negative side). If it still isn't working, try using a new battery or a new motor.

So what is going on here? Let's take a look inside the vibration motor!

Motors use electricity to move. In a vibration motor, an unbalanced weight is spinning around inside it. You can see the unbalanced weight in the picture; it is the green part on the right. Because it is unbalanced, when the motor spins very quickly it starts to vibrate. It's kind of like when you have laundry in the dryer - if the laundry is unbalanced, the whole dryer will shake. A vibration motor works the same way, except that it is spinning much faster.

If you would like to, feel free to decorate your Bristle Bot. Remember to disconnect the red wire while you are decorating, otherwise it will keep vibrating! I tried to model my Bristle Bot after the cake delivery robot from the book If: Ball, Then: Catch.

I also attached an LED, which you can learn about in the activity Build an LED Sparky. To attach the LED, I bent them so that it could touch both sides of the battery, with the long leg of the LED touching the positive side of the battery.

Here is my cake delivery robot!

I'm not sure I would trust him with my birthday cake...

I hope you enjoy making Bristle Bots and learning about vibration motors!

This activity is based on the book If: Ball, Then: Catch, available here!


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