Crocodile Dentist

Crocodile Dentist

by c_sung meghna tomotomo | updated January 21, 2015

Based on the children's game of the same name...



In Crocodile Dentist, the crocodile has many teeth, one of which is sore. During a game, individuals take turns pulling teeth while the crocodile's jaws are open. When the sore tooth gets pulled, the crocodile shuts his jaws the the person who pulled the sore tooth loses.

So we design this using an arduino, push buttons and an actuator.

January 12, 2015 at 12:45 PM
Created by meghna, tomotomo, and c_sung
Comments (1)
This might be a good place to leave a design brief. What is your project about overall? What do you hope to accomplish? Then from there you break down into project plan, etc. It's a good way to help clarify what you're doing both for yourself and for others.
almost 2 years ago

The element of the game we are prototyping is the snapping of the jaws as the result of random sore tooth being pulled.

1. Brainstorming

  • Tooth pulling
  • Moving jaws

2. Prototyping

  1. Build teeth/jaw circuit and program Arduino
  2. Build structure
  3. Put circuit and structure together
  • Materials
    • 4 teeth buttons 
    • 4 corresponding LEDs & breadboard
    • Arduino Uno
    • Servomotor (used as actuator to move jaw)
    • Other materials: foam core, acrylic

January 12, 2015 at 2:10 PM
Created by c_sung and meghna
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The jaw consists of two pieces - upper and lower. A servomotor attached to a rod attached to the top piece will be the actuator that moves the upper jaw. The rod rests in a wedge on the lower jaw and can rotate freely.

January 14, 2015 at 6:35 PM
Created by c_sung and meghna
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January 14, 2015 at 6:36 PM
Created by c_sung
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After building the teeth circuit, we added in our servomotor which will be used to control jaw movement. The video shows the complete functioning circuit on a breadboard. A sore tooth is selected at random and when pressed, the servomotor is triggered to close the jaws. The Arduino then resets the whole circuit and randomly selects a tooth to be the new sore tooth.

All we need now is to build the jaws and structure to contain the circuitry.



Design Files
January 14, 2015 at 7:40 PM
Created by meghna and c_sung
Comments (4)
This is looking great. Are you planning to randomize the 'sore' tooth each time the game is played? You can do that by redefining the sore tooth each time the servo gets triggered.

Also, what will the interface between the tooth and the push buttons look like? It would be helpful to have a sketch of how your electronics + form factor will fit together.
almost 2 years ago
Oh.. the random algorithm is already up and running(even in this...).
And yes.. we'll upload the drawings soon! :)
almost 2 years ago
Ah I see - you can upload the code here as a "design file" (:
almost 2 years ago
Oh! I was going to ask about that! Thanks.. ill do that. :)
almost 2 years ago

We redesigned the jaws. The jaws will be made entirely of foam core. The upper jaw is attached to a servomotor so that it can rotate to simulate opening/closing of the jaws. The servomotor is mounted on top of the lower jaw

January 15, 2015 at 3:43 PM
Created by c_sung
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January 15, 2015 at 4:19 PM
Created by c_sung and tomotomo
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We obtained four colorful push buttons for the teeth. :)

January 16, 2015 at 12:53 AM
Created by c_sung
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We plan to have the jaw actuator attached to the bottom piece of the jaw. We adjusted the height of the servomotor used by adding a piece of foam core to the bottom so that the horn could rotate without obstruction.

January 16, 2015 at 1:05 AM
Created by c_sung
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We checked to see if the spacing would work out.

January 16, 2015 at 1:06 AM
Created by c_sung
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We cut the lower jaw out in one piece using foam core. Using a pencil, we made four holes where the teeth will fit in.

January 18, 2015 at 9:18 PM
Created by c_sung
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Would laser cut the holes next time! Although they looked fine they were a bit clumsy...

January 18, 2015 at 9:22 PM
Created by c_sung and meghna
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Instead of following our design plans and having just one piece of foam core for the upper jaw, we decided to make our crocodile slightly more crocodile-like and gave its head more structure. Its eyes even have eyelashes. :)

January 18, 2015 at 9:25 PM
Created by c_sung
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As seen in the picture, we cut the foam core, bent it and stuch the bent part. But it would be better if we cut it off and the stuck it like a T instead of the L we have here: for better stability.

January 18, 2015 at 9:32 PM
Created by c_sung and meghna
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The final functioning prototype included:

1. Foam Fabrication, the movable head(snout) and the bottom jaw.
2. Colorful teeth (made of push buttons), which on being pressed can result in closing of the mouth.
3. The circuit as described earlier was used and the arduino placed inside the jaw
4. The opening and closing of the jaw is done using a servo motor shaft attached to the upper movable snout.
5. So the goal was achieved: the mouth closed in case a sore tooth was pressed and then the game reset (with a new random sore tooth being selected)

We had to callibrate the jaw position (using the servo) and then the angle it had to move (found that the range 45- 0 worked out great). initial postion should be open mouth so just had to close it asnd open it again after a short delay.






January 18, 2015 at 9:37 PM
Created by c_sung and meghna
Comments (0)

One thing that I would change for our design would be the upper jaw and how it is attached to the motor. The upper jaw that we made was heavy and since we ran out of time, it was not attached very well to the motor so it was not very stable.

For the team project, I helped with the brainstorming process. I was mainly involved in the design of the hardware, which included the structure of the jaws, and the mechanism to move the jaws. I was also involved in building the hardware.

I was not involved in the electronics for the project, and hope to be more involved in electronics for the final project. I would like to develop my skills in this area, as I have limited experience in it.

January 18, 2015 at 9:50 PM
Created by c_sung
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I did the arduino programming and helped with the circuit design. 

We could have done better but we spent a lot of time deciding little things.. Make better plans nest time i suppose. :)
I would have liked to do better fabrication of our prototype: the jaws, with a separate cover for the electronic components and maybe a PCB instead of wires.
Use Laser cut plastic/ 3D printed/injection molded components instead of foam core to make it look and work better.

Ultimately, shape and cut and color to make it look like a crocodile.. (and not only the mouth!) :D
I really enjoyed working on this thing.. I had a lot of fun bouncing off crazy ideas for the design. All thanks to Christina and Tomo! Yay!

Also thanks a lot Cole, for helping us out of the servo-actuator design block! 




January 18, 2015 at 10:14 PM
Created by meghna
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I would add LED in each tooth so that users can figure out which teeth are taken by looking if LEDs on the teeth are on or of. I would also make circuitry as small as possible so that I does not look messy.


I planned and made circuits, My knowledge of arduino programming helped Meghna to find bugs we had quickly. Though soldering circuits, I leaned that the way I had done was wrong and I leaned the good way to solder wires.


i would like to improve arduino programming to help coding in case we need more programming. 

January 18, 2015 at 10:40 PM
Created by tomotomo
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