Crocodile That Opens and Close Its Mouth for Halloween Parties

Hey friends in this instructables i will show you an idea for Halloween that will add spark to your parties!

I will show you how i made this Crocodile That Can Open and Close Its Mouth when someone tries to come near its mouth.

Now you may wonder why one will come near to its mouth? This is because we will keep chocolates or gifts inside its mouth so its obvious that someone will come close to grab it.

When this happens the mouth automatically closes and this leaves everyone surprised!

The logic behind working of this project is very simple, we are using the simple object detection sensor that goes by the name ultrasonic sensor and it is controlled by arduino, and for the servo movements we are using micro servo.

There are many ways by which you can use this project, one idea is you can arrange a game at your party, keep something inside the mouth and whoever grabs it from the mouth without its teeth touching can be the winner.

I recommend to build this project and i have provided everything you need to build this, and also there is a working video given at the end of this.

If you made this project post it on the i made it section! Have a great Halloween, continue reading..

Here are the list of components you will need to build this project

Arduino nano from here

Ultrasonic sensor

Micro servo

Piece of cardboard

Color paper(depending on the color of your crocodile)

Empty box

compass and pencil

Ruler and pen for marking

Double sided adhesive

Hot glue and superglue

Arduino IDE and programming cable

Scissors

Halloween party!

There are plenty of ways by which you can make a crocodile, But i will show you a very simple and neat way to do this.

I have taken a strip of cardboard and marked the areas as shown in the steps, Use a ruler to bend the cardboard and create a hinge kind of structure.

The main goal here is to make the mouth of croc, After you have made till here you can use color paper to cover the cardboard, In my case I will be using green color, The choice of color is left to your taste.

Use paper glue to blend the paper and color paper together, allow it to dry completely before proceeding with the next steps.

If you are making the different design make sure the mouth can open and close manually, if this can be done we can add servo to control this automatically later.

In the first phase i will show how to make teeth from paper, These are safe even when the croc bites!!

Take a strip of paper and fold it 6 times horizontally and mark a triangle, Nut with paper scissors cut these and when you unfold the paper you have the teeth ready in no time, This is the easiest way, if you don't want to follow these method i will suggest you one more.

Draw triangles on paper and cut them one by one, this is time consuming but one advantage here is you can have a chance to select the size of each teeth.

Paste them to the edges and now your croc teeth are ready!, You can add more details to this by coloring.

In my case i just used the hot glue to the corners and then pasted by paper teeth here and allowed it to dry completely.

This part makes your croc 50% complete, The leftover part is making the details like eyes and nose and now in the next step we will see how that is done.

What a fun! From the first image on this step you can see the croc opening and closing the mouth! That i will show it later

To begin with to make this look like a crocodile i will add the eyes, Making these is very simple, Cut a circle and cut its base.

Glue the green color paper onto this first and allow it to dry, now cut a smaller piece of paper which is white in color and glue it on top of the first layer.

Now finish the eyes by coloring the corners black, Use black marker for this purpose, Once this is complete drop hot glue and add these eyes.

Noses are very easy to make! Cut a piece of cardboard and color it with black color, This completes the croc body and we can now build circuit for this.

Connections are made easier for anybody to understand with my written explanations below, I will explain it to you component wise.

HC-SR04 Ultrasonic Sensor Connections

This is also called as ultrasonic sensor and you can follow these connections to micro controller

VCC is Connected to the 5V pin of the Arduino Nano and GND to the GND pin of the Arduino Nano

Trig is Connected to D3 of the Arduino Nano whereas the Echo is Connected to D2 of the Arduino Nano

Servo Motor has 3 wires

The signal is Connected to D9 of the Arduino Nano and the power pins VCC to the 5V pin of the Arduino Nano and the GND to the GND pin of the Arduino Nano.

I have placed the nano board on the breadboard to make the connections much more easier for you to understand

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Manually the mouth moves when the thread is pulled, i will use the fishing wire for this purpose because it has very little elasticity and it won't break easily compared to such threads compared to availability.

The second option if you don't have fishing wire is the normal sewing thread, but you might need to use 3 folded threads here.

Instead of manual pulling, we will upgrade this project with automatic and for that servo will be used.

Secure the horns of the servo with screws if you have not done that yet, To place the servo inside the box i will use a popsicle stick and hot glue

After the glue is dry tie the other end of the thread to the servo horn and later glue the entire crocodile to the top of the box.

Adjust the mouth opening wideness and now adjust the other end of wire and then fix it using hot glue or super glue.

Now we are almost in the very last step of completion and I cant wait to test this out.

Like you even i was excited to test this project, and indeed it worked to my expectations.

I will use the 10000mah power bank to power this project, You can hide the power bank behind this and also if you want to hide them i suggest using an external battery.

Using additional components will add more wires to the circuit and the control system will add up to the overall cost, so i just went with the power bank.

Just connect the cable between the power bank and the arduino board and then you are good to go.

Place the chocolate inside the mouth so it is visible to others, when they approach to take the chocolate the mouth closes making them to get a surprise.

If you see its working it's so much fun, show it to your friends and make them feel happy.

Thats all about this project, if you still have any questions about its building i would recommend watching the video tutorial of this project on the below steps

Did you miss the fun? Say no! Here is the working video of this crocodile in action!

You can use this at parties and add more fun to the event, If you have any questions about this croc you can ask me in the comments box, and I will answer those.

Feel free to mix this design or circuit with some other creative projects like these and let me know how it went for you, Happy Halloween, and have a great day