Spooky Laughing Skull

This is a project made by Marc Mariné and Pau Gil, two ELISAVA students currently in the third year of the degree.

We were challenged to create a functional halloween decoration thanks to the arduino hardware and other components so that it is not a static decoration.

Our proposal is a spooky skull which, at first, is static, but when it detects someone passing by, its eyes light up and it laughs, in order to scare the person who approaches it.

Electronic Parts:

• Arduino board
• Jumpers
• Red LEDs (2)
• Servomotor
• Ultrasound detector
• Protoboard
• Batery
• Batery connector

Materials:

• Skull with articulated jaw (plastic)
• Steel wire rope
• Small Hinge (PLA)
• 3D printed skull holder (PLA)
• M3 Screws and nuts
• Tin wire

Tools:

• Tin soldering iron
• Cutter

The arduino is at the heart of our project. We will connect all the components thanks to its hardware, in the same way as in the diagram shown at the top of this section.

The main power source of the circuit will be a 9V battery which will be connected directly to the arduino through the corresponding port.

To insert all the components inside the skull, we will make an opening in the lower back part with a cutter. This will be the entrance door for all the components, which we will transform into a kind of trap door. We design and 3D print a hinge, you can also buy it, which will be fixed to both parts to make the trap door.

In addition, we will make holes in all those parts where components have to protrude, whether it is the servomotor (on the side near the jaw, like picture 4) or the LEDs (through the eye sockets, like picture 5). We will do this with the hot soldering iron, melting the plastic being careful not to burn anything. Any component that needs to be attached, will be fixed with hot silicone on the inside so it looks clean on the outside.

To make the circuit work the way we want it to, before we start writing code, we made this flow diagram to get an idea of what we exactly want.

Then, we write the code to make the skull perform the desired functions:

In order to make the jaw mobile and functional, we will make a small hole with the hot soldering iron, so that we can put some tin wire in it and make a knot so that it doesn't come out. The other end we will tie it to the servomotor, to create the lever that will move the jaw.

In order to make our project a halloween decoration, we have decided to make it stand upright with a stand that we will 3D print to demonstrate how it works in an easy way.

That's why we will use the design shown in the first picture. This way the skull is supported in the air with enough space to open the jaw properly and with a small compartment to insert the ultrasonic detector.

As a last step we will test the code to see if the skull laughs as desired, modifications can be made to the one we have hung to make it laugh faster or slower and also adjust the opening of the mouth.

To conclude this project, we would like to demonstrate how it works in a short video we have prepared.

We see how when an individual approaches the skull, it detects him and suddenly laughs in order to scare him. When the individual moves away, the skull will return to its initial state.

The last step would be to decorate it in style, put a layer on it, surround it with another decoration of your choice to camouflage it, etc.