Halloween Skeleton Arm

This project is a Halloween product that has an electronic circuit with motors implemented to make automatic movements activated by a sensor. This automatization is developed with the software program arduino.

This halloween decoration consists of an arm with a small lighthouse meant to scare people. When it detects people nearby, it starts to move the hand rotationally. This movement consists of a 90 degrees rotation and a scary light inside the lighthouse. After a few seconds, if nobody is around to activate the circuit again, the arm returns to its initial position and turns off the light. 

ELECTRONICS:

For doing our project we bought a useful pack that included an ELEGOO Medium Starter Set Compatible with Arduino IDE and 5V Relay Set, Power Supply Module, Servomotor and an UNO R3 Prototype Development Board. However, we'll only use some of those things:

The arduino microcontroller board, the UNO R3 Prototype Development Board, connector cables, the ultrasonic sensor HC-SR04 and 220 ohms resistors. In addition tot his, the nema 17 stepper motor, with 1.5A high torque of 420mN has been bought apart. If you prefer to, or already have one available, you can use a servo motor. It's up to you!

FOR THE MODEL:

Supplies for the skeleton arm

• wooden chopsticks
• twine (or string)
• hot glue gun or hot glue,
• acrylic paint
• brown paper bag 
• dryer sheets
• pliers
• butcher paper (or newspaper), 
• large bowl 
• glue 
• water
• a small amount of flour

Supplies for the lantern

• cardboard
• a hot glue gun or hot glue
• ruler
• pen
• plastic (from old packaging)
• Scissors and cutter.
• Glue 
• Butcher paper (or newspaper)
• sticky tape
• Black acrylic paint
• Old cap

A schematic of the electrical connections, made with Fritzing

Here you can find a flow diagram of the code, plus the actual arduino file we used.

Once you connect and download the electronic part (previous step), you have to build the model. If you prefer, you can buy a skeletal arm, a lantern and a box to store the electronic system and to hang it on the wall. If this is not possible below we leave you the steps you have to follow to build it:

Step 1: THE SKELETAL ARM

Here you have a video from Get Crafty Crafty that perfectly explains how to do it!

https://youtu.be/5txfbC4tJT4

Step 2: THE LANTERN

Here you have a video from My world Easy Craft that perfectly explains how to do it!

https://youtu.be/m8gp8v1kY0c

Step 3: THE BOX  

Here we’ll put all the electronic parts. To ensure proper operation, make some holes on the box, so that the sensor and wires work without problem. (You'll find the image above)

Step 4: THE ASSEMBLY

To put it all together we will join the lantern with the skeletal arm with a string (from the old cup of the lantern to the middle finger of the arm). To connect the arm to the box, we will introduce the arm to the stepper motor. Once we have all this part, we will put among the arm the wires that connect the leds, joining it with sting. We will place the leds at the top of the old cap of the lantern, introducing it inside of the lantern.

The next step is covering the arm with some black paper to hide the electronics.

This is how our skeleton arm ended up.

After doing this little project we’ve achieved the capacity to develop an interactive digital product, learning along the way some of the technical features arduino offers. We have been able to create a functional prototype starting off some coding basics and ended up with a fun, easy-to-make halloween decoration. We hope you liked it!