My church hosts a trunk-or-treat event every year as an alternative or supplement to trick-or-treating. It can be very fun, so this year I decided to make my own display for kids and parents to interact with. The story is that the skeleton awoke from his coffin, and now wants to guard his candy. He will hit anyone who tries to take his candy, so you must press the button in order for him to stop, but only for a little bit.
VideoDesigningI began my project by thinking of what theme would work the best, so I decided on making a skeleton. Next was the question of what should it do. I chose to make it wave its arm and also have lights and a display for a message. Finally I also added a jack-o-lantern to the design.
Building the CoffinI had to build this project in 4 days, so I looked around and found 2 nice U haul boxes. Cardboard is a cheap material and it's easily reusable, so I decided to use the cardboard boxes. I made a simple sketch of a coffin and traced it onto each flattened box and cut it out, providing a top half and lower half. Next, I cut the flaps of the boxes to match the length of each side and taped them together. After the coffin body was completed I hot glued everything into place to ensure rigidity.
The waving hand is the integral part to this project, so making it strong enough to withstand over one hundred people was tough. I decided to use a servo, mainly because it was simple and didn't require a separate driver to operate. The arm is on a hinge, and it connects to two pieces of wood that have a dowel running through them. This enables the servo's force to be multiplied and also not bear the weight of the arm directly. When the servo moves towards 180 degrees the arm moves down, and vice-versa.
I chose a Teensy 3.5 for several reasons. It has a built-in SD card reader, many GPIO pins, and a very fast clock speed. I used a 128x128px OLED to display a simple graphic of a pumpkin, along with my name. I soldered a white arcade button to a GPIO pin and GND, along with a servo header and 2 3-pin JST-SM connectors for the LED strips.
People who came up to my display loved it, especially kids who were surprised by the colors changing and the arm stopping.
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