In the spirit of this year upcoming Halloween, we found this amazing, scare your pants off, project by a guy called Cabe Atwell. It is called the “Scary Door”, and is a Halloween effect prop brought to life using Raspberry Pi. In a shout out to the classic “what’s behind the door/wall” scare tactic, Cabe has used current technology to take this well-worn gimmick to another level.
The door itself is made-up of a wooden frame with pieces of sheet metal attached to the wood, and a small window is cut-out in order to place a 24″ 1080p TFT panel behind it. Cabe spent hours editing video from YouTube to play on the screen, using Sony Vegas Movie Studio HD to create the effect that someone, or something, was slamming up against the steel door trying to get out.
“I found the door had a butcher shop, creepy basement door feel,”
He then needed to create the physicality of the effect of an entity slamming into the door, so six BIMBA two-way pistons were used to hit the door in several different places. To begin with the pistons were too powerful and left dints in the metal sheeting, so Cabe added more sheet metal in the strike area of each piston to combat this.
He used five-way solenoid air-valves to enable him to control the pistons in both directions, driven by an eight-relay board. To split the air from the air compressor needed to power the pistons, he built a six way air manifold to connect it to, with push-to-fit air hoses also running from the manifold to the valves and then the pistons.
To trigger the effect to work, he used a break-beam device with built-in relay functionality, enabling him more control over what he did or did not want to trigger. Placing the device on the floor a couple of meters away from the door, when he walked past and broke the beam the door was triggered and the magic began.
Cabe did not want to put too much stress on just one Raspberry Pi, so decided to use two of the boards to share the responsibility. One of the boards would be used to play the video content, playing a different video from a series each time it was triggered. The piston half of the project was controlled by the second Raspberry Pi and a Piface Digital. The Piface has two built-in relays that handle the AC and DC and has 8 open collectors ports for easy triggering of the solenoid air-valves when connected to the eight-relay board.
Using two lines of code, one to start and one to end, to trigger the relays, he used Vegas to time at what point he wanted the pistons to hit the door so it would coincided with what was happening in the video. Each line of code contained the time at which to fire the piston, and using Vegas made this easier and less time-consuming. He used C to write the video output program and C++ on the relay/Piface code.
After many set-backs like the unexpected power of the pistons making dints in the door, and the program triggering the next video before the last one had finished, Cabe overcame these obstacles to produce a brilliant spooky themed prop to celebrate Halloween in style. You can get details of all the materials used and downloadable files of schematics and code on the Element 14 community link below.
All image and video credits go to Cabe Atwell.
Source: Element 14 Community blog