The best cauldrons are full of bubbling, steamy potions of great magical potential. We don’t have many of those in the real world, though, so sometimes we have to make do with a simulacra. [wannabemadsci] has built just that, with this fogging cauldron prop that uses no fog fluid or dry ice, running solely with water instead.
The heart of the build is a piezo element that vibrates at ultrasonic frequencies to atomize water. They’re available from websites like AliExpress complete with a driver circuit to energize the piezo element. The water is delivered from a wetted fiber wick, and quickly becomes a fog when the piezo is energized.
The disk was installed in a custom PVC water cup with the wetted wick, along with the electronics. The assembly was then lowered into an off-the-shelf plastic cauldron party favor to complete the look. The trick is to mount the piezo element sideways to get a nice-looking distribution of fog. A green LED was installed to light the cauldron from within.
The resulting effect is a sinister-looking glowing cauldron with a steady stream of fog emanating from the top. It’s a great piece of Halloween decor, and as a bonus, it doesn’t require any fancy chemicals to make it work. If you’re thirsty for more, be sure to check out the winners of last year’s Halloween Hackfest. Video after the break.
Impatient Severed Fingers – [Amanda] came up with a cute use for some mini servos and a zombie hand prop. The five severed fingers were attached to one end of a plastic rod. The other end was mounted to each of five servos which were laid out in the appropriate hand shape and attached to a fixed base. An Arduino running a basic sweep sketch animated the motors at slightly staggered intervals, creating a nice rolling effect. Even with the moving parts exposed this prop would be awesome to have on display, or set the ambiance with its continuous tapping…
Angry Spectral Delta – [Nathan Bryant] made an actual costume for his delta robot from Robot Army. By attaching a small plastic skull to the end effector and draping a tattered piece of fabric over the rest of the mechanism he effectively transformed the delta into a little ghost with a sassy personality. The head swiftly bobbed about, all while staying parallel to the table… until it intermittently came unhinged and hung limply, which was a nice added effect!
Robotic Exorcism Baby – This doll could turn its half skeleton, half baby face 180 degrees and then laugh at your fear. By attaching two servo motors together, [Jeremy] was able to create a pan and tilt mechanism which acted as the baby’s contorting neck and chattering jaw. The micro controller sending commands to the motors was hidden modestly under her dress.
Stabby Animated Cardboard Shadowbox – Among the animatronic devices seen at the event was a shadowbox made by [Brandon] hidden in a dark conference room nearby. When one happened to walk past the seemingly unoccupied space, they’d glimpse the silhouette of an arm stabbing downward with a knife through a windowsill. Being lured in for further investigation you’d find that the shadow was being cast by some colored LEDs through a charmingly simple device. A cutout made from recycled card stock was attached to a single servo. This whole mechanism itself rocked back and forth slightly as the motor moved, which wasn’t intentional but added some realism to the motion of the stabby arm.
