Ultrasonic Array Powers This Halloween Spirit Writer

October 12, 2021 by Dan Maloney 16 Comments

The spooky season is upon us, and with it the race to come up with the geekiest way to scare the kids. Motion-activated jump-scare setups are always a crowd-pleaser, but kind of a cheap thrill in our opinion. So if you’re looking for something different for your Halloween scare-floor, you might consider “spirit writing” with ultrasound.

The idea that [Dan Beaven] has here is a variation on the ultrasonic levitation projects we’ve seen so many of over the last couple of years. While watching bits of styrofoam suspended in midair by the standing waves generated by carefully phased arrays of ultrasonic transducers is cool, [Dan] looks set to take the concept to the next level. Very much still a prototype, the setup has a 256-transducer matrix suspended above a dark surface. Baking powder is sprinkled over the writing surface to stand in for dust, which is easily disturbed by the sound waves reflecting off the hard surface. The array can be controlled to make it look like an unseen hand is tracing out a design in the dust, and the effect is pretty convincing. We’d have chosen “REDRUM” rather than a pentagram, but different strokes.

[Dan] obviously has a long way to go before this is ready for the big night, but the proof-of-concept is sound. While we wait for the finished product, we’ll just file this away as a technique that might have other applications. SMD components are pretty small and light, after all — perhaps an ultrasonic pick-and-place? In which case, sonic tweezers might be just the thing.

Continue reading “Ultrasonic Array Powers This Halloween Spirit Writer” →

Halloween Build: Exquisite Ray Gun Has Sound Effects

October 7, 2021 by Al Williams 8 Comments

When we first saw [lonesoulsurfer’s] ray gun, we thought it looked oddly familiar. Sure, it looks like a vintage ray gun you might see in a dozen 1950-era movies or TV shows. But still, there was something oddly familiar about it. Turns out, the core piece of it is an old-fashioned timing light used when doing a car tune-up.

This is no unobtrusive Star Trek phaser. It looks substantial and has a cool sound generator that not only gives it something to do but also sports cool control knobs out the top of the gun. The design files for the sound circuit are in a Google drive folder if you want to recreate the build.

Continue reading “Halloween Build: Exquisite Ray Gun Has Sound Effects” →

Flame-Spitting Dragon Head Heats Up Halloween

October 4, 2021 by Donald Papp 4 Comments

Halloween is looming, and [Jonathan Gleich] decided that an ideal centerpiece would be a flame-spitting dragon’s head. It started with an economical wall-mount dragon’s head, combined with a variety of off-the-shelf components to become something greater.

Dragon head with arc ignitor lit — Spark from high-voltage ignitor, right at the torch opening.

The fire comes from a kind of propane torch sold as a weed killer set, which looks a little like a miniature tiger torch. The flow of propane is limited by a regulator (which keeps the flame short and fixed), and controlled with a gas-rated 12 V solenoid valve. Ignition is done with the help of a spark igniter that fires up on demand, fed by a high-voltage ignition coil. The two combine at the Dragon’s mouth, where the flame originates, but the electrical components are otherwise isolated from the gas elements as much as possible.

The dragon head is made of acrylic, and if exposed to enough heat acrylic will first melt, then burn. To help avoid a meltdown, the dragon breathes fire only intermittently. [Jonathan] also gave the mouth area a heat-resistant barrier made from generous layers of flame-blocking mortar and sealants from the hardware store. The finishing touch comes in the form of bright red LEDs in the eyes, which give the head a bit more life.

Watch the ignitor in action and see the head spewing flames in the two short videos embedded below. The head should make for some good pictures come Halloween, and is a good example of how repurposing off-the-shelf items can sometimes be just what is needed for a project.

Interested in something smaller, but still fiery? Check out this pet fire-breathing dragon project for all your robotic animal companion needs. Continue reading “Flame-Spitting Dragon Head Heats Up Halloween” →

Get Yer Halloween On!

October 2, 2021 by Elliot Williams 3 Comments

Halloween is basically built for the hacker. Besides the obvious fabrication of absurd costumes, there’s also the chance to showcase your skills, be they mechanical, audio, or video. It’s also a great time to show off our coolest tricks to inspire the young proto-hackers. If you need inspiration, we’ve got 150 ideas.

My personal problem with Halloween, though, is that I always start at the last minute, and my ideas far outreach my time budget. Or because it’s all done in the last minute, a whole bunch of ideas that should “just work” in theory run into the immovable object that is practice. At least that’s what happened with last year’s spooky sound effects — my son and I spent so much time collecting and recording scary audio samples that I ran out of time while still getting the sensitivity on the motion detector set just right, and then the battery died halfway through the night.

But this year will be different, I swear! I’m going to get it done early and test it out, with the luxury of time to debug the inevitable spiders. And you can swear too. Get started now on your Halloween project. Or at least next weekend.

What’s your favorite Halloween Hack?

Contests

If you need any more encouragement to fire up your black and orange hacking machine, think of Hackaday.io’s Halloween Hackfest. It runs until Oct 28, and all you have to do to enter is document your Halloween project on IO and press the “Submit” button. The deadline is the 28th, which still gives you a couple of nights to debug whatever didn’t work before the real deal. Prizes are shopping sprees at Digi-Key, and Adafruit is doubling the gift certificate if you use any Adafruit parts in the build.

If you don’t give a pumpkin about stupid ol’ Halloween, that’s cool too. (Grinch!) The 2021 Hackaday Prize has entered the final wildcard round. If your project didn’t fit in any of the previous categories, I’m pretty sure it’ll fit just fine in the anything-goes phase. Go nuts. We’d love to see what you’re working on.

Left: kids stomping spiders projected on a driveway. Right: the setup.

Make This Halloween A Spider-Stomping Good Time

September 30, 2021 by Kristina Panos 11 Comments

We can count on one hand the number of times that we haven’t needed a coat on Halloween night around here. Even if it was fair and sunny the day before, you can count on Halloween being appropriately windy, cold, and spooky. Trick-or-treating only keeps a kid so warm, and we would have loved to happen upon a house with a spider-stomping sugar-burning good time of a game going on in the driveway.

[Kyle Maas] built this game a few years ago, and it has proved quite popular ever since. It’s so popular, in fact, that they have to have someone on duty with a vaudeville hook to yank spectators off the playing field. The point is to stomp as many spiders as you can in a set amount of time, though you only need to stomp one to win. It can handle one to four players, depending on the size of the projection, but [Kyle] says it’s kind of hard to track more than two at a time.

The setup is fairly simple, provided you can reliably affix your projector to something sturdy. [Kyle] used a Structure sensor for the 3D scanner, but you could easily use a Kinect instead. Conversely, the calibration was challenging. [Kyle] ended up using a DSP math trick known as the inverse bilinear transform to be able to calibrate the system using the 3D scanner itself.

If you’re more into scaring the children, just rig up a coffin bell. Either way, don’t forget about our Halloween Hackfest contest, running now through Monday, October 11th. There are more details over on IO. While you’re there, why not check out the list of entries?

Spooky Coffin Bell Spooks Passers By On Halloween

September 21, 2021 by Lewin Day 3 Comments

Being buried alive isn’t fun, we imagine. Fear of it led to the development of various safety coffin ideas in the 18th and 19th centuries, and [Glen Akins] wonderful Halloween prop riffs on that tradition today.

The safety coffin was a simple solution for those afraid that this might happen to them. One concept had a bell which was installed above freshly dug graves with a string extending into the coffin. One who found themselves accidentally buried alive could then pull the string to ring the bell and summon help.

[Glen’s] installation eliminates the coffin and the dead body, and simply mounts a bell on a post. Inside, there’s an ultrasonic rangefinder that detects passers by. When someone walks closely enough to the prop, a microcontroller triggers a servo which rings the bell with a haunting urgency.

It’s a simple build, but appropriately installed with its LED lighting, it really does pop. It would be a wonderful way to add atmosphere and mood to a Hallowe’en party or haunted house. We’ve seen some great Hallowe’en hacks over the years, and some of the best are pumpkins. Video after the break.

Continue reading “Spooky Coffin Bell Spooks Passers By On Halloween” →

New Contest: Halloween Hackfest

August 10, 2021 by Mike Szczys 4 Comments

It’s as if Halloween was made for hardware hackers. The world is begging us to build something cleaver as we decorate our houses and ourselves for the big day. And one thing’s for sure: the Hackaday crowd never disappoints. This year we’re fully embracing that with the Halloween Hackfest, our newest contest beginning today along with the help of our sponsors Digi-Key and Adafruit.

The animated video combined with the 3D-printed prop makes for an excellent effect.

Wait, isn’t it the beginning of August? Why are we talking about Halloween? The procrastinator’s dillema, that’s why! Start working on your build now and it will be epic by the time the day actually rolls around. Decorating for trick-or-treaters is a good place to start. For our money, projected heads are a really cool party trick, like these singing Jack-o-laterns, or these disembodied heads inspired by Disney’s Haunted Mansion. Or maybe you’re more of a flamethrower-hidden-in-pumpkin type of person?

It doesn’t take much tech to bring a good costume to life — a few LED strips make a plain old princess dress light up the night and builds some permanent memories for the lucky little one who’s wearing it. Speaking of memories, we doubt the little one will remember this mechwarrior family costume, which is why you’ve always got to make a video of these things.

Over the year’s we’ve seen claw machines for candy delivery, and even a pumpkin piano. Of course pumpkin carving is an entire category unto itself where five-axis CNC machines are fair game. Look around, get inspired, and build something!

Three top winners will receive $150 shopping sprees in Digi-Key’s parts warehouse. If your build happens to use an Adafruit board, your prize will be doubled. We’ll also be awarding some $50 Tindie gift cards to the most artistic projects.

Get started now by creating a project page on Hackaday.io. In the left sidebar of your project page, use the “Submit Project To” button to enter in the Halloween Hackfest. You have from now until October 11th to spill the ~~beans~~ pumpkin seeds on what you’ve made.