Spooky Coffin Bell Spooks Passers By On Halloween

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.

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New Contest: Halloween Hackfest

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.

Teach Your Air Compressor To Blow Eggs

As fun as it is to decorate Easter eggs, the road to a hollow hen’s egg is a gross and gooey avenue. Trust us, it sucks to blow out eggs, and it’s hard to get it right. Plus, you know, there’s that whole salmonella thing. [Phil] decided to speed things up this year by using an air compressor to do the dirty work.

Of course, one must approach this problem delicately because eggs are fragile. It would be nice to drill the egg instead of poking the end with a needle, but how are you gonna pull that off without breaking it? As it turns out, all you need is a bench vise, the right piece of PVC, a bit of rubber to keep the egg safe, and some hose clamps to keep the business part together.

[Phil] built a two-stage contraption that serves both purposes — the bottom cup safely cradles the egg for drilling, and the identical top cup connects to the air compressor, which blows the goo out of the bottom hole. [Phil] might have used negative pressure instead, but doesn’t have a vacuum pump or hose. Be sure to check out the brief demo video below.

Don’t want to mess around with real eggs? There are tons of ways to beautify fake eggs, but few of them are as cool as lasers.

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Raspberry Pi Spigot Puts Digits Of Pi On Tap

What did you do for Pi Day? Play with your Raspberry Pi 400? Eat some pizza or other typically round objects and recite all nine digits you’ve got memorized? That’s about where we were at this year. But not [bornach], no. [bornach] went all out and built a spigot that spews digits of Pi well past the first nine decimal places.

This clever spigot sculpture implements the spigot algorithm for generating digits of Pi one-by-one in a stream on to a chain of 8×8 matrices, and does so using a Raspberry Pi (of course). The point of the spigot algorithm is to store as few numbers as possible at any given time by reusing variables. We love the way the digits materialize on the matrix, almost as if they are ink being activated by water. Be sure to check out the build and demo video after the break.

That 10k pot on the top really does control the spigot — since the Pi has no ADC, [bornach] is using the potentiometer to charge a capacitor and using the time it takes to reach the threshold to decide whether the faucet is open or closed. There are a couple of hacks at play here, including the Popsicle-stick LED matrix bracing and the HAT [bornach] fashioned so the daisy-chained 8×8 LED modules could interface with the Pi.

We love Raspberry Pis of all eras around here, especially the darling new Pico. Diminutive as it may be, the Pico can be sliced even smaller with a hacksaw if you don’t mind losing a few GPIO pins.

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Dreaming Of A Transparent (PCB) Christmas

[Carl] wanted to put his force sensors on a transparent PCB and had to ask his board vendor for a special sample. Flexible PCBs are available on transparent substrates made of PET, but they are not as common as polyimide boards. As [Carl] found out, these boards are a bit thicker, a bit less flexible, and don’t hold up to very high heat as well as the standard boards. Undeterred, he designed a 3D Christmas tree using the clear boards. The result that you can see in the video below looks pretty good and would have been hard to duplicate with conventional means.

When you build the board it is as a flat spiral, but lifting it in the center allows it to expand into a conical tree shape. The circuit itself is just an LED blinker, but the flexible board is the interesting part.

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Building A Website-Controlled Christmas Tree

Back in the day, Christmas lights were simple strings of filament bulbs, and if you really splashed out, you could get some that flashed. These days, we expect a lot more capability out of our blinking decorations. [JT] has put together a rather nifty website-controlled setup for his own tree.

The setup is a little different than builds you may be used to. The website runs on a cloud-hosted virtual machine on Digital Ocean, rather than running locally. This allows anyone on the web to visit the site, and use the interface to control the lights on the Christmas tree. An image of the tree is used as the interface, and allows users to set the color of each individual LED on the tree. The LEDs themselves are driven from an NodeMCU ESP8266, which uses its WiFi connection to query the website itself and grab the color data as needed. [JT] has also included a secondary interface, where the chat of the Youtube livestream can be used to control the LEDs, too.

It’s a build that’s a touch more complicated than most typical online LED blinkers, but one that teaches useful skills in interfacing on the web and using virtual machines. We’ve seen other builds in this genre too; even some that are reactive to “Christmas fever” itself. Video after the break.

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Simple Christmas Tree Christmas Tree Ornament

When the only tool you have is a hammer, every problem looks like a nail. An LED ornament for the Christmas tree can be built in any manner of simple, easy implementations. You certainly don’t need an ARM Cortex M4 CPU running at 120MHz having a mouthful of three letter features like FPU, ETM, ETB, ECC, RWW, TCM, EIC, AES, CAN bus and much, much more. But [Martin Held] built a super simple LED Christmas tree ornament using the ATSAME51 series micro-controller, which he regularly works with and had on hand, and lots of bi-color LEDs. He already had schematic symbols and programmers for the device from other projects where he uses it more extensively, so putting it all together in time for the festive season was that much faster for him, despite the fact that the micro-controller was most likely the cheapest part of the BOM, besides the passives.

At this point it might be tempting to argue that it would have been so much simpler to use addressable LED’s, such as the WS2812B or the APA102C. You can drive them using a more basic micro-controller, and not require so many GPIO pins. But using such “smart pixel” LED’s for hand assembled prototypes can sometimes lead to unexpected results. If they are not stored in sealed tape/reel form, then storage conditions can have an adverse effect leading to dead pixels. And, they need a specific baking procedure before being soldered. Doing that for a few LEDs at home can be tricky.

So for the LED’s, he again went a bit off the beaten path, selecting to use three different color styles of bi-color LED’s with easy to hand-solder, 1206 footprints. This allows him to get a fairly random mix of colors in the completed ornament.

The LED array is pseudo-charlieplexed. One terminal of each LED goes to a GPIO pin on the micro-controller and the other terminal of all the LED’s are connected to a single complimentary pair of N-channel/P-channel MOSFETs — connected in totem-pole fashion. Depending on which MOSFET is switched on via a GPIO pin driving the gate pin high or low, the second terminal of each LED gets connected to either supply or ground. In combination with the GPIO pins being driven high/low, this allows the bi-color LED to be biased in either direction. Getting each LED to emit one color is simple enough — setting all LED GPIOs low, and MOSFET gate GPIO high will bias the LEDs in one direction. Reverse the GPIO logic, and the LEDs will be biased in the other direction. If this is done slow enough, the two colors can be differentiated easily. If the driving logic is made fast, changing states every 10us, the two separate colors merge to form a third hue. With some clever bit of code, he also adds some randomness in the GPIO output states, resulting in a more appealing twinkling effect. [Martin] does a detailed walk through in the video embedded below.

If you have the same bunch of parts lying around and wish to replicate the project, be warned that the KiCad source files will need some work to clean up errors — [Martin] was in a hurry and knew what he was doing so there are some intentional mistakes in the schematic such as using the same symbol for the N-channel and P-channel MOSFETs, and uni-directional LED symbol in place of the bi-directional one. And for programming, you will need one of these pricey pogo-pin style cables, unless you decide to edit the PCB before sending off the Gerbers.

[Martin] built just three of these bespoke ornaments, retaining one and giving away the other two to a neighbour and a co-worker. But if you would really like to build a tree ornament with addressable LEDs, then check out the Sierpinski Christmas Tree which can be cascaded to form an array of tree ornaments.

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