It’s holiday time again! And that means it’s time to break out the soldering iron and the RGB LEDs! If you’re going to make a custom PCB to put those LEDs on, you’ll notice that you get few copies of your PCB in your order, so, might as well design it such that you can combine them all together into a single Sierpinski Christmas Tree, just like [Landon Carter] did.

Each PCB “tree” has three connections which can be used as either inputs or outputs by soldering one of two bridge connections on the PCB. The power and signal goes up and down through the tree, rather than across, so the connections go one on the top of the tree and two on the bottom. This way, each tree in the triangle can easily be connected, and each triangle can be easily connected to another. Each individual tree has three WS2812b-mini addressable RGB LEDs and the tree is controlled by an external Arduino.

The first order of 10 PCBs came in, which makes a 9 member tree – next up is a 27 member tree. After that, you’re going to need some pretty high vaulted ceilings in order to put these on the wall. On the upside, though, once the holidays are over, everything can be easily disconnected and packed away with the rest of the decorations. If you, too, are interested in RGB LED decorations, there are a few on the site for your perusal.

Building radio receivers from scratch is still a popular project since it can be done largely with off-the-shelf discrete components and a wire long enough for the bands that the radio will receive. That’s good enough for AM radio, anyway, but you’ll need to try this DIY FM receiver if you want to listen to something more culturally relevant.

Receiving frequency-modulated radio waves is typically more difficult than their amplitude-modulated cousins because the circuitry necessary to demodulate an FM signal needs a frequency-to-voltage conversion that isn’t necessary with AM. For this build, [hesam.moshiri] uses a TEA5767 FM chip because of its ability to communicate over I2C. He also integrated a 3W amplifier into this build, and everything is controlled by an Arduino including a small LCD screen which displays the current tuned frequency. With the addition of a small 5V power supply, it’s a tidy and compact build as well.

While the FM receiver in this project wasn’t built from scratch like some AM receivers we’ve seen, it’s still an interesting build because of the small size, I2C capability, and also because all of the circuit schematics are available for all of the components in the build. For those reasons, it could be a great gateway project into more complex FM builds.

You’ve probably seen a flipbook. That’s a book with pictures on each page. Each picture is slightly different than the last one so if you flip rapidly through the book you get a little animation. We like the German word, Daumenkino, which translates as “thumb cinema” and that seems appropriate. [Barqunics] put a decidedly new twist on this old technology. His flipbook senses a viewer and automatically flips the pages using a motor. You can see the Arduino-controlled device in the video below.

The presence detection is a ubiquitous sonar sensor. The frame is easy to make since it uses cardboard and hot glue. A DC motor like you find on many toy cars or robots provides the rotation. No 3D printing needed, but we did think it would be easy to 3D-print or laser-cut the pieces.

You’d think the flipbook would date back to antiquity, but apparently, the earliest known ones are from the mid-1800s. However, the idea isn’t that different from a phénakisticope or a zoetrope other than those devices use a disk or drum that would be easy to rotate. Something to consider if you plan to recreate this project.

We should have guessed there would be automated ways to generate images for a flipbook. That opens up a lot of interesting ideas for projects, too.

The band Kraftwerk hit the music scene with its unique electronic sound in the 70s in Germany, opening the door for the electronic music revolution of the following decade. If you’re not familiar with the band, they often had songs with a technology theme as well, and thanks to modern microcontroller technology it’s possible to replicate the Kraftwerk sound with microcontrollers as [Steven] aka [Marquis de Geek] demonstrates in his melodic build.

While the music is played on a Stylophone and a Korg synthesizer, it is fed through five separate Arduinos, four of which have various synths and looping samplers installed on them (and presumably represent each of the four members of Kraftwerk). Samplers like this allow pieces of music to be repeated continuously once recorded, which means that [Steven] can play entire songs on his own. The fifth Arduino functions as a controller, handling MIDI and pattern sequencing over I2C, and everything is finally channeled through a homemade mixer.

[Marquis] also dressed in Kraftwerk-appropriate attire for the video demonstration below, which really sells the tribute to the famous and groundbreaking band. While it’s a great build in its own right and is a great recreation of the Kraftwerk sound, we can think of one more way to really put this project over the top — a Kraftwerk-inspired LED tie.

How do you instantly make any game better? By lighting it up and playing at night. We would normally say ‘drinking’, but we’re pretty sure that drinking is already a prerequisite for cornhole — that’s the game where you toss bean bags at holes in angled boards.

[Hardware Unknown] loves cornhole, and was gifted a set of portable, folding boards that light up around the ring for nighttime action. These turned out to be the perfect basis for reactive boards that light up and play sound whenever points are scored. Both boards have a vibration sensor to detect bags hitting the top, and an IR break-beam sensor pair across the hole. An Arduino Nano reads from the sensors and controls an amplifier and a DF Player for sound.

Players get a point and a song for landing a bag on top of the board, and three points and a different song for making it in the hole. We love the Easter egg — anyone who manages to trip both the vibration sensor and the break-beam detector at the same time will be treated to the sound of a flock of honking geese. Check out the build journey after the break.

No good at cornhole? This one doesn’t let you miss.

Are you running out of ways to entertain yourself and your family? If you’ve read all the books and watched all the movies, it might be time to explore the psychic abilities of silicon. [Hari Wiguna] has just the trick to keep them guessing for a good long time.

This trick doesn’t take much, just a couple of Arduinos, some momentary buttons, a number pad, and a large helping of math. As you can see in the demo after the break, there is nothing connecting the two, not even 802.11(n). On the randomizer Arduino, [Hari] generates random numbers with the push of a button until the audience sees one they like. Then [Hari] locks in the number with the other button.

What happens next is key: the randomizer generates another random number, but uses it as a hint to set a sentinel digit. The randomizer Arduino subtracts the larger of the two digits in the number from nine and stores the result as the flag. When the next number comes up that has the flag digit in the correct place, the number after that will be the random number chosen at the beginning.

The psychic Arduino’s secret is that it knows the first guess it receives is special. It does the same sentinel digit math as the randomizer, so when the guesser enters the guess with the sentinel digit, it knows the next number entered is the winner. Clear as mud? Check out the second video below where [Hari] explains the trick, a new take on a magic classic.

Looking for a more exciting way to generate random numbers? Try using fish tanks, lava lamps, or muons from outer space.

Beer pong is a fun enough game for those of a certain age, but one thing that it lacks is a way of cranking up the difficulty setting independent of the amount of beer one has consumed. At least, that was the idea [Ty] had when he came up with this automated beer pong table which allows the players to increase the challenge of this game by sliding the cups around the top of the table.

The build uses a belt-driven platform under a clear cover with a set of magnets attached. Each of the cups on the table has a corresponding magnet, which allows them to slide fairly easily back and forth on the table. The contraption is controlled by an Arudino Nano with a small screen and dial that allows the players to select a difficulty level from 1 to 10. The difficulty levels increase the speed that the cups oscillate on the table, which certainly adds another layer of complexity to this already challenging game.

While we hope to eventually see a beer pong table that can automatically arrange the cups as the game is played, we do appreciate the effort to make an already difficult game even more difficult. Of course, if you have problems with the difficulty level you might want to pick up a PongMate CyberCannon Mark III to help with those clutch beer pong shots.

A spirit level, you know the kind of level with a little bubble in a tube of fluid, is a basic construction tool. [DesignBuildDestroy] took an Arduino, a gyroscope chip, and an OLED, and made a 3D printed level with no bubble, but it does have a nice digital display.

It is funny when you realize that at one time a gyroscope was a high tech item reserved for missiles and aircraft. Now you can grab a six-axis sensor for pennies. Even, better, the code used in the project can offload the Arduino for a lot of processing.

Initially, the device lived on a breadboard, which is always a good idea to get the kinks out of things. Thanks to the OLED, the Arduino can calibrate itself without a PC and do other tricks. The display is easy to read, but we thought there should be a mode that shows a little bubble made with an O character. Seems like that would be a fun rainy day project. We did like the automatic screen rotation, though.

We’ve seen a nice level done with a Raspberry Pi before. If you need something smaller, how about something the size of a dime?

We suppose it’s a bit early to call it just yet, but we definitely have a solid contender for Father of the Year. [DIY_Maxwell] made a light-up hockey game for his young son that looks like fun for all ages. Whenever the puck is hit with the accompanying DIY hockey stick (or anything else), it lights up and produces different sounds based on its acceleration.

Inside the printed puck is an Arduino Nano running an MPU6050 accelerometer, a 12-NeoPixel ring, and a piezo buzzer. [DIY_Maxell] reused a power bank charging circuit to charge up the small LiPo battery.

The original circuit used a pair of coin cells, but the Arduino was randomly freezing up, probably because of the LEDs’ current draw. Be sure to check out the video after the break, which begins with a little stop motion and features a solder stand in the shape of a 3D printer.

Got a house full of carpet or breakables? You could always build an air hockey table instead.

What’s the use of waiting around for something to break in order to hack into something else? As long as it’s just sitting around not being used, who cares? [OmniSaiRen] had a  Behringer MIDI controller just taking up space. Instead of selling it, they decided to build it into something they would definitely use — a multi-volume controller with mute keys and other useful macros.

After gutting the case, [OmniSaiRen] gave it a couple coats of glossy white paint that looks really nice with the black keycaps and knobs. The plan was to use the original encoders, but [OmniSaiRen] replaced them with potentiometers when they couldn’t get the encoders working with the Arduino Nano. We are sad to report that Cherry Blues only made it to the build because they have all black housings and were also lying around taking up space, but maybe [OmniSaiRen] will grow to love them.

If you’re tired of all the mousing and clicking it takes to turn down this or that volume, you need to build one of these things. It runs on deej, an open source volume mixer that works with Linux and Windows, so what are you waiting for? If you only want a single hardware volume knob, you can’t go wrong dialing it in rotary style.

Via r/duino