Magnets (especially those ball magnets!) are endlessly fascinating, aren’t they? It’s almost dangerous to combine them with LEDs, because how are you supposed to get anything done with something like [andrei.erdei]’s Arduino Magnetic Board beckoning from beyond your keyboard?

This tons-of-fun board uses ball magnets to light up RGB LEDs as they roll around on the sexy Plexiglas field. Underneath the LED matrix is an orchestra of 36 reed switches — those little glass gas-filled grains of rice with axial leads that snap together or fly apart in the presence of magnetic fields. The LEDs are controlled with an Arduino Pro Mini, and so is the 8Ω speaker for sound effects.

[andrei.erdei] has already developed a few applications for this delightful desk toy, and they’re all on GitHub. There’s a chase game that involves tilting the board to catch the next red dot with the magnet, a light painting game, and a sequencer that mimics the ToneMatrix. Roll past the break to check out the series of short demo videos.

Want to play with reed switches but can’t source any at the moment? You could just make them yourself.

While almost everyone has a heater of some sort in their home, it’s fairly unlikely that the heat provided by a central heating system such as a furnace is distributed in an efficient way. There’s little reason to heat bedrooms during the day, or a kitchen during the night, but heating systems tend to heat whole living space regardless of the time of day or the amount of use. You can solve this problem, like most problems, with an Arduino.

[Karl]’s build uses a series of radiator valves to control when each room gets heat from a boiler. The valves, with a temperature monitor at each valve, are tied into a central Arduino Mega using alarm wiring. By knowing the time of day and the desired temperature in each room, the Arduino can control when heat is applied to each room and when it is shut off, presumably making the entire system much more efficient. It also has control over the circulating pump and some of the other boiler equipment.

Presumably this type of system could be adapted to a system which uses a furnace and an air handler as well, although it is not quite as straightforward to close vents off using a central unit like this as it is to work with a boiler like [Karl] has. With careful design, though, it could be done. Besides replacing thermostats, we can’t say we’ve ever seen this done before.

Thanks to [SMS] for the tip!

Recreating classic games in software is a great way to get better at coding or learn to code in the first place. If you do it in hardware though, you’ll gain a lot more than coding skills. Just ask [Kelly] and [Jack] did, when they built this Arduino-based electronic Connect Four for a school project.

We love that their interpretation manages to simplify game play and make it more fun than the original version. All the players have to do is turn it on and start pushing the arcade buttons along the bottom to choose the column where they want to make a play. The LEDs animate from top to bottom to imitate the plastic disc dropping down through the board. If a win is detected — four in a row of the same color going any direction — the board fills up with the winning color and the game starts over.

The state machine doesn’t currently do anything about tie situations, so there’s a reset button hidden on the side. As [Kelly] and [Jack] explain in their walk-through video after the break, that is something they would like to address in the future, along with making it possible to choose whatever battle color you want. We think a reset animation that mimics the look of the discs spilling out the bottom would be cool, too.

If you’ve never implemented a game on hardware before, something like this might be a bit daunting. May we suggest a game of 4×4 Tic Tac Toe instead?

People get into electronics for all kinds of reasons, but we would guess that the ability to blink the blinkenlights is probably pretty high on the survey results. [Kuchbert] has been going to Deichkind shows for the last decade and has wanted to build one of the German techno-rap band’s signature tetrahedral LED hats for about as long.

Up inside the hat is an Arduino Nano driving WS2812B LEDs and a portable battery to power everything. Thanks to an HC-05 Bluetooth module, the show can be controlled with an Android app. The many, many holes in the acrylic panels were milled out, but they could just as easily be laser-cut, or if you have infinite patience, drilled by hand. The code is coming once it has been cleaned up a bit. Everything else you’d need is already there waiting. This helmet even has its own lil’ music video, which we’ve carefully beat-matched in after the break.

Naturally, this makes us think of all the Daft Punk helms that have blinked by on this blog over the years. This hand-soldered one might be the most meticulously made.

As wonderful as mechanical keyboards are, most of the pre-fab and group buy models out there have zero media controls. If you want rotary encoders and OLED screens to show what function layer you’re working in, you’ll probably have to build your own keyboard from the ground up.

Hackaday alum [Cameron Coward] got around this problem by building an electromechanical buddy for his keyboard that works as a volume control. Now that we don’t rely on them to make phone calls, rotary dials are a fun throwback to a time that seems simpler based on its robust and rudimentary technology. This one is from a lovely burnt orange Bell Trimline phone, which was peak rotary dial and one of the idea’s last gasps before tone dialing took over completely.

Operationally speaking, [Cameron] is reading in the dial’s pulses with an Arduino Nano and using a Python script to monitor the serial connection and translate the pulses to volume control. We like that this is isn’t a volume knob in the traditional sense — it’s a game of percentages. Dialing ‘2’ gives 20% volume across all programs, and ‘8’ raises it to 80% of maximum. Need to mute? Just dial ‘0’, and you’ll begin to understand why people wanted to move on from rotary dialing. It won’t take that long, but it’s not instant. Check out the demo after the break.

This isn’t the first time we’ve seen a rotary dial used to control volume, but that’s one of the minor selling points of this rotary cell phone.

Were tarot card readers deemed non-essential in your part of the world (and do you think they saw it coming?) More than ever, we all need diversions that are for entertainment purposes only. And what better basis for entertainment than a mystical fortune-telling robot that can read your tarot cards?

This fantastic-looking ‘bot stands on the shoulders of [Scott Bezak]’s trailblazing method for easy DIY split-flap displays. Push the rather inviting-looking button on the top, and the flaps start flipping around to find your fortune. Once the fates have aligned, a thermal printer on the front spits out an image of your card along with an interpretation.

It’s obvious that [i_mozy] put quite a lot of effort into this slick machine, and we think the stickers look especially great. All the details of physical tarot card readings are accounted for, including a random number to decide the card’s position, and LEDs to represent the card’s element. Suspend your disbelief and check out the demo/promo video after the break.

Split-flap displays are a great choice no matter what you want to show. We’ve seen them used to display everything from the weather to the current Spotify track.

Via r/duino

We know you’re out there spending a lot more time with your loved ones, and appreciate that you may be running out of ways to keep everyone entertained. [Mukesh] dropped us a tip because he has the antidote to boredom — a new twist on that old chestnut, Tic Tac Toe.

Instead of the usual 3×3 configuration, [Mukesh] made the grid 4×4 so the game would be more engaging. Game play is otherwise the same — this Tic Tac Toe still results in a lot of draws, but they take longer and you can’t see them coming a mile away. What’s even more engaging is that you get to push clicky buttons that light up, and don’t have to draw a grid before every game.

Under the hood is an Arduino Uno that controls 16 push buttons and their corresponding RGB LEDs. Whoever goes first is blue, and player two gets pink. If you win, your color floods the board for a brief victory animation. If the game is a tie, the board turns red. We really like the printed two-piece buttons that house the LEDs and actuate the push buttons while keeping the two separate. Toe your way past the break to check out the build video.

Intrigued by the 4×4 version, but need a build that takes more time? Try building your TTT in TTL.

Let’s face it, we probably all sit at our computers for way too long without getting up. Yes, there’s work to be done, games to be played, and the internet abounds with people who are wrong and must be down-voted and/or corrected. We totally get and respect all that. However, if you want to maintain your middle- and long-range vision, you should really get up regularly and gaze out the window for a bit.

In fact, the Arduband does you one better. Its Arduino Nano and accelerometer check your position every ten minutes. If you haven’t changed your Z by the third check, then it’s time for a break. The combination of an RGB LED, buzzer, and vibrating disc motor working together should be enough to pull you out of any computerized stupor, and they won’t give up and go back to sleep until you have stood up and remained upright for one minute.

We like that [ardutronics123] spun up a board and made it small enough to be wrist-mounted using a watch strap. It would work just as well worn around your neck, and would probably even fit in your pocket. Blink a few times before you check out the build video after the break.

Arduband would be great on the go, but who does that anymore? If you spend every day at the same desk, you could point a time-of-flight sensor at your chair and start a timer.

We’ve all been there. A big bag of resistors all mixed up. Maybe you bought them cheap. Maybe your neatly organized drawers spilled. Of course, you can excruciatingly read the color codes one by one. Or use a meter. But either way, it is a tedious job. [Ishann’s] solution was to build an automatic sorter that directly measures the value using a voltage divider, rather than rely on machine vision as is often the case in these projects. That means it could be modified to do matching for precise circuits (e.g., sort out resistors all marked 1K that are more than a half-percent away from one nominal value).

There is a funnel that admits one resistor at a time into a test area where it is measured. A plate at the bottom rotates depending on the measured value. In the current implementation, the resistor either falls to the left or the right. It wouldn’t be hard to make a rotating tray with compartments for different values of resistance. It looks like you have to feed the machine one resistor at a time, and automating that sounds like a trick considering how jumbled loose axial components can be. Still, its a fun project that you probably have all the parts to make.

An Arduino powers the thing. An LCD screen and display control the action. If you want some practice handling material robotically, this is a great use of servos and gravity and it does serve a practical purpose.

We have seen many variations on this, including ones that read the color code. If you ever wanted to know where the color code for resistors came from, we took a trip to the past to find out earlier this year.

At the heart of many amateur radio and other projects lies the VFO, or Variable Frequency Oscillator. Decades ago this would have been a free-running LC tuned circuit, then as technology advanced it was replaced by a digital phase-locked-loop frequency synthesiser and most recently a DDS, or Direct Digital Synthesis chip in which the waveform is produced directly by a DAC. The phase-locked loop (PLL) remains a popular choice due to ICs such as the Si5351 but is rarely constructed from individual chips as it once might have been. [fvfilippetti] has revisited this classic circuit by replacing some of its complexity with an Arduino (Spanish language, Google Translate link).

A PLL is a simple circuit in which one oscillator is locked to another by controlling it with a voltage derived from comparing the phase of the two. Combining a PLL with a set of frequency dividers creates a frequency synthesiser, in which a variable frequency oscillator can be locked to a single frequency crystal with the output frequency set by the division ratios. The classic PLL chip is the CMOS 4046 which would have been combined with a pile of logic chips to make a frequency synthesiser. The Arduino version uses the Arduino’s internal peripherals to take the place of crystal oscillator, dividers, and phase comparator, resulting in an extremely simple physical circuit of little more than an Arduino and a VCO for the 40 metre amateur band. The code can be found on GitLab, should you wish to try for yourself.

It would be interesting to see how good this synthesiser is at maintaining both a steady frequency and minimal phase noise. It’s tempting to think of such things as frequency synthesisers as a done deal, so it’s always welcome to see somebody bringing something new to them. Meanwhile if PLLs are new to you, we have just the introduction for you.