A 3D-printed magnetic fidget business card with ID storage.

2024 Business Card Challenge: Magnetic Fidget Card

If you want someone to keep your business card around, you should probably make it really cool-looking, or have it do something useful. It’s kind of the whole point of the 2024 Business Card Challenge. And while we’d normally expect electronics of some persuasion to be involved, we must admit that this magnetic fidget card definitely does something, at least when manipulated. And even when it’s just sitting there, the card has a storage slot for IDs, or whatever you want.

Have you ever played with a magnetic fidget? They are quite satisfying, and making one yourself is likely to be even cheaper than making one of the spinning variety. This one uses a whopping 16 neodymium magnets, which means that it’s probably quite aurally satisfying as well as fun to handle.

And of course, since it’s 3D-printed, you can put whatever you want on the faces and update them easily if something changes. Bonus points to [Bhuvan Bagwe] for designing some for the Hackaday crew!

A battery-testing business card.

2024 Business Card Challenge: A Battery Tester With Blinkenlights

Readers of a certain vintage will no doubt remember that for a brief time, some alkaline batteries came with a built-in battery tester. Basically, you just pushed really hard with your fingernails on the two ends of the strip, and it either lit up the little strip (or didn’t if it was dead), or made the word ‘good’ appear if energized.

But those days are long gone. What you need now is to either grab the voltmeter, stick out your tongue, or build yourself a battery-testing business card. Even the normies will enjoy this one, mostly because LEDs. Forty-seven of them to be exact, which will come to life and demonstrate that [Greg] is capable of making working electronic gadgets. No way does this card end up at the bottom of a desk drawer.

As far as grasping the batteries goes, [Greg] had several ideas, but ultimately landed on pogo pins, which we think is a fabulous solution. Be sure to check out the neat interactive BOM, somewhere in the middle of which is the CH32v003 RISC-V microcontroller. In the video after the break, you can see [Greg] using a Flipper Zero to program it.

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A PCB business card that plays tic-tac-toe with red and blue LEDs.

2024 Business Card Challenge: Go Tic-Tac-Toe-to-Toe With Them

There is perhaps no more important time to have a business card than when you’re in college, especially near the end when you’re applying for internships and such. And it’s vital that you stand out from the crowd somehow. To that end, Electrical & Computer Engineer [Ryan Chan] designed a tidy card that plays tic-tac-toe.

Instead of X and O, the players are indicated by blue and red LEDs. Rather than having a button at every position, there is one big control button that gets pressed repeatedly until your LED is in the desired position, and then you press and hold to set it and switch control to the other player. In addition to two-player mode, the recipient of your card can also play alone against the ATMega.

The brains of this operation is an ATMega328P-AU with the Arduino UNO bootloader for ease of programming. Schematic and code are available if you want to make your own, but we suggest implementing some type of changes to make it your own. Speaking of, [Ryan]  has several next steps in mind, including charlieplexing the LEDs, using either USB-C or a coin cell for power, upgrading the AI, and replacing the control button with a capacitive pad or two. Be sure to check it out in action in the two videos after the break.

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A solar-powered decibel meter the size of a business card.

2024 Business Card Challenge: NoiseCard Judges The Sound Around You

Let’s face it: even with the rise of the electric car, the world is a noisy place. And it seems like it has only gotten worse in recent years. But how can we easily quantify the noise around us and know whether it is considered an unhealthy decibel level?

That is where the NoiseCard comes in. This solar-powered solution can go anywhere from the regrettable open office plan to the busy street, thanks to a couple of 330 µF capacitors. It’s based on the low-power STM32G031J6 and uses a MEMS microphone to pick up sound from the back of the card, which the code is optimized for. Meanwhile, the LEDs on the front indicate the ambient noise level, ranging from a quiet 40 dB and under to an ear-splitting 105 dB or greater.

When it comes to building something the size of a business card, every component is under scrutiny for size and usefulness. So even the LEDs are optimized for brightness and low power consumption. Be sure to check it out in action after the break in various environments.

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2024 Business Card Challenge: Integrated Game Card

[Dan Schnur] has a simple strategy to ensure their business card stays on the client’s desk and doesn’t just get lobbed in a drawer: make it into a simple gaming platform. This entry into the 2024 Business Card Challenge is based around the tinyjoypad project, integrating an SSD1306 OLED display, joypad, and push button.

Powered by the superstar ATTiny85, the electronics are really not all that much, just a sprinkling of passives to support the display and the six switch inputs from the joystick and push button. Or at least, that’s how much we can glean from the PCB images, as the PCB design files are not provided in the project GitHub.

Leaving the heavy lifting of the software to the tinyjoypad project, the designer can concentrate on the actual job at hand and the reason the business card exists to stay at the forefront of the client’s mind. In the meantime, the card can be a useful distraction for those idle moments. A few such distractions include a tiny version of Missile Command (as shown above), tiny tris, and a very cut-down Q-bert.  Sadly, that last game isn’t quite the same without that distinctive sound.

2024 Business Card Challenge: PCB Business Cards For Everybody

PCB business cards for electronics engineers might be very much old news in our circles, but they are still cool, not seen too much in the wild, and frankly inaccessible to those in other industries. For their entry into the 2024 Business Card Challenge, [Dima Shlenkevitch] is helping a little to alleviate this by providing a set of design examples and worked costs with suppliers.

Original green is still the cheapest option.

[Dima] lists key features every PCB business card should include, such as the expected thickness, restrictions for placing NFC components, and some aesthetics tips. Make sure to choose a supplier that allows you to remove their order number from the manufactured PCB, or it will look out of place.

Ordering PCBs with these specifications to keep costs reasonable requires effort, so [Dima] offers some example designs along with the results. If you want to have pretty gold lettering and graphics, you will need ENiG plating, increasing the price. Non-standard solder mask colors can also raise the price.

Will this help with the practical aspects of driving the PCB design software and actually placing the order? Obviously not, but the information provided gives you a leg up on some of the decisions so you don’t go down an expensive rabbit hole.

2024 Business Card Challenge: BAUDI/O For The Audio Hacker

[Simon B] enters our 2024 Business Card Challenge with BAUDI/O, a genuinely useful audio output device. The device is based around the PCM2706 DAC, which handles all the USB interfacing and audio stack for you, needing only a reference crystal and the usual sprinkling of passives. This isn’t just a DAC board, though; it’s more of an audio experimentation tool with two microcontrollers to play with.

The first ATTiny AT1614 is hooked up to a simple LED vu-meter, and the second is connected to the onboard AD5252 digipot, which together allows one to custom program the response to the digital inputs to suit the user. The power supply is taken from the USB connection. A pair of ganged LM2663 charge-pump inverters allow inversion of the 5V rail to provide the necessary -5 V for the output amplifiers.  This is then fed to the LM4562-based CMoy-type headphone amplifier.  This design has a few extra stages, so with a bit of soldering, you can adjust the output filtering to suit. An LM1117 derives 3.3 V from the USB input to provide another power rail,  mostly for the DAC.

There’s not much more to say other than this is a nice, clean audio design, with everything broken out so you can tinker with it and get exactly the audio experience you want.