So what if we’re halfway through 2024? People who needed to fidget all along still need something to do with their hands. So why not hand them a solution with your information on it?

Not only will this spin nicely, the spinning action will use magnets to energize PCB coils and light up LEDs for some persistence of vision action. Designing the PCB was easier than you might imagine thanks to KiMotor, a KiCad plugin to automate the design of parametric PCB motors.

Mechanical testing went pretty well with the bearings and magnets that [mulcmu] had on hand, along with a scrap PCB as the sacrifice. Although a bit difficult to hold, it spins okay with just the bearing and the shaft. Once the boards arrived, it was time to test the electrical side. So far, things are not looking good — [mulcmu] is only getting a few tens of mV out of the rectifier — but they aren’t giving up hope yet. We can’t wait to see this one in action!

Hurry! This is the last weekend to enter the 2024 Business Card Challenge! Technically you have until Tuesday, July 2nd, but you know what we mean. Show us what you’ve got!

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.

[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.

In Terminator 2: Judgment Day it’s revealed that Skynet becomes self-aware in August of 1997, and promptly launches a nuclear attack against Russia to draw humanity into a war which ultimately leaves the door open for the robots to take over. But as you might have noticed, we’re not currently engaged in a rebellion against advanced combat robots.

The later movies had to do some fiddling with the timeline to explain this discrepancy, but looking at this 2024 Business Card Challenge entry from [M. Bindhammer] we think there’s another explanation for the Judgement Day holdup — so long as the terminators are rocking 555 timers in their chrome skulls, we should be safe.

While the classic timer chip might not be any good for plotting world domination, it sure does make for a great way to illuminate this slick piece of PCB art when it’s plugged into a USB port. Exposed copper and red paint are used to recreate the T-800’s “Brain Chip” as it appeared in Terminator 2, so even when the board isn’t powered up, it looks fantastic on display. The handful of components are around the back side, which is a natural place to put some info about the designer. Remember, this is technically supposed to be a Business Card, after all.

This build is a great example of several badge art techniques, which we think is worthy of a closer look even if you’re not personally into the Terminator franchise. While it’s far from the most technologically advanced of the entries we’ve seen so far, it does deliver on a design element which is particularly tricky to nail down — it’s actually cheap enough that you could conceivably hand it out as a real business card without softly weeping afterwards.

Remember, you’ve still got until July 2nd to enter your own creation into the 2024 Business Card Challenge. So long as the gadget is about the same size and shape as a traditional card, it’s fair game. Bonus points if you remember to put your name and contact info on there someplace…

What’s the easiest way to break the ice with someone you’ve just met? If you’re not immediately talking shop, than it’s probably the time-tested subject of the weather. So what better way to get the conversation started than with a lovely solar-powered circuit sculpture of a business card that displays the weather?

We love that the frame has a built-in stand; that’s a great touch that really turns this card into something that someone might keep on their desk long-term. The brains of this operation is an ESP32 TTGO E-paper board, which checks the battery voltage first before connecting to Wi-Fi and getting data from the OpenWeatherMap API. It displays the information and then goes to sleep for 15 minutes.

For power, [BLANCHARD Jordan] is using a 5 V solar panel and a small battery from an old vape pen. We love to see projects that keep those things out of the landfills, so don’t sleep on using them.

You have just a few weeks left to enter the 2024 Business Card Challenge, so fire up those soldering irons and get hackin’!

The progress for electronics over the past seven decades or so has always trended towards smaller or more dense components. Moore’s Law is the famous example of this, but even when we’re not talking about transistors specifically, technology tends to get either more power efficient or smaller. This MIDI keyboard, for example, is small enough that it will fit in the space of a standard business card which would have been an impossibility with the technology available when MIDI first became standardized, and as such is the latest entry in our Business Card Challenge.

[Alana] originally built this tiny musical instrument to always have a keyboard available on the go, and the amount of features packed into this tiny board definitely fits that design goal. It has 18 keys with additional buttons to change the octave and volume, and has additional support for sustain and modulation as well. The buttons and diodes are multiplexed in order to fit the IO for the microcontroller, a Seeed Studio Xiao SAMD21, and it also meets the USB-C standards so it will work with essentially any modern computer available including most smartphones and tablets so [Alana] can easily interface it with Finale, a popular music notation software.

Additionally, the project’s GitHub page has much more detail including all of the Arduino code needed to build a MIDI controller like this one. This particular project has perhaps the best size-to-usefulness ratio we’ve seen for compact MIDI controllers thanks to the USB-C and extremely small components used on the PCB, although the Starshine controller or these high-resolution controllers are also worth investigating if you’re in the market for compact MIDI devices like this one.

If you want to make a good first impression on someone, it seems like the longer you can keep them talking, the better. After all, if they want to keep talking, that’s a pretty good sign that even if you don’t become business partners, you might end up friends. What better way to make an acquaintance than over a friendly game of tic-tac-toe?

This one will probably take them by surprise, being a 4×4 matrix rather than the usual 3×3, but that just makes it more interesting. The front of the card has all the usual details, and the back is a field of LEDs and micro switches. Instead of using X and O, [Edison Science Corner] is using colors — green for player one, and red for player two. Since playing requires the taking of turns, the microcontroller lights up green and red with alternating single-button presses.

Speaking of, the brains of this operation is an ATMega328P-AU programmed with Arduino. If you’d like to make your own tic-tac-toe business card, the schematic, BOM, and code are all available. Be sure to check out the build and demo video after the break.