My friend, Missa, sports a unique tattoo – a heart shaped circuit board etched onto her arm. Inspired by this piece of body art, I embarked on a personal project: to design a real, functional circuit board that mirrored her tattoo. This wasn’t just about replicating a design; it was about creating a working piece of technology that was born from a heart tattoo idea. With her birthday approaching, I envisioned it as the perfect, personalized gift, blending the worlds of tattoo art and electronics.
Alt text: Close-up blurry photo of Missa’s heart circuit board tattoo on her arm, inspiration for a DIY electronics project.
The challenge was immediately apparent and intriguing. Typically, circuit board design starts with functionality – defining what the circuit needs to do and then designing its appearance. Here, I was flipping the script. The visual design, the heart tattoo itself, was the starting point. The goal was to reverse-engineer functionality into this pre-existing aesthetic.
Adding to the complexity, the tattoo’s design seemed to originate from an artistic, rather than engineering perspective. Elements like traces leading to the board’s edge without connection and surface mount components lacking visible traces posed design puzzles. It was clear artistic license had been taken in the tattoo design, requiring me to adopt an “engineering license” in return to bridge the gap between art and function.
Alt text: Top layout design of the heart-shaped circuit board, meticulously crafted to resemble the original tattoo art.
After hours of conceptualizing and tinkering, the circuit board layout began to take shape. My aim was a one-to-one component match with the tattoo. Where the tattoo depicted an 8-pin chip, I incorporated an 8-pin Atmel microcontroller, the attiny85. The tattoo’s rectangular elements were reimagined as functional components: LEDs (red and green), a capacitor, and current-clamping resistors.
The tattoo art presented a further design constraint: three of the depicted chip’s pins appeared to be routed off the board’s edge without purpose. This left only five usable pins. Fortuitously, aligning the chip in a specific orientation allowed these five pins to correspond with the essential functions: power, ground, reset, and two I/O pins needed to control the LEDs. To maintain visual fidelity to the original heart tattoo design, I even added non-functional vias (the green circles in the design), mimicking artistic details that served no electrical purpose.
Alt text: X-ray view of the heart circuit board layout, showing red traces on the front mirroring the tattoo and blue traces on the back for internal connections.
This “x-ray” view reveals the dual nature of the design. The red traces on the front layer are a direct visual echo of the tattoo, while the blue traces on the back form the functional circuitry, connecting components and enabling operation. At the heart’s base, a rectangular space was allocated for a 12mm lithium coin cell battery holder. Size was a key consideration – it needed to fit discreetly within the heart shape while providing sufficient power for the LEDs and be easily replaceable. Researching coin cell specifications and availability led me to the CR1225, a balance of size and adequate pulse discharge for the LEDs.
On the reverse side, hidden from view on the front which needed to be a tattoo replica, I included a personal touch: “Happy Birthday Missa!” and her birthday date.
Alt text: Close-up of the manufactured heart circuit boards fresh from PCBWay, showcasing the physical realization of the digital design.
The design files were sent to PCBWay, a fabrication service, and within a week, a batch of five circuit boards arrived. The rapid transformation from digital design to tangible object remains a fascinating aspect of modern manufacturing. This project marked my first venture into non-rectangular board design. The heart shape was sourced from online clip art, refined in Adobe Illustrator to closely match Missa’s tattoo, and then imported into Eagle, my PCB design software, using a helpful online tutorial for custom board outlines.
Alt text: Assembled heart circuit board with surface mount components soldered in place, cleaned with isopropyl alcohol, ready for operation.
Surface mount soldering, while new to me at the time, was essential to replicate the tattoo’s component style. Using tweezers for placement, the small components were soldered onto the board. Post-soldering flux residue was effectively cleaned with 99.9% isopropyl alcohol, leaving a pristine finish, a tip I learned from a friend.
The completed board, now operational, was programmed to blink a message. The green LED spells out “Happy Birthday Missa” in Morse code, while the red LED cycles through prime numbers from 2 to 23. The code, available on GitHub, was developed using RULOS, a lightweight microcontroller “operating system” I co-created. A Morse code generator library was also developed as part of this project. To streamline software development, a desktop simulator was created, allowing for debugging and testing in a more user-friendly environment before deploying to the physical microcontroller. Upon compiling for the microcontroller and loading the code, the board functioned perfectly on the first attempt!
Alt text: The heart circuit board in action, LEDs blinking, presented as a unique and personalized birthday gift.
Missa’s birthday party arrived, and the heart circuit board tattoo, now a real, blinking object, was presented. Her reaction was one of delight. The size, determined by scaling the tattoo photo based on an assumed chip width, was surprisingly accurate, fitting almost perfectly over her actual tattoo. This project, born from a simple observation of a heart tattoo design, proved to be both an enjoyable endeavor and a valuable learning experience, demonstrating how a Design A Heart Tattoo concept can evolve into a tangible and functional piece of personalized technology.
