Introduction
Timekeeping is an art that has fascinated makers for decades. While digital clocks are ubiquitous, there's something inherently captivating about analog displays—especially when they repurpose vintage-style meters. A recent project by lcamtuf demonstrates this beautifully: a clock built from three voltmeters, each needle sweeping across a custom dial to mark hours, minutes, and seconds. This build isn't just a timepiece; it's a conversation starter that merges old-school aesthetics with modern microcontroller programming.
The Brains of the Operation: AVR128DB28 Microcontroller
At the core of the voltmeter clock is an AVR128DB28, an 8-bit microcontroller still in active production. Running at a modest 8 MHz, this chip is responsible for driving the three voltmeters with precise pulse-width modulation (PWM). Unlike off-the-shelf PWM modules, the code here was handcrafted by lcamtuf, giving full control over the duty cycle and timing. This approach ensures that each needle moves smoothly and accurately to the correct position—no jitter, no drift.
Displaying Time with Analog Voltmeters
The three voltmeters are Baomain 65C5 models, originally intended for measuring electrical signals. Each meter has been fitted with a custom-printed face that divides the scale appropriately:
- The hour meter has 13 divisions (1–12 plus a marker for 12:00).
- The minute and second meters both have 61 divisions (0–60).
The PWM signal from the microcontroller is a continuous stream of 1-bit pulses. By varying the duty cycle, the average voltage seen by the meter changes, causing the needle to deflect proportionally. It's a simple but effective method that lets the clock display time with a classic analog feel.
Customization and Calibration
Building a clock with analog meters requires careful calibration. Each voltmeter has its own mechanical tolerances, so lcamtuf had to tweak the PWM values to ensure consistent needle positions. The custom dials also needed precise alignment—both in print and assembly—so that the needle points exactly at the correct number. The result is a display that reads time at a glance, just like a traditional watch or wall clock.
The Wooden Enclosure: Kerf-Bent Elegance
All the electronic components are housed in a beautiful wooden case. The sides feature delicately kerf-bent panels, a woodworking technique where parallel cuts (kerfs) are made along the inside of a board, allowing it to bend into smooth curves. This gives the clock a sleek, sculptural appearance that complements the metallic bezels of the voltmeters. The enclosure not only protects the electronics but also adds a retro-futuristic vibe that fits perfectly with the analog dials.
Similar Hackaday Projects: A Community Obsession
This clock is not the first of its kind on Hackaday. Over the years, makers have repeatedly combined old-school dials with modern electronics—from nixie tubes to analog meters. The appeal lies in the tactile nature of moving parts and the charm of seeing time measured by a needle sweep, rather than blinking digits. A video of lcamtuf's clock (available after the article) shows the satisfying rollover behavior as minutes and seconds click into place, a moment that pure digital clocks cannot replicate.
Conclusion
Lcamtuf's voltmeter clock is a testament to the maker spirit: taking simple components and turning them into something functional and artistic. By combining a widely available microcontroller, off-the-shelf voltmeters, and custom woodworking, he created a timepiece that stands out. Whether you're a seasoned hacker or a curiosity-driven hobbyist, this project offers inspiration for your next clock build—or your first foray into analog-style digital control.