Hackaday named Christian’s electromechanicalanalogdigitalclock, ekaggrat singh kalsi’s BEZICRON, and Tim’s candle-flame time base as the top three entries in the 2025 One-Hertz Challenge. The open-ended contest asked makers to make something happen once per second, as close to one hertz as possible; Hackaday reported over 100 entries and a $150 DigiKey gift certificate for each top-three winner.
What was the 2025 One-Hertz Challenge?
Hackaday announced the challenge in June 2025 with a deliberately broad prompt: “Do something, anything, but do it once a second.” The aim was to make an event occur at or near one hertz—the frequency of one cycle per second—without restricting entrants to a particular device, clock design, or timing method. Hackaday’s September 5 results announcement reported over 100 entries. Hackaday’s winners announcement says each of the three top entries received a $150 gift certificate from sponsor DigiKey.
Who were the top three winners?
| Winner and project | Timing approach | Output or display | Accuracy evidence in Hackaday’s announcement |
|---|---|---|---|
| Christian — the electromechanicalanalogdigitalclock | A mains-powered stepper motor and photochopper generate a one-hertz signal. | A 12-bit CMOS-logic counter and DAC drive vintage moving-coil meters to show the time. | No independent accuracy measurement is reported. |
| ekaggrat singh kalsi — BEZICRON | Cams and levers shape and stretch hair bands into numerals; the colon supplies the one-hertz pulse. | Hair bands form the clock’s numerals. | No independent accuracy measurement is reported. |
| Tim — candle-flame time base | A wire in a candle flame feeds a CH32xxx microcontroller’s capacitive input; the project measures flame oscillations and divides the frequency. | An LED flashes at one hertz. | No independent accuracy measurement is reported. |
How each winning project worked
Christian’s electromechanicalanalogdigitalclock
The project turns a mechanical rotation into a timing signal. A mains-powered stepper motor drives a photochopper, which produces a one-hertz pulse. CMOS logic chips count those pulses in a 12-bit counter, and a digital-to-analog converter translates the count into signals for vintage moving-coil meters. A brass frame and spring suspension support and isolate the noisy motor.
BEZICRON by ekaggrat singh kalsi
BEZICRON makes its display physically rather than with conventional digits. Cams and levers bend and stretch hair bands into numerals, while the clock’s colon provides the one-hertz pulse. Its striking feature is the mechanical display: elastic bands become the shapes used to read the time.
#1 Best Overall
- Frequency counter accurately measures frequencies from 10Hz to 2.7GHz across both input channels, supports Direct Counting up to 10MHz and Proportional Counting from 10MHz to 100MHz, precise for low and high signals
- Frequency counter equipped with multiple functions including Frequency Measurement, Period Measurement, Cumulative Count, and Self-Check Functions, designed for quick testing with high accuracy and reliable values
- Frequency counter features an 8-digit LED display that shows characters 0-9 in a continuous cycle, ensuring clear and easy-to-read results
- Frequency counter offers selectable gate times of 0.01s, 0.1s, and 1s, allowing users to customize measurement duration for different applications
- Frequency counter achieves a highest input sensitivity of 20mVrms, with exceptional stability rated at ±3 x 10^-9s for reliable operation
Tim’s candle-flame time base
In Hackaday’s description, a wire placed in a candle flame connects to a capacitive input on a CH32xxx microcontroller. The project measures oscillations in the flame, divides the measured frequency, and uses the resulting one-hertz timing to flash an LED. Hackaday’s winner announcement does not report an independent test of how accurately or consistently the flame-derived timing tracks one hertz.
What distinguished the three approaches?
The winners interpret the same one-second constraint in very different ways: one derives a pulse from a motor and counts it electronically, one makes the display itself a mechanical spectacle, and one extracts a timing signal from flame behavior. The comparison is about their reported designs, not a precision ranking: the announcement gives no common test measurements with which to compare their timing accuracy.
Rank #2
- 🎯 High Sensitivity & Exceptional Stability - Achieves a top input sensitivity of 20mVrms to detect weak signals, coupled with outstanding stability rated at ±3 x 10^-9s. Users can select gate times (0.01s, 0.1s, 1s) to customize measurement speed and precision for different applications.
- ⚡ Wide Frequency Range & Dual-Channel Input - Accurately measure frequencies from 10Hz to 2.7GHz across both input channels. It supports Direct Counting (up to 10MHz) and Proportional Counting (10MHz-100MHz), making it a versatile and precise tool for a vast array of low and high-frequency signals
- 🛠️ Multifunctional & High-Precision Measurement - Engineered for professional testing, this counter integrates multiple functions including Frequency Measurement, Period Measurement, Cumulative Count, and a Self-Check Function. It delivers quick, high-accuracy, and reliable readings for complex diagnostic tasks.
- 👁️ 8-Digit LED Display - Features a high-brightness, 8-digit LED display that cycles through characters 0-9 with a self-test function. This ensures results are exceptionally clear, easy to read from various angles, and verifies display integrity at a glance.
- 🔋 Portable & Efficient Low-Power Design - Its novel, lightweight design and efficient circuit ensure low power consumption without sacrificing performance. This makes the TFC2700L equally suitable for demanding fieldwork and stable laboratory environments, offering true portability and reliability.
- Motor and electronics: Christian’s clock combines a stepper motor, photochopper, CMOS counter, DAC, and analog meters.
- Mechanical display: BEZICRON uses cams, levers, and hair bands to make numerals.
- Environmental signal: Tim’s project senses candle-flame oscillations and divides the measured frequency to produce an LED pulse.
Other projects Hackaday highlighted
Beyond the three top entries, Hackaday grouped honorable mentions into four themed categories:
- Ridiculous: Brian Stuparyk’s electromechanical function generator; alnwlsn’s pitchblende-powered “atomic” clock; and Sean B’s “Nothing but NAND” Nixie clock.
- Timelords: a vintage atomic-clock restoration; GPS synchronization for quartz wall clocks; and a GPS-disciplined crystal-oven oscillator.
- Clockwork: Simon Newhouse’s Nixie frequency-counter clock; hayday’s DCF77 clock; and Andrew Tudoroi’s RPi TinynumberHat9 clock.
- Coulda Used a 555: Tom Goff’s Logic Bombe; Mark Valentine’s capacitor-free timer; and Paul Gallagher’s “One Hurts” clock.
These mentions show how wide the prompt was: projects could explore unusual timing sources, clock mechanisms, or playful ways to meet the once-a-second constraint.
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Best Value
- Novel style, lightweight.
- Cycle cumulative measurement.
- Both importations frequency ranges: 10Hz to 2.7GHz
- Highest input sensitivity: 20mVrms.
- 8 high brightness LED display windows, 0 to 9 characters display simultaneous in cycle a self-test function.
Rank #4
- What is TinyGTC? The TinyGTC is a portable high-precision dual-channel frequency counter and timer with a built-in GPS-disciplined oscillator (GPSDO). Featuring 40ps resolution for accurate frequency, phase and time interval measurements, it supports battery power and touch operation, making it ideal for ham radio calibration, SDR tuning, RF testing and electronics DIY projects
- High-Precision Dual-Channel Frequency & Phase Measurement: Equipped with two independent high-resolution counter/timers with 40ps time resolution, measures frequency, phase, count and time intervals with accuracy up to 5e-12 per second; supports gapless interpolated reciprocal counting for stable results across 0.1Hz-7GHz (Channel A) and 0.1Hz-350MHz (Channel B)
- Built-in GPSDO with Multi-Reference Stability: Integrated GPS-disciplined oscillator (GPSDO) with premium TCXO delivers ADEV of ~1e-10 at 1-100s, automatically locks to GPS for excellent long-term frequency stability; supports external 10MHz reference input for calibration of SDR boards, signal generators and radio gear
- Portable Battery-Powered Design with Intuitive Control: Built-in rechargeable 4000mAh battery for fully handheld field use; 4-inch responsive touchscreen plus a backup jog wheel for reliable operation in all conditions; compact form factor fits easily in toolkits, ideal for on-site antenna tuning and radio turning
- Rich Analysis Functions & Flexible Data Export: Supports real-time charting, histogram, ADEV, FFT and FM deviation analysis directly on device; enables USB data logging, SD card storage and SCPI remote control for long-running measurements, fully compatible with TimeLab and professional analysis software
Rank #3
- Seesii TinyGTC ZC412 Handheld Frequency Counter: A cost-effective device with an ultra-wide 0.1 Hz—12.8 GHz frequency range, delivering precise data for RF development and frequency calibration. It features a built-in GNSS/GPS disciplined oscillator for measurement accuracy, and is equipped with a 4.0-inch HD touchscreen and a Micro SD card slot supporting up to 32GB for full-process data handling and storage
- Broad Frequency Coverage: The Frequency Dual Timer/Counter offers an impressive frequency range from 0.1 Hz to 12.8 GHz, encompassing both ultra-low and high frequencies. It accurately measures ultra-low-frequency and audio signals starting at 0.1 Hz, while the 7 GHz band supports mainstream wireless communications. With its extensive coverage and versatility, this single unit handles diverse full-band testing needs
- Dual-Channel Measurement: The device is equipped with two independent input channels (A & B) for simultaneous measurement and comparison, improving test efficiency and reducing errors. Channel A supports 0.1Hz–350MHz, extendable to 7GHz/12GHz with a GHz prescaler. Channel B is identical to Channel A, except that it does not include the GHz prescaler function. Ideal for interference troubleshooting, amplifier gain measurement, lab and field testing
- Ultra-High Precision: The TinyGTC features two independent counter/timers with 40 ps resolution, enabling gapless time, frequency, and phase measurements. Advanced reciprocal counting and ADEV stability deliver frequency-independent accuracy of 1e-11~1e-12 per second—providing lab-grade precision for research, development, and testing in TDR, pulse, and long-term stability applications
- GPS Synchronized Internal Clock: The TinyGTC incorporates a built-in GNSS/GPSDO that locks to GPS UTC for continuous calibration and long-term high precision. Its disciplined oscillator delivers stable 8kHz–150MHz frequencies as a clock source and accepts external references, including atomic clocks, to fully utilize its 12-bit resolution—designed for precision timing in communication base station testing, distributed sensor networks, and field research
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