Will Kalman's LogiClock Is a Retro Timepiece Three Decades in the Making

Maker Will Kalman has built an electronic clock with a difference: its design goes back to 1983, as an ambitious attempt to duplicate an expensive commercial timepiece seen in the window of a popular mall store.

"Circa 1983, 14 year-old me was enamored of a clock seen at The Sharper Image store in the mall. It consisted of concentric rings of 60 LEDs of the classic 5mm domed package type," Kalman recalls. "It featured a cool '60ths' LED animation that would circle the clock once each second. It had a price tag of an astonishing $250 — almost $800 in today's money! About five years later, just a year or two out of high school, a friend and I decided that we knew enough to build that clock ourselves and maybe we could make it for much less money."

The clock in question was a high-end wall clock, designed for The Sharper Image's cutting-edge clientele — though Kalman and friend's attempts at recreation focused on a smaller design that could be used as a desk clock. Initial prototypes were made, but other demands on its creators' time would mean the concept would languish in a drawer for a good three decades.

Three years ago, Kalman remembered the long-abandoned project and set about finishing the job — turning to modern tools like KiCad and PCB production houses, but eschewing microcontrollers in favor of the discrete logic that would have powered the original. The new design turns to 74393 dual four-bit binary counters to keep track of the 60 LEDs in each of the clock's three concentric rings — displaying seconds, minutes, and hours in electronic mimicry of the hands of an analog clock, plus "jiffies," with a spare counter dividing by 12 to drive the hour hand precisely.

Elsewhere on the board is a 3.93216MHz crystal and a 744060 binary divider, which provides a 240Hz clock signal for multiplexers and 60Hz for the jiffy counter, while four 74154 4-to-16 line multiplexers drive the LEDs — an approach decided on back in 1988, as a cost-saving alternative to having 16 dedicated non-multiplexed decoders. A 555 timer holds the counter reset lines during power-up.

"I brought out three lines to a pin header on the back: 5V power, ground, and reset," Kalman notes. "I have a [Raspberry Pi] Pico W that I'd like to program to get the current time via NTP [Network Time Protocol] and at midnight/noon each day, tap the reset line to zero the counters to 12:00 to automatically set/correct the time. I had other ideas like bringing out the clock line to set an arbitrary time by resetting the clock to 12:00 and feeding in fast clock pulses to set the time, maybe that's an idea for V2."

The LogiClock is documented on Hackaday.io complete with a schematic — and Kalman finally brought closure to the project by sending one of the new clocks to the childhood friend who had helped with the original 1988 prototypes.