Maker Will Kalman has constructed an digital clock with a distinction: its design goes again to 1983, as an formidable try to duplicate an costly industrial timepiece seen within the window of a preferred mall retailer.
“Circa 1983, 14 year-old me was enamored of a clock seen at The Sharper Picture retailer within the mall. It consisted of concentric rings of 60 LEDs of the traditional 5mm domed bundle sort,” Kalman remembers. “It featured a cool ’60ths’ LED animation that will circle the clock as soon as every second. It had a price ticket of an astonishing $250 — virtually $800 in immediately’s cash! About 5 years later, only a yr or two out of highschool, a good friend and I made a decision that we knew sufficient to construct that clock ourselves and perhaps we might make it for a lot much less cash.”
The clock in query was a high-end wall clock, designed for The Sharper Picture’s cutting-edge clientele — although Kalman and good friend’s makes an attempt at recreation centered on a smaller design that might be used as a desk clock. Preliminary prototypes had been made, however different calls for on its creators’ time would imply the idea would languish in a drawer for a very good three a long time.
Three years in the past, Kalman remembered the long-abandoned challenge and set about ending the job — turning to trendy instruments like KiCad and PCB manufacturing homes, however eschewing microcontrollers in favor of the discrete logic that will have powered the unique. The brand new design turns to 74393 twin four-bit binary counters to maintain observe of the 60 LEDs in every of the clock’s three concentric rings — displaying seconds, minutes, and hours in digital mimicry of the palms of an analog clock, plus “jiffies,” with a spare counter dividing by 12 to drive the hour hand exactly.
Elsewhere on the board is a 3.93216MHz crystal and a 744060 binary divider, which supplies a 240Hz clock sign for multiplexers and 60Hz for the jiffy counter, whereas 4 74154 4-to-16 line multiplexers drive the LEDs — an strategy selected again in 1988, as a cost-saving various to having 16 devoted non-multiplexed decoders. A 555 timer holds the counter reset strains throughout power-up.
From a breadboard experiment in 1988 to a completed KiCad challenge in 2024, it has been a protracted journey for the LogiClock. (📷: Will Kalman)
“I introduced out three strains to a pin header on the again: 5V energy, floor, and reset,” Kalman notes. “I’ve a [Raspberry Pi] Pico W that I might prefer to program to get the present time by way of NTP [Network Time Protocol] and at midnight/midday every day, faucet the reset line to zero the counters to 12:00 to robotically set/right the time. I had different concepts like bringing out the clock line to set an arbitrary time by resetting the clock to 12:00 and feeding in quick clock pulses to set the time, perhaps that is an thought for V2.”
The LogiClock is documented on Hackaday.io full with a schematic — and Kalman lastly introduced closure to the challenge by sending one of many new clocks to the childhood good friend who had helped with the unique 1988 prototypes.