Software engineer and “funskilling hobbyist” Ken Yap has saved a 50-year-old radio alarm clock from the scrapheap, giving it a whole new life — for the fourth time.
“Once upon a time, in a country far far east away, a clock with a split-flap display was born,” Yap writes. “It had, besides the mechanical clock, an AM/FM radio which could be used as a wake alarm. It was already n-th hand when I adopted it from a garage sale sometime in the early 90s. The mechanical display worked for a few years, then the motor failed. Not wanting to throw out this bedside appliance, I took the board from one of the first digital clocks I built back in the mid-70s, connected a four-digit LED panel of similar vintage to it, and turned it into an electronic radio alarm clock.”
This vintage split-flap radio alarm clock is now on its third or fourth life, depending on how you count, thanks to a few decades of upgrades. (📷: Ken Yap)
That served as the clock’s second life, with a National Semiconductor MM5316 clock chip — surface-mounted on a custom PCB, despite being a through-hole DIP chip — and the parts needed to drive the four seven-segment LEDs. A later upgrade, still using the same clock board, put the clock on its third life, with a more compact four-digit LED panel.
“After many years of service, a couple of years ago the 5316 started playing up and the set buttons became erratic,” Yap explains of how the clock began its fourth life. “I only set the time twice a year, at DST changes, as power outages are very rare here so I put up with the annoyance. But after I designed and built [a] 3 line to 32 line output expander and found the second of two Toshiba 4-digit LED panels in my spares box, I formed the idea to replace the 5316 with a MCU [Microcontroller Unit].”
The clock’s second life saw it receive a custom-built clock circuit using a National Semi MM5316. (📷: Ken Yap)
That upgrade sees the original clock housing play host to an STMicroelectronics STM8-based Blue Pill microcontroller board — which provided the computational grunt to deliver an improved user experience. “Instead of Fast and Slow set buttons, the hours and minutes can be set independently, and as the seconds zeros when the minutes are changed, the clock can be synchronized with the correct time,” Yap explains.
The project is documented in full on Hackaday.io — including the most recent repair work, to replace a failed electrolytic capacitor.
