Inazuma Denki's One Pulse Per Second Timing Source Is an Upcycled Quartz Crystal Clock Mechanism
After Seiko clock died an untimely death, its heart lives on — powering this timing module for any circuit that needs one-second pulses.
Electronics enthusiast Inazuma Denki has suggested a novel use for the quartz mechanism from an old, discarded clock: as a time reference source for other projects, offering a logical one pulse per second output.
"What I have here is the electronic module from a Seiko analog clock," Denki explains. "The clock was purchased back in 2013 and work well until last year in 2022. The problem was that it was stopping intermittently. I tried replacing the batteries, but that didn't solve the issue. I opened up the clock module on the back to see if there was any problem with the gears or battery connections, however I couldn't find any obvious problem."
Rather than throw the whole clock away, though, Denki opted to reuse the core mechanism — the crystal oscillator module which zaps a small chunk of rock with electricity and counts its vibrations in order to output a signal once per second and keep the original clock ticking. The salvaged module wasn't destined for a new clock, though, but a time source for other electronic circuits.
"This little electronic module contains three parts," Denki explains. "The first is the battery holder. The second part is the electronics section itself. Under [a] blob […] we have a chip, there's a small capacitor just over here, and then there's the crystal. The quartz crystal is the key to accurate time, owing to its frequency stability. The coil is what makes up the third part of the module."
Taking this module, minus the coil, Denki built a boxed circuit which outputs one pulse per second via an open collector output — serving as an accurate time source for other projects, easily connected via banana plug cables. Denki offers two possible ways the project could have been wired up, though a post from James Brown in the video's comment section suggests a modification for reducing the power draw.
"If we assume a AAA battery has a capacity of about 860mAh," Denki writes in reply, "then my circuit would operate for about 280 days. In stark contrast, yours would last about 38 years!"
The full project. including schematics, is documented in the above video and on Denki's YouTube channel.
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