A school clock from the 1950s  brought back to life with a new  custom digital controller.

Project Details

When I first came across this clock I immediately fell in love with its aesthetic. Inspecting it, I quickly realized that it wasn’t a conventional clock, but what I didn’t realize at the time was that it was an old slave clock, likely from an old school. With simple master/slave clocks like this one, schools would have a master clock which would send out a pulse to all of the slave clocks to signal them to adjust their time. 

With no real electronics knowledge outside of basic DC circuitry I had no idea how to make it work but I decided to see if I could.

I discovered that it took a 24v pulse to an electromagnet in order to advance the minute hand. There was no turning the clock back, it could only go forward with a loud “ka-chunk” noise. Enlisting the help of my dad, we came up with a basic analog circuit that pulsed the power every minute and it worked well.

Over the next few years as my interest in electronics grew with my other projects, I decided to revisit the clock. It still worked well but I decided to make it a bit more accurate and clean the circuit up. 

I designed a custom circuit board with an onboard AVR microcontroller and a real time clock module which gave it a much higher degree of precision over the previous analog circuit. A small 14×2 character display with some buttons to set the time on the clock module was also added in case the RTC battery ever died. 

Project Client

Personal project


PCB design & assembly

Firmware design

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