Intro: Harddisc Clock
The basic idea for this clock was to create a unique principle of time display.
Also I wanted to use only parts from unused devices.
So I found an old 5 1/4" harddisc that uses a synchronous motor to spin the discs and a stepper motor to position the heads. The spin motor had 16 pole positions. Perfect :-)
So I could use 12 out of 16 positions to display the hour.
On each hour segment the head should indicate the minutes on a linear way from inner to outer position.
I designed a digital circuit that uses the mains frequency of 50Hz as timebase. This is a very long time stable timebase!
Some counters divide this signal into subsignals for driving the stepper and the hour motor.
Two buttons speed up the counters for setting hours and minutes.
For driving the hour motor I could use the transistors from the original pcb.
This circuit doesn't use any micro controller and hence there are definitely no software bugs ;-)
An old computer AC adapter was used for the power supply.
I assembled all on a diy pcb and put it between the original pcb and the drive so it looks as if the harddisc was not modified.
In the videos you can see how the time is set and the principle how time display works.
If you want to remake this clock you need to find a (very) old fashioned harddisc that uses a stepper motor and a synchronous motor. This might be a challenge nowadays.
Due to the type of motors you might need to modify the schematic.
Also if your AC power has 60Hz instead of 50Hz.
With some basic electronic knowledge and effort this should be feasible.