Auto tuner for anniversary clock

An anniversary clock is a mechanical clock which has a time keeping mechanism called torsion pendulum, where  a horizontally rotating pendulum is suspended by a thin wire called torsion spring.  Anniversary clocks run much longer (up to one year before winding is required) than ordinary pendulum clocks because the rotating speed is very slow.  The name "anniversary" came from  the fact that winding is required once every year.  Anniversary clocks are less accurate than ordinary pendulum clocks.

The method of tuning torsion pendulum vibrating frequency is similar to the method for tuning ordinary pendulum (see this page).  Instead of applying vertical force to the pendulum, the tuning device applies horizontal force to imitate changing the elasticity of the torsion spring.  When the magnetic force pushes back the pendulum, that is equivalent to strengthening the torsion spring which shortens the pendulum period.  Below is the overall photo.

Here is the back of the base plate where you can see a coil to generate magnetic flux and a magnetic sensor (digital compass, HMC5883) to detect pendulum position.

Here is the magnet attached to the pendulum (flat silver square below white ball).

The external tuning device comprises ESP32 with OLED display (WEMOS LOLIN32 OLED), H bridge driver (L9110).

The display shows the time from internet and the clock accuracy, along with graphs of accuracy and coil current alternating every 5 seconds.  In contrast with the tuning device last year whose resolution was 1 second, this device calculates the accuracy to the resolution of 0.01 seconds.  The photo below shows accuracy of -0.04 seconds and relative current of 113.  The graph is showing the last 5 hours of accuracy trend.

Here is the accuracy (blue, left scale in second) and coil current (red, right scale in relative quantity -1023 to 1023) for 24 hours.  You can see the accuracy is within one second.

Here is the same graph with about one month of data.  During this period, clock location was changed, sensor position was changed, main spring was winded up, etc.  Because of these activities, you see the big jump in accuracy and output, but the accuracy came back to within 1 second.

Here is the schematic diagram.

Source code is here.