Given that my clock driver is complete and seems to work quite nicely I think I will move on to other projects however if anyone else is considering building their own variant to drive a vintage clock then I’ll leave just a couple of extra notes:
The connections I used were as follows:
LCD Driver : RS Pin 9, Enable Pin 8, 4 bit Data on Pins 7,6,5&4.
Clock Module: Data in on Pin 2, Power control on Pin 3.
H-Bridge Control: Enable A5, Direction1 Pin 12 and Direction2 Pin 11
Buttons on pins A3, A2 and A1.
All these can be changed in software if required.
If your clock does not require alternate pulses to change polarity then you don’t need an H-Bridge, just drive the voltage you need using a single FET. Beware however that the coil in the clock is inductive so a scrubber diode might be advisable.
My menu system is very simple: RUN, SET, TZDIF, MANUAL and VERSION. The first button changes mode with a long press, the other two buttons are up and down.
The controller needs to be told the current state of the hands when first powered using the MANUAL setting and thereafter it remembers the hand position even during power failure by recording the current state in EEPROM. I use a levelling technique to reduce wear on any one EEPROM location, simple and should last the lifetime of the device.
Finally, be aware that the polarity of the clock does matter! A pulse of the positive polarity will have no effect if applied when a negative pulse is required and vice versa. Easily sorted out by swapping if you find yourself appearing to be one minute out and unable to advance.
Have fun and keep those vintage clocks in their original form!
And a nice video of the smaller version of my clock being made… https://www.youtube.com/watch?v=0LhkTH0tN-E