Clock with CD81 (Japanese) Nixies

Another kit from Frank Techniek, and similar to the IN14 clock design, although somewhat smaller thanks to the smaller CD81 nixies which were made by Hitachi, and used in desktop calulators. The digits are 12mm high and very sharp. The tube is 36mm high including tip. PCB dimensions for this clock are 172mm x 63mm x 65mm (WxHxD). Further details here.

This was the first Nixie clock I built, and to be honest, its still my favorite. The CD81 tubes are lovely, and Franks software produces a great digit fading effect. Surface mount (SMD) components are extensively used which makes the finished project very compact. The clock is powered by a standard 12 volt DC unregulated wall socket adapter.


PCB and tubes.
CD81 nixie clock - PCB and tubes

A high voltage generator converts 12V into a regulated 142V, the supply for the nixie tubes, is situated far right.
The microcontroller (PIC 16F87x) is left, mounted on the PCB underside - as is a 5V regulator, the supply for the circuit. The Dallas DS1302 (IC104), 32.768 KHz crystal, and SuperCap (underside) are the RTC option parts.

Top view.
CD81 nixie clock - PCB Top View

Although its possible to manually set the clock (with the rear 'set' button), it will set and adjust itself when a valid DCF77 signal is present (eg, from an external DCF77 module).

Other configurable options include fading effect on/off, flashing neons on/off, 12/24 hour mode, and -1 hour adjustment for the UK.

Completed (flash photo).
CD81 nixie clock - flash photo

The photos do not do these tubes justice, they are incredibly sharp!

And glowing in the dark.
CD81 nixie clock - \ in the dark

Additional files: