The clock was to sit on a bookcase with a vertical aspect. Four ZM1022 nixies (bought on Ebay) for hours and minutes. The digits would fade in and out as they change, overall brightness would be set by sensing the room illumination using an LDR. The nixies would turn off entirely if left in a quiet room but illuminate on hearing a sound sensed by a microphone.

Seconds would be indicated using a GC10B dekatron counter. The display would act in a pendulum fashion swinging once per second or take one minute to orbit entirely.

The high voltage supply for the dekatron and nixies was to use a voltage multiplier (Cockcroft-Walton). The clock would not have any facility to set the time but use a modified GPS time signal broadcast locally from a GPS receiver in the house loft on the 900 MHz licence-free band.

The box is made from thin MDF and veneered on the front (my second attempt at veneering in 35 years). The chassis inside was used to mount all of the PCBs using brackets as necessary. The electret microphone was just glued to the box and the LDR was glued to the front.

Schematics and PCBs

The Eagle files can be downloaded here.


The software is currently awaiting a full re-write and is not available. Sorry.