Numitron Clock

From neurotica.com

Since money was tight for the 2008 holiday season (again...Viva Bush!), I built another clock as a Christmas gift for someone. Last year's clock (which she loved) uses Nixie tubes for displays, but the new one uses Numitron tubes. Numitrons are an old display technology that implements a seven-segment display (the familiar "figure 8" pattern) using segments made of what are essentially incandescent lamp filaments. The result is an aesthetically-pleasing, sharp, warm display.

The Numitron tubes are Russian IV-9 units, multiplexed using 2N2222 and 2N2907 transistors. The processor is a standard 8751. The firmware is written in a mix of C (using the SDCC compiler) and assembly language. The RTC chip is a Philips PCF8593, interfaced via a bit-banged I2C bus.

Photos

The completed clock.

Top view showing components.

Bottom view showing wiring.