Sputnik 1, the first artificial satellite, was launched in 1957. It captured the attention of the entire world with the eerie beeps it transmitted, which could be received by radio amateurs everywhere in the world. Fifty years after this historic event, it seems fitting to build a clock in the shape of the Sputnik satellite that combines a nostalgic Nixie tube display with a modern microcontroller.
Technology has changed a lot in recent decades. Launching a satellite that simply transmitted a beep signal was a major achievement in 1957, but now we routinely put satellites into orbit that can transmit hundreds of television channels.
This design uses a combination of modern and old-fashioned technology. The shape of the Sputnik and the Nixie tubes are elements of old-fashioned technology, while the low-loss switching regulators for the supply voltages and the microcontroller-based control logic are examples of modern technology.
In the components list, ‘R15’ should read ‘R9’. Capacitor C8 is listed as 4μF7 400V, but appears as 10μF/350V in the schematic. Either value will work as only little current is drawn from the high-voltage supply, and even 4μF7/180V will work in this circuit.