Using a small 12mmx34mm Nixie tube, I made a tiny clock that is powered by a rechargeable LiPo battery. The frame created by the PCBs lends both surface area necessary for high voltage generation from the 3.7V LiPo, the temperature-compensated RTC, the SAMD21E microcontroller, and the high voltage drive circuitry. The frame also provides a modicum of structural rigidity. An MCP1711 low quiescient current linear regulator feeds the control electronics, while a small transformer-based boost converter system provides enough current for a couple of these small tubes. The assembly measures around 20mm wide x 38mm tall by 12.3mm thick, barely thicker than the tube itself. The next version will likely decrease the length of the long axis.
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