Nixie Clock

I haven't done a project in while and decided I wanted to build another clock. I've always liked the look of Nixie tube clocks and decided to build one. This time I wanted to try using surface mount parts to keep the costs down.

For hardware, this clock uses six IN-14 Nixie tubes for the digits and two IN-3 tubes for the digit separators. An ATmega328 (I'm still not sure if I'm going to use an external crystal or not, but there is room for one on the PCB) is the main controller and a DS3231 RTC is used for time keeping.

Nixie tube with high voltage power supply in background.

Nixie tube testing.

The actual drivers for the Nixie tubes are two HV5622 32-bit shift registers that are rated for 230V.

The packaging that these came in was quite extensive.

During my tests on the Nixie tube, I found that the forward voltage drop across the IN-3 tubes was around 44 V and the forward voltage drop across the digits in the IN-14 tubes was on average (lowest was 124, highest was 130) around 127 V.

I designed the PCB in KiCAD since the free version of Eagle didn't support boards larger than 4 x 3.2 inches. It was a good learning experience and KiCAD is relatively easy to use. I sent the design to OSHPark for fabrication. It should ship out in about a week from now.

The PCB was designed in KiCAD. Fill zones are hidden in this picture.

The PCB rendered by OSHPark.

In preparation for the SMD soldering, I bought a cheap SMD practice board from eBay. It wasn't that difficult to solder, even with the relatively large default chisel tip that comes with the FX-888D. I messed up really badly at first, but quickly realized the flux is the solution to everything. Just apply some flux on the pins and drag the solder across. Perfect solder joints almost every time.