In the early 1970's I made a digital clock using the only electronic digital displays avaliable, ""Nixie" tubes, which are neon gas discharges with ten cathodes shaped as numbers. These are the original end-view Burroughs B-5042 Nixies, not the side-view ones used today in "retro" clocks. They were then too expensive for consumer products, but I was able to recycle counter asemblies which were originally used in lab equipment. Two os these, the NIXIEs and the cabinet are all that remains in the present implementation. This was a very big deal at the time The now ubiquitous 32768 Hz watch quartz crystals had not then been invented, so the first implementation used a 480 hz tuning fork, shown. Sometime later a second version used a 2.15 MHz AT-cut crystalwhich requiried an extensive divider with an odd ratio. Orignally the oscillator was contained in a thermostatically-controlled oven in a vacuum bottle, but this was later discarded. These were put in a large metal box. The photo shows its contents, plus the assembly in the clock which received the one-minute signal from it. This was actually used as a bedside alarm clock for several years, but eventually it was put on a back shelf and almost forgotten. In 2008, I was looking for a Picaxe project and remembered that the old clock had a nice wooden box. I like to put my projects in nice wooden boxes. I have been trying different types of display: LCD panels, character LEDs, and military incandescent 7-segment. A Nixie beats them all for impact and was used in a then recent magazine article DIY clock. I took it down and decided I could put it all in the wooden box, discarding the metal box. For this third version the hard parts I did not have to change for this implementation included the original high-voltage power supply, which is not so easy to make anymore. I just removed some unneeded parts from it and added 10-volt and 5-volt regulator ICs. The Nixies came conveniently in counter assemblies. Three of the counters were commercial 2x5 dividers using discretes, and the tens of hours was home-made. Since it was an alarm clock it had a means to set the alarm time to the nearest five minutes using rotary switches and a diode matrix. This is conveniently all part of the display assembly. The only extra I needed was to bring out the tens of hours line so I could display and use AM or PM. For control it used the original Rev-Ed demo project board with the darlington driver, which can drive the display and the alarm relay, which runs off 10 volts. I added a small board for the oscilator, and a serial imput for the controls, using a parallel to serial shift register. I added ain n RF transmitter 2013 when I wished to use the alarm function to run the pump on my spa automatically to warm it up before I got up in the morning to drink my coffee in it. The current, fourth, version retains only the chassis from the third version, plus the box , NIXIEs, and the original transistor-based minutes counters. The hours counters are rebuilt to the proper dimensions and pinout to plug into the existing chassis. It is Leonardo based and has an accurate DS3234 clock. It uses an external 10-vot supply and a DC-DC switching converter for the high voltage. It uses the CD4017 decade counter with 10 positive decoded outputs. To reduce ageing of the NIXIEs there is an automatic shutoff after a few minutes, which is programmable. A doppler radar module restores the display when activated.

Here are the instructions:

Here are the Display Modes:

Here are the clock photos

Here are the circuit diagrams

Here is the code