| Nixie Tube Digital Clock |
As a person who grew up in the vacuum tube age, the word "nixie tube" has a very nostalgic sound. Nixie tube was often used as the indicator when digitalization began. Frequency counter, shop's register machine, calculator, clock, etc. are so. Now I can cheaply buy digital clock using liquid crystal or LED, but I want to see the indicator with the vague depth of the nixie tube again. So I decided to make a nixie tube clock. It costed about 16,000 yen in total, but I believe it is cheaper than one output transformer for a vacuum tube amplifier maniac.
A few decades have passed since the manufacture of nixie tube, but still Russian made can be
purchased by mail order. However, it seems that the price has soared so much that there are many
maniacs who make nixie tube clock recently. The picture is Russian made nixie tube IN-16. I bought
six cute nixie tubes with a pipe diameter of 13 mm and a length of 40 mm. The price was 1,300 yen
per tube. There are 13 legs and it was quite difficult to solder it to the board, so I cut the
legs to diagonal direction before soldering. The white socket was intended to keep its feet from
getting tangled, so I used it as it was.
If you put the mouse, it will be enlarged. (Same below)
It is the board kit of the clock control part and DC-DC converter that converts DC 12 V into DC
5 V and DC between 140 V and 200 V. However, the converter is photographed after soldering the kit
and assembling it. The price of the two kits was 7,000 yen.
I tested whether the nixie tube lights normally by using the assembled DC-DC converter. Connecting
DC 150 V to the anode via a 10 kΩ resistor and connecting the corresponding cathode to the ground,
"5" is displayed. I was relieved because all 6 nixie tubes displayed correct figures properly.
It is wiring situation of the display part board. The substrate is TAKACHI's TNF63-119 and is
a glass epoxy board of 63 mm x 119 mm x 1.6 mm. Wiring was done with colored vinyl wires of 0.2
square mm of 10 colors. I wired the same feeling as the color code of the resistance. The wiring
method to the nixie tube is as follows. The second, fourth and sixth nixie tubes are wired to
all the pins except for "," pins, but the first one is only wired to the anode, 3 pins for 0, 1, 2,
and the third and fifth are only wired to the anode, 6 pins for 0, 1, 2, 3, 4, 5. I, old man
nearly 70 years old, was trembling hands while doing such the fine work.
This is the block diagram of the nixie tube clock I made this time. In addition, when nobody is
looking at the clock when going out or at night, a switch that turns off the nixie tube and a CDS
sensor with a diameter of 12 mm have been installed to automatically adjust the brightness
according to the surrounding brightness. However, with a small and less sensitive CDS sensor,
the brightness slightly changed, so it was not possible to set the nixie tube to turn off when
the room became dark. Since the display is reset to zero when the power supply turns off at the
time of power outage or the like, the pattern of the printed circuit board is cut and the crystal
oscillator and the clock control by the super capacitor of 5.5 V 0.1 F via the reverse current
preventing diode, I backed up the DC 5 V power supply of the IC 16F648 A. Since the holding time
is about 10 minutes it is only useful when changing the location of the clock, but I think it is
better than nothing.
It is a completed nixie tube digital clock. The base was cut with a cutter knife to a 160 mm x
100 mm light green acrylic board with a thickness of 2 mm. The power supply was diverted from
handheld AC adapter with10V-1A. Since the load is light, a voltage close to 12 V was obtained.
Although the lifespan of the nixie tube is said as 10,000 to 200,000 hours, I hope that it will
live longer than me.
It is the back of the nixie tube clock. A voltage of DC 150 V or more is applied to the
terminals of the DC-DC converter, so it is dangerous if my cat licks or touches it, so I stuck
the remaining acrylic board and made it into L shape. With this, no human being or cat worries
about electric shock.