3

LENS

where I wanted the tubes, I turned the board
and tube assembly upside down and marked
where the tip of each tube met the line. I
then centre-punched these marks, drilled
pilot holes, and got to work with the step bit.
This is not the first project where I
wished I had a drill press, but it is certainly
doable without.
The great advantage of the step bit
approach is that it allows you to dispense
with all that measuring malarkey and just
keep going until the holes are the right size.
That said, using digital calipers is a more
convenient way to check the hole size as you
go along.
Unless you have a machine shop, or are a
lot handier than me, you will still end up with
slightly misaligned holes. This is not really
an issue since the holes need to be little bit
bigger than the tubes (we will be applying
around 180 volts of direct current to the tube
pins, so contact with a metal case would not
be good).
Oversizing the holes also provides space
for including an insulating grommet where
the tube pins pass through the case.
Conveniently, the grommets will also hide
minor misalignment issues.
Although the driver board was designed
to be an Arduino shield, I couldn’t install
it like that for this project. For one thing,

it couldn’t be stacked with the Ethernet

shield. For another, I figured I might as well

mount the Arduino and Ethernet shield so

their external connections (power, USB, and

Ethernet port) would be accessible from

the rear of the case. This actually greatly

simplified mounting of the driver board and

tube assembly, which could be secured to

the underside of the case with small nuts

and bolts.

Connections between the driver board

and the Arduino (and the Arduino and

Ethernet shield) would now be all by jumper

wires, with the Arduino and Ethernet shield

mounted separately to the bottom of

the case.

With that taken care of, I needed to

figure out where to put the LCD display

and switches. The B&K enclosure had a

rectangular cut-out in the front panel almost

exactly the right height for the display.

The cut-out was too long, but I solved that

problem with a piece of black metal mesh

removed from an old speaker.

The front panel also had nine square

holes where various buttons had been

located. Nine holes meant nine switches,

to which I assigned the following names

and functions:

• DST Quick way to switch between
  DST (BST) and Standard Time
  (GMT). Depending on the time
  server being used, this may not be
  strictly necessary


• 12/24 Selects 12-hour or 24-hour
  display formats on the Nixie and
  LCD displays


• Tweet If the clock has not tweeted
  that day, it will tweet immediately


• Web Starts the clock’s web
  server (mainly for configuration
  and instructions


• Tubes Off Turns off Nixie tubes

Right

I removed just

enough electronics to

fit in the new boards

Right

Step drill bits are

great for making

holes in thin material