Fig. E: Red paint undercoat. Fig. F: Black paint partially
rubbed away along the edges, exposing the red undercoat for an antique effect.
Fig. G: Finished amp meter clock with the lid open to
show the circuitry. Fig. H: Clock displaying the analog
to a blinking 12:00.
To help line up the scales on the plates, I printed
extra marks where the screw holes were. And so
that the original scales would not show through
the paper, I put the new scales on the backs of
the plates, which were blank (and symmetrical).
Boxing It Up
This is the type of project that needs a good box, to
display the meters and conceal the wires and such.
My wife suggested that a nice wooden box would
look good on the mantle, and we chose one at a
local craft store.
Mounting the meters meant drilling a wide central
hole for the back of the meter itself, surrounded
evenly by 4 small holes for the mounting screws.
I made a paper template as a guide (Figure B, previous page) and drilled accordingly, but it was hard to
get the mounting holes accurate enough, so I used
a larger bit and a keyhole saw to clear out enough
space for them to fit (Figure C). The meters all fit
tightly in the central holes, so I didn’t bother putting
nuts and washers on the mounting screws (Figure D).
For the power source, I considered putting batteries in the box, but the Arduino pulls 20mA–30mA,
so even with D cells, they would need to be changed
about every 5 weeks. Instead I decided to use a wall
168 Make: Volume 13
wart and ran the cord through a hole in the back
of the box. The buttons for setting the clock and
changing modes I left on the breadboard inside.
Finally, I wanted the box to be an aged black, to
match our furniture. I accomplished this effect by
first putting down a coat of red paint and allowing
it to dry (Figure E). I then followed it with black and
lightly wiped the wet paint off the edges, exposing
small amounts of red underneath (Figure F).
The end result is a unique clock and a great conversation starter that can be displayed prominently
in my home, and now in yours, too!
Gene Scogin is a computer programmer who enjoys a
variety of hands-on projects.