DHS tribute threat level indicator
A while ago, I stumbled upon Biegert & Funk's QlockTwo - a beautiful word clock retailing for about $1,200 -
and wanted to build something along these lines pretty much ever since.
I believe there are three DIY remakes of that design in existence today:
That said, I had a suspicion that this display method and its appearance can be approximated more easily - and wanted to use it for something even
more pointless. This page documents exactly that - an attempt to pay homage to QlockTwo and to the Department of Homeland Security at the same
time: a wall-mounted, knob-operated, color-coded DHS threat level indicator.
- Doug Jackson's version: uses etched copper board. I do not like the aesthetics of
this one, although your mileage may vary.
- Christian Aschoff's take: letters cut out in vinyl by a
commercial printer, then applied to the back of an Ikea picture frame. The result is very nice.
- Ruud Burger's approach: a nearly perfect,
verbatim copy using a large-format vinyl cutter, paper backing, and a wooden frame. Looks great in low light.
Yup, that's right.
1. Preparing the display surface
The most important part of the design is a 25 x 25 cm, 3 mm thick sheet of clear acrylic, ordered from TAP Plastics:
After removing the protective foil and masking it properly, I applied several coats of generic, glossy spray paint to the back of the sheet. My hope was
this will yield a nice, shiny surface when viewed from the other, non-painted side.
Surprisingly, this assumption proved to be correct:
Note that once the foil is peeled off the front, you need to handle it with care - it scratches easily.
2. Adding illuminated text
I further hoped that removing the paint selectively from the rear surface should allow for backlit shapes to seamlessly
appear on the front, while still keeping the piece perfectly shiny and smooth. To test this
assumption, I arranged the desired goofy lettering in a CAD application (using
Lekton04 and Marketing Script typefaces)
and then created CAM toolpaths to engrave them to the depth of 1 mm, with a 1 mm diameter tool.
With the toolpaths done, it's time for CNC machining! I mounted the sheet, painted side up, on my Roland MDX-540
mill - and sent the data to the device.
Here is the result of this work - so far, so good!
3. Finishing touches
I proceeded to glue on external walls and internal dividers, using strips of cut-to-size, 25 mm wide black acrylic ordered from the same source. The
purpose of all this is to provide some room for the electronics, absorb incidental light, and prevent light bleed between backlit sections.
I also poured some translucent, tinted epoxy resin into the machined letters; this makes them nearly invisible when backlight is off, and diffuses
the light when the illumination is on. I used MAX CLR HP epoxy from
Polymer Composites, mixed in some alumina
to make it translucent, and then added 7701 series transparent dyes from Eager Plastics.
The result, when held in front of a light source, looks this way (protective film still installed, hence the halos):
4. Electronics and final appearance
Electronically, the device is very unremarkable - it uses a recycled 5V, 500 mA power supply, switched through a cheap, five-position
coupled with a
fancy $2.50 knob. The switch alternates
between five banks of three to six high-intensity LEDs
(with lens ground off to further diffuse their light). Several 1W resistors are used to limit current - and
that's it. Oh, the "dial-a-threat" segment is permanently illuminated white.
Various views of the completed project:
A crummy video of the device in action can be seen here (white balance isn't great):
Oh, and my son's version is here.
5. Closing words
Well, that's it. Here's a very short project FAQ for the really, really curious:
- What's the total cost? The materials and electronic components cost under $15. The project should take no more than
three days to build.
- Will you make me one? Nope, sorry. I can send you CAD models, NC toolpaths, and a detailed parts list, though. If you don't have a mill - in many
regions, you can get much of the work done at a local makers community center or at a college; or you can send it to a commercial company to do the
machining for you.
- Damn, CNC machines are expensive, right? Not really - you can own a seemingly decent CNC mill for $600 or so, and set it up at
home. It's actually far more practical than MakerBot and similar prototyping tools - click here to read more.
- Can I do it without a CNC mill at all? Yes - using vinyl cutter is another obvious option. Many companies offer inexpensive,
custom vinyl cutting; and desktop machines start under $200. See Ruud Burger's or Christian Aschoff's work mentioned earlier on this page.
- Why not just use black acrylic? You would need to machine letter outlines all the way through the sheet, thus sacrificing the seamless
appearance of the front surface.
- Then how about machining in black acrylic, and then placing another transparent sheet in front? That may work, but
gluing them together without leaving any marks is not trivial. Spray painting is pretty hassle-free in comparison.
- Why DHS threat levels, anyway? In short, I'm a great fan.
If you have any other questions or comments, you can reach me at firstname.lastname@example.org. I am also on
Your lucky number: 16426068