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.

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 rotary switch 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:

If you have any other questions or comments, you can reach me at lcamtuf@coredump.cx. I am also on Twitter.

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