Blue LED Clock


A few days ago, I ran across this custom PC case via the Make blog:

WMD PC Case Mod

G-Gnome’s “WMD” Case Mod

Build process, part I
Build process, part II

It’s an amazing piece of work–all hand-tooled metal, with lots and lots of polishing.

One thing that caught my attention was the clock display. It looked cool, I loved the way it used individual round LEDs as pixels instead of big segments and made the digits look rounder, and I wanted one. I read through the story. I found that the clock is the CK-3000 from Electronics USA. It’s $360.

That’s just crazy.


Then two thing happened at about the same time. I emailed my friend Jeremy the links to the WMD PC case, and I started thinking about building my own clock as a backlash against the price tag on the CK-3000. Then I was talking to Jeremy about building an eye-searing blue LED model; and the next thing you know, we’re starting to discuss actual details.

Jeremy writes:

I’m mostly after a scary looking display (I realize red would be scarier, but I like blue). Being big(ger than a sane person would want a display) is part of that because something that big MUST be important, but it has to be a manageable size. 3 or 4 feet would probably be the limits for me to find a permanent spot to hang it in the computer room and smaller is not necessarily worse if we can get the feel of the thing right. Being ominous on its own is good, but it should definitely DO something. A regular clock would be bare minimum, a clock that freaks out and does a flashing doomsday 1 minute countdown every hour (or randomly… that would be scarier) would be the kind of thing I’m going for.

And I replied:

Can we make it do that in _response_ to something? Lights turned on or off, loud noise, silence? We can definitely add a horn/buzzer/piercing alarm to sound continuously/beep down the seconds/beep frantically for the last few seconds.

Um, if it’s going to be ominous, it should have a hundredths display, so some of the digits are changing too rapidly to see. The hundredths might remain blank during normal operation and only kick in when we’re down to a minute left, or something.


I think I may actually build one or two of these. I’d use the LogoChip for timekeeping and display decoding, probably supplemented by watching the 60Hz on the power line. I got a string of 5mm blue LED Christmas lights last winter, and I might get more, or I might get some frosted blue LEDs on eBay.

To drive the display, I’m interested in using Allegro Microdevices’ A6275 and/or A6276, 8- and 16-bit constant-current LED drivers. I saw them used in something linked from the Make blog that I can’t remember now, I ordered a couple of 8-bit sample chips to play with, and I recommended them to Muaz Halim for use in the TechArt exhibit Firefly Environment.

2 Responses to “Blue LED Clock”

  1. Commander Data says:

    When I was doing digital design circuits using 74xx series, I designed a clock using BCD counters and drove the LEDs using open collector ICs driv ers. Your project just reminded me of it. The clock was used to time soap box derby races before Laser diodes was invented (or perhaps it has but not as prevalent and available as now.)

  2. Keith Neufeld says:

    Commander Data, that’s very cool.

    When I was a kid playing with 7400-series digital logic circuits, my brother and I had different generations of Tyco slot car tracks. I bought the parts and always intended to build a two-digit seven-segment lap counter, but never got around to it. That sure brings back memories.

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