Resistor Color Code Clock (v1.0)

Know your resistors, tell the time

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Here is the original RCCC (Resistor Color Code Clock) that I began building for the 2006 Hack-a-Day Design Challenge. Though it was not completed by the entry deadline, it was eventually brought to life. Is it a shelved project? Yep. All these years later, it is on a shelf displaying the time.

This page about v1.0 of the RCCC could be more about wrestling with ancient file formats. The circuit board was designed using TurboCAD 9.0 for Windows. Not having a working Win32 environment, at the moment, will slow things down.

The basic idea was to have a credit card sized circuit board that did something, hopefully in an interesting way. This clock uses a battery-backed RTC for time keeping functions and the Z8 handles the display and time-setting functions. The blue segment of the 10 hour's LED is used as a light sensor. Aim a flashlight at that LED to trigger the the display to show the date, and again to start the set time process.


Why poplar? It carves so nicely. The most visible excavations are for the crystal, battery and holder, and the largest is for the power connector.

JPEG Image - 132.45 kB - 04/17/2020 at 17:51



You can see that the illuminated part of the resistor's bands is much narrower than the final base.

JPEG Image - 196.03 kB - 04/17/2020 at 18:02



I'm fairly certain that this is the code flashed in to the working RCCC. The Zilog development system was used for the build.

x-csrc - 33.69 kB - 04/15/2020 at 15:26



The original TurboCAD 9.0 drawing.

tcw - 77.00 kB - 04/15/2020 at 15:19



Upon resurrecting my TurboCAD install, this is what it exported in AutoCAD's DWG format.

DWG Drawing - 1.85 MB - 04/15/2020 at 15:16


View all 6 files

  • 1 × Z8F0812 Microprocessors, Microcontrollers, DSPs / Microcontrollers (MCUs)
  • 1 × GM5WA06260 LEDs and Accessories / Light Emitting Diodes (LEDs)
  • 1 × X1226 Clock and Timer ICs / Real-Time Clocks

  • Files Uploaded

    Darrin B04/15/2020 at 15:45 0 comments

    When was the last time you used the regsvr command? That and some twiddling with html has resurrected TurboCAD. With TCW up and running, I've tried a few exports of the RCCC board layout. Uploaded are the original TCW drawing, DXF and DWG exports. The C code to run things is there, too. It requires ZiLOG's dev studio.

    Known Issues:

    This version of the clock needs a capacitor, or two, to be added to the RTC's crystal oscillator. Also, the I2C interface code has a bug when writing to the RTC.

View project log

  • 1
    Don't build this

    Well, if you really want to...

    Between a few flaws and things that seemed like a good idea at the time, I suggest waiting for the V2.0 of the clock. I'll start to post that as soon as I wrap up posting this version.

  • 2
    Resistance is crucial

    The 'resistor' started life as the acrylic roller in a SpeedBall Brayer screen-printing toolkit. A bit of light sanding created the diffusion bands on the roller. The end caps are brass garden hose caps whith holes drilled for the heavy copper wire to be soldered in to.

  • 3
    First base

    The first base, a half inch thick slab of poplar, didn't quite work. It turned out that the resistor worked like a lens, focusing the wide angle LED's output in to a very small stripe on the surface. To see anything at all, you had to position yourself within the viewing angle.

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Darrin B wrote 04/21/2020 at 17:26 point

Black was tricky. Settled on RGB 0,0,0. Ambient light bleeds in to it, but it's usually not too tough to figure out. At night, you have to guess where the zeros are but the small red seperator in the middle helps work out the spacing of the bands.

  Are you sure? yes | no

Inaki Nagore wrote 04/25/2020 at 11:39 point

Thank u for your answer Darrin =)

  Are you sure? yes | no

Inaki Nagore wrote 04/20/2020 at 20:44 point

And the black light? How do you represent it?

  Are you sure? yes | no

Darrin B wrote 04/16/2020 at 00:12 point

Brown is a sort of dimmer version of orange, the RGB value is 02,01,00. Grey is a bluish version of dimmed white, RGB 03,03,05. The maximum is 0x40,0x40,0x40, since the sign bit is used in the fades from one color to the next.

  Are you sure? yes | no

crun wrote 04/15/2020 at 20:52 point

How do you do brown and grey lights?

  Are you sure? yes | no

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