Ice Tube Clock, meet the ChronoDot

[Alex] ramped up the precision of his timepiece by adding a ChronoDot to the Ice Tube Clock. These two items are among our favorites; the Ice Tube Clock for its old-style multi-digit display, and the ChronoDot for combining a DS3231, battery, and components into a nice small package.

There is a schematic link at the very bottom left of [Alex's] writeup. He mentions that he depopulated the clock crystal and its capacitor pair from the board and patched into the clock input on the AVR. A 100K pull-up resistor is included in the wiring as called for in the DS3231 datasheet. Although not specifically referenced, we assume that [Alex] reprogrammed the ATmega168 clock select fuses to use an external clock signal.

Now he can sit back knowing that the clock will be within 10 seconds per year accuracy.


  1. therian says:

    I went for harder solution by building xtalOven

  2. fartface says:

    Why not measure the decay of a cesium atom?

    Man you hackers are getting lazy.

  3. svofski says:

    Last time I checked, the DS3231/DS3234 has +/-2 minutes per year accuracy. Where did you get the 10 seconds figure?

  4. The IceCube clock already uses an external clock. there was no reprogramming required. Yes, sorry, less than a minute a year

  5. strider_mt2k says:

    A timely hack!


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