customized lavet stepper motor clock movement controllerDesigned by Geppetto Electronics, Ships from United States of America
Welcome Astronomy Magazine readers You have reached the right place. The Crazy Clock is available with Sidereal, Martian, Lunar or Tidal clock firmware, in 12 or 24 hour movements, with or without ...Read More…
You have reached the right place. The Crazy Clock is available with Sidereal, Martian, Lunar or Tidal clock firmware, in 12 or 24 hour movements, with or without calibration. Simply use the menus above to select the movement you'd like.
This is a replacement controller board for a lavet stepper motor driven clock movement. These type of clock movements are ubiquitous in cheap wall clocks. They typically are in black or clear plastic inch-and-a-half square boxes with a single AA battery holder and have second hands that jump from one second to the next.
This board will alter the timing of the pulses that move the second hand in various ways (depending on the firmware), while still maintaining a long-term average rate of one pulse per second (which is required for the clock to remain accurate).
The board (and in turn, the clock movement) is powered by a single AA battery, which should last around 12 months or so. The clock should be accurate to within about 30 seconds per month (±10 ppm, typical for these sorts of clocks).
If you buy the board by itself, you must obtain a suitable clock movement and disable its controller. Then connect the stepper coil to the clock terminals on the Crazy Clock board, then wire the movement's battery terminals to the battery terminals on the board. You should be able to fit the Crazy Clock controller in some unused space inside the movement and it will look completely normal. There's an instructional video above that illustrates the process.
If you buy the complete movement, you will get a modified and tested movement, ready to install in the clock of your choice (a clock face is not included, but attachment hardware is). The movement will come with a threaded shaft with a maximum face thickness of 1/4" and plain black hour and minute hands and a red second hand. You have a choice of either a standard 12 hour movement (one complete rotation of the hour hand every 12 rotations of the minute hand) or a 24 hour movement (one complete rotation of the hour hand every 24 rotations of the minute hand). The movement is a Quartex Q80. It's a perfect substitute for the clock movements that come with custom clocks designed at Zazzle (their hands will fit on these movements, and the 12 and 24 hour movements both fit on their faces). Alternative hands and other useful accessories can be obtained from Klockit.
The normal accuracy specification of the clock is 10 ppm, which is around 25 seconds per month. Optionally, the clock's accuracy can be measured and a compensation factor applied in the firmware. With this done, the initial accuracy of the clock is increased to approximately 0.5 ppm, or about 15 seconds per year.
Eight different "novelty" firmware files are available, each with a different sort of craziness. They range from subtle to straight-up clown-car crazy, but each will still tick a total of 86400 times a day. There are also five different "alternate timebase" firmware files available, each of which ticks regularly, but with a longer or shorter daily tick count. You pick which firmware you like when you buy. There is an ISP header on the back of the board you can use with a pogo-pin adapter and an AVR programmer if you change your mind.
All of the "novelty" clocks tick 86400 times per day, so they keep accurate time, but exactly how they tick differs for each. All of the "alternate timebase" clocks tick regularly, but with a longer or shorter day (where a day is defined as 86400 ticks - 24 complete circuits of the minute hand).
There is also a "normal" clock firmware file available on GitHub, which reverts the controller to normal behavior (86400 regular ticks per day).
For those that want to experiment with the firmware, it is open source (GPL v2), and consists of a "base" of common code that sets up a 10 Hz interrupt cycle that drives the behavior of the clock. The base exports methods that "tick" or "sleep" (you call one or the other in an infinite loop) as well as a random number generator. What this means is that your code need only decide every tenth of a second whether it wants to tick the clock or not, and all of the rest of the details of how that is made to happen are all taken care of for you. The base takes around .75K of flash, 11 bytes of RAM and 6 bytes of EEPROM (for storing the PRNG seed and trim factor). The rest is available for your code.
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