An Introduction to Clock Dividers and Psychological Warfare

A while ago, [nsayer] was inspired by a Hackaday post to build one of the most insidious means of psychological warfare. I speak, of course, of the [Lord Vetinari] clock, a clock that ticks at random intervals, but still keeps accurate time. His build, the Crazy Clock, is a small controller board for off-the-shelf clock movements that adds the [Vetinari] feature to any clock by soldering only a few wires.

The Crazy Clock is a pretty simple device consisting of only a 32.768 kHz crystal, a microcontroller, and a few transistors to pulse the movement of a clock mechanism. While psyops is great, it recently occurred to [nsayer] that this device could be used for other build.

Since the output of the Crazy Clock doesn’t necessarily have to be connected to a clock movement, [nsayer] decided to connect a LED, generating a 60Hz flashing light for a phonograph strobe. This is easy with timer prescalers and clock dividers; the original 32.768 kHz signal is divided by 8 to produce a clock that ticks every 4.096 kHz.  Divide that again by 120, and you get 34 2/15. Yes, this is all stuff you learned in fourth grade, and if you’re smarter than a third grader you can eventually whittle a 32.768 kHz clock down to a nice, round, binary number – exactly what you need for computing time.

[nsayer] posted a 240 fps (vertical) video of his Crazy Clock blinking at 60 Hz. You can see that below.

20 thoughts on “An Introduction to Clock Dividers and Psychological Warfare

    1. That’s a good idea, but the Crazy Clock as it is today is designed to fit entirely inside the standard Lavet stepper motor movement. As such, there isn’t enough room to get too fancy, I’m afraid. One of the biggest limitations is that the Crazy Clock has no idea where the hands are pointing (for that, you need to add position sensors of some sort to the gear train somewhere). That puts some limits on the sorts of Crazy you can design in.

      That said, driving a lavet stepper is super easy, and if you’re building your own funky clock, there’s no rule that says that you’ve got to fit everything inside the movement case.

      1. The way you initialize Primex radio-synchronized clocks comes to mind (they have a base station that broadcasts a time code received in one location from a GPS receiver, they are common on campuses)…you press a button on the clock when the hands pass certain marks.

        1. Commercial WWVB clocks tend to have the ability to either force the hands directly to 12 or know when they are at exactly 12, but they also tend to have direct step control over at least the minute hand in addition to the second hand. I have a La Crosse in our living room and when you put the battery in, the minute hand will sweep until it and the hour hand are at 12, then it stops until it gets a fix, then steps the minute hand all the way until the actual time, and then runs normally.

  1. In case anyone wants a link to the original documentation (including schematic) of the Crazy Clock, it’s here: http://www.geppettoelectronics.com/2014/08/crazy-clock-user-guide.html

    The firmware is at GitHub, here: https://github.com/nsayer/Crazy-Clock

    There are a wide variety of choices for the Crazy Clock. Most of them are novelty clocks that keep accurate time, but tick in non-uniform ways. There are also three alternate timebase clocks for which a day (defined as 24 complete revolutions of the minute hand) takes more or less than 24 normal hours.

    1. Theirs was actually my original inspiration. My thought process was actually the opposite – I wanted to make something extremely small via SMD so that it could be installed inside the movement.

      In fact, my actual goal is to build a board that is an exact replacement of the OEM board and work out a deal with a manufacturer to include my board in place of theirs. Alas, the sole manufacturer in North America was not interested in working with me, and I don’t speak Mandarin.

  2. None of this makes any sense. How is it “psychological warfare” to have a clock that keeps the right time but ticks randomly? How does that “psychologically” affect anyone? Not to mention in the video it’s one continuous flash anyway, so not random.

    Throw some “modern art” terms in and you have a perfect “thing” to put in an art display, where all the hipsters come and comment how “groundbreaking” it is.

    1. I guess you didn’t read the book where the clock idea comes from?
      Imagine waiting in a silent room, hearing only the clock ticking. Most of the ticks happen in regular intervals, as you subconsciously expect, but every once in a while one happens a little to quick. Or too late. You never know what will happen next. It would slowly drive you mad.

        1. Judging by the sarcasm in that statement you underestimate the way our brain acclimates to tune out regular noises like a ticking clock. Trying to sleep near one of these clocks would be a nightmare. Each time it ticks off-beat it messes with your brain and it has to process if the noise is a possible ‘threat’ it will keep you sleeping rather poorly.

    2. The video is not of the clock. The video is of a project that repurposes the hardware that goes into the clock.

      As for the psychology of the actual clock, well, having built more than a few I can tell you that one artifact of how the hardware and firmware work together, the clock ticks rather more loudly than they often do straight out of the box (that’s a feature). I could envision seeking an audience with a Machiavellian dictator would be a rather nerve-wracking experience, and then to every once in a while have the regular ticking of a clock (likely the only noise in the room) “stutter tick”…

  3. From the business side, why not talk to the marketing/retail people first? Manufacturers don’t like to risk capital and production capacity without orders, and there won’t be orders without a product and neither happen without demand – the eternal dilemma.

    If ThinkGeek or someone similar with a bit of vision told your standoffish manufacturer that they’d order 10,000 or so it might be a very different conversation. Or perhaps they’d hook you up with a translator.

    1. It’s a bit of a chicken-and-egg thing. The marketing/retail people will ask you how quickly you can turn an order for 10k units and then you have to explain that you have to first find a manufacturing partner and then their eyes sort of roll backwards into their heads…

  4. So what effect does this have when installed in a record player? All the record players I’ve seen, have been of the extremely cheap variety with no strobe. Does it directly mess with play back speed? Or does it just make it impossible to calibrate the playback speed? Driving anyone mad who attempts to calibrate the machine.

    1. No, this doesn’t actually install in or connect to the phonograph. If the phonograph doesn’t actually have the strobe “pips” on the edge of the platter, then this would not do anything by itself. You can, however, print a piece of paper with the appropriate strobe pattern. Here’s a forum post with one: http://www.lencoheaven.net/forum/index.php?PHPSESSID=6rhbiuukplgvpg42c3gm3ee964&topic=13510.msg227810#msg227810

      You would shine the 60 Hz flashing light (originally it was intended to be a mains powered neon bulb, but in fact the line frequency is not particularly accurate in the short term) and adjust the turntable speed until the appropriate pattern appeared to stop moving.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.