Arch Ball Clock

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DIY Clocks are great since there is an inherent motion element. Most of the clocks that we use are very boring but that doesn’t have to be the case, have a look at this Arch Ball Clock for example. It tells the time in a very interesting way. Code and plans are available so that you can make your own, you could also purchase a kit from Nuts and Volts.

Via: Nuts and Volts Blog

"Each arch has a steel ball bearing which is allowed to roll freely on the arch.

  1. Print and cut out the arch patterns downloaded earlier.
  2. Use spray glue to attach the patterns to 1/2 inch medium Density fiberboard (MDF).
  3. Cut the wood almost to the pattern line and then sand to line. Make sure that the inner portion of the hour and minute arches are smooth and nick free as the ball bearings need to roll freely.
  4. Cut two 2"x3-3/4" pieces of MDF for the feet at the end of the large arch.
  5. Cut a groove on the inside of the hour and minutes arches leaving a track for the balls to ride on. The balls do not ride inside the groove but on the outer rim.
  6. For mounting the hour and minutes arches drill a hole that will allow for a tight press-fit onto the motor shaft.
  7. Cut out a recess in the large arch for the stepper motor to sit in. This allows the motor shaft to stick through far enough to allow the the"

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18 Comments


  1. Allow the what?


  2. Hi A Muffin,

    Thanks for catching that. I didn’t notice that, it should probably end with “hour and minute arches to be attached” but I will make the official correction when the creator updates his site.


  3. I really like that design of clock, not much into timepieces usually unless they’re digital, which this is, sort of.

    The one thing that’s got me a bit baffled is how it keeps accurate time, there’s no external clock chip that I can see, having recently got into programming PICAXE chips I know there’s not internal clock in the sense of days/hours/minutes/seconds that you can read, so looking through the code my only guess is they’ve calculated the time each command takes to execute and put delay loops in to make the program itself run like clockwork.


  4. Haku, there is an interrupt on input7 incrementing the second timer, so I guess there is an external 1Hz signal that they use. Unfortunately there is no schematic, but looking at the traces on the photo it looks like input7 is wired to some other pin of the pic itself … It’s hard to tell since traces run on the back of the PCB. Maybe they’re diverting a PWM signal or something. I agree that it’s somewhat weird that they chose to use a chip without RTC or timer to make a clock …




  7. Since the clock is using stepper motors it isn’t running off of batteries. Therefore, the timing pulse is coming from
    the 60Hz signal out of the wall – conditioned of course – therefor an onboard RTC or timer isn’t needed.


  8. Pertneer – now that’s a neat trick! how reliable is the 60hz signal?
    It should be noted this clock would run slow in the UK/Europe etc. if the pulse count number in the PICAXE program wasn’t modified for a 50hz signal.

    Anyone know why they chose stepper motors instead of miniature servos? Would have simplified the circuitboard & program code somewhat.


  9. The way I understand it – the 60Hz is very accurate. The code is available for download and may be modified for 50Hz. The schematic is available in the July 2009 issue of Nuts and Volts magazine.
    Servo motors were used on the original design but they made too much noise for the other members of the family.


  10. I just finished the Arch Ball Clock using the nut & volts circuit board and all the components specified, even the heat sinks. After 45 minutes run time, the heat sink on the 12V regulator is 140 degrees F, and the stepper motors are 135 degrees F. The rectifier diodes are about 110 degrees F. This is in my 74 degree air conditioned room. I consider this to be too hot for normal constant use and probably won’t leave my house with this running. Is this operating temperature considered normal and acceptable?


  11. The heat sinks will get hot as well as the stepper motors – which is normal for both. I’ve been running mine for over a year without any problems.


  12. The voltage regulator has an internal thermal shutdown so if it gets too hot it will shut itself down. It has a maximum junction temperature of 150 degrees Celsius (302 degrees Fahrenheit).
    Stepper motors are known to run warm. The stepper motor in the parts list has a maximum temperature rise of 80 degrees Celsius or 176 degrees Fahrenheit. This is the maximum increase in motor temperature above ambient that will occur in open air, during continuous operation at maximum running current at low speeds. So a maximum rise of 176 degrees F above the 74 degrees F ambient is 250 degrees F. So 135 degrees Fahrenheit is certainly within the maximum temperature rise rating of the stepper motor.


  13. Hi All,

    I got the kit and soldered very part but the 2200 uF Cap. Turns out I don’t have a cap that big. In that size, Radio Shack has axial caps only which would look pretty ugly. Any chance I can use 1 1000uF cap or will I end up with CPU resets?

    Crossing my fingers,
    Michael


  14. Good question and to be honest with you I don’t know if you’d end up with resets or not. It is certainly worth a try. Please let us know the results.


  15. I assembled the circuit with the 1000uF cap. Since I don’t have the arches built yet, I don’t know if the resets are happening. So far all I know is the stepper motors move as expected when I move them with the push buttons. I’ll keep you informed.


  16. Hello again,

    I’ve kept the 1000uF cap and have some nice oak arches. The clock sort of works. The hour arch seems to behave correctly. The minute arch seems to move more than 18 degrees per 5 minutes. I have looked at the code and (though I have never looked at picaxe code before) I do not think this is the result of a reset because the startup state seems to de-energize the stepper motors. My initial thought is either the arch is physically slipping on the motor shaft or the motor is misstepping. I have to dig down a bit more to figure this one out.

    I saw you had 2 different stepper energizing sequences (labelled “low torque” and “high torque”). The “low” sequences are commented out. Can you elaborate on their use? I have not looked at the motor data sheets yet but assume, the step size will be different and the number of steps (a constant in your code) will have to be changed as well.

    Still hoping to be finished in time for Christmas!

    Michael


  17. If I remember correctly, the code was written a long time ago, I had trouble with the motors slipping with the low torque. These stepper motors aren’t very strong and it’s possible that the arch is too heavy. Try to support the arch with a finger as it moves and see if that makes a difference.


  18. Hi again and Happy New Year,

    I changed the code slightly. I have just about doubled the inter-step delay and the physical clock has been running for the last 5 hours! I attribute my earlier problems to misstepping.

    It takes slightly more than a minute to go from minute 59 to minute 0 and I was worried I might have keep track of the lost minutes, but your code effectively has a one minute buffer so as soon as my clock goes from 59 to 0, it immediately advances to 1. I am happy with this and I hope the watch maker I made it for will be happy also.

    Thanks again,
    Michael Jamet

    ————————————-
    Some of my projects are documented at:
    sites.google.com/site/bunchofprojects
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