Build your own microcontroller based clock timing machine.

lmester

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Dec 30, 2009
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This is an open source project for an electronic clock timing machine. Used to measure the rate and beat error of a clock plus many other features. Optional precision timebase is available. Total cost for parts is aproximately $40. A circuit board is now available. This makes assembly much easier.

Click for more info.


Timer-case 001s.jpg

NewPCB 004s.jpg

ClockData1.png
 

measuretwice

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Jul 28, 2019
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Are you the creator? I like it. The clock is listed as a 10Mhz TCXO ....I would suggest anyone building one splurge for the high precision TCXO, you can get like 0.1 ppm for $20.
 

lmester

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Are you the creator? I like it. The clock is listed as a 10Mhz TCXO ....I would suggest anyone building one splurge for the high precision TCXO, you can get like 0.1 ppm for $20.
Yes, this is my project. One reason that I chose 10MHz for the clock was that it's also a common output frequency for atomic clocks and GPSDO's. I used a GPSDO to test the timer. If you're the lucky owner of a shortt synchronome clock, This timer can be made accurate enough to test it:D

For nearly all mechanical clocks a standard crystal will be fine. If you use it to measure the performance of quartz clocks you'll want the TCXO and would need to calibrate it with an atomic clock or GPSDO. Also, make sure to get a TCXO that has a calibration screw. Some TCXO's can't be field calibrated.

I've used it to compare some quartz movements. The cheap Chinese movements are sometimes very poor compared to a Takane brand movement.
 

measuretwice

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I think you are right, more than accurate enough. I was probably off track, recalling a theoretical discussion on checking very accurate quartz watches, the better than 10 seconds a year stuff....something that has about zero practical use in my life but seemed an interesting challenge if designing a watch timing device.

Anyway, great design and thanks for making it open source. I think there was mention of a watch pick up to it that might be coming?

Mike
 
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Betzel

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If only it came as a kit, with OSS to run under linux. Heathkit is (after so many stops/starts) operating again. Who knew?

Since it's open source, I think I can mention it on the BHI forum to help increase exposure.
 

praezis

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An awesome project! I can imagine, how many hours you had to invest.

My questions:
- What kind of pickup do you use?
- how come that above graphs of rate and beat error look nearly identical?

Frank
 

lmester

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An awesome project! I can imagine, how many hours you had to invest.

My questions:
- What kind of pickup do you use?
- how come that above graphs of rate and beat error look nearly identical?

Frank
Several different pickups are available. Optical, piezo (vibration) and inductive have been the most useful. See my web page for details. This plot was done with an infrared optical sensor. Place it so that the pendulum rod interrupts the beam.

As for the beat error following the rate. I've no real idea. Possibly varying power input to the pendulum. This would also change the rate. You can see from the plot that the change in beat error is very small. Only about 3.5 milliseconds.

I've been working on this project since 2014. About 8000 lines of code to run the PIC chip. It's had several upgrades over the years. One was a request for precision hardware timing. The timer output is not dependent upon software response times. Hardware timers on the chip are used. another was the ability to measure pendulum velocity.

The last thing that I've done was to provide a circuit board design. Many more people have built this project now that a board is available. It makes assembly much easier.
 
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Rockford's early high grade movements by Greg Frauenhoff