The Time Traveler’s Clock User Manual “A Man with a watch knows what time it is. A man with two watches is never sure.” --Lee Segall “A man with three clocks is more sure than a man with two clocks.” --Tim Van Baak Table of Contents Description and Background of the Time Traveler’s Clock, the “TTC”...
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o GPS Antenna • Connections o Main Power Input o Backup Battery Charger Input o GPS Antenna Input o Cesium 10MHz Output o Cesium 1pps Output o GPS 1pps Output o Chronometer Tick Output o Timing Printer • Initial Setup o Connecting the Power Supplies o Connecting the GPS Antenna o Winding and Setting the Chronometer...
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• Locking the Chronometer for Storage or Shipment Appendices Schematic Diagram • Description of the Circuit Operation • • Firmware...
Description and Background of the TTC Description of the TTC Functional Modules GPS Receiver and Clock The most precise and accurate time signal currently available on Earth is from the global constellations of navigational satellites, such as GPS (US), Glonass (Russia), Beidou (China), and Galileo (European Union).
must calculate the actual current time using the rate error and the number of days since the chronometer was set to correct time. The TTC contains a servo mechanism which provides a mechanical twisting motion to the chronometer once per second to keep the chronometer synchronized with the GPS timing receiver (which in turn is stabilized by the cesium CSAC).
Figure 2: GPS and RTC Display UTC Navigational Time There are many standards for time and date. Besides the standard local time zones, there is a basis time known as Coordinated Universal Time (UTC). UTC is defined as the time at the zero meridian which passes through Greenwich, UK. It is regulated by an international committee, the International Time Bureau.
Figure 3: Leonardo’s Time Viewer Why Do You Need a Time Traveler’s Clock? Imagine you’re traveling in time and space. Just like navigators of old, you’ll want to have some “bearings” back home, so you can return or go to a new destination. Time will essential to navigation, and we can assume that UTC will always be a good time to know.
even just their mechanical chronometer. The TTC has you covered for any imaginable eventuality. (And, if you’ve spent a lot of money on your yacht or aircraft, you’d certainly want to have the absolute, ultimate, most-reliable timekeeper available.) History of Prototypes Cesium Breadboard Prototype The first experimental design was constructed with a Hamilton 21 chronometer, a Microchip/Jackson Labs cesium chip-scale atomic clock (CSAC) (later used in the MCB...
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must be periodically measured to determine if winding is required. As the chronometer runs down, the winding input stem must be allowed to rotate backwards, so the chronometer may continue operation. Finally, provision must be made for manually winding the chronometer. The successful winding mechanism uses a titanium-geared radio-control servo motor fitted with a drive pinion.
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Figure 5: Winding Mechanism Pyramid Cesium CSACGPSDO Prototype The next generation of prototypes was built in a pyramidal shape with proportions from the Great Pyramid of Giza. The bottom of the enclosure was black acrylic with a window for the electronic displays, and the upper cover was clear acrylic to allow viewing of the controls and chronometer.
latitude independently from that supplied by the CSAC GPS Disciplined Oscillator. The Maxim RTC system was unchanged except for software refinements. The gimbal support and servo system were like those on the Cesium Breadboard Prototype. The problem of not being able to manually wind the chronometer without disassembling the housing remained and needed to be fixed.
allow the GPS to maintain accurate time during “holdover”, when a GPS signal is not available. This simpler design works as well as the cesium CSAC/GPS-Disciplined- Oscillator module, is less expensive, and is less complicated. In the Cube Box, the chronometer gimbals were mounted on an aluminum lazy-susan bearing that was cut away at the rear;...
support bearing was changed from the lazy-susan bearing to a precision V-groove circular rail with four support bearing rollers; the rear part of the rail was cut away to allow the chronometer to be rotated for winding. This bearing arrangement was more precise, so the servo synchronizing mechanism performed much better.
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wooden box, gimbals, chronometer case, and a clockwork which incorporates a fusee mechanism for near-constant winding force as the mainspring winds down, a detent escapement, and a temperature-compensated balance wheel fitted with a helical hairspring. When the US Navy realized the upcoming need for thousands of such chronometers in the years prior to World War II, the only company which could fill the need was Hamilton Watch Company of Lancaster, Pennsylvania.
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assured. Each instrument could be regulated to keep time within a second per day, and—more important—its deviation from perfect time would be a very precise value which would not change over the life of the chronometer. Each chronometer supplied to the Navy (and, also, to the US Army Corps of Engineers) came with a record telling when it was set to time as well as its measured error per day.
Figure 10: Hamilton 21 Marine Chronometer GPS Clock Advantages and Deficiencies The various global navigational satellite systems (GNSS systems, including the US GPS, Russia’s Glonass, Europe’s Galileo, and China’s Beidou) rely on very-high precision time keeping in order to allow a receiver to calculate its own position. Each satellite broadcasts its current time and its ephemeris (the parameters of its orbit).
When GNSS time signals are available, the quartz, silicon, and mechanical clocks are kept synchronized to satellite time. Silicon Clock Advantages and Deficiencies One of the redundant clocks contained in the TTC is an integrated-circuit chip (Dallas DS3231) which contains a temperature-corrected quartz oscillator of its own and an extremely-low power microprocessor which maintains correct time, even if it’s main power supply is lost, using a small backup battery.
ServoSync Design Evolution The conception of the Time Traveler’s Clock includes the means by which a mechanical chronometer is kept in perfect synchronization with an atomic- or GPS-based time signal. A very small rotary motion (on the order of +/- 0.5mm) applied to the gimbal- mounted chronometer will cause the balance wheel and detent escapement to fall into resonance with that motion.
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Lazy-Susan Design: A simpler ball bearing of the type used for “lazy Susan” rotary tables was used. This bearing has cast aluminum races, steel balls, and a plastic carrier for the bearing balls. The inner and outer rings and the plastic ball carrier are cut to provide clearance for the chronometer to be tilted forward for manual winding.
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V-groove Circular Rail Design The final in the “Metal Cube Box” uses a V-groove bearing arrangement in which a stainless steel ring is supported by four small, plastic-covered ball-bearings with V- grooves to match the outer periphery of the ring. The stainless steel ring is attached to the chronometer gimbals.
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Figure 16: Time Traveler’s Clock System Schematic Diagram...
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Figure 17: Hamilton 21 Chronometer Starting Instructions...
Installation and Connections • What’s Included o The Time Traveler’s Clock 1. The TTC should be set up in a place where a window is available nearby for the GPS antenna (SMA extension cables may be used if necessary). o Timing Printer and Supplies 1.
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Figure 18: Rear Panel Connections Connections • o Main Power Input 1. Plug the UPS DC supply charger into an AC mains outlet (100-240V). 2. Plug the 12V DC output from the UPS into the jack on the left side of the rear panel labeled “Main 12VDC”.
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• Winding and Setting the Chronometer o The chronometer is provided fully wound but “stopped” by an internal friction element which prevents the balance from rotating. The starting procedure is detailed on the instruction panel in the lid of the TTC. (See Figure 13) o It is important to follow the Starting Instructions precisely, or damage can result to the chronometer.
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chronometer was fully wound. After the hand goes past “48 hours”, the chronometer will stop and will need to be restarted and re-set. 4. Any time the chronometer stops because of not being wound, follow the “Starting Instructions” carefully and do not shock the chronometer. Otherwise, damage may be done to the sensitive escapement mechanism in the chronometer.
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o Rate Atomic and Rate Error Measurement 1. The “Rate Atomic” button is a push-on/push-off button. It is lit green when the “Rate Atomic” function is engaged. Engaging this function prevents the ServoSync motion being turned off at midnight when the timing of the chronometer is measured.
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2. Procedure for manual winding: • Push the lower latch and tilt the upper portion of the case backwards to access the controls and the chronometer. Remove the GPS and RTC Display by lifting it up and backwards (it is •...
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• Other Control Panel Indicators and Buttons o “Atomic” blinks green once per second, powered by the 1pps signal from the cesium clock. o “GPS” blinks blue once per second, powered by the 1pps signal from the GPS receiver; it should be in sync with the Atomic light (the blue Atomic light blinks quickly exactly as the blue GPS light turns off).
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most likely will have been turned off and its 12V DC Power output will need to be turned back on. o Once AC and DC power is available: 1. The Main 12V battery-backup supply should start recharging its battery 2. the electronics and displays should turn back on 3.
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