DE102012008215B4 - Device for realizing a reference clock with automatic connection of the internal system time to earth rotation - Google Patents

Abstract

Device for realizing a long-term stable reference clock, which automatically adjusts itself, the earth's rotation and the daily twilight cycles are used as a reference time and this consists of a microcomputer or a hardwired or programmable digital logic and a real-time clock including clock generator, which at initial startup with current time and current date, characterized in thata) the determination of the dawn, dusk or dawn and dusk times in conjunction with the time of the real time clock forms a statistical mean value after the system has been operating for a sufficient period of time (b) from the time the reference value is established, a comparison is made between the reference value and the current statistical mean of the dusk cycles; It is used for comparison to the regular tracking of the real-time clock.

Description

The invention relates to a reference clock with an internal real-time clock with a highly stable clock generator, the internal system time is continuously synchronized with the seasonal sun-dependent sunrises and sunsets. In addition, the exemplary application of the reference clock according to the invention will be described in a device for temporary power reduction of centrally controlled lights.

a) According to the prior art consist of electronic clocks or real-time clocks, from a clock generator and a subsequent device for digital preparation and digital output and / or display of the current times. Here, the long-term stability, which depends on the frequency constancy of the clock generator, a quality standard for the appropriate application. According to the state of the art, so-called real-time clocks, or "real-time clocks" or RTCs provide the time in a form which can be processed by humans and / or by electronic systems. The time is displayed in seconds, minutes, hours, day, month, year.

To stabilize the frequency of the clock generator quartz crystals based on crystal or ceramic oscillators have been used for a long time. However, since these quartz crystals have a temperature-dependent frequency run in addition to the temporal aging, either the operating temperature must be kept constant in order to increase the temporal precision, or the temperature run of the quartz must be compensated by suitable measures. As a basic requirement of course, the operating voltage of the clock generator to stabilize.

To stabilize the operating temperature of the clock generator or oscillator according to the prior art, the quartz crystal is mounted together with the electronic components of the oscillator in a housing which is heated constantly to a temperature of about 50 ° C to 80 ° C. Since these clocks or oscillators in addition to long-term stability also have a low phase jitter, or a good short-term stability, they are usually used only in high-frequency instruments or high-frequency communication devices. However, such discretely constructed temperature-stabilized clock generators or oscillators with quartz ovens are complicated and therefore relatively expensive.

Alternatively, however, according to DE 10 2008 060 386 A1 Also integrated circuits available which have an internal heating element for stabilizing the operating temperature. However, the temperature-stabilized quartz oscillators require not inconsiderable electronic power to heat the components, and are therefore usually used in mains-powered devices.

The second way to stabilize the frequency of the clock generator is to compensate for the temperature-induced frequency drift of the quartz crystal.

Corresponding integrated circuits or ICs which operate according to this method are offered by different manufacturers. Both simple designs with low temporal constancy and complex solutions for temperature-compensated quartz oscillators TCXO with high temporal and temperature-related accuracy of + - 5 ppm up to + - 2 ppm are offered. This means an annual inaccuracy of + - 158 seconds to + - 63 seconds.

Even with these high-precision real-time clocks or RTC, which are available as ICs, the clock generator is stabilized by a quartz crystal or ceramic resonator, which is disposed within the IC package. Alternatively, IC based RTC are also available for external oscillating crystals or ceramic resonators. Since quartz crystals and / or ceramic resonators, as already stated, have a temperature-dependent frequency sweep, their temperature run is stabilized by different compensation measures. Here are simple analog circuits, as well as complex corrective measures using digital correction tables known.

Thus in the patents DE 037 84 376 T2 such as EP 0 248 589 B1 an analog frequency tracking using a thermistor and a voltage-controlled capacitance variation diode described.

In the patent US 5,668,506 A is an analog frequency tracking for a temperature-compensated quartz oscillator TCXO described whose temperature-related correction curve in a digital Memory is stored and controlled by a temperature sensor, a tracking voltage for a capacitance variation diode is generated.

US 7,371,995 B1 describes an analog frequency tracking controlled by a digital signal processor.

In the EP 0 879 442 B1 For example, a method is described which uses a clock to control a switch which is placed over the day-night twilight cycles. The brightness is continuously recorded and from the slope of the brightness change the times of dusk are detected. From this and from the information at which geographical position the system is located, the local time is closed by means of an internal calendar and, if necessary, the internal clock is corrected.

In the patents US 5 117 206 / US Pat. No. 5,995,970 A / US Pat. No. 6,160,458 A / US Pat. No. 6,414,559 B1 / US Pat. No. 6,476,682 B1 Frequency compensations for a temperature-compensated quartz oscillator TCXO are described whose temperature-related correction curves are also stored in digital memories. In these applications, the frequency tracking of the internal quartz crystal or ceramic resonator is carried out by internal switched capacitors. The connection of these compensation capacitors to the quartz oscillator or resonator is effected by a semiconductor logic which takes place according to the compensation value selected from the compensation table according to the crystal temperature or internal IC temperature measured by an internal temperature sensor.

Furthermore, applications are known in which the real-time clock is synchronized with an official standard time. These are standard times, which are provided worldwide by the satellites of the GPS Global Positioning System / Navstar, or in Central Europe by the DCF77 Longwave Normal Time Sender. These radio systems deliver a standard time that is constant for 1 sec.

b) The state of the art for the patent application of the aforementioned real-time clocks or RTC in street lighting systems, is as follows.

Usually street lighting systems are switched centrally by means of a program-controlled clock and / or a twilight switch. This causes the lights to light only during twilight and night hours.

For power supply and for switching on and off of the individual lights here are different designs of the 230 V AC power supply network, as well as several technologies and methods for switching known.

c) For example, the lights can be fed in the simplest case by a separate 230 V lamp circuit, which is switched centrally. Here, the supply networks of street lighting in three-wire technology (phase, neutral and protective earth) are performed. The phase of this circuit is turned on at dusk and turned off at dawn. The switching control is done by central twilight switch.

d) Furthermore, the supply networks of the street lighting can be performed as a multi-conductor network with multiple switched phase lines. With multi-conductor networks, it is possible to use one of the additional lines as a control line to reduce the luminaire performance at certain times, or to switch off some of the luminaires. For this purpose, the additional control line is usually supplied with mains voltage for full illumination and to reduce (dimming) the lighting, this mains voltage is switched off.

e) Another possibility is that the street lights are powered by a phase of the 230 V supply network or a separate, non-switched line, or the lights are distributed evenly across the three phases of the supply network.

The switching on and off of the lights, as well as the dimming of the lights is done in this technology by switching signals which are modulated on a high-frequency or low-frequency carrier signal in a suitable manner. This carrier signal is generated by a transmitter and is in turn superimposed on the supply network. For evaluation of these switching signals and for switching, a corresponding receiver with at least one switching output is installed in each luminaire. These in new, or modernized Utilities used technology, for example according to DE 20 2010 002 701 U1 or DE101 28 258 A1 however, is not the subject of the invention described herein.

If the cable guides described in d) and e) and / or the complex carrier frequency technologies are not available, there is an increasing demand for the temporary reduction in the power of the street lighting from the point of view of energy saving. In older networks, the additional control line mentioned under d) is often not available and a conversion of these networks is inevitably associated with a considerable installation and cost. Retrofitting with carrier frequency systems according to e) is also associated with considerable effort.

In order to realize a night shutdown, or night reduction / dimming of the lighting for consumption reduction even with these older or simple cable networks, various applications and methods are known in the prior art.

For example, an electronic power switch is known, which is built into each luminaire and measures the centrally controlled duty cycle and compares it with the data stored on an internal data store power-on data of the previous day. By means of this data, the time of night shutdown or dimming of the lights is then determined. With a rotary switch, the switch-on time and the switch-off time for the dimming can be set at fixed intervals with this technology.

Another product also calculates the time range for the dimming from the previous switching cycle of the last day. The dimming time can be selected here in fixed preset ranges of 6, 8 or 10 hours.

Out DE 44 18 315 C2 or the same WO 95/33361 A method is known which uses the previous switching cycles to calculate the dimming times and calculates the dimming times from them. This method already provides comparatively precise, reproducible values, which already take into account the time lag due to different geographical positions in the longitude.

DE 10 2009 033 358 A1 treats the subject with similar approaches, using the center of the on and off time as the reference time.

In US 05450302A a dimming time derived from the on-time of the previous day is described.

WO 2006/126240 A1 excludes the duty cycle on the season and accordingly drives different nocturnal brightness curves.

CH 549927 describes a method wherein the described twilight switch operates with time delays to minimize switching hysteresis.

The publications DE 39 02 785 A1 such as DE 100 52 541 A1 describe methods for dimming discharge lamps.

In DE 197 31 150 A1 a method of phase blanking for data transmission to the switching modules is described.

The publication WO 2007/091175 A1 with the priority date of 07.02.2006, as well EP1982564 takes up most of the technical details described above and tries to formulate an all-encompassing patent specification.

The aforementioned real-time clocks and switching devices have, depending on the method used, as well as the design of the central control, more or less pronounced system-specific disadvantages. Thus, according to the current state of the art, with the exception of the normal times transmitted by radio, it is not possible to keep a plurality of real-time clocks operating in a function combination sufficiently synchronously at the same time over a relatively long period of time. As a result, when using several of the aforementioned devices in a system or a functional composite, depending on the current weather events, compulsorily switching hystereses and temporal inaccuracies of the switching on and off the switched consumers. Thus, for example, it has hitherto not been possible to enable sufficiently synchronous switching / dimming of an entire road train, with the switching times of the individual switching devices being able to deviate in part by more than one hour from the intended switching time.

The present invention is therefore based on the object to provide a device which, without parallel synchronization by radio or carrier frequency transmission, or without the presence of wired switching lines to optimize the long-term stability and temporal precision of real-time clocks.

This is achieved by providing the device described below according to claim 1:

1. a) aus der Ermittlung der Morgendämmerung, der Abenddämmerung oder den Zeiten der Morgen- und Abenddämmerung in Verbindung mit der Uhrzeit der Echtzeituhr ein statistischer Mittelwert gebildet wird, welcher, nachdem das System ausreichend lange in Betrieb ist, als Referenzwert einmalig und dauerhaft gespeichert wird;
2. b) ab dem Zeitpunkt, von welchem der Referenzwert erstellt wurde, ein Vergleich zwischen dem Referenzwert und dem aktuellen statistischen Mittel der Dämmerungszyklen erfolgt;
3. c) dieser Vergleich zur regelmäßigen Nachführung der Echtzeituhr verwendet wird.

Device for realizing a long-term stable reference clock, which automatically adjusts itself, the earth's rotation and the daily twilight cycles are used as a reference time and this consists of a microcomputer or a hardwired or programmable digital logic and a real-time clock including clock generator, which at initial startup with current time and current date is set,
characterized in that

1. a) the determination of dawn, dusk or dawn and dusk times in conjunction with the time of the real-time clock constitutes a statistical average which, once the system has been in operation for a sufficient period of time, is stored once and permanently as a reference value;
2. (b) a comparison is made between the reference value and the current statistical mean of the twilight cycles from the date on which the reference value was established;
3. c) this comparison is used to regularly update the real-time clock.

Description:

The invention describes a reference clock with an automatic correction function, which is characterized by a high long-term stability. The special feature is that this long-term stability is realized without complex, highly stable time standards and that no connection or synchronization to a public standard time standard is required. As reference according to the invention, the daily sunrises and sunsets determined by the earth's rotation are detected and evaluated. In addition, embodiments for the application of this reference clock will be described.

The reference clock according to the invention consists, at least, of an electronic real-time clock with clock generator, as well as of a microcomputer and a programmable, non-volatile semiconductor data memory, as well as a computer program, by means of which the function or method according to the invention is realized. Furthermore, a connection to a photosensor must be included to detect the dawn and dusk. In order for the power supply to be guaranteed for intermittent mains operation for at least 24 hours, it must be buffered.

For this purpose, preferably batteries or high capacitive capacitors are used. Optionally, the power can also be provided by photovoltaic cells or solar cells, which can also serve to detect the dawn and dusk at the same time.

The real-time clock or real-time clock contained in the reference clock according to the invention, abbreviated RTC, describes an electronic clock according to the state of the art, which defines the time in the form of year, month, day, hour, minute, second and optionally the fraction of a second. The system time is counted up with the smallest time resolution and the displayed time data is output to the microcomputer through an interface for further processing.

Alternatively, the aforementioned hardware, as well as their function according to the invention can also be realized by a programmable or hard-wired logic, for example according to the state of the art by ASIC application-specific integrated circuit, or FPGA Field Programmable Gate Array, or CPLD Complex Programmable Logic Device.

The electronic individual components for the realization of the aforementioned device correspond to the prior art. New and decisive, however, is the realization of the automatic correction function, as well as the method of continuous temporal correction of the real-time clock and its subsequently described tracking of the internal system time according to the Earth's rotation and the seasonal sun.

If a watch is to provide a minute-by-minute indication in autarkic operation over a period of several decades, it usually requires a high-precision internal time standard, or synchronization with an external and highly accurate time standard.

Inexpensive watches usually use quartz crystals, ceramic resonators or other resonant resonating systems. These watches are not suitable for the aforementioned requirements as sole time standard.

For some time, however, realized as integrated circuits real-time clocks are available in which the physically given temperature run of the clock generator is compensated by the stored in an internal semiconductor memory correction data. These circuits allow the realization of relatively inexpensive, but high-precision real-time clocks.

Here is an example of the accuracy of commercial temperature-stabilized quartz watches according to the patents US 5 117 206 / US Pat. No. 5,995,970 A / US Pat. No. 6,160,458 A / US Pat. No. 6,414,559 B1 / US Pat. No. 6,476,682 B1 :

The data sheet of a real-time clock or real-time clock ICs realized according to the aforementioned patents describes the internal time base with a gear accuracy of + - 5 ppm in the temperature range from - 40 ° C to + 70 ° C. This IC requires no external oscillating quartz and allows the following accuracy:
+ - 0.432 sec / day / + - 3 sec / week / + - 13.4 sec / month / + - 157.68 sec / year

A prior art and exemplified IC fabricated according to the aforementioned patents is defined in the best version in the temperature range of 0 to + 40 ° C with + - 2 ppm, a deviation of + - 63.07 seconds means per year.

But even with such high accuracy, this would still mean a +20 minute deviation in 20 years for an uncorrected long-term operation.

In these considerations, however, the natural aging of the quartz crystal is not yet taken into account, since this long-term component would also have to be included in the stored correction data.

The use of the reference clock according to the invention described below by way of example is intended inter alia for temporary power reduction in public lighting systems. Here, such a deviation would mean that in a lighting system with several lights at the same set switching time, the lights in the period of 40 minutes could arbitrarily switch sequentially. That would not be acceptable.

A real-time clock that should be used for such a purpose must therefore be regularly synchronized with a more accurate time standard. There are e.g. Radio transmitter, for Europe usually the long-wave transmitter DCF77 in Mainflingen, which is a highly accurate time standard and sends out corresponding coded data, or wired time standards, e.g. via the NTP (Network Time Protocol), after which the quartz watches can be synchronized. In addition, the emissions of the GPS navigation system can be used as a highly accurate time base.

This in EP 0 879 442 B1 described method provides a still relatively inaccurate time because the time is calculated from the geo-position data and from the slope of the brightness curve. Influences such as the orientation of the photosensor, one-sided shadowing, different clouding situations can not be considered or only with great effort.

The method of the reference clock presented here, however, is a relatively simple and inexpensive alternative to stabilize the internal real-time clock with simple means for decades to the minute, without the connection to external wireless or wired time standards is required.

The basic idea of the reference clock according to the invention is based on using the rotational speed of the earth as a time reference, according to which a commercially available, and according to the state of the art, realized by semiconductor real-time clock is synchronized at regular intervals.

Compared with the International Atomic Time (TAI) formed by atomic clocks, the absolute accuracy of the Earth's rotational speed is limited by geophysical processes. The mean annual deviation therefore fluctuates and is currently well below one second within one year.

Thus, the following mean annual accuracy can be assumed: $$\begin{array}{l}\left(\text{60 seconds}\right)\times \left(\text{60 minutes}\right)\times \left(\text{24 hours}\right)\times \left(\text{365 days}\right)=31536000\text{Seconds a year}\\ \text{accuracy}=+-1\text{Second per}31536000=0.0317\text{ppm}\end{array}$$

So that the Coordinated Universal Time (UTC), which is based on the rotational speed of the Earth, does not differ from the day-night change by more than one second, a leap second is inserted after a deviation of 0.9 seconds or the coordinated world time UTC is stopped by one second. Thus, the difference of the Coordinated Universal Time (UTC) to the International Atomic Time (TAI) is always less than one second per year.

For the detection according to the invention of the average earth rotation speed, the morning and evening twilight time is used in each case. The object to be achieved for the realization of the reference clock is, inter alia, to eliminate the different twilight times, which result mainly from different levels of cloud cover, so that these times can be used for tracking the real time clock contained in the reference clock.

For the temporal synchronization according to the invention, the complete annual twilight profiles for the 365 days are mapped in tables or mathematically generated curve courses in a fixed-value data memory on which the microcomputer can access. These expected target data are then compared daily by the microcomputer with the detected current twilight values, evaluated and determined the statistical deviation.

In doing so, the daily fluctuations in times, e.g. arising from different degrees of cloudiness, are taken into account accordingly. The method of the reference clock described here makes it possible to drastically reduce these fluctuations with relatively little computational effort, so that the resulting correction values can be used as a reference for the continuous synchronization or readjustment of the internal real-time clock.

When commissioning the reference clock for the first time, the internal system time of the real-time clock must be set to the current time and date. Furthermore, it is useful, as will be described, to perform an advance referencing by storing a previously determined correction value. For this purpose, at least one data interface must be provided, by means of which this can be realized. This may be a wired computer interface, a radio or infrared interface, or as described below, a clocked data transmission over the supply network, wherein a data transfer is realized by rhythmic ON-OFF switching of the 230 V network.

Definition of terms: In the following description, the term logging is used for detecting and logging the middle twilight threshold.

The logging, detection and logging of the mean earth rotation by determining the twilight cycles is carried out according to the following procedure:

By a photosensor, or optionally by the evaluation of the terminal voltage of a solar cell, which can simultaneously supply the necessary energy for operation of the reference clock, the ambient brightness is measured. Here, a twilight switch is formed by means of a trigger circuit with fixed or variably adjustable threshold, which generates a switching signal from the average twilight value, so that the time of the onset of dusk and the time from the end of dawn can be logged.

When designing this twilight switch and defining its switching hysteresis, care must be taken that the brightness value at which it is switched to night and back again to day is dependent on environmental conditions, such as e.g. Cloudiness, temperature or operating voltage, extraneous or artificial light is not or only insignificantly influenced.

In addition, suitable precautions must be taken to prevent switching on and off several times in the event of slight fluctuations in brightness during the twilight phase. Eg with the help of time delays or a switching hysteresis, or a combination of both. The time delays as well as the switching hysteresis can be realized on the software as well as on the hardware side.

If this device is used for time-controlled power reduction of lighting systems, these lights are normally switched centrally via a central twilight switch with a photosensor such that the 230 V power supply is turned on by this. The 230 V switch-on and switch-off signal of the luminaires can be used for logging the twilight cycles.

To determine a reference from the dusk times, the dawn, dusk or the times of dawn and dusk can be used. The method presented here uses the measured time period between dawn and dusk.

It is irrelevant for the accuracy of the clock, whether the times in minutes or whether the times are logged in minutes and seconds, because the logged times due to the aforementioned boundary conditions such as varying degrees of cloudiness can vary greatly and therefore rounding errors are eliminated by the required subsequent statistical evaluation have to.

Determining a reference from the logged dusk times:

One possibility is to log the twilight times on the semiconductor memory of the processor to store a table with the predicted twilight times for an entire annual cycle based on the latitude of the location, to compare it with the date of the real-time clock and derive a reference value from it.

However, this means that the location and weather-related brightness fluctuations have a great influence on the time, which must be eliminated with the appropriate effort.

A better method is to derive a sufficiently accurate reference from the switching cycles of twilight times using statistical methods. This is then used to determine a reference to the real time.

For a constant value to be formed from the information of date, switching cycle and statistical mean, the seasonal and site-related temporal variations in the statistical acquisition of the switching cycles must be taken into account.

If the arithmetic mean of the time of dawn and the time of dusk is used as a reference, a correction shall be made in accordance with 1 to perform the time equation curve shown.

The calculation and the theory of the time equation curve is well known in astronomy and will therefore not be explained further.

The method of correction described here is relatively insensitive with respect to different locations. Naturally, however, it is not suitable for use north or south of the two polar circles.

For Germany, Austria, Switzerland the in 1 time equation curve used for the correction. For locations further north or south, the use of a time equation curve optimized for these regions is recommended.

The time average can be calculated according to the following formula: $$\left(\text{Time of the dawn}+\text{Time of dusk}\right)\text{/}2+\text{correction value},$$

The value thus obtained is adjusted for seasonal fluctuations and is still subject to weather-related fluctuations.

To obtain a stable value from this, the value is either stored in a table and used to calculate the arithmetic mean, or, more effectively, continuous arithmetic integration is performed. The more switching cycles that are included in this integration, the lower the fluctuations or the lower the influence of weather-related fluctuations.

The value representing the statistical mean is meaningfully not calculated as an integer, but in such a way that the seconds can be derived from it.

The value obtained in this way is relatively stable and differs depending on the accuracy of the correction curve, the statistical method and the number of statistics used in the course of the decades only in a very narrow bandwidth and can be used as the basis for tracking the real-time clock. How out 3 It can be seen that, with a statistical mean of 50 days, the daily fluctuation of the statistic value without special optimizations is already significantly less than one minute, after an operating time of one year, well below 5 seconds.

In the 1 The equation of time shown changes over the decades in the range of seconds and, if the clock is to be accurate to the second, must be adjusted accordingly or offset.

As a result, the accuracy of the reference clock according to the invention becomes better and better as the operating time increases.

Stability optimizations of the statistically determined value:

Out 3 It can also be seen that the temporal fluctuations caused by varying levels of cloudiness may, for some days, tend unilaterally in the same direction, following the principle of randomness. To avoid this, as well as other temporary errors, the method described below can be used.

In this case, it is checked whether the times of the detected twilight cycle are within the expected frame of the data stored in the read-only memory. If the time points are far out of the frame, they are certainly exceptional situations, such as temporary shadowing by persons / animals or maintenance operation of, for example, lighting and are not taken into account in the continuous statistical calculation.

Exceptional weather situations, however, play a significant role in the stability of the statistically determined value. Observations have shown that the temporal variations of the average value due to different clouds are usually relatively small and vary between 0 and 5 minutes. However, deviations of more than one hour are not exceptional during afternoon heavy thunderstorms or winter cloud cover with snowfall.

It therefore makes sense to ignore these values when determining the statistics. The difficulty, however, is to set a general and meaningful limit. A better method is to consider all values, but according to the magnitude of the deviation from the mean with different weighting.

Since the weather-related deviations for the switch-on time and the switch-off time generally only in one direction (earlier switching on in the evening and later off in the morning) and on the other hand, the brightness gradients are practically constant in a clear sky (because there is no clearer sky than a clear sky ), it makes sense to take this into account when weighting.

These optimizations improve the result only to a small extent. Experiments have shown that good results are already achieved if equally high values are included in the statistics, which contain a positive or a negative sign, depending on whether the measured value is greater or smaller than the mean already calculated. For low-accuracy applications, this method may already be sufficient.

Adjusting the clock after the statistically determined reference value:

After commissioning the reference clock for the first time and setting the time for the first time, the system-internal time depends exclusively on the accuracy of the internal real-time clock and the precision of its clock generator. At the same time, the creation of statistics for the twilight cycles is started. If the system is in operation for a sufficient period of time, the statistical mean value is stored as a reference value once and permanently.

Alternatives to creating the reference value:

In general, the above and described method of creating the reference value with the integrated real-time clock will be the optimal method.

Nevertheless, there are situations in which it may be more advantageous to determine the reference value in a different way. For example, if the reference clock is operated in a network, as usual for street lighting, and some new reference clocks are added at a later date. In the meantime, it is possible that in the meantime the central photosensor serving as twilight sensor, which switches on the 230V power supply of the luminaires at dusk, has been changed in its switching characteristic. This could lead to a slightly different result for the new reference clocks when calculating the reference value. In order to avoid this, the newly added reference clocks can already be set to the same reference value as the reference clocks previously available in the system network before they are installed. For this purpose, it should be possible to read the reference values of the previously installed reference clocks in order to then read these into the newly installed reference clocks.

Another possibility is that the corresponding reference value is calculated separately from the geo-position data of the intended place of use and the new reference clocks to be newly installed are preset with this reference value.

For the calculation, the known conversion formulas from the WOZ (true local time) to the CET (Central European Time) can be used.

• - Ausrichtung und / oder einseitige Ost-West-Verschattung des Photosensors:
  • Eine einseitige Verschattung führt zu einer unterschiedlichen Uhrzeit bei der Detektion von der Morgendämmerung und von der Abenddämmerung und führt damit zu einer Verschiebung des statistischen Mittelwertes.
• - Hysterese des Photosensors:
  • Der Photosensor weist eine Schalthysterese auf, die verhindern soll, dass bei Eintritt oder Ende der Dämmerung und schwankender Helligkeit durch unterschiedlich starke Bewölkung der Sensor mehrfach schaltet. Diese Eigenschaft bewirkt allerdings auch, dass der Helligkeitswert, der die abendliche Dämmerung detektiert, einen anderen Helligkeitswert darstellt, als der Wert, der die morgendliche Dämmerung detektiert. Dies bewirkt ebenso eine zeitliche Verschiebung des detektierten Mittelwertes.

It should be noted that a calculation of the reference value from the geo-position data will lead to a lower accuracy. The absolute statistical average, which is generated on site from the twilight cycles, depends essentially on the following factors:

• Alignment and / or one-sided east-west shading of the photosensor:
  • A one-sided shading leads to a different time in the detection of dawn and dusk and thus leads to a shift in the statistical average.
• - Hysteresis of the photosensor:
  • The photosensor has a switching hysteresis, which is intended to prevent the sensor from switching several times at the onset or end of twilight and fluctuating brightness due to different levels of clouding. However, this property also causes the brightness value that detects the evening twilight to represent a different brightness value than the value that detects the morning twilight. This also causes a temporal shift of the detected mean value.

However, this effect can be minimized by designing the photosensor and the subsequent circuitry defining the trigger threshold to define different switching hystereses for the detection of dusk and dawn. The switching between the two hystereses can then take place, for example, at 12:00 and 24:00. By this design, the triggering then takes place at the same brightness values.

Other factors such as the influence of extraneous light, the direction in which the photosensor is aligned, additionally influences the absolute value of the statistical mean value.

If the determination of the reference value is made according to the first mentioned method, in which the reference value is created and adopted by the integrated real-time clock, then the absolute value of the mean value and thus the absolute value of the reference value is irrelevant, because when creating this value all o.g. Factors have already flowed into the determination of the value.

However, if the reference value is calculated exclusively from the geo-position data, the above-mentioned factors lead to a corresponding deviation. System-related factors such as the properties of the photosensor and its hysteresis can be taken into account mathematically, factors such as the orientation of the photosensor, shading, extraneous light usually not.

Set the optimal time to create the reference value:

It is not possible to establish a general rule for the preparation of this date, because the determination of this time, depending on the application and use of the reference clock / s can be done under other aspects.

In the event that the real - time clock contained in the reference clock is set once during commissioning, the determination of this time can be made in accordance with 2 shown graphic done. How out 2 As can be seen, the deviations resulting from the statistics and the deviation resulting from the drift of the real-time clock are in opposite directions as the operating time progresses. Both deviations add up and form the curve 3 ,

The curve 3 follows first the statistical deviation 2 down and approach the curve 1 , the drift of the real-time clock or RTC. It then rises again along the drift of the RTC.

Point of time 4 at which the curve 3 has reached its low point, is the optimal time to create the reference value.

If the statistics are kept continuously as sliding statistics over the same number of cycles, even if no further optimizations are made, the maximum deviation over the entire service life of the clock remains at the value 5 and it fluctuates by the maximum value due to the continued statistics 6 ,

In the 2 The graphic shown is not drawn to scale for better representability and therefore not provided with real values. Likewise, the graph of the statistic values depends on the statistic generation method, and may have a different form depending on the method.

From the time the reference value was created, the time of the real-time clock included in the reference clock is regularly reset as follows: $$\text{New time}=\text{current time}+\text{reference value}-\text{current statistical mean},$$

A change in the time of day means that the statistical average only changes slowly during the next twilight cycles. Each additional cycle would re-adjust the real-time clock time in the same direction, which would lead to overcorrection and excessive clocking times.

In order to avoid this, each table entry in the statistic must be corrected by the same amount at the same time as the time is changed, or this amount must be taken into account in the case of mathematical integration.

If the reference clock is in operation for a sufficiently long time, it can be assumed that the statistical average will tend not to change any more and that the value fluctuates within the same limits within seconds due to weather conditions. If the clock of the real-time clock continues to be tracked according to the above-mentioned method, this fluctuation has a direct effect on the display of the reference clock.

This fluctuation can be drastically reduced if, from now on or successively increasing, the method for tracking the real-time clock or the method for generating the statistical mean value is changed.

The fact that the weather-related fluctuations of the statistical average ( 0 to several seconds / day) are significantly larger than the drift of the real-time clock, can be used to eliminate these short-term fluctuations.

For this purpose, the weighting of new twilight cycles is either greatly reduced from now on with each further calculation of the statistical mean value, or the real-time clock is only adjusted by a fraction of a second during readjustment. This causes the time to fluctuate only slightly and that it gradually approaches the exact mean. It is also possible to use a combination of both methods.

When choosing the step size for adjusting the real-time clock, care must be taken that the step size is large enough to compensate for the drift of the real-time clock under all conditions.

Time for adjusting the clock:

The time for adjusting the clock depends on the intended scope. If the watch is operated as a normal clock for time display, it is advisable to adjust the clock at a time when the clock is rarely observed. For example, at 2:00 in the night.

If the clock is not used for time display, but for the switching of lights, for the timed dimming of lights or for other time-controlled and synchronously departing switching operations, the time should be synchronized with a specified switching operation.

Daylight Saving Time:

Since the watch has an internal date display, an automatic daylight saving changeover to the regional summer time can be implemented.

Substitute operation or emergency operation in case of failure of the real-time clock:

In sensitive applications, in which the safe function of the reference clock has a very great importance, their reliability can be increased by the design and function features shown below.

In the event that the reference clock or its internal real-time clock is no longer ready for operation due to a technical defect or due to a power failure or electromagnetic interference, an optional replacement operating mode may be provided.

If the real-time clock has a malfunction, an error flag is set by the latter, which can be read out by the microcomputer and evaluated accordingly. In addition, at each twilight cycle, the date can be checked for change. A new twilight cycle with the same date then indicates a malfunction.

In this case, the system switches to the replacement operating mode.

Already during normal operation, a precautionary statistic of the duration of the twilight cycles is created for this case, continuously updated and stored in the read-only memory. Here, the time between the two daily twilight cycles is logged and the statistical average calculated.

If now switched to the replacement mode, the microcomputer takes over the function of the real-time clock and generates the time accordingly. Due to the lower precision of the clock generator of the microcomputer, however, the temporal stability of the reference clock will inevitably deteriorate.

Although no seasonal corrections can be made during the replacement operation, the reference time, which establishes the relationship between the real time and the twilight switch cycles, can still be used. If an automatic daylight saving changeover is configured, the switching times can be shifted by half an hour and thus realize a "half summer time" all year round. It is also conceivable that the season is concluded on the basis of the predetermined, seasonally different twilight cycles and that the approximate period for a summer time changeover is determined from this.

Substitute operation is terminated when the time is manually reset. Thus, after elimination of the fault, the normal operation can be continued.

Redundancy: The real-time clock as well as the microprocessor with its associated components can, for example, also be present twice as a functional unit. In this case, the two separate functional units A and B work in parallel, whereby normally the function of A is realized. If the functional unit A now has a malfunction, its function is taken over by B. This design feature of the redundancy has long been known and corresponds to the prior art.

Programming the time and data transfer:

The transmission of the parameters necessary for commissioning and operation can be carried out in a variety of ways, e.g. via serial interface, USB interface or other wired computer interfaces.

When using the reference clock in the network, for the dimming of area lighting systems, however, the parameter data are preferably transmitted via the common 230 V power supply network. As a simple method, which is also capable of obstructing obstacles such as To overcome electromagnetic or electronic switches, it is possible to perform the transmission of information as a rhythmic switching on and off of the supply voltage.

For safety reasons, this data transmission should preferably be carried out in bright daylight in order to avoid irritation of the road users.

The coding of the information is preferably carried out by the short-term switching on / off of the 230 V AC power supply. For this purpose, the time length of the ON and OFF times, as well as the pauses between the individual bit and the characters are defined in time. For example, the known ASCII code with corresponding short-long changes can be used to define the individual characters.

However, in order to reduce the number of bits to be transmitted, a special code is preferably used according to the invention. This code for the input of the dimming times preferably consists of four Ausschaltfolgen with different lengths of time. For example, long, long, short, long.

If this string is received by the microcomputer of the system, two more turn-off sequences are expected, the duration of which is measured in each case. To avoid unnecessarily long programming times, every second is interpreted by the system as quarter of an hour.

To simplify the input, the dimming times are viewed from midnight. The first transmitted time information (start of dimming) is the time in quarter hours before midnight, the second transmitted time information (end of dimming) is the time in quarter hours after midnight.

Entering Long, Long, Short, Long, 8 Seconds, 20 Seconds Means, for example, that the dimming should start at 22:00 and end at 5:00.

The data transmissions are checked by the device according to the invention for plausibility. Only meaningful inputs are accepted as changes. This prevents unwanted changes due to random switching sequences.

If the device for automatic dimming is integrated into a luminaire, another method for transmitting the configuration data offers itself:
The data is transmitted by means of a coded light signal, eg infrared light. It is thus possible to change configuration changes, such as the dimming times, from the ground without tools through the transparent luminaire cover. Change requests eg from local residents can be met individually without much effort.

To check the configurations, the operating states and as acknowledgment information for a successful reprogramming, it makes sense to provide a corresponding display option. Since this system saves costs by saving energy, this display should also cause the least possible additional costs. Therefore, the use of a simple light-emitting diode is proposed here. By rhythmically blinking in a predefined manner, all configurations and operating states can be displayed.

In the basic state, after switching on, for example, the mode becomes the dimming time 1 and the dimming time 2 displayed, similar to when entering the configuration.

The above example with the dimming times is displayed as follows:
Long, long, short, long, break, 8th short impulses, break, 20 short pulses.

This means: mode one, 8x15 minutes before midnight (10:00 pm) dimming start, 20x15 minutes after midnight (5:00 am) dimming end.

To provide other information, such as Time, date, reference time can be indicated, which can be initiated by previous initiation by an appropriate code.

Application Example 1,

Dimming street lighting and other surface lighting systems:

The inventive function of the reference clock can be integrated into various applications. As an inventive example of application, an autonomously operating switching device for surface lighting systems will be described below.

The device described, which includes a reference clock according to the invention, serves to dimming street lights preferably at predefined night time for energy saving, or turn off. As already stated, it is necessary for acceptance and for reasons of traffic safety that a simultaneous switching is ensured with all lamps as precise as possible matching switching times. Furthermore, for reasons of traffic safety, dimming may only be carried out within the time limits provided for this purpose.

To realize this function, a programmable switching device powered by the 230 V supply network of luminaires is installed in each luminaire.

This device includes at least one reference clock according to the invention, the required to operate the reference clock 230 V power supply with buffering and at least one preferably electronic relay. The buffering of the power supply is required to maintain the power supply of the reference clock during the day phase, ie the time in which the lights are normally switched off by switching off the 230 V mains.

These may preferably be chemical batteries or high-capacitance capacitors.

The function according to the invention is, as already mentioned, implemented by the reference clock with integrated real-time clock and a microcomputer with the associated components and a computer program. At least the following components are present:

A preferably commercially available IC, which includes the function of the real-time clock and the clock generator and a commercially available microcomputer and a built-in microcomputer and / or realized as a separate programmable read only memory and a photosensor for detecting the daylight and / or a connection realized in other ways an external photosensor, for the detection of daylight. These aforementioned components together with the computer program, by which the functions are realized, the reference clock according to the invention.

The connection to the said external photosensor is preferably carried out by the detection of the on and off times required for the operation of the luminaires 230 V AC supply network.

In addition, a 230 V power supply, which is preferably buffered by a capacitor or rechargeable battery, or a power supply which is used by chemical batteries to supply the aforementioned components is required to operate the reference watch. The buffering of the 230 V power supply must be designed so that an operation of at least 24 hours can be realized.

So that the lamps can be switched or dimmed at the intended times, at least one of the reference clock, preferably a semiconductor relay or a thyristor or transistor, is present.

The previously known switching devices with similar application goals, have no way to realize seasonal corrections of the switching behavior. Due to the internal calendar of the reference clock according to the invention, however, it is possible to clearly definable calendar data or the corresponding seasons, different switching behavior and thereby realize precise and explicitly programmable in advance dimming times.

The aforementioned components are installed in a housing made of metal or plastic and are hermetically sealed in this preferably by insulating potting compounds.

The shape of this housing is preferably designed as a round or square tube. These housings consist of previously known methods either from pipe sections or prefabricated fittings. The potting compounds preferably consist of two-component resins, two-component elastomers, two-component foams or two-component silicone compositions. Optionally heat-crosslinkable or otherwise crosslinkable potting compounds can be used. Both the design of the housing, as well as the hermetic encapsulation of the electronics corresponds to the prior art.

The electrical connection is made either by insulated wires, which protrude from the potting compound, or from one or more terminal strip / s for external wiring, which protrude from the potting compound.

The device according to the invention with the reference clock and the switching components can be mounted both in the luminaire and in the base of the luminaire pole in the area of the fuse and terminal box. Here, the device according to the invention is protected by the hermetic sealing of the components against harmful environmental influences such as moisture.

• - Das Modul ist für Wartungs- und Installationsarbeiten ohne Hilfsmittel wie Leitern und Hubsteiger zugänglich
• - Das gleiche Modul ist für unterschiedliche Leuchtentypen verwendbar
• - Anzeigeelemente für den Systemzustand sind ohne Hilfsmittel wie z.B. Leitern oder Hubsteiger zugänglich

This type of mounting in the foot of the luminaire pole has the following advantages:

• - The module is accessible for maintenance and installation work without tools such as ladders and lifting platforms
• - The same module can be used for different types of luminaires
• - System state indicators are accessible without tools such as ladders or elevators

Application Example 2,
as a system clock in control systems and regulations that operate independently in open-air areas and rely on an independent, long-term stable time.

It is conceivable to use this system for the tracking of real-time clocks in traffic control systems or other controls that are used independently in the open area and are dependent on a long-term stable time. These clocks are then particularly reliable due to the independence of external time signals.

LIST OF REFERENCE NUMBERS

1

Increasing Deviation of the Real Time Clock (RTC) As Time Increases

2

Decreasing deviation of the statistical average with increasing number of measured twilight cycles

3

Sum of the deviations from 1 and 2

4

Optimal time to create the reference

5

Maximum deviation over the entire lifetime, using the statistical mean value without additional optimizations

6

Maximum fluctuation range, using the statistical mean value without additional optimizations

7

Curve of the measured time by the middle of the time of dawn and dusk is plotted

8th

Curve the value of 7 to the correction value off 1 corrected

9

Arithmetic mean of 8, calculated from the first value

Claims (6)

Device for realizing a long-term stable reference clock, which automatically adjusts itself, the earth's rotation and the daily twilight cycles are used as a reference time and this consists of a microcomputer or a hardwired or programmable digital logic and a real-time clock including clock generator, which at initial startup with current time and current date, characterized in that a) from the determination of the dawn, the dusk or the times of dawn and dusk in conjunction with the time of the real time clock, a statistical average is formed, which, after the system sufficiently long in operation is stored as a reference value once and permanently; (b) a comparison is made between the reference value and the current statistical mean of the twilight cycles from the date on which the reference value was established; c) this comparison is used to regularly update the real-time clock. Device according to Claim 1 , characterized in that the determination of the reference value for tracking the real-time clock from the statistical average of the current and the previous morning and evening twilight cycles, and that this statistics is continued in such a way that for very large daily temporary deviations of the influence of this temporary value is minimized to the statistically continuous average by means of lesser or successively decreasing weighting and that then this correspondingly weighted average is used to correct the real time clock. Device according to Claim 1 , characterized in that the determination of the reference value for tracking the real-time clock from the statistical average of the current and the previous morning and evening twilight cycles, which is corrected by the time equation curve and that this reference value is compared regularly with the continued statistical average and a difference the real-time clock is corrected at a regular setting cycle by a fixed value independent of the difference whose sign corresponds to that of the determined difference. Device according to Claim 1 , characterized in that for programming the microcomputer and the data memory, and for presetting the time of the real time clock and for selecting the operating modes, a wired computer interface and / or a serial infrared data transmission interface is present and that an operating mode for switching between summer time and winter time and an operating mode for presetting the degree of longitude or its temporal effect is present. Device according to Claim 1 , characterized in that the power supply is a preferably powered by batteries or high-capacitive capacitors mains-powered 230 V power supply, which ensures the power supply for at least 24 hours and at least one controlled by the microcomputer or the digital logic switching or dimming, preferably semiconductor relay or thyristor or transistor is present. Device according to Claim 1 or 5 , characterized in that for programming the microcomputer and the data memory, as well as for presetting the time of the real time clock and for selecting the operating modes, a data interface is provided, in which the data transmission is effected by the rhythmic switching on and off of the 230 V AC supply network, wherein the defined length of these switch-on and switch-off is assigned to a logical 1 or 0 signal and the total time of the preferably 4 to 8-bit data packet is defined and this programming, or functional influence by the user preferably outside of the times takes place in which the or the semiconductor relay or thyristor or transistor are turned on.

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