Abstract: The electric wave clock is the emerging accurate time product, is directs the atomic vibration frequency to take the time datum. The design take the PIC16F873 monolithic integrated circuit as a core, by the receiving element, the central processing display unit and the power source unit three main part constitutions, uses in receiving the atomic transmitting station by the supper long wave intermittence launch signal, obtains a more accurate time, has the widespread application prospect in the military and the scientific experiment as well as the people daily life.
Key word: Electric wave clock; PIC monolithic integrated circuit; Atomic clock
The electric wave clock and watch is one kind of emerging time product, is draws out the atomic vibration frequency takes the time datum. The goal is causes the universal time synchronization to be unified. Is mainly to solve the present quartz clock’s and watch’s precision problem. Quartz clock and watch mechanical clock and watch already accurate many, but the difference in duration of sunshine still had one-and-a-half second second error. This kind of error regarding people’s daily life not tremendous influence and correction necessity, but regarding the military and the scientific experiment, is the major problem which must solve. In some important situations, the error between 0.01 second, the result will also lose the great distance.
The electric wave clock’s principle, is it has an atomic transmitting station, the routine launching signal, frequency every three millenniums only miss for one second, is accurate. The electric wave clock is the time product which makes by the atomic precision. The transmitting station sends out the signal is not toward the outside has sent unceasingly, but is the intervalic launch. Therefore the electric wave clock or the wave meter are receivers actually, receive atom transmitting station signal [4].
Regardless of electric wave clock, the wave meter, in fact is a receiver, its outward appearance and the quartz clock, the quartz table are the same, the structure with the quartz clock, the quartz table is also same, only increased a receiving device, the comparison to install and to revise the installment. Compared with installs and revises the installment to use in being punctual, electric wave clock can press the atomic vibration frequency code to make the comparison regularly, revises the accurate time, because just had this kind of comparison revision installment, the electric wave clock can achieve forever the accurate effect. Therefore, regardless of being the electric wave clock or the wave meter, they have the antenna.
1. based on PIC monolithic integrated circuit’s electric wave numerical code clock’s principle of work:
Electric wave clock, is also called the wireless control to count the clock (English name is: Radio controlled timepieces). The electric wave clock and watch takes a system’s technical principle is: First, carries on by the standard time time service center the standard time signal the code (commercial code to carry on encryption), the use low frequency (20KHz-80KHz) the carrier way sends the time signal by the radio long wave broadcasts. The electric wave clock and watch accepts this low frequency is radio when the code signal through the built-in miniature radio reception system, carries on by the special-purpose integrated chip when the code signal demodulation, again the control mechanism automatic control clock’s and watch’s time which supposes by the timing unit. Through this kind of technical process, causes all receive this standard time signal the clock and watch (or other timing unit) maintains with the standard time time service center standard time highly the synchronization, then complete electric wave clock and watch demonstration strict consistent time.
Time signal’s receiver (i.e. electric wave clock) the big structure is divided three parts: Receiving element, central processing display unit and power unit. Detailed divides mainly by the receiving antenna, the Pre-amplifier, the tuned amplifier, automatically increases the electric circuit, the filter, the demodulator, the square-wave former, the time information processor and the monitor is composed, its function principle is as follows: As receiver’s electric wave clock’s and watch’s receiving antenna from spatial induction receive by time service center launch real-time time signal, because the signal is weak, front end must pass through the amplifier, send the great talent output to deliver the tuned amplifier to carry on chooses the frequency to enlarge, then carries on the filter, carries on the reshaping after the profile former, after the filter, carries on the detection again harmonious, from the carrier the extraction time signal, namely a string orderly pulse, this pulse arrives at the received signal processor to carry on transformation processing again, after the time returns to original state, delivers the monitor to carry on the demonstration separately.
2. the main circuit explained:
2.1 electric wave accepting circuit
At present, the etalon time electric wave generally as the 20KHz-80KHz carrier way sends take the frequency the time signal by the radio long wave broadcasts. The electric wave signal’s receive chip completes by U4226B the IC, this chip external connection receiving coil, 2 40 KHz quartz oscillators and the corresponding resistance electric capacity and so on can complete to the electric wave receive and processing. U4226B the IC chip can receive from 40KHz to the 80KHz between electric wave signal, is only needs to match by the corresponding exterior part then. What here design is receives 40KHz the signal. After U4226B receive electric wave signal, output time encoding signal TCO (TIME CODE OUTPUT). The electric wave accepting circuit sees chart 2.1. At present what our country uses is 68.5KHz. The antenna receive effect and the electric wave intensity and the arrival direction have the inseparable relations. When the electric wave arrival direction and the antenna become vertical receives the effect to be remarkable. If the signal arrives from antenna’s both sides possibly is unable the correct received signal. This design uses receiving element and the display control unit separates the design, the two use the cable connection. Through observes LED then to understand the normal receive or not.
Figure 2.1 electric wave accepting circuit
2.2 received signal amplifying circuit
The electric wave accepting circuit outputs the TCO signal is 0V to the 5V signal impulse, to enable the signal impulse to have the good rise and the drop along, has used the triode amplifying circuit. The concrete electric circuit sees chart 2.2 to show. In the electric circuit the LED1 light emitter diode is the TCO signal monitoring device. Because the antenna receiving element and the expression treating plant is lays aside separately, between uses the cable connection. Because uses the electric cable to be able to introduce the noise, we use the electro-optic to transform PC1 isolate the accepting circuit and the processing electric circuit from the electricity. The triode Q3 base electrode meets has electric capacity C21 to use in filtering the noise, but the C21 capacity cannot be too big, will otherwise affect the received pulse signal the rise and the drop along characteristic.
Figure 2.2 received signal amplifying circuit
2.3 CLOCK clocks send inspire the electric circuit
When the electric wave signal not normal or the received signal is too weak causes the receive defeat, our electric wave clock still needed to continue to work, therefore needs to design the clock to send inspires the electric circuit. PIC16F873 used the high stability to send inspires the crystal. It sends inspires the frequency is 12.8MHz, PIC step execution time is the 4/12.8=0.3124 microsecond. When the electric wave signal can receive normally, clock’s precision with sends inspires the crystal precision to have nothing to do with. According to atomic clock’s standard time its precision is 1E-13, namely one year like is 31536000 seconds, the error is 317098 years only misses 1 second [7].
2.3 CLOCK sends inspires the circuit diagram
2.4 LCD control circuit and KEY key’s input circuit
The time expression and the hypothesis carry in the LCD display monitor. This design has used the SC1602BSLB liquid crystal display monitor. The data feeds output may use 4BITS or the 8BITS width. This design uses the 4BITS pattern. The controller PIC side uses RB port’s high 4 to take PIC and between the LCD display monitor’s data bus. RB port’s RB0 and RB1 take to the LCD pilot wire. Simultaneously RB2 to RB7 also as KEY key’s input port [5]. Its circuit design sees chart 2.4 to show. And RS is REGISTER SELECT, namely to order the register and data register’s cut signal. E is ENABLE SINAL, is the LCD display monitor enables the signal end. Also has V0 is CONTRAST the ADJ end, may adjust the LCD demonstration contrast gradient with it. To the post which does not use earths completely. Moreover the SC1602BSLB display monitor also has the back light to demonstrate, so long as adds on power source then [6] in a/K end.
Figure 2.4 control circuits and so on PIC and LCD, KEY key
2.5 LCD controls and output circuit
Uses the RA port and the RC port comes for the exterior electric circuit to carry on the actuation. The design has the demonstration in the electric circuit to demonstrate its movement condition with LED. Its circuit design audience shown in Figure 2.5. LED2 (RX) the use may also suppress PIC the use electric current size.
2.6 exterior installment control circuit
This design’s electric wave demonstrated that the clock is equipped with 4 kind of timed control functions. These 4 kind of timed control installment for independent control device. Figure 2.6 is one of them’s control device. Carries on the control by PIC16F873 counter output signal control triode Q5, Q6, Q7 and the Q8 collecting electrode fixed time to the RL1 relay. 4 control devices then establish the different time to carry on ON/OFF to 4 different installments to control [1][2].
Figure 2.5 LED control and output circuit diagram
Figure 2.6 exterior installment control circuit
2.6 exterior installment control circuit
2.7 power circuits
The power source circuit diagram sees chart 2.7 to show. The exchange AV voltage which outputs by the transformer is 12V. Through bridge-type rectified output its peak voltage 16.8V. Because loss output approximately about 16V. After the electric circuit, meets three end constant voltage converter
Outputs the stable 12V DC voltage. In the electric circuit used C28 to serially connect the use to the C32 5 electric capacities. When AV voltage stop has the short spare function. The capacity is 4.7UF, the pressure resistance is 2.5V. Will possibly cause the electric current to 5 series connection condenser charge to be oversized, in the electric circuit will also be equipped with limiting resistor R27 (200 ohms). Therefore the biggest charging current is 60mA, duration of charging association president some. The D2 establishment is to prevent AC to input time the stop the reverse current which from the electric capacity comes.
Figure 2.7 power source circuit diagram
3rd, electric wave numerical code demonstration clock complete circuit diagram
The overall system complete circuit diagram sees chart 3.1.
4. the electric wave demonstrates clock’s control processing software design
Overall system processing control software design flow like chart 4.1.
Figure 3.1 electric wave numerical code demonstration clock circuit diagram
Figure 4.1 electric wave clock’s software design flow chart
5. The signal encoding introduced:
Various countries’ electric wave clock and watch technology principle is the same, but each major country about standard time signal through agreement (i.e. code system) actually different. For example: US, when code code number WWVB, the frequency is 60 KHz; Germany, when code code number DCF, the frequency is 77.5 KHz; Britain, when the code code number is MSF, the frequency is 60 KHz; Japanese two Taiwan, when the code code number is JJY, the frequency respectively is 40 KHz and 60 KHz; China, when the code code number is BPC, the frequency is 68.5KHz. this enables a national the electric wave clock and watch in another country normal received signal and calibration time [4]. Moreover, different national and the local radio traffic’s electric wave environment is different, some national wireless communication disturbance is small, like Germany. But Chinese, US’s radio environment is bad, this also causes the electric wave clock and watch is a country product. At present entire service pattern’s electric wave clock and watch product has not entered the market. Line SOC develops platform 499 Yuan S3C44B0 ARM7 development board 378 Yuan S3C2410 ARM9 development board 780 Yuan AT91SAM
6. Conclusion:
This system take the PIC16F873 monolithic integrated circuit as the core part, including receiving element, central processing display unit and power unit. Using the software programming, realized the supper long wave receive through the keyboard control and the liquid crystal display to analyze and to process the function, did not have when the signal the clock function, the LCD control and the KEY key control function as well as after revising the exact time demonstration function, achieved the hardware circuit simply as far as possible stable, reduced the electromagnetic interference and other environment disturbance.
This technology is mainly by the very economical cost, the gain standard time signal. But the standard time is the modern society important technology support, may form the application standard time industrial - - time technological industry which in the electric wave clock and watch product foundation provides. May very economically and gains the high accuracy standard time conveniently through this technical people, satisfies the people to the standard time demand. Besides applies in the daily life, the electric wave clock and watch technology may also widely apply in domains and so on military, scientific research, communication, transportation, posts and telecommunications, computer, industrial control, social life.
7. Reference:
1. The PIC monolithic integrated circuit crosses the threshold with actual combat Zhang Mingfeng the Beijing University of Aeronautics and Astronautics Publishing house 2004
2. PIC16F87x Data Sheet http://www.microchip.com/
3. PIC software and hardware system design - based on PIC16F87X series Liu Du kind electronics industry publishing house 2005
4. Electric wave clock introduction http://www.icsky.cn
5. PIC monolithic integrated circuit principle http://www.teachersong.com/pic
6. The PIC series monolithic integrated circuit connection technology and the application system design Wang Youxu Xu Jieli to pull the Beijing University of Aeronautics and Astronautics Publishing house 2000
7. The clock actuates the principle and realizes Xing the group Corwin day river micro computer information in 2005 the 21 volume 7th issue
