JPS59126963A - Frequency discriminating method - Google Patents

Abstract

PURPOSE:To discriminate automatically and easily two frequencies which are known as a power source frequency or the like, by comparing the period of an input signal with a reference time to discriminate its length. CONSTITUTION:The voltage from a commercial power source 6 passes through a transformer 7 and a full-wave rectifying circuit and is smoothed by a capacitor C1, and a constant voltage power supply circuit 8 supplies an operating power Vcc to a CPU5. A diode D5 generates a negative half-wave rectified waveform from the voltage of the secondary winding of the transformer on a basis of the power source voltage Vcc and inputs it to a clock input terminal CLK. meanwhile, the CPU5 detects the time when the level of the clock input CLK is switched, and the CPU5 discriminates the level of the clock input CLK when a reference time, which is set to be shorter that the period of 50Hz and longer than that of 60Hz, elapses after this switching time. The frequency is discriminated in accordance with this level, and processings corresponding to each power source frequency such as setting a frequency division ratio are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a frequency discrimination method that can be suitably applied to, for example, electronic equipment that uses a commercial power frequency.

(Background of the Invention) For example, an electronic timer measures time using a power supply frequency. This is because commercial power supplies have high frequency accuracy, making it possible to measure time with high precision, and commercial power supplies have a much lower frequency than ordinary crystal oscillators or oscillators that use C, R, L, etc. as time constant elements. Therefore, the frequency division ratio can be small, so the frequency division circuit can be simplified, and in the case of a soft timer using a microprocessor or the like, the number of processing steps and memory capacity used can be reduced.

By the way, two types of commercial power supply frequencies are used in Japan depending on the area: 501-1z and 601-1z. Therefore, it is necessary to change the input wiring, switches, and other elements depending on whether the timer or the like that operates using the above-mentioned power supply frequency is used in a 50 H2 area or a 60 Hz area. Due to this problem, the operator has to perform the switching work depending on the power supply frequency, and sometimes forgets to switch.
Mistakes in the selection of circuit constants, etc. may occur, leading to a significant deviation in the operating reference frequency.

(Objective of the Invention) The present invention has been made in view of the above-mentioned problems in the conventional type, and provides a method for automatically and easily distinguishing between two frequencies whose frequencies are known in advance, such as the power supply frequency. The purpose is to Furthermore, by applying this method to electronic equipment that uses a power supply frequency, the present invention aims to eliminate the need for change work when changing the power supply frequency.

(Structure and effect of the invention) In order to achieve the above object, the present invention compares the period of the input signal with a reference time and determines the length of the period, thereby determining whether the frequency of the incoming horn signal is one of the pre-known frequencies. It is characterized by determining whether

According to the present invention, since the frequency of an input signal, for example, a commercial power supply, can be automatically determined, especially when applied to an electronic device that operates using a commercial power supply frequency, wiring connections, switches, etc. can be changed depending on the power supply frequency. This saves time and effort, and prevents mistakes in setting the frequencies used by devices. Also, the reference time is, for example, 50H of commercial power supply.
When distinguishing between z and 60Hz, it is more than 1/60 second or 1
Simplification of the circuit configuration of equipment to which the present invention is applied J5, as it only needs to be set within a relatively wide range of less than 150 seconds.
You can also try to reduce the loss by 1~. Furthermore, in electronic equipment equipped with a CPU such as a microprocessor, the method of the present invention can be easily implemented by a program, and the accuracy requirements for the CPU driving clock are lenient, so it is also possible to It is possible to simplify the configuration and reduce costs. In this case, since dedicated hardware for determining the power frequency is not required, only one power frequency input terminal is required for frequency determination and utilization.

(Explanation of Examples) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the appearance of an electronic digital timer to which the present invention is applied. In the figure, 1 is a digital switch for setting a time limit, 2 is a display element for showing the elapsed time, and 3 is a display element for indicating the elapsed time.
is the case.

FIG. 2 shows the electrical circuit of the timer of FIG. This timer is equipped with a CI (CI) U 5 and measures time by counting the frequency of a commercial power supply 6 as a clock input. By incorporating the method of the present invention as a program in the CPU 5, the above-described timer can be used as part of the initialization operation of this timer. The power supply frequency is determined based on the clock input, and the conversion coefficient between the number of input clocks and the elapsed time is automatically switched.

In Figure 2, commercial electricity? I! The voltage from i6 is power supply 1
~ Descended by Lance 7, Dio-1~D+.

1) It is rectified by a full-wave rectifier circuit consisting of 2, D3, and Da, smoothed by a capacitor CI, and supplied to the constant voltage power supply circuit 8. This constant voltage power supply circuit 8 is connected to the CPU 5
An operating power supply Vcc is applied to.

The 7 nodes of the diode D5 are connected to one end of the secondary windings of the power supply 1 to the lance 7, and the cathode is pulled up to the constant voltage power supply Vcc through the resistor R1, and is connected to the clock input of the CPU 5 through the resistor R2. Connected to terminal CLK. Therefore, while the anode side of the diode D5 is higher than the power supply voltage Vcc, the diode D5 is in the cathode side voltage range Vcc, and when the anode side voltage becomes lower than Vcc, this anode side voltage appears on the cathode side. That is, the diode D5 generates at its cathode a negative half-wave rectified waveform based on the voltage Vcc from the power transformer secondary winding voltage. Capacitor C2 is the clock input terminal CL of CPU5.
Protect K from surge voltage.

FIG. 3 shows the voltage waveform applied to the clock input terminal CLK of CPtJ5. The dotted line is the threshold voltage of the input terminal CLK, which is normally approximately 1/2 vcc.

In the CPU 5, when this threshold voltage is exceeded, the level is high, and when it is below the threshold voltage, it is low, and the level is low.
” is judged as.

Next, referring to FIGS. 3 and 4, the frequency discrimination operation performed by the CPU 5 in FIG. 2 will be explained.

After the power is turned on, it is determined whether or not the level of the clock input to the input terminal CLK is set to 'PATODO'. If the level is "H", it waits until it becomes "L" level, and if it is "L" level, it waits until it becomes "'H" level in the next step.

In other words, here the clock input is from 'L' level to '
l- (point A in Figure 3 where the light switches to "level") is detected.Next, wait until a reference time (for example, 18 m5) has elapsed, which is shorter than the cycle of 50H2 and shorter than the cycle of 60H2. Determine the level of the clock CLK after the lapse of time (point B in Figure 3).As can be seen from Figure 3, if this level is 'H', the power supply frequency is 6.
01-IZ, and if it is "L", it is 501-1Z, so processing is performed according to each power supply frequency, such as setting the clock number-elapsed time conversion coefficient and frequency division ratio.

Note that the reference time of the upper j can be obtained by multiplying by 31 the CPU drive clocks generated using the crystal oscillator XTAL. Furthermore, since this reference time can be set within a relatively wide range as described above, the present invention can also be applied to the case where a drive clock is generated using a CR with low frequency accuracy instead of a crystal oscillator.

Note that, of course, according to the present invention, two types of frequencies other than 50H2 and 60Hz can be discriminated. Also, the ratio of the periods T1 and T2 of the two frequencies is T+/d2
Even in the case of 〉2, T1>t+>-r+/2 and 2
Two reference times j+ and j2 are set such that T2>j2>72, and whether or not the input instantaneous level is at the reference time t1 is determined to be the period T1, and whether or not the period is T2 at the reference time t2 is determined. All you have to do is determine. moreover,
By combining two frequency discriminations, 3
Of course, it is possible to discriminate between two or more frequencies.

[Brief explanation of the drawing]

FIG. 1 is an external view of an electronic digital timer to which the present invention is applied, FIG. 2 is an electric circuit diagram showing the general configuration of the timer in FIG. 1, and FIG. Figure 4 shows the voltage waveform diagram shown in Figure 2.
This is a flowchart for explaining the operation of the PU. 5...CI) U, 6...Commercial power supply,
7...Power transformer, CLK...Tarlock input terminal. Patent Applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Tatsuo Ito Agent Patent Attorney Tetsuya Ito Drawing No. 1 (No change in content) Figure 2 Figure 4 Procedures Amendment Written March 11, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi yQ 1. Indication of the case 1982 Patent Application No. 1738 2. Name of the invention Frequency determination method 3.7 Relationship with the case of the person acting as the municipal judge Patent applicant address 10 Hanazono Tsuchido-cho, Ukyo-ku, Kyoto City Address Name <2
94> Representative of Tateishi Electric Co., Ltd. Tate 5 ￥ Yu 4, Daitanukito 〒105 Address 2-8-1-6 Toranomon, Minato-ku, Tokyo, subject of amendment 1 Figure J 7,? IIi Positive Contents As per attached

Claims (1)

[Claims] 1. A frequency determination method for automatically determining which of two previously known frequencies the frequency of an input signal is, the instantaneous value of the input signal being set to a predetermined threshold value. When the instantaneous input signal level changes from a high level to a low level or from a low level to a high level, a predetermined period that is longer than one period and shorter than the other of the two frequencies is detected. A frequency discrimination method, characterized in that the frequency is discriminated based on the height of the instantaneous level of the input signal when a reference time has elapsed. 2. The input signals have frequencies of 50H2 and 6, respectively.
The frequency discrimination method according to claim 1, which is a 0H2 commercial power source. 3. In an electronic device that includes a CPU and uses the frequency of a commercial power source, the claim 1 is based on the commercial power frequency supplied to one input terminal of the CPU in order to utilize the power frequency. How to determine power frequency.