JP2557490B2 - Pulse detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention detects a pulse of a contact pulse that is output for each unit usage amount of electricity, gas, water, etc., and remotely detects the pulse of a device. Regarding the circuit.

(Prior Art) Conventionally, there is one shown in FIG. 10 as a pulse detection circuit used in this type of remote meter-reading device. In this device, a voltage is applied to a contact 1 that generates a pulse output for each unit use by a resistor 2 of a current control detection unit.
When is open, “H” level is input to the detection unit 4 through the filter 3, and when the contact 1 is closed, a current flows through the contact 1 through the resistor 2 to the detection unit 4 through the filter 3. “L” level is input. In this case, the detection unit 4 detects the state of the contact 1 at the "H" or "L" level, so that pulse counting can be easily performed by an IC counter or the like. However, when the contact 1 is closed, the current always flows through the resistor 2, so that the current consumption increases. Therefore, it is conceivable to increase the value of the resistor 2 in order to reduce the current consumption, but if the resistance value is increased, the contact current decreases, which causes a problem that the S / N against noise decreases.

Next, FIG. 11 shows another conventional example. In this case, a voltage is applied to the contact 1 through the resistor 2 of the current control detection unit, but the return path of the current is opened and closed by the opening / closing unit 5, so the contact current flows only when the opening / closing unit 5 is closed. Then, when capturing the contact state, the opening / closing section 5 is closed, and when the contact 1 is open, the “H” level is sampled, and when the contact 1 is closed, the “L” level is sampled through the filter 3. Given to part 6. In the sampling unit 6, after closing the opening / closing unit 5, it takes a sufficient time for the signal to be added to the filter 3 and the contact state via the filter 3 is input. Detect changes,
It is designed to detect pulses. In this case, the contact current flows only during sampling, which has an effect of reducing current consumption, but the sampling interval must be shorter than the minimum pulse width of the detected pulse. For this reason, when the pulse width range to be detected is wide, the number of times the contact current is flown by sampling in a short cycle even for a pulse having a long closing time, resulting in a disadvantage that wasteful current consumption also increases.

Next, FIG. 12 shows a different conventional example. In this device, the contact 1 and the detector 4 are insulated by a photocoupler 7. In this case, the contact 1 is connected to the LE of the photocoupler 7 from the resistor 8 having a high resistance value in order to reduce the contact current.
A voltage is applied through D and the current limiting resistor 9. Since the current value needs to be increased to drive the photocoupler 7, the capacitor 10 is charged from the power supply 11 via the resistor 8 when the contact 1 is opened, and the moment the contact 1 is closed. The charge of the capacitor 10 is LE of the photocoupler 7.
A current flows through the contact point 1 through D and the resistor 9, and the fact that the current flows is detected by the phototransistor side of the photocoupler 7 and then detected by the detection section 4 through the filter 3. In this case, the contact current is reduced by the high resistance 8 even when the contact 1 is closed, and the electric charge stored in the capacitor 10 is used to detect that the contact is closed and detected with a large current value. Therefore, by reducing the discharge current limiting resistor 9, S /
Although a decrease in N can be prevented, in order to obtain a signal that passes through the filter 3, it is necessary to increase the capacitance of the capacitor 10 and increase the discharge time determined by the values of the discharge current limiting resistor 9 and the capacitor 10. However, if the value of the capacitor 10 is increased, the time for charging the capacitor 10 through the higher resistance 8 than the power supply 11 becomes longer while the contact 1 is open, and as the value of the resistance 8 is increased to reduce the current, the followability becomes worse. There was a problem that

(Problems to be solved by the invention) In a device for remote meter reading of the amount of electricity, gas, water, etc. used, the IC counter and CPU are often used to store the measured values from the IC memory, and there is a power failure. At times, there is a strong demand for not only holding the measured value but also executing the measuring operation. Therefore, in recent years, means for compensating for power failure by a battery and driving the device itself by a battery have been adopted. In this case, the current consumption of the circuit is being reduced by using a low current consumption C-MOS IC, etc., but on the other hand, the improvement of S / N for noise resistance and the difference of the measuring instrument transmission method are mentioned. The current consumption of the pulse detection circuit occupies a large proportion of the total current consumption in order to widely deal with the difference in pulse width due to the difference in the pulse width. It is a big obstacle.

In order to solve the above problems, it is an object of the present invention to provide a pulse detection circuit which is excellent in noise resistance and consumes a very small current, but is capable of detecting a pulse having a wide pulse width.

[Structure of the Invention] (Means for Solving Problems) The present invention provides a current control detection unit that supplies current to a contact in order to detect the state of the contact and detects whether or not the current flows. , A filter that removes the influence of chattering and external noise of the contact from the current detection result signal, and the operation of the current control detector when the operation is started with the contact closed and current flows to the contact. A timer that outputs a signal for a finite time longer than when the signal passes through the filter and a current control detector that prevents current from flowing to the contact when it is detected that current has flowed to the contact when the contact is closed. When the timer is activated and the signal output after a certain period of time has passed, the current control detector reverses the state in which current flows to the contact, and when the output of the finite time from the timer ends. If it is detected that a current has flowed to the contact, the current control detection unit disables the current flow to the contact.If no current is detected to the contact, the current control detection unit detects the current It comprises a flip-flop that outputs a signal that causes the current to flow, and a detector that counts the number of times the contacts are opened and closed by the current detection signal from the current control detector or the state signal of the flip-flop.

(Function) When the contact is in the open state, the current control detector is in a state in which the current can flow, but since the contact is open, the current is not consumed. When the contact changes from open to closed, a current that allows sufficient S / N for noise resistance to flow from the current control detector flows through the contact.
Normally, a current value of about 10mA to 20mA is used, but it may be arbitrarily determined depending on the purpose of use and environment of use. When a current flows through the contact, it is detected by the current control detection unit, and when the detection signal passes through the filter, the flip-flop is inverted, so that the current supply from the current control detection unit is stopped,
It consumes no current. Here, the current is consumed only for the minimum time necessary for the signal that detects that the current has flowed to pass through the filter, and there is no waste of current. Further, the chattering of the contact occurs when the contact is switched, and the filter can be used even if the chattering cannot be removed as long as it can remove the noise applied except when the contact is switched. It is also possible to reduce the current consumption by shortening the time for passing through the filter. Because the current supply is cut off if the moment when the contact is switched from open to closed can be detected, the chattering thereafter does not affect the operation. Also, the timer output can be set longer than the normal chattering time, because it can be set shorter than the minimum time from when the contact opens until the contact closes next. Chattering when the contact switches from open to closed has already been completed at the time of reversal. Conversely, if there is chattering when the contact switches from closed to open when the timer operates and flips the flip-flop, even if it is determined that the contact is closed during chattering, the contact will close. The contact open can be detected at the next timer operating time which is set to be shorter than the minimum time from when the contact opens to the next, and conversely the contact closes even if it is determined that the contact is open during chattering. It is in the process of switching from to open, and there is no problem to judge it as open. However, switching from open to closed may be detected by chattering immediately after the contact is determined to be open.Therefore, counting the output of the filter directly with a counter, etc. may cause erroneous counting. It is necessary to provide a filter that can remove chattering in the previous stage. However, such a filter is irrelevant to the contact current and can reduce current consumption.

The timer is started when the switch from open to closed is detected, and the flip-flop is inverted when the time set to be shorter than the minimum time from when the contact is opened to when the contact is closed next has elapsed. Thus, the current can be supplied from the current control detector to the contacts. If the contact is open, the flip-flop is latched in this state because the current detection signal cannot be obtained. If the contact is closed here, the current detection signal is obtained, so that both the current detection signal and the timer output are input to the flip-flop. When both the current detection signal and the timer output are input, the flip-flop outputs a signal that causes the current control detection unit to supply current, and the current flows through the contact point and the current control detection unit passes through the filter to pass the current. A detection signal is obtained. Then, when the timer output ends, only the current detection signal is input to the flip-flop. Therefore, the flip-flop inverts the output, the current control detector stops the current supply, and the timer is restarted. Therefore, it is only the output time of the timer that supplies current to the contact when the contact remains closed.
Since this output time only requires the minimum time necessary for the current detection signal to pass through the filter, it can be made sufficiently smaller than the time when the contacts are closed. Electricity in general
The contact pulse output from measuring instruments such as gas and water is such that the contact is closed for half of the pulse period and the contact is closed for a certain period of time. Since it takes about 1 pulse for several minutes, it is possible to take a sufficiently long time until it is detected that the contact is once closed and then opened. Therefore, even if the contact is kept closed, the output time of the timer is sufficiently smaller than the cycle in which the timer operates, and even if current flows to the contact during the output time of the timer, the total current consumption is Small enough.

By repeating the above operation, the output obtained from the filter is the same pulse signal as the number of times of contact opening and closing in the contact pulse transmitting section. Here, the pulse signal obtained from the filter changes when the contact is switched from open to closed, with the pulse signal changing with a delay of the time for passing through the filter.
When the contact is switched from closed to open, the maximum operation time of the timer is delayed, so the pulse signal waveform obtained from the filter does not match the pulse waveform transmitted from the contact. However, since the purpose of detecting pulses of measuring instruments such as electricity, gas, and water is to count the number of transmitted pulses, there is no problem.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration of the embodiment. In this case, the contact 21 is connected to the current control detector 23 controlled by the output of the flip-flop 22. And the current control detector
The current detection signal at 23 is applied to the reset input terminal ▲ ▼ of the flip-flop 22 via the filter 24. on the other hand,
The output terminal Q of the flip-flop 2 is connected to the current control detector 23 and the trigger signal terminal TRG of the timer A25,
Is connected to the set input terminal ▲ ▼ of the flip-flop 22. Then, the opening / closing operation of the contact 21 is counted by the detection unit 26 as an output signal of the filter 24.

FIG. 2 is an input / output logic table of the flip-flop 22 used in this embodiment. The set input (▲ ▼ input) and the reset input (▲ ▼ input) are negative logic and the output (Q output) is positive logic. is there. However, when the current detection signal is detected by the current control detector 23 and the output signal of the timer 25 is not input, the current supply is stopped and the current supply is stopped. It does not matter if the output is not changed in the state where both are not input.

FIG. 3 (a) shows a concrete example of the timer 25 in this embodiment, and FIG. 3 (b) shows its operation timing. In this case, when the trigger signal TRG is input (change from “H” to “L” state in FIG. 3 (b)), the output signal ▲ ▼ (“L” state in FIG. 3 (b)) after a certain period of time. ).

Here, the fixed time period in which the timer 25 operates is a time period set to be shorter than the minimum time period from when the contact is closed to when the contact is closed next. In the case of FIG. 3, it is determined by the reference clock CK and the number n of flip-flop stages. Further, the output time of the timer 25 is longer than the time required for the signal whose current is detected by the current control detection unit 23 to pass through the filter 24, and the passing time of the filter 24 from the minimum contact closing time of the contact pulse to be detected. The time is set to be shorter than the time obtained by subtracting, and is one cycle time of the reference clock in FIG.

FIG. 4 shows a concrete example of the current control detection unit 23 in the same embodiment. In this case, current is supplied from the output Q of the flip-flop 22 to the contact via the resistor 231 and the contact of the resistor 231
It detects the voltage level on the 21st side and knows whether or not a current flows.

Next, the operation of the embodiment thus configured will be described.
In FIG. 5, when the contact 21 is open, the current control detector
Since no current is detected at 23, "H" is input to the reset input ▲ ▼ of the flip-flop 22 and the output Q of the flip-flop 22 is also "H". When the contact 21 is closed, a current flows from the current control detector 23 to the contact 21, and when the current detection signal passes through the filter 24, the flip-flop
22 reset input ▲ ▼ becomes "L" and output Q becomes "L"
Therefore, the current control detection unit 23 stops the current supply to the contact 21, the operation of the timer 25 is started, and the timer
“L” from 25 to the set input ▲ ▼ of flip-flop 22
Is output and the output Q of the flip-flop 22 becomes "H".
If the contact is open at this point, the current detection signal from the current control detector 23 becomes "H", so that the reset input ▲ ▼ of the flip-flop 22 becomes "H" after the passage time of the filter 24 and the output Q becomes Return to "H". As a result, the detection unit
At 26, it is detected that the reset signal ▲ ▼ of the flip-flop 22 is switched to "L", and the count value is updated.

By the way, when counting contact pulses with a minimum period of 10 seconds and the same opening and closing times, noise and chattering can be eliminated by 10%.
When a ms filter is required, the conventional one described in FIG. 10 has the following average consumption current when the current flowing through the contact is 10 mA.

10 [mA] × 5 [sec] / 10 [sec] = 5 [mA] In contrast, in the case of the present invention described in FIG. 1, the same current and the same filter time are used, and the operating time of the timer 25 is When the output time is 4 seconds and the output time is 20 ms, the average current consumption is 10 [mA] x (0.01 + 0.02) [seconds] / 10 [seconds] = 0.03 [m
A]. That is, under such conditions, as shown in FIG. 5, when the contact 21 changes from open to closed, the current control detection unit
When the current of 10mA flows from the contact 23 to the contact 21 for 10ms, the current detection signal passes through the filter 24, the reset input CL of the flip-flop 22 becomes "L" and the output Q becomes "L", the current control detector 23 stops supplying current to the contact 21. From this state, the operation of the timer 25 is started, and when a fixed time (4 seconds) has elapsed, the set input PR of the flip-flop 22 becomes "L" and the output Q becomes "H". In this case, since the contact 21 remains closed at this point, the set input PR of the flip-flop 22 is "L" and the output Q is "H" due to the timer output, and the current control is performed during the timer time of 20 ms. Detection unit 23 to contact 21
Current flows through. Then, when the timer time expires, the flip-flop is activated by the current detection signal passing through the filter 24.
When the reset input CL of 22 becomes “L” and the output Q becomes “L”, the current control detection unit 23 stops the current supply to the contact 21,
Restart timer 25. Then, again, a certain time (4
Seconds), set input PR of flip-flop 22
Becomes "L" and the output Q becomes "H", but since the contact 21 is opened at this point, the same operation as described above is executed thereafter.

Therefore, in this way, it is apparent from the above calculation of the average current consumption that the current consumption is 1/167 lower than that of the conventional one.

Next, FIG. 6 shows the case where the contact signal is short like noise. In this case, since the current detection signal does not pass through the filter 24, the flip-flop 22 does not perform the inverting operation and the count in the detection unit 26 does not change.

Next, FIG. 7 shows a case where the contact 21 remains closed at the output of the timer 25. In this case, since the set input ▲ ▼ of the flip-flop 22 becomes “L” by the output from the timer 25 and the contact 21 is closed, the current detection signal from the current limit detection unit 23 remains “L” and the flip-flop 22 Since the reset input ▲ ▼ of is also L, the timer 25
The output Q of the flip-flop 22 returns to "L" at the time when the output of is finished. Further, since the reset input ▲ ▼ of the flip-flop 22 does not change, the detection unit 26 does not count.

 Next, another embodiment of the present invention will be described with reference to FIG.

FIG. 8 shows a circuit configuration of the other embodiment. In this case, FIG. 8 uses a timer 27 that is capable of outputting periodically after being once triggered until it is reset. Here, the trigger input TRG of the timer 27 can be obtained from the output of the filter 24, but such a timer 27 may be triggered from the output of the flip-flop 22.

FIG. 9 (a) is a concrete example of the timer 27 in the other embodiment, and FIG. 9 (b) is an operation timing chart thereof. In this case, the trigger signal TRG is input (9th (b)
When in the “L” state in the figure), the output signal is
▼ is output for a limited time ("L" state in Fig. 9 (b))
Is trying to occur.

Others are the same as those in FIG. 1, and the same portions will be denoted by the same reference numerals and detailed description will be given.

Even in this case, the same effect as that of the above-described embodiment can be expected.

As described above, according to the present invention, when the contact is in the open state, the current can be supplied to the contact, but the contact is closed for only the time required for removing noise and chattering. When it detects that a current has flown, it stops the current supply to the contact and opens the filter at a cycle set as long as possible within a range shorter than the minimum opening / closing cycle of the contact to be detected until the contact opens. It is configured so that the number of times the contacts are opened and closed can be detected by passing an electric current for the shortest possible time.

 As a result, the following effects can be expected.

(1) The current flows through the contacts by passing through a filter for removing noise at a predetermined cycle when the contacts switch from open to closed and when the contacts remain closed. The current consumption can be very small, since only the time required for

(2) Since the current can be reduced, power outage compensation and battery capacity for battery drive can be reduced, and the device can be downsized and the price can be reduced.

(3) Since the current consumption is reduced, it is possible to reduce the restrictions imposed by the battery capacity and the like when increasing the value of the current passed through the contacts to improve noise resistance and improve S / N.

(4) It can be applied to the same circuit from a pulse with a short closing time to a pulse with a long closing time, and the current consumption increases with the maximum pulse frequency rather than the pulse width, so the pulse frequency of electricity, gas, water, etc. is low. Suitable for counting.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing input / output logic of a flip-flop used in the same embodiment, and FIG. 3 is a circuit configuration diagram of a timer used in the same embodiment. And its operation timing chart, FIG. 4 is a circuit configuration diagram showing a current control detection unit used in the embodiment, FIGS. 5 to 7 are operation timing charts for explaining the operation of the embodiment, and FIG. FIG. 9 is a block diagram showing another embodiment of the present invention, FIG. 9 is a circuit configuration diagram of a timer used in the other embodiment and its operation timing chart, and FIGS. 10 to 12 are conventional pulse detection circuits, respectively. It is a block diagram for explaining. 21 …… contact, 22 …… flip-flop, 23 …… current control detector, 24 …… filter, 25,27 …… timer, 26 …… detector.

Claims (1)

(57) [Claims] 1. A current control detector for supplying a current to a contact to detect a contact state and detecting the presence or absence of the current, and a current detection signal of the current control detector for detecting the influence of chattering or external noise on the contact. A filter to remove, a timer that generates an output after a fixed time after the contact changes from the open state to the closed state, and a flip-flop, the contact is in the open state, and the current control detection unit outputs a current. In a state in which the flip-flop is outputting a signal that allows the current to flow, the contact is opened to closed, the current detection signal passes through the filter, and the current is not allowed to flow from the current control detection unit. Inversion of the signal that causes the flip-flop to output the current, and when the timer is started after the contact has changed from closed to open, a current is applied to the contact. And a detection unit that counts that a signal that causes the current control detection unit to allow a current to flow when the current has not been detected is again inverted to the state in which the flip-flop is outputting. Pulse detection circuit.