JPH0123753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ultrasonic pulse detection device that detects the presence of a human body by transmitting ultrasonic waves and receiving reflected waves reflected from the human body.

[Background technology]

FIG. 1 shows a block diagram of a conventional ultrasonic pulse detection device. In the figure, 1 is a transmission circuit, which includes an ultrasonic oscillation circuit 2 that generates a group of ultrasonic pulse trains at regular intervals, a drive circuit 3 that amplifies the oscillation output of this ultrasonic oscillation circuit 2, and an output of the drive circuit 3. and a diode circuit 4 in which diodes are connected in antiparallel to apply the voltage to the vibrator 5. When a human body exists within the reach of the ultrasonic pulses transmitted from the transducer 5, the ultrasonic pulses reflected from the human body cause the transducer 5 to vibrate, and the electrical signals generated thereby are transmitted to the receiving switch. It is input to circuit 6. Since the electrical signal at this time is weak, the diode circuit 4
is not conductive, and the impedance of the transmitting circuit 1 seen from the vibrator 5 during reception is high. The electrical signal inputted to the reception switch circuit 6 is amplified by an amplifier 7, detected and amplified by a detection amplifier 8, and inputted to a gate circuit 9. The gate circuit 9 is configured to allow a signal to pass only during a time period in which a reflected wave returns after a certain period of time after the ultrasonic oscillation circuit 2 oscillates an ultrasonic pulse. The output of the flip-flop 10 is inverted by a signal passing through the gate circuit 9, thereby operating the notification section 11. In an ultrasonic pulse detection device used for an automatic door or the like, a relay is connected in place of the notification section 11, and the contacts of this relay are used to open and close the automatic door. However, in such conventional examples, the power remains on all the time, so
There was a problem that power consumption increased. In addition, in the conventional case, because ultrasonic pulses are constantly transmitted at appropriate intervals, even if a passerby temporarily enters the detection area, it is always detected and automatically detected. Ultrasonic pulse detection devices used in doors and the like have had a problem in that the door opens even if a person who has no intention of entering the building passes through the detection area. For this reason, it was necessary to secure sufficient space in front of the entrance where an automatic door using an ultrasonic pulse detection device was installed. Furthermore, when such an ultrasonic pulse detection device is used for home visitor notification, etc., there are many cases where there is a passageway where people come and go within the detection area, and even if a human body passes through, it will be detected and notified. Therefore, there was a problem that the user would be notified even though he or she was not a visitor, which was inconvenient for the user.

[Purpose of invention]

The present invention has been made in view of the above points, and aims to reduce power consumption by intermittently thinning out the oscillation of ultrasonic pulses, and also prevents passersby from being mistakenly detected as visitors. It is an object of the present invention to provide an ultrasonic pulse detection device that can prevent such problems.

[Disclosure of the invention]

The configuration of the present invention will be described below with reference to illustrated embodiments. FIG. 2 shows a block diagram of an embodiment of the present invention. The configuration of the transmitting circuit 1 and the configuration of the receiving switch circuit 6 are the same as those in the conventional example shown in FIG. 1, so blocks having the same functions are designated by the same reference numerals and their explanation will be omitted. In the circuit shown in FIG. 2, power is supplied to the transmitter circuit 1 and the receiver switch circuit 6 by transistors.
This is done via contacts A and B of the Tr and switch SW. Transistor Tr is intermittent oscillation circuit 1
It is turned on and off by the oscillation output of No. 2.
The intermittent oscillation circuit 12 includes inverters I ₁ to I ₃ and resistors.
R _S , R _T , and an astable multivibrator 13 consisting of a capacitor C _T , and a D flip-flop 1
4, and an AND gate _G1 . Oscillation period of astable multivibrator 13
T _C is determined by T _C =2.2C _T R _T. FIG. 3b shows the oscillation output of this astable multivibrator 13. The D flip-flop circuit 14 is
The output is connected to the D input, and the clock input φ
The oscillation output of the astable multivibrator 13, which is input to the multivibrator 13, is frequency-divided. The output Q of the D flip-flop circuit 14 is connected to one input of an AND gate _G1 . In addition, the other input of AND gate _G1 is connected to an astable multivibrator 13.
output is connected. FIG. 3c shows the output Q of the D flip-flop 14, and FIG. 3d shows the output of the AND gate _G1 . As shown in the figure, the output of AND gate _G1 is T _D for a certain period of time.
only during this period, the oscillator 5 becomes H level.
The system oscillates a group of ultrasonic pulse trains intermittently as shown in FIG. 3e. FIG. 3a shows how the vibrator 5 oscillates a group of ultrasonic pulse trains at appropriate intervals when the contact A of the switch SW is connected to the contact C side. Note that the switch SW constitutes a switching means. In Fig. 3, the period T _E which is longer than the time width including a large number of ultrasonic pulse trains indicates one cycle of the signal output from the AND gate _G1 , and is determined by T _E = 4.4C _T R _T. . Further, the period T _D during which the output of the AND gate G ₁ is at the H level is determined by T _D =1.1C _T R _T. Therefore, the transistor Tr is, of T _E ,
Since it is turned on only during the period T _D , the current consumption is reduced to 1/4. In the example, T _E =
1 sec, T _D =250 msec, and as shown in FIG. 3e, ultrasonic pulses are transmitted twice during the time T _D. Note that if the intermittent oscillation circuit 12 is constructed of an IC (for example, CMOSIC) that can be driven with low power consumption, the increase in current consumption due to the addition of this circuit will be negligible. However, if T _E = 1 sec as mentioned above, ultrasonic waves are only output during the period of T _D = 250 msec, and no ultrasonic waves are output during the remaining 750 msec, so it is simply a case that the human body is within the detection area. The probability that the ultrasonic pulse detection device will operate just by passing through is reduced. Furthermore, if there is a visitor, the human body will be present in the detection area for a period of T _E =1 sec or more, so detection can always be performed. Note that when it is desired to detect an intruder such as a thief at night, it is convenient to switch the above-mentioned switch SW to the contact point C side using the daylight sensor output to increase the detection ability. In addition, when using solar cells and secondary batteries together as a drive power source, if you set it to thinning drive during the day and constant drive at night, ultrasonic waves will not be activated during the day when there is a lot of foot traffic and false alarms are likely to occur. In addition to suppressing the number of pulse train occurrences and reducing false alarms,
By increasing the amount of charge to the next battery, and by increasing the number of times the ultrasonic pulse train is generated at night to warn against intruders, effective use of power source energy is achieved. can be achieved.

Next, FIG. 4 is a circuit diagram of another embodiment of the present invention. In this embodiment, the oscillation output of the astable multivibrator 13 is directly applied to the base of the transistor Tr. In addition, the resistor R _T for determining the time constant of the astable multivibrator 13 is a variable resistor.
It consists of R _T1 and _RT2 , and diodes D ₁ and D ₂ of opposite polarity are connected in series, respectively. Figure 5a
shows an example in which the period T _pN during which the output of the astable multivibrator 13 is at H level is 250 msec, and the period T _pFF during which the output of astable multivibrator 13 is at L level is 750 msec. This shows the state of oscillation. The period T _pN is determined by T _pN = 1.1 C _T R _T1 , and the period T _pFF is determined by T _pFF = 1.1 C _T R _T2 . In this embodiment, since R _T1 +R _T2 is constant, the oscillation period T _E =T _pN +T _pFF of the astable multivibrator 13 is constant (1 sec). In Figure 5c, the period T _pN is 750 msec and the period T _pFF is 250 m.
sec, and Figure d shows how the vibrator 5 oscillates in this case. In this embodiment, the variable resistor for determining the time constant of the astable multivibrator 13 is
By changing the values of _RT1 and _RT2 , the detection ability and power consumption of the ultrasonic pulse detection device can be adjusted.

Note that the resistor R _T constitutes a switching means.
Furthermore, by making the duty ratio of the intermittent oscillation circuit 12 variable or its oscillation period variable, it is advantageous because the power consumption and detection ability can be adjusted as necessary.

〔Effect of the invention〕

As described above, the present invention provides pulses having an on period longer than the time width of at least one ultrasonic pulse train out of a group of ultrasonic pulse trains produced by a transmitting circuit, and having a period longer than a time width including a large number of ultrasonic pulse trains. An intermittent oscillation circuit that oscillates a signal, a switching element that is driven on and off by the output of the intermittent oscillation circuit and supplies power supply voltage to the transmitter circuit and receiver circuit when on, and a duty ratio of the intermittent oscillation circuit output that can be switched to large or small values. Since the switching device is equipped with a switching device, the transmission of the ultrasonic pulse train by the transmitting circuit can be stopped while the switching element is off, reducing power consumption and making it possible to use batteries or solar cells as a power source. This has the effect of eliminating the need for AC100V wiring, and by making it possible to change the duty ratio of the intermittent oscillation circuit output to large or small using the switching means, it is possible to transmit ultrasonic pulse trains. If the intermittent oscillation circuit output is stopped for a certain period of time during the off period of one cycle, there is less risk of false alarms occurring when a person temporarily passes through the detection area. This has the effect that if a person remains stationary for a long time, the detection operation can be performed reliably. Furthermore, by making it possible to change the duty ratio of the intermittent oscillation circuit output to a large or small value using a switching means, if you set it to thinning drive during the day and constant drive at night, it will be possible to reduce the By suppressing the number of occurrences of sonic pulse trains to reduce false alarms, and by increasing the number of occurrences of ultrasonic pulse trains at night to warn against intruders, we can prevent false alarms during the day and reduce false alarms at night. This has the effect that not only can reliable precautions be taken in the event of a disaster, but also that power source energy can be used effectively.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional example, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is an explanatory diagram of the same operation, and FIG. 4 is a block diagram of another embodiment of the present invention. FIG. 5 is an explanatory diagram of the same operation. 1 is a transmitting circuit, 6 is a receiving switch circuit, 12 is an intermittent oscillation circuit, 13 is an astable multivibrator, and Tr is a transistor.

Claims (1)

[Claims] 1. In an ultrasonic pulse detection device consisting of a transmitting circuit that transmits a group of ultrasonic pulse trains at regular intervals and a receiving switch circuit that receives and detects reflected waves, the transmitter circuit transmits a group of ultrasonic pulse trains. an intermittent oscillation circuit that oscillates a pulse signal that has an on period longer than the time width of at least one of the ultrasonic pulse trains and has a period longer than the time width that includes a large number of ultrasonic pulse trains; An ultrasonic pulse detection device comprising a switching element that is driven on and off and supplies a power supply voltage to a transmitting circuit and a receiving circuit when on, and a switching device that can change the duty ratio of the output of an intermittent oscillation circuit between large and small values. Device. 2. The ultrasonic pulse detection device according to claim 1, wherein the intermittent oscillation circuit has an output duty ratio that is continuously variable.