KR20080004505U - Ultrasonic Detect Circuit - Google Patents

Abstract

The present invention relates to a method for detecting a reflected wave returning by firing ultrasonic waves, and comparing an ultrasonic signal reflected after firing ultrasonic waves with a fixed DC reference voltage to detect an object, an obstacle closer to a target than a target. If present, the signal reflected by this obstacle is compared with a fixed DC reference voltage, thus failing to detect the actual target.

In addition, since the transmission / reception sensor is closely attached, when the transmission / reception sensor and the target are close to each other, there is a problem in that the target cannot be detected by the interference of the ultrasonic signal.

In order to solve this problem, in the present invention, in order to change the reference voltage by the rate at which the ultrasonic signal is attenuated according to the distance, the discharge voltage of the capacitor is used as the reference voltage, and compared with the reference voltage and the received ultrasonic signal, Even when there is an obstacle or when the transmission / reception sensor and the target are in close proximity to each other, the effect is ignored and the target can be accurately detected.

Transceiver ultrasonic sensor, discharge voltage, attenuation, reference voltage, reflected wave

Description

Ultrasonic Signal Detection Circuit {Ultrasonic Detect Circuit}

1 is an exemplary configuration of an ultrasonic signal detection circuit according to the present invention

2 is an operation principle of the ultrasonic signal detection circuit according to the present invention

3 is an operation principle diagram of a conventional ultrasonic signal detection circuit

*** Explanation of symbols for the main parts of the drawing ***

1: Ultrasonic Launcher

2: ultrasonic receiving sensor

3: High Pass Filter

4: amplification unit

5: integral part

6: comparator

7: microprocessor

8: DISPLAY part

U1: OP Amp

R1: OP amplifier output resistance

R2, R3: Rechargeable Resistor

R4: discharge resistor

D1: charging diode

C1: charge and discharge capacitor

The present invention relates to a method for detecting a reflected wave returning by firing ultrasonic waves, and more particularly, accurately detects only ultrasonic waves reflected by a desired target without being affected by surrounding obstacles. It is a technology that can detect the presence or absence of an object and the distance from the object by accurately detecting the close distance between the target and the transmission / reception sensor even if it causes interference.

When the ultrasonic wave is emitted and reflected on the object, attenuation occurs. The attenuation of the ultrasonic signal reflected from a distant object occurs more than the reflection from an object at a close distance, and thus the received signal is smaller in size.

In the present invention, in order to change the reference voltage of the comparator by the rate of attenuation with distance, the discharge voltage generated when the current charged in the capacitor is discharged through the resistor is referred to as the reference voltage of the comparator. Compared with the reference voltage and the received ultrasonic signal, the transmitting and receiving ultrasonic sensor is closely attached so that the ultrasonic signal is directly reflected from the transmitting ultrasonic sensor without receiving much attenuation from the transmitting ultrasonic sensor to the receiving ultrasonic sensor. The present invention relates to an ultrasonic detection method that can accurately find a target without being affected.

Conventionally, as shown in (d) of FIG. 3, when the fixed reference DC voltage and the received ultrasonic signal are applied to a comparison circuit using an OP amplifier, and the magnitude of the ultrasonic signal is larger than the reference DC voltage, as shown in FIG. The "HIGH" pulse signal was generated to interrupt the microprocessor to detect the object. In this way, if there is an obstacle at a closer distance than the target object as shown in (b) of FIG. 3, the size of the signal reflected by the obstacle is larger than the signal reflected from the actual target at a distance. Since it is compared with the DC voltage, the wrong distance is measured as shown in FIG. In addition, since the transmitting ultrasonic sensor and the receiving ultrasonic sensor are close together, the signal entering the receiving ultrasonic sensor directly from the transmitting ultrasonic sensor should be ignored in software even if the "HIGH" pulse signal is generated in the comparator. There is a disadvantage that there is an area that cannot be detected.

In order to solve the problem of the conventional ultrasonic signal detection method as described above, in order to eliminate the influence of the ultrasonic signal input from the transmitting ultrasonic sensor directly to the receiving ultrasonic sensor, and the ultrasonic signal reflected by the surrounding obstacles, Correspondingly, it is a technical task to detect a desired target by varying the reference voltage of the comparator without fixing it to a constant DC voltage.

In order to achieve the above object, it is characterized in that the circuit is configured to apply the discharge voltage of the capacitor, which decreases with an exponential function, to the inverting terminal of the comparator OP amplifier and compare it with the received ultrasonic signal.

Preferred configuration examples for implementing the present invention in detail with reference to the accompanying drawings as follows.

1 illustrates a specific configuration example of a circuit according to the present invention, FIG. 2 illustrates an operation principle of a circuit according to the present invention, and FIG. 3 illustrates a conventional ultrasonic reception operation principle.

Referring to FIG. 1, the main configuration includes an ultrasonic launcher 1 for emitting 40 KHz ultrasonic waves, an ultrasonic receiver sensor 2 for converting reflected waves of emitted ultrasonic waves into electrical signals, and an audible frequency signal among various signals. A high pass filter (3) for removing only the ultrasonic signal and an amplifying unit (4) for making the filtered weak signal sufficiently large, an integrating unit (5) for clearing the amplified signal, and an amplified signal; The display unit displaying the measured distance value and the microprocessor unit 7 which calculates the distance from the object by obtaining the time difference between the transmission and reception of the ultrasonic wave using the pulse signal and the comparator 6 comparing the reference voltage to make a pulse signal. It is a part (8).

2 (d) shows the comparison unit 6 of FIG. 1 in detail. The discharge voltage signal is applied to the inverting terminal of the OP amplifier U1, and the received ultrasonic signal is a non-inverting terminal of the OP amplifier U1. Is applied to compare the two signals. The microprocessor unit 7 transmits a pulse signal having a frequency of 40 KHz through the transmitting ultrasonic sensor and at the same time sends a "LOW" signal to the right terminal of the resistor R2 to receive the current charged in the capacitor C1 through the resistor R4. Discharge through. This discharge voltage is reduced by the attenuation ratio of the ultrasonic wave as shown in FIG. 2 (b) and applied to the inverting terminal of the OP amplifier U1, and the received ultrasonic signal is applied to the non-inverting terminal of the OP amplifier U1 so that the two signals are reduced. Are compared to generate a pulse signal as shown in FIG. 2C through the resistor R1. This pulse signal is applied to the microprocessor unit 7 to interrupt and calculate the time difference between transmission and reception. For the next discharge, the microprocessor unit 7 sends a "HIGH" signal to the right terminal of the resistor R2 to charge the capacitor C1 via the resistor R2, the resistor R3, and the diode D1.

Since the attenuation occurs until the ultrasonic wave is fired and received, the reference voltage is reduced by an exponential function by the corresponding ratio, so only the ultrasonic wave reflected from the target is detected. There is an effect that can overcome the spatial constraints.

In addition, the accurate distance can be measured when the transmitting and receiving ultrasonic sensors are close together. If the distance between the transmitting and receiving ultrasonic sensors is narrow, the ultrasonic signal input directly from the transmitting ultrasonic sensor to the receiving ultrasonic sensor can be recognized as a target, and the signal is ignored. Because it should be close distance is difficult to measure the problem.

When measuring the height of a liquid such as water, if the height of the liquid is getting higher and closer to the ultrasonic sensor, the ultrasonic signal within the range of the distance directly input from the transmitting ultrasonic sensor to the receiving ultrasonic sensor is ignored. Inaccurate measurement of the height of the sensor occurs, so the ultrasonic transmitting and receiving sensor should be installed some distance away from the maximum liquid height.

If it is not possible to secure a certain amount of space at the maximum liquid height, it may be a useful design that can measure the exact distance because the ultrasonic sensor and the target may be installed close.

Claims (2)

To receive the accurate ultrasonic signal, the ultrasonic launcher 1 for emitting 40 KHz ultrasonic wave, the ultrasonic receiving sensor unit 2 for converting the received ultrasonic wave into an electrical signal, and the signal of unwanted audible frequency are removed By comparing the high pass filter unit 3 for receiving the reflected wave only, the amplifying unit 4 which makes the filtered signal into a sufficiently large signal, the integrating unit 5 which cleanly forms the amplified signal, and the amplified signal and the reference voltage. A comparison unit 6 for outputting a pulse signal, a microprocessor unit 7 for calculating a distance from an object by obtaining a time difference between transmission and reception of ultrasonic waves using the output pulse signal, and a display unit for displaying a measured distance value ( 7) Ultrasonic signal detection circuit characterized in that.        The ultrasonic signal detection circuit according to claim 1, wherein the comparator (6) comprising an op amp compares the voltage generated by discharging the current charged in the capacitor with the received ultrasonic signal.

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