KR940006909Y1 - Distance acknowledge circuit using ultrasonic sensor - Google Patents

Abstract

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Description

Distance Recognition Circuit Using Ultrasonic Sensor

1 is a distance recognition circuit diagram of the present invention.

2 is a voltage waveform diagram of an offset signal generating circuit of the present invention.

3 is a voltage waveform diagram of the present invention.

4 is a distance recognition circuit diagram of the prior art.

5 is a voltage waveform diagram of the prior art.

6 is an ultrasonic wave transmission path diagram of a distance recognition circuit using an ultrasonic sensor.

* Explanation of symbols for main parts of the drawings

11: microcomputer 13: oscillator

14: ultrasonic transmitting sensor 15: ultrasonic receiving sensor

16 amplification circuit 17 demodulation circuit

18: offset signal generating circuit

The present invention relates to a distance recognition circuit using an ultrasonic sensor, and more particularly, to a distance recognition circuit that can extend the range of distance that can be measured by an ultrasonic sensor due to a phenomenon in which ultrasonic waves are directly transmitted from a transmitting sensor to a receiving sensor. It is about.

As shown in FIG. 4, a distance recognition circuit using a conventional ultrasonic sensor includes a microcomputer 1 that collectively controls system operation, an oscillator 3 that generates a square wave corresponding to a resonance frequency of an ultrasonic sensor, And an ultrasonic transmitting sensor 4 for transmitting an ultrasonic signal, an amplifying circuit 6 for amplifying the input signal and generating a DC offset equal to a voltage branched by an internal variable resistor, and an input signal state. Therefore, it consists of a demodulation circuit 7 for outputting a high (5v) and a low (Ov) voltage, and an ultrasonic receiving sensor 5 for receiving an ultrasonic signal.

Looking at the operation of the conventional design configured as described above is as follows.

The microcomputer 1 outputs a low voltage OV through an input / output terminal I / O and then outputs a high voltage 5V.

At this time, the microcomputer 1 operates after initializing the internal timer, and outputs a low voltage OV again through the input / output terminal I / 0 after a predetermined period dt.

The voltage waveform of the input / output terminal I / O of the microcomputer 1 is as shown in FIG.

The output of the AND gate 2 having the input / output terminal I / O of the microcomputer 1 as one input and the output of the oscillator 3 as the other input is as shown in FIG. 5 (b).

Therefore, the ultrasonic transmitting sensor 4 which uses the output of the AND gate 2 as an input transmits ultrasonic waves for a predetermined time dt at which the input / output terminal I / 0 of the microcomputer 1 outputs a high voltage.

The transmitting ultrasonic waves are transmitted to the ultrasonic receiving sensor 5 through two paths as shown in FIG. 6, one of which is directly transmitted as a dotted line, and is transmitted at a relatively weak intensity, and the other is reflected and transmitted to an obstacle such as a solid line. Obstacles are nearby and transmitted at a relatively high intensity.

Ultrasonic receiving sensor 5 generates a sine wave with an amplitude proportional to the intensity of the received ultrasonic wave, the output of which is as shown in (C) of FIG.

The relatively small amplitude sinusoids in the front part are due to the directly transmitted ultrasound waves and the relatively large amplitude sinusoids in the back part are from the ultrasound waves reflected by the obstacle.

An amplifying circuit 6 having the output of the ultrasonic receiving sensor 5 as an input amplifies the input signal and generates a DC offset. The offset voltage is determined as a voltage branched by an internal variable resistor. The sine wave by the directly transmitted ultrasonic wave should be preset to a value slightly larger than the threshold voltage so that it is not less than or equal to the threshold voltage of the demodulation circuit 7.

At this time, the output of the amplifying circuit 6 is shown as shown in (d) of FIG. The demodulation circuit 7 having the output of the amplifying circuit 6 outputs a high voltage while the input signal is below the division voltage, and the output voltage is shown as (e) in FIG.

The interrupt (INT) terminal of the microcomputer 1, which has the output of the demodulation circuit 7 as an input, causes an interrupt to the microcomputer 1 when the input signal changes from a low voltage to a high voltage. By this, the microcomputer 1 reads the internal timer value, finds the time dt for the ultrasonic wave to be reflected by the obstacle, and calculates the distance from the obstacle from the time.

However, in this conventional technique, in order that the demodulated signal does not output a high voltage by the directly transmitted ultrasonic wave, the sine wave by the directly transmitted ultrasonic wave is slightly larger than the divided voltage so that it is not less than the dividing voltage of the demodulation circuit. The offset voltage of the amplifier circuit must be set to the value.

As a result, when the obstacle is far away, the intensity of the ultrasonic wave reflected back to the obstacle is weak. If the amplitude of the sine wave is small and does not exceed the sine wave amplitude by the ultrasonic wave directly transmitted, the ultrasonic wave is reflected back to the obstacle. The demodulation signal does not output a high voltage.

That is, the distance that can be measured by the ultrasonic sensor is limited due to the phenomenon that the ultrasonic wave is directly transmitted from the transmitting sensor to the receiving sensor.

The present invention has been devised to solve such a problem and will be described below with reference to the accompanying drawings.

The present invention amplifies and offsets the microcomputer 11, the oscillator 13 generating a square wave corresponding to the resonant frequency of the ultrasonic sensor, the ultrasonic transmitting sensor 14, and the input signal as shown in FIG. An amplification circuit 16 for generating a DC offset as much as a signal, a demodulation circuit 17 for outputting a high (5v) and a low (Ov) voltage according to an input signal state, and an ultrasonic receiving sensor 15 And an offset signal generation circuit 18.

In addition, the offset signal generation circuit 18 includes a transistor Q1 turned on / off in response to an input signal, a transistor Q2 turned on / off in accordance with the transistor Q1, and transistors Q1, Q2, and Q3. Capacitor (C) for charging and discharging according to the on / off of, a comparator (COMP) for outputting a high voltage (5V) when the non-inverting input terminal voltage is greater than the inverting input terminal voltage, and the output of the comparator (COMP). The transistor Q3 is turned on and off depending on the state.

Reference sign Vcc is a constant current power supply, C1 is a capacitor, and VR1 is a variable resistor.

Referring to the operation and effects of the present invention configured as described above are as follows.

First, the operation of the offset signal generating circuit 18, which is the core of the present invention, is set in advance so that a voltage slightly higher than the division voltage of the demodulation circuit 17 is input to the inverting (-) input terminal of the comparator COMP. .

When a high voltage is input to the input signal, transistor Q1 is " on " and thereby transistor Q2 is " on ".

After that, the capacitor C is rapidly charged to have a high voltage.

At this time, since the voltage of the capacitor C is applied to the non-inverting (+) input terminal of the comparator COMP, the non-inverting input terminal voltage is greater than the inverting input terminal voltage, so that the comparator COMP outputs a high voltage. Q3) is "on".

Then, when the input signal enters a low voltage, transistor Q1 is "off", which causes transistor Q2 to "off".

The capacitor C then gradually discharges through the resistor R and the transistor Q3.

As a result of the discharge, when the voltage of the capacitor C becomes lower than the voltage applied to the inverting (-) input terminal of the comparator COMP, the comparator COMP outputs a low voltage, which causes the transistor Q3 to turn off. The capacitor C stops discharging.

That is, the offset signal generation circuit 18 having the voltage of the capacitor C as the output terminal has an output signal as shown in FIG. 2B with respect to the input signal as shown in FIG.

At this time, since the micro Kim computer 11 outputs a low voltage OV through the input / output terminal I / O and then outputs a high voltage 5 V, the micro computer 11 operates after initializing an internal timer.

After a certain time (dt), the low voltage (OV) is output again through the input and output terminals (I / O).

The input / output terminal (I / O) waveforms of the microcomputer 11 are as shown in FIG.

The output of the AND gate 12 having the input / output terminal I / O of the microcomputer 11 as one input and the output of the oscillator 13 as the other input is as shown in FIG.

Therefore, the ultrasonic transmission sensor 14 which uses the output of the AND gate 12 as an input transmits ultrasonic waves for a predetermined time (dt) at which the input / output terminal I / O of the microcomputer 11 outputs a high voltage.

The transmitted ultrasound is transmitted to the ultrasonic receiving sensor 15 through two paths as shown in FIG. 6, one is directly transmitted as a dotted line, and is transmitted at relatively weak field, and the other is reflected by an obstacle as a solid line. As it is transmitted, obstacles are far away and transmitted at very weak intensity.

The output of the ultrasonic receiving sensor 15 for generating a sine wave with an amplitude proportional to the intensity of the received ultrasonic wave is as shown in FIG.

The relatively small amplitude sinusoids in the front are due to the transmitted ultrasound directly, and the very small amplitude sinusoids in the back are due to the ultrasound reflected from the obstacle.

An amplifying circuit 16 having an output of the ultrasonic receiving sensor 15 as an input amplifies the input signal and generates a DC offset, the offset voltage of which is a micrometer as an output signal from the offset signal generating circuit 18. It is synchronized with the transmission circuit at the input / output terminal I / O of the computer 11 to have a high voltage immediately after the transmission signal, and as time passes, it becomes closer to the division voltage of the demodulation circuit 17.

At this time, the output of the amplifying circuit 16 is as shown in (d) of FIG.

The demodulation circuit 17 having the output of the amplifying circuit 16 outputs a high voltage while the input signal is below the threshold voltage, and the output voltage is as shown in FIG.

The interrupt (INT) terminal of the microcomputer 11, which uses the output of the demodulation circuit 17 as an input, causes an interrupt to the microcomputer 11 when the input signal changes from a low voltage to a high voltage. By the interrupt, the microcomputer 11 reads the internal timer value, finds the time dt for the ultrasonic wave to be reflected back to the obstacle, and calculates the distance to the obstacle from the time.

As described above, the present invention has a weak intensity of the ultrasonic waves reflected back to the obstacles because the obstacles are far away, and thus the amplitude of the sine wave is small. Since the demodulation signal outputs a high voltage by the returning ultrasonic waves, the distance range that can be measured by the ultrasonic sensor has a performance advantage that is much larger than that of the conventional art.

Claims (1)

Microcomputer 11, an oscillator 13 for generating square waves corresponding to the resonant frequency of the ultrasonic sensor, and an amplification circuit 16 for amplifying an input signal with an ultrasonic transmission and reception sensor 14, 15 and generating an offset. In the distance recognition circuit using the ultrasonic sensor provided with a demodulation circuit 17, the transistor Ql is turned on / off according to the input and output terminal (I / O) signal of the microcomputer 11, The transistor Q2 turned on / off according to the transistor Ql, the capacitor C charged and discharged according to on / off of the transistors Ql, Q2, and Q3, and the input voltage are compared with the set voltage. And a comparator COMP for selectively outputting a “high” (5V) or low (0V) voltage, and a transistor Q3 that is turned on / off according to the output state of the comparator COMP. The offset voltage of the demodulation circuit 17 immediately after the ultrasonic signal is transmitted by controlling the offset voltage of A distance recognition circuit using an ultrasonic sensor, characterized in that an offset signal generation circuit (18) is provided to generate a voltage that is greater than the voltage and approaches the division voltage of the demodulation circuit (17) as time passes.