CN213211328U

CN213211328U - Parking area parking stall detecting system based on earth magnetism

Info

Publication number: CN213211328U
Application number: CN202021400851.2U
Authority: CN
Inventors: 胡飞
Original assignee: Wuhan Jiaxiang Technology Co ltd
Current assignee: Wuhan Jiaxiang Technology Co ltd
Priority date: 2020-07-16
Filing date: 2020-07-16
Publication date: 2021-05-14
Anticipated expiration: 2030-07-16

Abstract

The utility model provides a parking area parking stall detecting system based on earth magnetism, include: the power supply circuit is connected with the input end of the detection control circuit through the magnetoresistive sensor, the two-stage amplifying circuit and the serial digital-to-analog conversion circuit which are sequentially connected in series. The utility model discloses utilize switched capacitor loop and band gap reference voltage source circuit to reach the high frequency ripple that lies prostrate the rank to the ripple range and restrain, under the circumstances of guaranteeing that the circuit is stable, safe, improve the accuracy that the parking area parking stall detected, promote user experience.

Description

Parking area parking stall detecting system based on earth magnetism

Technical Field

The utility model relates to a magnetic resistance sensor technical field especially relates to a parking area parking stall detecting system based on earth magnetism.

Background

Along with the automobile industry which has been rapidly developed, the increase speed of automobile ownership in China is very rapid, and the rapid increase speed of automobiles brings convenience to the life of people and brings a plurality of problems, such as the problems of disordered parking, difficult parking and the like caused by a plurality of automobiles.

The important component part of public transport facility is regarded as in the parking area, along with the continuous development of transportation, people require constantly to improve to the management, all want to enjoy facility, swift service in the parking process, a lot of parking areas all detect the parking stall through magnetoresistive sensor, but magnetoresistive sensor is relatively poor to the inhibition ability of high frequency ripple, can influence the testing result to the parking stall, so, need a parking area parking stall detecting system based on earth magnetism urgent, can accurately detect the parking stall.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model provides a parking area parking stall detecting system based on earth magnetism to solve the high frequency ripple and restrain magnetic resistance sensor, cause the not enough technical problem of parking area parking stall detection accuracy.

The technical scheme of the utility model is realized like this: the utility model provides a parking area parking stall detecting system based on earth magnetism.

On the basis of the above technical solution, preferably, the method includes: the device comprises a power supply circuit, a magnetoresistive sensor, a two-stage amplifying circuit, a serial digital-to-analog conversion circuit and a detection control circuit;

the power supply circuit is connected with the input end of the detection control circuit through the magnetoresistive sensor, the two-stage amplification circuit and the serial digital-to-analog conversion circuit which are sequentially connected in series.

Further preferably, the magnetoresistive sensor includes: the circuit comprises a first-stage operational amplifier circuit, second-stage and third-stage operational amplifier circuits, a switched capacitor loop and a band-gap reference voltage source circuit;

the first-stage operational amplifier circuit is connected with the input end of the band-gap reference voltage source circuit through a second-stage operational amplifier circuit, a third-stage operational amplifier circuit and a switched capacitor loop which are sequentially connected in series.

Further preferably, the switched capacitor loop includes: a switch SW1-4, a capacitor C1-3 and an operational amplifier U1;

in the second step, the first step is that, the output end of the three-stage operational amplifier circuit is connected with a port 1 of a switch S1, a port 2 of a switch S1 is connected with one end of a capacitor C1, a port 2 of a switch S1 is connected with one end of a capacitor C2, the other end of the capacitor C2 is grounded, a port 2 of a switch S1 is also connected with a port 2 of a switch SW3, a port 1 of a switch SW3 is grounded, the other end of the capacitor C1 is connected with a port 1 of a switch SW2, the other end of the capacitor C1 is also connected with a port 2 of a switch SW4, a port 1 of the switch SW4 is grounded, a port 2 of a switch SW2 is connected with a positive input end of an operational amplifier U1, a positive input end of the operational amplifier U1 is also connected with one end of a capacitor C3, a reverse input end of the operational amplifier U1 is grounded, the other end of a capacitor C3 is connected with an output end of the operational amplifier U1.

Further preferably, the bandgap reference voltage source circuit includes: the circuit comprises a resistor R1-4, a triode Q1-2 and an operational amplifier U2;

the output end of the switched capacitor loop operational amplifier U1 is connected with the forward input end of a band-gap reference voltage source circuit operational amplifier U2, the switched capacitor loop output end is further connected with the other end of a resistor R1, one end of the resistor R1 is connected with a power supply and is connected with the other end of a resistor R2, the other end of the resistor R2 is connected with the reverse input end of an operational amplifier U2, the switched capacitor loop output end is further connected with the collector of a triode Q1, the emitter of the triode Q1 is connected with one end of a resistor R4, the other end of the resistor R4 is grounded, the emitter of the triode Q1 is further connected with the other end of a resistor R3, one end of the resistor R3 is connected with the emitter of a triode Q2, the collector of the triode Q2 is connected with the reverse input end of an operational amplifier U, and is connected with the output end of the operational amplifier U2, and the output end of the operational amplifier U2 is connected with the input end of the two-stage amplifying circuit.

The utility model discloses a parking area parking stall detecting system based on earth magnetism has following beneficial effect for prior art:

(1) the utility model discloses an add the switched capacitor loop to optimize the switched capacitor loop, can restrain the high frequency ripple that ripple amplitude reaches volt level in the circuit, can promote the accuracy that parking area parking stall detected, promote user experience;

(2) the utility model discloses a band gap reference voltage source circuit can improve the stability of circuit, reduces the ripple range and reaches the influence of the high frequency ripple at volt rank to the circuit.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural view of a parking space detection system based on geomagnetism in a parking lot of the present invention;

fig. 2 is a circuit diagram of a switched capacitor loop of the present invention;

fig. 3 is a circuit diagram of the bandgap reference voltage source circuit of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work all belong to the protection scope of the present invention.

As shown in fig. 1, the utility model discloses a parking area parking stall detecting system based on earth magnetism, it includes: the power supply circuit is connected with the input end of the detection control circuit through the magnetoresistive sensor, the two-stage amplifying circuit and the serial digital-to-analog conversion circuit which are sequentially connected in series.

And the power supply circuit is used for providing a sufficient power supply for the geomagnetic detection system of the parking spaces of the whole parking lot.

A magnetoresistive sensor, comprising: the circuit comprises a first-stage operational amplifier circuit, second-stage and third-stage operational amplifier circuits, a switched capacitor loop and a band-gap reference voltage source circuit.

The primary structure of the first-stage operational amplifier circuit and the primary structure of the first-stage CMOS operational amplifier circuit are a sleeve structure and a folding cascode structure. The parasitic capacitance and the equivalent impedance of the common-gate tube source end of the sleeve structure are small, and the secondary pole generated at the common-gate tube source end is large, so that the sleeve structure has good frequency characteristics. In addition, the sleeve operational amplifier also has the advantages of high gain, low power consumption and the like. But its output swing range is small. In addition, the input common mode voltage of the sleeve structure, the bias voltage of the PMOS cascode transistor and the NMOS cascode transistor all need to be strictly confirmed. The folded cascode operational amplifier not only has the advantage of high gain, but also has output swing amplitude superior to that of a sleeve structure. Although the folded cascode operational amplifier has poor power consumption and pole frequency and a sleeve structure, the input common-mode voltage range is large, and when an NMOS tube is used as an input tube, the input common-mode voltage can be V_ddWhen the PMOS transistor is used as the input transistor, the input common mode voltage can be 0V.

The second and third-stage operational amplifier circuits have three kinds of commonly used amplifier output types, namely, a type A amplifier, a type B amplifier and a type AB amplifier. The working point of the output transistor of the class A amplifier is located at the middle point of a linear region, the transistor does not have current cut-off in the whole period of a signal, the transistor is kept in an amplification region, the conduction angle of the transistor is 180 degrees, and therefore the class A amplifier does not have crossover distortion and switching distortion. Its power remains constant during the positive and negative half cycles of the signal. When the class A amplifier works, the power consumption is large, the efficiency is very low, and the efficiency of the class A amplifier generally cannot exceed 25%. Class B amplifiers typically employ a push-pull configuration. Its operating point is at the cut-off point and its current is low when there is no signal in the circuit. When there is a signal, in the positive period of the signal, one output tube current rises, while the other is in the off state. When the signal enters a negative cycle, the output tube in the pushed structure has opposite working states. The class B amplifier has the advantage of high efficiency, which can reach 78%. But its disadvantages are also evident, its crossover distortion is significant. Class AB amplifiers also typically employ a push-pull configuration. The operating point of the class AB amplifier is between the cut-off region and the saturation region, but close to the cut-off region. When the driving voltage is lower, the output tubes are all conducted and work in the A-type state; when the driving level is high, the output tubes are all cut off, and the amplifier works in class B. Although the AB class operation has obvious distortion when just entering the A class state and the B class state, the AB class has higher efficiency than the A class, and the crossover distortion is better than the B class. It conceals yoga, and AB class can also realize rail-to-rail output. In this embodiment, the linearity is improved by the class AB operational amplifier.

A switched capacitor loop, as shown in fig. 2, comprising: a switch SW1-4, a capacitor C1-3, and an operational amplifier U1, the second, the output end of the three-stage operational amplifier circuit is connected with a port 1 of a switch S1, a port 2 of a switch S1 is connected with one end of a capacitor C1, a port 2 of a switch S1 is connected with one end of a capacitor C2, the other end of the capacitor C2 is grounded, a port 2 of a switch S1 is also connected with a port 2 of a switch SW3, a port 1 of a switch SW3 is grounded, the other end of the capacitor C1 is connected with a port 1 of a switch SW2, the other end of the capacitor C1 is also connected with a port 2 of a switch SW4, a port 1 of the switch SW4 is grounded, a port 2 of a switch SW2 is connected with a positive input end of an operational amplifier U1, a positive input end of the operational amplifier U1 is also connected with one end of a capacitor C3, a reverse input end of the operational amplifier U1 is grounded, the other end of a capacitor C3 is connected with an output end of the operational amplifier U1.

It will be appreciated that the coupling of the high frequency signal to the output terminal via the miller compensation capacitor causes it to exhibit high frequency ripple. In the extreme case of process mismatch considerations, the input offset voltage can reach 10mV, which will result in output ripple amplitude on the order of volts. For a circuit with an output swing of 5V, the ripple will cause a great disturbance to the output signal, and the high-frequency ripple is suppressed by the switched capacitor loop in this embodiment.

It should be appreciated that parasitic capacitance can have a large impact on the performance of the integrator due to the difficulty in controlling the parasitic capacitance during industrial fabrication, as shown in fig. 3, when SW1 is closed, parasitic capacitances C2 and C1 are connected in series and the input voltage charges both capacitances. When SW3 is closed, the upper and lower stages of the parasitic capacitor C2 are grounded, and the charge held by the parasitic capacitor C2 is continuously transferred to the output terminal, so that the parasitic capacitor does not affect the circuit.

The bandgap reference voltage source circuit, as shown in fig. 3, includes: the output end of the switched capacitor loop operational amplifier U1 is connected with the positive input end of a band-gap reference voltage source circuit operational amplifier U2, the output end of the switched capacitor loop is further connected with the other end of a resistor R1, one end of the resistor R1 is connected with a power supply and is connected with the other end of a resistor R2, the other end of the resistor R2 is connected with the reverse input end of the operational amplifier U2, the output end of the switched capacitor loop is further connected with the collector of a transistor Q1, the emitter of the transistor Q1 is connected with one end of a resistor R4, the other end of the resistor R4 is grounded, the emitter of the transistor Q1 is further connected with the other end of the resistor R3, one end of the resistor R3 is connected with the emitter of a transistor Q2, the collector of the transistor Q2 is connected with the reverse input end of the operational amplifier U395, the base region of the transistor Q2 823 is connected with, and is connected with the output end of the operational amplifier U2, and the output end of the operational amplifier U2 is connected with the input end of the two-stage amplifying circuit. The resistor R1-4, the triode Q1-2 and the operational amplifier U2 give different coefficients to the quantity with the positive temperature coefficient and the quantity with the negative temperature coefficient, and then the two are added, so that the zero temperature coefficient appears as a result, and then the power supply is stably and continuously provided through the zero temperature coefficient, the stability of the circuit is improved, and the influence of high-frequency ripples on the circuit is reduced.

The output current of the magnetic resistance sensor is small, the load capacity is poor, and the internal resistance is large. The voltage signal collected by the sensor must be amplified to facilitate subsequent processing of the signal. In order to amplify the collected signal without distortion, the input impedance of the input stage of the amplifying circuit needs to be increased as much as possible, and the output impedance of the amplifying circuit needs to be reduced as much as possible in order to increase the load capacity of the circuit. The present embodiment employs an AD623 integrated amplifier as a front-end amplification circuit of a two-stage amplifier. The AD623 integrated amplifier can be used as an instrumentation amplifier when the power supply is single. The external single variable resistor can adjust the amplification factor, the amplification factor can be controlled to be 1-1000 times, and the amplification attenuation is 20dB when the signal frequency is 100K and the amplification factor is set to be 1000 times. The common mode rejection ratio of the amplifier is increased along with the increase of the amplification factor, the amplification factor is 100 times when the single power supply is used, and the common mode rejection ratio is 80dB when the signal frequency is 100K, so that the distortion problem caused by the signal amplification can be effectively prevented. The AD623 can also work in a dual-power mode, and the debugging of a prototype can be facilitated by adopting the dual-power mode.

A serial digital-to-analog conversion circuit is characterized in that an analog signal obtained by an amplifier can be identified by a microprocessor only by an analog-to-digital converter with 10 bits in consideration of precision, an input-output clock is closed in an initial state, a data output end is in a high-impedance state when a chip selection signal is set to be high, a serial port signal enables the chip selection signal to be set to be low and enables a clock signal when the chip selection signal starts to work, the high-impedance state of the data output end is removed, then the serial port provides the clock signal for a clock array pin, and a conversion result is read from the data end. The input-output signals are 10-16 clock cycles in length, the first 10 clock cycles being used to take the analog signal.

And the detection control circuit is used for realizing the detection of the parking spaces in the parking lot.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides a parking area parking stall detecting system based on earth magnetism which characterized in that includes: the device comprises a power supply circuit, a magnetoresistive sensor, a two-stage amplifying circuit, a serial digital-to-analog conversion circuit and a detection control circuit;

2. The geomagnetic-based parking space detection system according to claim 1, wherein the magnetic resistance sensor comprises: the circuit comprises a first-stage operational amplifier circuit, second-stage and third-stage operational amplifier circuits, a switched capacitor loop and a band-gap reference voltage source circuit;

3. The geomagnetic-based parking space detection system in a parking lot according to claim 2, wherein the switched capacitor loop comprises: a switch SW1-4, a capacitor C1-3 and an operational amplifier U1;

the output end of the second and third-stage operational amplifier circuits is connected with a port 1 of a switch S1, a port 2 of a switch S1 is connected with one end of a capacitor C1, a port 2 of a switch S1 is connected with one end of a capacitor C2, the other end of the capacitor C2 is grounded, a port 2 of a switch S1 is also connected with a port 2 of a switch SW3, a port 1 of a switch SW3 is grounded, the other end of a capacitor C1 is connected with a port 1 of a switch SW2, the other end of a capacitor C1 is also connected with a port 2 of a switch SW4, a port 1 of the switch SW4 is grounded, a port 2 of a switch SW2 is connected with a forward input end of an operational amplifier U1, a forward input end of the operational amplifier U1 is also connected with one end of a capacitor C3, a reverse input end of the operational amplifier U1 is grounded, the other end of a capacitor C3 is connected with an output end of the operational amplifier U1, and an.

4. The geomagnetic-based parking space detection system in a parking lot according to claim 2, wherein the bandgap reference voltage source circuit comprises: the circuit comprises a resistor R1-4, a triode Q1-2 and an operational amplifier U2;