Train rotating speed sensor interface circuit

Abstract

The utility model discloses a train rotating speed sensor interface circuit, which comprises a signal input interface circuit, a reference voltage setting circuit, a hysteresis comparator and a level conversion and isolation circuit, and is characterized in that the input end of the signal input interface circuit is connected with a rotating speed sensor, and the output end of the signal input interface circuit is connected with the first input end of the hysteresis comparator; the output end of the reference voltage setting circuit is connected with the second input end of the hysteresis comparator; the input end of the level conversion and isolation circuit is connected with the output end of the hysteresis comparator, and the output end is connected with rear-end processing equipment. Voltage and current pulse signals of the rotating speed sensor are accessed through the rotating speed signal input interface, and pass through the reference voltage setting circuit and the hysteresis comparator to effectively suppress high-frequency interference at high and low level stages of rotating speed pulses. And a rotating speed signal which is consistent with the rotating speed pulse frequency of the sensor, is matched with the level of the rear-end processing equipment and has no interference is provided for the rear-end processing equipment after passing through the level conversion and isolation circuit.

Description

Technical Field

[0001] This utility model belongs to the field of sensing and detection technology, and in particular relates to a train speed sensor interface circuit. Background Technology

[0002] In the rail transit industry, train speed is one of the most commonly used and important physical parameters. Currently, train speed is detected using dedicated speed sensors. Based on different detection principles, the commonly used speed sensors are mainly photoelectric sensors and Hall effect sensors. Regardless of the detection principle used, the speed sensor is mounted on the axle, and its output is either a voltage pulse signal or a current pulse signal. Back-end equipment extracts this pulse signal to determine the time it takes for the axle to rotate per revolution, thereby calculating the train speed.

[0003] Train speed sensors play a crucial role in train operation, helping drivers accurately monitor train status and ensuring safe and stable travel. Simultaneously, train speed sensors can improve train operating efficiency, reduce energy consumption, and have a significant positive impact on the environment. The typical principle of speed signal detection is as follows: Figure 3 As shown, the speed pulse signal output by the speed sensor is input through the speed input interface. The pulse signal conditioning circuit performs functions such as pulse anti-interference, shaping, level conversion, and signal isolation. The signal acquisition circuit unit samples the pulse signal and calculates the train speed. Due to the complex operating conditions of trains, the speed sensor operates in a harsh environment with numerous interference factors, often susceptible to external forces such as impact and friction, making the speed detection signal and its transmission process easily affected. The actual speed signal waveform detected by the train speed sensor is shown in the figure below. Figure 4 As shown in the figure, waveform ① is the voltage pulse signal output by the voltage-type sensor, and waveform ② is the current pulse signal output by the current-type sensor. Figure 4 It can be seen that the speed pulse signal exhibits significant high-frequency interference in both the low-level and high-level phases. The signal amplitude varies between VH1 and VH2 in both phases, and between VL1 and VL2 in the low-level phase. This is a difficult problem to solve in the design and fabrication of train speed monitoring circuits. Therefore, speed pulse signal conditioning technology is a core technology for speed signal detection. Developing a speed sensor interface circuit for train speed monitoring to reliably extract train speed pulses is a pressing issue that needs to be addressed. Utility Model Content

[0004] The purpose of this invention is to overcome the defects in the existing technology and provide a train speed sensor interface circuit.

[0005] To achieve the above objectives, the specific technical solution of the train speed sensor interface circuit of this utility model is as follows:

[0006] A train speed sensor interface circuit includes a signal input interface circuit, a reference voltage setting circuit, a hysteresis comparator, and a level conversion and isolation circuit, wherein:

[0007] The input terminal of the signal input interface circuit is connected to the speed sensor, and the output terminal is connected to the first input terminal of the hysteresis comparator.

[0008] The output of the reference voltage setting circuit is connected to the second input of the hysteresis comparator.

[0009] The input terminal of the level conversion and isolation circuit is connected to the output terminal of the hysteresis comparator, and the output terminal is connected to the back-end processing device.

[0010] The signal input interface circuit receives the speed pulse signal from the speed sensor as the input signal. After suppressing high-frequency interference of the input signal through the reference voltage setting circuit and the hysteresis comparator, an intermediate signal is obtained. Finally, the intermediate signal is level-converted through the level conversion and isolation circuit to obtain the final output signal.

[0011] Preferably, the input terminal of the signal input interface circuit can receive voltage-type speed pulse signals or current-type speed pulse signals.

[0012] Preferably, the signal input interface circuit includes a power supply circuit, which provides operating power to the speed sensor.

[0013] Preferably, the signal input interface circuit includes diodes TVS1, TVS2, and TVS3, resistors R1, R2, and R3;

[0014] The diodes TVS1, TVS2, and TVS3 are all transient suppression diodes;

[0015] The negative terminal of the diode TVS2 is connected to the first end of the resistor R1 and serves as the input terminal for the voltage-type speed pulse signal.

[0016] The negative terminal of the diode TVS1 is connected to the power supply VDD and serves as the positive terminal of the power supply circuit.

[0017] The negative terminal of the diode TVS3, the first end of the resistor R3, and the first end of the resistor R2 are connected and serve as the input terminal of the current-type speed pulse signal.

[0018] The positive terminals of diodes TVS1, TVS2, and TVS3, as well as the second terminal of resistor R3, are all connected to ground terminal GND and serve as the negative terminal of the power supply circuit.

[0019] Preferably, the first end of the resistor R1 is connected to one end of the magnetic bead Z1, and the other end of the magnetic bead Z1 is connected to the negative terminal of the diode TVS2;

[0020] The first end of the resistor R2 is connected to one end of the magnetic bead Z2, and the other end of the magnetic bead Z2 is connected to the negative terminal of the diode TVS3.

[0021] Preferably, the reference voltage setting circuit includes resistors R4 and R5, which are connected in series between the power supply VDD and the ground terminal GND.

[0022] Preferably, the resistance values ​​of resistor R4 and resistor R5 are equal.

[0023] Preferably, the hysteresis comparator includes comparator IC1, resistor R6, and resistor R7;

[0024] The positive and negative terminals of the power supply of the comparator IC1 are connected to the power supply VDD and the ground terminal GND, respectively.

[0025] The second end of resistor R1 and the second end of resistor R2 are both connected to the inverting input of comparator IC1;

[0026] The common terminal of resistors R4 and R5 is connected to one end of resistor R6. The other end of resistor R6 and one end of resistor R7 are both connected to the positive input terminal of comparator IC1. The other end of resistor R7 is connected to the output terminal of comparator IC1.

[0027] Preferably, the level conversion and isolation circuit includes resistors R8, R9, and R10, a high-speed optocoupler IC2, and a transistor Q1;

[0028] One end of the resistor R8 is connected to the output terminal of the comparator IC1, and the other end is connected to the base of the transistor Q1;

[0029] One end of the resistor R9 is connected to the power supply VDD, and the other end is connected to the anode of the input terminal of the high-speed optocoupler IC2;

[0030] The cathode of the input terminal of the high-speed optocoupler IC2 is connected to the collector of the transistor Q1, and the emitter of the transistor Q1 is connected to the ground terminal GND.

[0031] One end of the resistor R10 is connected to the power supply VCC, and the other end is connected to the collector of the output terminal of the high-speed optocoupler IC2, and serves as the output terminal of the output signal.

[0032] The emitter of the output terminal of the high-speed optocoupler IC2 is connected to the ground terminal DGND.

[0033] The train speed sensor interface circuit of this utility model has the following advantages: The train speed sensor interface circuit consists of four parts: a speed signal input interface, a reference voltage setting circuit, a hysteresis comparator, and a level conversion and isolation circuit. It can provide working power for the train speed sensor. The voltage and current pulse signals of the speed sensor are input through the speed signal input interface. After passing through the reference voltage setting circuit and the hysteresis comparator, the high-frequency interference in the high and low level phases of the speed pulse is effectively suppressed. After passing through the level conversion and isolation circuit, the back-end processing equipment is provided with a speed signal that is consistent with the speed pulse frequency of the sensor, matches the level of the back-end processing equipment, and is free from interference. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the interface circuit of this utility model;

[0035] Figure 2 This is a circuit diagram of the interface circuit of this utility model;

[0036] Figure 3 This is a schematic diagram of the structure of a speed signal detection circuit in the prior art;

[0037] Figure 4 The waveforms of the voltage and current signals output by existing speed sensors are shown. Detailed Implementation

[0038] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of this utility model and should not be construed as limiting the scope of protection of this utility model.

[0039] The terms "top surface," "bottom surface," and "full surface" refer to the normal operating state of the train speed sensor interface circuit. They are used only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0040] like Figure 1As shown in the figure, a train speed sensor interface circuit includes a signal input interface circuit, a reference voltage setting circuit, a hysteresis comparator, and a level conversion and isolation circuit. The input end of the signal input interface circuit is connected to the speed sensor, and the output end is connected to the first input end of the hysteresis comparator. The output end of the reference voltage setting circuit is connected to the second input end of the hysteresis comparator. The input end of the level conversion and isolation circuit is connected to the output end of the hysteresis comparator, and the output end is connected to the backend processing device. The signal input interface circuit receives the speed pulse signal of the speed sensor as the input signal, suppresses the high-frequency interference of the input signal through the reference voltage setting circuit and the hysteresis comparator to obtain an intermediate signal, and finally performs level conversion on the intermediate signal through the level conversion and isolation circuit to obtain the final output signal.

[0041] The above train speed sensor interface circuit consists of four parts: a speed signal input interface, a reference voltage setting circuit, a hysteresis comparator, and a level conversion and isolation circuit. Among them, the voltage and current pulse signals of the speed sensor are connected through the speed signal input interface, and after passing through the reference voltage setting circuit and the hysteresis comparator, the high-frequency interference in the high and low level stages of the speed pulse is effectively suppressed. After passing through the level conversion and isolation circuit, a speed signal that is consistent with the speed pulse frequency of the sensor, matches the level of the backend processing device, and has no interference is provided for the backend processing device. The speed sensors used for monitoring the train running speed are mainly of two types: voltage type and current type. Let the output signal of the voltage type speed sensor be PULSE_V, and its low level range is VL1~VL2, and VL1 < VL2, and the high level range is VH1~VH2, and VH1 < VH2. Let the output signal of the current type speed sensor be PULSE_I, and its small current range is IL1~IL2, and IL1 < IL2, and the large current range is IH1~IH2, and IH1 < IH2. These parameters can be obtained from the known speed sensor data manual.

[0042] A further improvement is that, as Figure 2As shown, the signal input interface circuit includes a power supply circuit to provide operating power to the speed sensor; the signal input interface circuit includes diodes TVS1, TVS2, and TVS3, resistors R1, R2, and R3; diodes TVS1, TVS2, and TVS3 are all transient suppression diodes; the cathode of diode TVS2 is connected to the first terminal of resistor R1 and serves as the input terminal for the voltage-type speed pulse signal; the cathode of diode TVS1 is connected to the power supply VDD and serves as the positive terminal of the power supply circuit; the diodes... The negative terminal of TVS3, the first end of resistor R3, and the first end of resistor R2 are connected together and serve as the input terminal of the current-type speed pulse signal; the positive terminals of diodes TVS1, TVS2, and TVS3, and the second end of resistor R3 are all connected to the ground terminal GND and serve as the negative terminal of the power supply circuit; the first end of resistor R1 is connected to one end of ferrite bead Z1, and the other end of ferrite bead Z1 is connected to the negative terminal of diode TVS2; the first end of resistor R2 is connected to one end of ferrite bead Z2, and the other end of ferrite bead Z2 is connected to the negative terminal of diode TVS3.

[0043] In the above-described speed signal input interface circuit, the speed sensor is powered by the power supply VDD of the speed signal input interface. The speed pulse signal is connected to the speed signal input interface via the output signal PULSE_V of the voltage-type speed sensor or the output signal PULSE_I of the current-type speed sensor. Diodes TVS1, TVS2, and TVS3 are used to prevent overvoltage damage to the speed signal input interface from the sensor connection lines. Ferrite beads Z1 and Z2 are used to suppress external high-frequency interference. Resistors R1 and R2 are input current-limiting resistors with values ​​above 100kΩ. Resistor R3 is used to convert the output signal PULSE_I of the current-type speed sensor into a voltage signal, and its value is selected according to the large and small current ranges of the connected current-type speed sensor. If the high and low level ranges of a conventional voltage-type speed sensor are VH1~VH2 and VL1~VL2, respectively, and the large and small current ranges of the required current-type speed sensor are IH1~IH2 and IL1~IL2, respectively, then VL1 / IL1 < R3 < VH2 / IH2.

[0044] Further improvements include, for example Figure 2As shown, the reference voltage setting circuit includes resistors R4 and R5, which are connected in series between the power supply VDD and the ground terminal GND. The hysteresis comparator includes comparator IC1, resistors R6 and R7. The positive and negative terminals of the power supply of comparator IC1 are connected to the power supply VDD and the ground terminal GND, respectively. The second terminals of resistors R1 and R2 are both connected to the inverting input terminal of comparator IC1. The common terminal of resistors R4 and R5 is connected to one end of resistor R6. The other end of resistor R6 and one end of resistor R7 are both connected to the non-inverting input terminal of comparator IC1. The other end of resistor R7 is connected to the output terminal of comparator IC1.

[0045] The reference voltage setting circuit is a voltage divider network formed by resistors R4 and R5. The hysteresis comparator consists of resistors R6 and R7 and comparator IC1. We take R4 = R5, and the voltage at point a, Va = VDD / 2. When the speed pulse voltage is less than the reference voltage Vb1 at the non-inverting input of comparator IC1... When Va*R7 / (R6+R7), the voltage at the inverting input of comparator IC1 is less than that at the non-inverting input, and the output is high (approximately the power supply voltage VDD). At this time, the reference voltage at the non-inverting input of comparator IC1 immediately changes to Vb2=(Vc*R6+Va*R7) / (R6+R7). When the speed pulse voltage is greater than Vb2, the voltage at the inverting input of comparator IC1 is greater than that at the non-inverting input, and the output flips to low (approximately the power supply ground GND). At this time, the reference voltage at the non-inverting input becomes Vb1 again. When the speed pulse is in a low-level state, its voltage varies within a range less than Vb2, and the output of comparator IC1 remains high. When the speed pulse is in a high-level state, its voltage varies within a range greater than Vb1, and the output of comparator IC1 remains low. Currently, most train speed sensors operate at a voltage of VDD=15V. Using resistors R4=R5=10kΩ, Vb2=VH1=13.2V, and Vb1=VL2=2.1V, Va=VDD / 2=7.5V. From the formula for Vb1, we get R6=(5.4 / 2.1)R7, and from the formula for Vb2, we get R6=(5.7 / 1.8)R7. We choose R7=100kΩ, and select the smaller of the two. Based on the nominal value of a 1% accuracy resistor, we choose R6=255kΩ. Therefore, Vb1≈2.113V, Vb2≈12.887V. Thus, when the speed pulse changes within a low-level voltage range below 12.887V, the comparator IC1 output remains high; when the speed pulse changes within a high-level voltage range above 2.113V, the comparator IC1 output remains low. Comparator IC1 can be implemented using general-purpose comparators such as LM311 and LM111. When the feedback resistor of the op-amp is removed or the feedback resistor approaches infinity (i.e., in open-loop state), the open-loop gain of the op-amp is theoretically considered to be infinite (in reality, it is very large; for example, the open-loop gain of the LM324 op-amp is 100dB, or 100,000 times). At this time, the op-amp forms a voltage comparator. When the voltage at the non-inverting input is higher than the voltage at the inverting input, the op-amp outputs a high level; when the voltage at the non-inverting input is lower than the voltage at the inverting input, the op-amp outputs a low level. Therefore, comparator IC1 can also be implemented using general-purpose op-amps such as OPA827 and TL082.

[0046] Further improvements include, for example Figure 2As shown, the level conversion and isolation circuit includes resistors R8, R9, and R10, a high-speed optocoupler IC2, and a transistor Q1. One end of resistor R8 is connected to the output of comparator IC1, and the other end is connected to the base of transistor Q1. One end of resistor R9 is connected to the power supply VDD, and the other end is connected to the anode of the input terminal of high-speed optocoupler IC2. The cathode of the input terminal of high-speed optocoupler IC2 is connected to the collector of transistor Q1, and the emitter of transistor Q1 is connected to the ground terminal GND. One end of resistor R10 is connected to the power supply VCC, and the other end is connected to the collector of the output terminal of high-speed optocoupler IC2, serving as the output terminal of the output signal. The emitter of the output terminal of high-speed optocoupler IC2 is connected to the ground terminal DGND.

[0047] In the level conversion and isolation circuit, the high and low levels of the power supply VDD range are converted to low and high levels of the power supply VCC range, and opto-isolation is performed. When the comparator IC1 outputs Vc at a high level, the transistor Q1 is turned on through resistor R8. The power supply VDD provides operating current to the LED in the high-speed optocoupler IC2 through resistor R9. The LED emits light, turning on the phototransistor in the high-speed optocoupler IC2, and the output signal PULSE is low. When the comparator IC1 outputs Vc at a low level, the transistor Q1 is turned off, so the LED in the high-speed optocoupler IC2 has no operating current, and the LED in the high-speed optocoupler IC2... When the phototransistor is turned off, the PULSE signal is pulled high through the pull-up resistor R10. Thus, when the voltage-type speed sensor output signal PULSE_V or the current-type speed sensor output signal PULSE_I is low, the comparator IC1 outputs Vc high, and after level conversion and isolation, the output signal PULSE is low. Conversely, when the speed pulse PULSE_V or PULSE_I is high, the comparator IC1 outputs Vc low, and after level conversion and isolation, the output signal PULSE is high, ensuring that the output level of the speed sensor is consistent with the input level of the back-end processing equipment. The high-speed optocoupler IC2 can be selected from common models such as 6N137, TLP118, and TLP116A. The transistor Q1 is a medium-frequency low-power transistor, and common models such as CS9014 and S8050 can be selected. Resistor R9 is selected based on the operating current of the LED inside the high-speed optocoupler IC2 and the power supply VDD voltage. Resistors R8 and R10 can be selected in the range of 5~10kΩ.

[0048] In summary, the train speed sensor interface circuit of this utility model consists of four parts: a speed signal input interface, a reference voltage setting circuit, a hysteresis comparator, and a level conversion and isolation circuit. It can provide working power for the train speed sensor. The voltage and current pulse signals of the speed sensor are input through the speed signal input interface. After passing through the reference voltage setting circuit and the hysteresis comparator, high-frequency interference in the high and low level phases of the speed pulse is effectively suppressed. After passing through the level conversion and isolation circuit, a speed signal with the same frequency as the sensor's speed pulse, matching the level of the back-end processing equipment, and free from interference is provided to the back-end processing equipment.

[0049] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A train speed sensor interface circuit, characterized in that, It includes a signal input interface circuit, a reference voltage setting circuit, a hysteresis comparator, and a level conversion and isolation circuit, wherein: The input terminal of the signal input interface circuit is connected to the speed sensor, and the output terminal is connected to the first input terminal of the hysteresis comparator. The output of the reference voltage setting circuit is connected to the second input of the hysteresis comparator. The input terminal of the level conversion and isolation circuit is connected to the output terminal of the hysteresis comparator, and the output terminal is connected to the back-end processing device. The signal input interface circuit receives the speed pulse signal from the speed sensor as the input signal. After suppressing high-frequency interference of the input signal through the reference voltage setting circuit and the hysteresis comparator, an intermediate signal is obtained. Finally, the intermediate signal is level-converted through the level conversion and isolation circuit to obtain the final output signal.

2. The train speed sensor interface circuit according to claim 1, characterized in that, The input terminal of the signal input interface circuit can receive voltage-type speed pulse signals or current-type speed pulse signals.

3. The train speed sensor interface circuit according to claim 2, characterized in that, The signal input interface circuit includes a power supply circuit, which provides operating power to the speed sensor.

4. The train speed sensor interface circuit according to claim 3, characterized in that, The signal input interface circuit includes diodes TVS1, TVS2, and TVS3, resistors R1, R2, and R3; The diodes TVS1, TVS2, and TVS3 are all transient suppression diodes; The negative terminal of the diode TVS2 is connected to the first end of the resistor R1 and serves as the input terminal for the voltage-type speed pulse signal. The negative terminal of the diode TVS1 is connected to the power supply VDD and serves as the positive terminal of the power supply circuit. The negative terminal of the diode TVS3, the first end of the resistor R3, and the first end of the resistor R2 are connected and serve as the input terminal of the current-type speed pulse signal. The positive terminals of diodes TVS1, TVS2, and TVS3, as well as the second terminal of resistor R3, are all connected to ground terminal GND and serve as the negative terminal of the power supply circuit.

5. The train speed sensor interface circuit according to claim 4, characterized in that, The first end of the resistor R1 is connected to one end of the magnetic bead Z1, and the other end of the magnetic bead Z1 is connected to the negative terminal of the diode TVS2. The first end of the resistor R2 is connected to one end of the magnetic bead Z2, and the other end of the magnetic bead Z2 is connected to the negative terminal of the diode TVS3.

6. The train speed sensor interface circuit according to claim 4, characterized in that, The reference voltage setting circuit includes resistors R4 and R5, which are connected in series between the power supply VDD and the ground terminal GND.

7. The train speed sensor interface circuit according to claim 6, characterized in that, The resistance values ​​of resistor R4 and resistor R5 are equal.

8. The train speed sensor interface circuit according to claim 6, characterized in that, The hysteresis comparator includes comparator IC1, resistor R6, and resistor R7; The positive and negative terminals of the power supply of the comparator IC1 are connected to the power supply VDD and the ground terminal GND, respectively. The second end of resistor R1 and the second end of resistor R2 are both connected to the inverting input of comparator IC1; The common terminal of resistors R4 and R5 is connected to one end of resistor R6. The other end of resistor R6 and one end of resistor R7 are both connected to the positive input terminal of comparator IC1. The other end of resistor R7 is connected to the output terminal of comparator IC1.

9. The train speed sensor interface circuit according to claim 8, characterized in that, The level conversion and isolation circuit includes resistors R8, R9, and R10, high-speed optocoupler IC2, and transistor Q1; One end of the resistor R8 is connected to the output terminal of the comparator IC1, and the other end is connected to the base of the transistor Q1; One end of the resistor R9 is connected to the power supply VDD, and the other end is connected to the anode of the input terminal of the high-speed optocoupler IC2; The cathode of the input terminal of the high-speed optocoupler IC2 is connected to the collector of the transistor Q1, and the emitter of the transistor Q1 is connected to the ground terminal GND. One end of the resistor R10 is connected to the power supply VCC, and the other end is connected to the collector of the output terminal of the high-speed optocoupler IC2, and serves as the output terminal of the output signal. The emitter of the output terminal of the high-speed optocoupler IC2 is connected to the ground terminal DGND.

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