RU2783744C1 - Daisy chain two-wire sensor measuring system and method - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical engineering, in particular to the field of communication technologies. The system contains: one or more slave modules, the main module and a daisy chain connection wire. The slave module is connected to one or more sensors and is designed to modulate the detected sensor signal into the corresponding current signal. The main module is cascaded in series with the first slave module, the slave module of the upper stage and the slave module of the lower stage in one or more slave modules by means of a daisy chain connection wire to form a daisy chain sensor network and is connected to the upper computer by means of a communication wire. The wire of the daisy chain connection is designed to supply power and transmit the current signal received by the slave module using modulation, so that the main module receives and then decodes the current signal in the wire of the daisy chain connection to obtain the corresponding sensor data.

EFFECT: simplifying the connection of modules, increasing control efficiency and protection against interference during signal transmission.

8 cl, 8 dwg

Description

FIELD OF TECHNOLOGY

[001] The present invention relates to the field of communication technologies and, in particular, to a daisy-chained two-wire sensor measurement system and method.

BACKGROUND OF THE INVENTION

[002] Most known sensor networks use bus technology such as RS485 network technology. Each node has two communication wires and also has two power wires when bus powered, and each node has an independent address. This type of network supports two-way communication, data upload and control command delivery, and is suitable as a general measurement and control system. However, in this type of network, the bus contains four wires, which complicates the cabling and increases the cost of wires and equipment. Each node requires an independent address, so the protocol is complex. Installation and debugging of the system are also inconvenient.

[003] Maxim's DS18B20 temperature sensing chip, widely used in the market, uses a single-wire sensor bus. In addition to the two power wires, only one communication bus is required. All integrated circuits are connected by three identical wires for data exchange, and each integrated circuit has a unique independent identification (ID) number. Thus, cabling is simplified to a certain extent. However, three wires are still required, and the nodes are distinguished by an ID number, and the ID number needs to be read during installation and deployment, which leads to inconvenience in replacement.

[004] As a general communication topology, a daisy chain network can be applied to the sensor network. In a daisy chain, each node has two pairs of transceivers and is connected to two communication wires. Each communication wire is connected to two nodes, and the nodes are connected in series with each other. Node data is forwarded by the adjoining node. Therefore, there is no need for addresses in a daisy chain network. However, a node in a daisy chain still needs an independent power wire and therefore needs two power wires and two communication interfaces. If a single wire is used for communication, each node must also be connected to four external wires, and the transfer of data from the end node to the master node requires many transfer operations. As a result, data can be easily lost, and it is not suitable for building a large-scale network.

[005] Some battery management applications, such as containerized lithium battery storage systems, often use hundreds of battery packs connected in series, and each battery pack consists of many lithium batteries connected in parallel. For the safety of batteries, it is necessary to measure the temperature of these batteries. The prior art solution requires many sensors and communication buses, resulting in a complex connection and making effective control difficult. In view of the foregoing, the present invention provides a daisy-chained two-wire measurement system and method.

DISCLOSURE OF THE INVENTION

[006] To solve the problems in the prior art, the present invention provides a daisy-chained two-wire sensor measurement system and method.

[007] The present invention is implemented through the following technical solutions.

[008] According to a first aspect, the present invention provides a daisy-chained two-wire sensor measurement system, comprising:

[009] one or more slave modules connected to one or more sensors and configured to detect a sensor signal and modulate the detected sensor signal into a corresponding current signal;

[0010] a master module serially cascaded to the first slave module, the upper stage slave module, and the lower stage slave module of said one or more slave modules via a daisy chain wire to form a daisy chain sensor network, and connected to the upper computer via a communication wire; and

[0011] A daisy chain wire configured to supply power and transmit a current signal received by the slave modules through modulation, so that the master module receives and then decodes the current signal in the daisy chain wire to obtain the corresponding sensor data.

[0012] In addition, the main module includes a power interface, a main bottom switch, a main bottom interface, a signal demodulation circuit, a main voltage stabilization circuit, a main controller, and a communication interface.

[0013] In addition, the power interface is connected to an external power supply and the main voltage regulation circuit. The main voltage stabilization circuit is connected to the main controller and is configured to stabilize the input supply voltage and output the stabilized supply voltage to the main controller and the peripheral circuit of the main controller.

[0014] In addition, the main bottom switch is connected to the main controller and connected in series with the daisy chain wire, and controls the conductivity of the slave top interface of the first slave module through the main bottom interface.

[0015] In addition, a signal demodulation circuit is connected to the main controller and configured to decode the current signal in the daisy chain wire to obtain the corresponding sensor data.

[0016] In addition, the communication interface is connected to the upper computer and transmits sensor data to the upper computer.

[0017] In addition, the slave module includes a slave upper interface, a slave lower interface, a slave voltage regulation circuit, a signal modulation circuit, a slave controller, and a slave lower switch. The slave module also contains a reverse connection protection circuit to prevent damage to the slave module circuitry when the daisy chain wire is reversed.

[0018] In addition, the slave upper interface of the slave lower stage module is connected to the slave lower interface of the slave upper stage module, or the slave upper interface of the first slave module is connected to the main lower interface of the main module.

[0019] Between the slave upper interface and the slave lower interface, a slave lower bus switch is connected to control the conduction of the lower stage slave module;

[0020] The slave voltage regulation circuit is connected between the slave upper interface and the slave controller, and is configured to stabilize the voltage input by the daisy chain bus and output the stabilized voltage to the slave controller and the peripheral circuit of the slave controller to supply power, and is configured to shield interference to the slave controller, caused by signal transmission when data is transmitted by the slave module.

[0021] The signal modulation circuit is connected between the slave upper interface and the slave controller, and is configured to modulate the sensor signal into a corresponding current signal and transmit the current signal to the master module via the daisy chain wire.

[0022] In addition, the signal modulation circuit uses a light emitting diode to perform signal modulation and displays the working state of the slave module during data transmission.

[0023] In addition, the slave module includes an internal sensor and an external sensor, and the slave controller is connected to the internal sensor and the external sensor to detect the internal sensor and the external sensor. The internal sensor is configured to obtain an internal parameter of the slave module. The external sensor includes, without limitation, one or more of a temperature sensor, an ultrasonic sensor, an acceleration sensor, a smoke sensor, a humidity sensor, a vibration sensor, a photosensitive sensor, or a proximity switch on a Hall sensor.

[0024] According to a second aspect, the present invention provides a daisy-chained two-wire sensor measurement method, wherein the measurement method uses the daisy-chained two-wire sensor measurement system described in the first aspect and includes the following steps:

[0025] S1: system initialization, activation of sampling of the sensor signal and encoding of the collected sensor signal;

[0026] S2: modulating the sensor signal into a corresponding current signal and sending the current signal to the daisy chain wire;

[0027] S3: decoding the current signal from step S3 to obtain the corresponding sensor data; and

[0028] S4: Determining whether there is a faulty slave module or abnormal sensor data based on the sensor data.

[0029] In addition, according to this method, the data transmission and fault location of an individual slave module includes the following time periods:

[0030] T0 represents a period of time in which the bus is turned off and controlled by the master module, in which period of time the master module turns off the master lower switch and all slave modules are in a power-off state;

[0031] T1 represents a period of time for synchronization, and in this period of time, the main module already turns on the main lower switch, and the power of the slave modules is sequentially turned on, and the duration of the period T1 is determined by the slave modules; slave modules prepare for data transmission after power-up and sampling of the signal from the sensor for T1, with the upper limit of the duration of T1 being T1max; and

[0032] T2 represents a period of time for data transmission, and in this period of time, the slave modules complete the acquisition of sensor data, process and transmit this data, while the duration of T2 has an upper limit T2max.

[0033] In addition, according to the above method, the data transmission and fault location of the N slave modules include the following steps:

[0034] S1: turning on the main lower switch by the main unit, terminating the period T0, and activating the timing for T1, with n set to 1;

[0035] S2: if no data is received by the master module during T1max, determining that n slave modules fail to read and proceed to step SE;

[0036] S3: activation of the timing for T2 after the main module receives data, stop collecting all data and wait for the completion of data transmission;

[0037] S4: if T2>T2max, determining that a data error occurs in the nth slave module, and proceeding to step SE;

[0038] S5: if there is a validation error in the data, go to step SE; if there is a fault in the data indicating an open or shorted sensor, go to step S6;

[0039] S6: set n to n+1 and enable timing for T1;

[0040] S7: proceed to step S2 and

[0041] SE: if n=N+1, indicating that the data of all slave modules has been received and data transmission is completed, turning off the main lower switch by the master module; if n<N+1, determining that there is a communication failure in the nth slave module.

[0042] The present invention has the following advantages.

[0043] In the present invention, a master module and a plurality of sensor detection slave modules are connected in series one after the other by a power wire to form a daisy-chained sensor monitoring network, which simplifies expansion. The wire is shared for power supply and communication, in other words, only the power wire is used to supply power to the master module and a plurality of slave sensor detection and communication modules, which simplifies the wiring in the field. The signal is transmitted in current mode, so that interference protection is enhanced and no address coding is required. In addition, the advantages of the present invention are low cost and low energy consumption.

[0044] In the present invention, a special daisy chain structure is used. The data of the lower stage sensor detection slave module is sent directly to the master module without being forwarded by the upper stage sensor slave detection module. Each slave sensor detection module is configured to only sample, transmit data, and control the bottom bus switch, which imposes low requirements on the slave controller and facilitates low cost implementation.

[0045] In the present invention, a two-wire bus is used, and cable routing is convenient. This technical solution can also be used for other sensor control systems. Each Slave Sensor Detection Module can also be connected to multiple external sensors and share a single data link, further reducing system cost and simplifying device installation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] To more clearly describe the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly describe the drawings required to describe the embodiments or the prior art. Obviously, the drawings in the following description show only some embodiments of the present invention, and other drawings can be derived from these drawings without creative effort by those skilled in the art:

[0047] in FIG. 1 is a schematic diagram of the structure of a daisy chain two-wire sensor measurement system in accordance with an embodiment of the present invention;

[0048] in FIG. 2 is a schematic diagram of the structure of a slave module according to an embodiment of the present invention;

[0049] in FIG. 3 is a wiring diagram of a slave module according to an embodiment of the present invention;

[0050] in FIG. 4 is a schematic diagram of the structure of a main module according to an embodiment of the present invention;

[0051] in FIG. 5 is a wiring diagram of a main module according to an embodiment of the present invention;

[0052] in FIG. 6 is a flowchart of a daisy chain two-wire temperature measurement method according to an embodiment of the present invention;

[0053] in FIG. 7 is a schematic diagram of the structure of a circuit used to measure the temperature of batteries in accordance with an embodiment of the present invention; and

[0054] in FIG. 8 is a timing diagram of a daisy chain two-wire sensor measurement system in accordance with an embodiment of the present invention.

IMPLEMENTATION OF THE INVENTION

[0055] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and fully described below with reference to the drawings in the embodiments of the present invention. Obviously, the embodiments described are part, and not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on non-creative embodiments of the present invention fall within the protection scope of the present invention.

[0056] Embodiment 1

[0057] As shown in FIG. 1, this embodiment provides a daisy-chained two-wire sensor measurement system comprising:

[0058] one or more slave modules connected to one or more sensors and configured to detect a sensor signal and modulate the detected sensor signal into a corresponding current signal;

[0059] a master module serially cascaded to the first slave module, the upper stage slave module, and the lower stage slave module in one or more slave modules via a daisy chain wire to form a daisy chain sensor network, and connected to the upper computer via a communication wire; and

[0060] A daisy chain wire connected between the master unit and the first slave unit or between the upper stage slave unit and the lower stage slave unit, and configured to supply power and transmit the current signal received by the slave units through modulation, so that the master unit receives and then decodes the current signal in the daisy chain wire to obtain the corresponding sensor data.

[0061] In this embodiment, the main module includes a power interface, a main bottom switch, a main bottom interface, a signal demodulation circuit, a main voltage stabilization circuit, a main controller, and a communication interface.

[0062] In this embodiment, the power interface is connected to an external power supply and a main voltage regulation circuit. The main voltage stabilization circuit is connected to the main controller and is configured to stabilize the input supply voltage and output the stabilized supply voltage to the main controller and the peripheral circuit of the main controller.

[0063] In this embodiment, the master bottom switch is connected to the master controller and is connected in series with the daisy chain wire, and controls the conductivity of the slave top interface of the first slave module through the master bottom interface.

[0064] In this embodiment, a signal demodulation circuit is connected to the main controller and configured to decode the current signal in the daisy chain wire to obtain the corresponding sensor data.

[0065] In this embodiment, the communication interface is connected to the upper computer and transmits sensor data to the upper computer.

[0066] In this embodiment, the slave module includes a slave top interface, a slave bottom interface, a reverse connection protection circuit, a slave voltage regulation circuit, a signal modulation circuit, a slave controller, and a slave bottom switch.

[0067] The slave upper interface of the lower stage slave module is connected to the slave lower interface of the upper stage slave module, or the slave upper interface of the first slave module is connected to the master lower interface of the main module.

[0068] A slave lower bus switch is connected between the slave upper interface and the slave lower interface to control conduction of the slave lower stage module.

[0069] The slave voltage regulation circuit is connected between the slave upper interface and the slave controller, and is configured to stabilize the voltage input by the daisy chain bus and output the stabilized voltage to the slave controller and the peripheral circuit of the slave controller to supply power, and is also configured to shield interference to the slave controller, caused by signal transmission when data is transmitted by the slave module.

[0070] The signal modulation circuit is connected between the slave upper interface and the slave controller, and is configured to modulate the sensor signal into a corresponding current signal and transmit the current signal to the master module via a daisy chain wire.

[0071] In this embodiment, the signal modulation circuit uses a light emitting diode to perform signal modulation and displays the working state of the slave module during data transmission. During data transmission, the light emitting diode flashes.

[0072] In this embodiment, the slave module includes an internal sensor and an external sensor, and the slave controller is connected to the internal sensor and the external sensor to detect the internal sensor and the external sensor, and the internal sensor is configured to obtain the internal parameter of the slave module.

[0073] In this embodiment, the external sensor comprises one or more of a temperature sensor, an ultrasonic sensor, an acceleration sensor, a smoke sensor, a humidity sensor, a vibration sensor, a photosensitive sensor, or a proximity switch on a Hall sensor.

[0074] In this embodiment, the connection is simple. Only two wires are used to connect the master module and the first slave module and connect the upper stage slave module and the lower stage slave module.

[0075] In this embodiment, the data of the slave module is sent directly to the master module without forwarding by an intermediate node, and a current signal is used for data transmission, which is suitable for a system with a long range and many nodes.

[0076] In this embodiment, there is no need for address encoding by the slave module. The protocol does not require an address field. It is convenient for installation, deployment, debugging, maintenance and replacement.

[0077] In this embodiment, only a voltage stabilization circuit, an analog-to-digital (AD) sampling circuit, a metal-oxide-semiconductor (MOS) switch, and a plurality of resistors are required in the slave module circuit, and there is no large capacitor and inductive element. This simplifies the implementation of the integrated circuit and further reduces the marginal cost.

[0078] In this embodiment, each node operates only when it needs to transmit data, and the rest of the time is in a power-down or sleep mode. In sleep mode, the module consumes about 10 uA. Even in a network containing 100 nodes, the average power consumption of the network is only 1 mA.

[0079] Embodiment 2

[0080] This implementation option provides a daisy chain topology. A one-way communication is performed in which a temperature detecting slave module sends data to a master module, wherein the temperature detecting slave module is connected to a plurality of temperature sensors that are typically distributed in an environment in which the temperature sensors are adjacent to each other.

[0081] For example, temperature sensors are attached to different parts of the same battery pack, so the temperature difference is small. Given that the main module spends a lot of time receiving a large amount of temperature sensor data, which affects the average data update rate, in this embodiment, a data compression algorithm is proposed.

[0082] In this embodiment, in order to further reduce the cost, intensity, and frequency of system failures, a low precision oscillator can be used as a clock source in the slave controller of the slave temperature detection module.

[0083] For example, an RC oscillator is used internally. For this purpose, this embodiment proposes a communication protocol that can tolerate a large clock error.

[0084] First, a temperature sensor failure is eliminated. If the temperature sensor is open, then Tn = Tmax; if the temperature sensor is short-circuited, then Tn = 0. The value in the range (0, Tmax) is the measured value of the temperature sensor. For example, if Tn = 1, then the corresponding temperature is -40°C; if Tn = 160, then the corresponding temperature is 120°C.

[0085] The minimum value Tmin of the N normal temperature values of the sensors that are collected by the slave controller is calculated as a reference value, and Tn' = Tn - Tmin is used as the temperature difference. As an example, consider four temperature sensors, then the corresponding transmission protocol consists of the following fields:

[0086] 1. Measurement interval field. The measurement interval field indicates the time to measure the measured value of each temperature sensor after the power of the slave temperature detection module is turned on, and the specific time interval maintained for separating the data signal waveform of the data transmission of the slave temperature detection module 12 of the upper stage.

[0087] 2. Clock field. The slave temperature module uses its own serial clock generator 1010 as a reference to inform the master module of the clock frequency used by the slave temperature module. Based on the time interval of receiving two "1's", the master module determines the reference clock used by the temperature detection slave module. The clock bit width is set to W in this field.

[0088] 3. Temperature reference field. The binary code Tmin is sent bit by bit at interval W. If all temperature sensors are short-circuited, then Tmin = 00000000b and the temperature difference field is empty. If all temperature sensors are open, then Tmin = 11111111b, and the temperature difference field is empty. If some temperature sensors are open and other temperature sensors are short-circuited, in other words, there is no normal temperature sensor, then Tmin = 00000000 b and the temperature difference field is not empty.

[0089] 4. Temperature difference field. The N temperature differences Tn' are sent sequentially according to the following coding rule: if the temperature difference is less than 8, then 10b+TN'3 is sent (TN'3 indicates a 3-bit binary number); if the temperature difference is 0, then send 1100b; if the temperature sensor is open, then send 1110b; if the temperature sensor is short-circuited, then send 1101b; if the temperature difference is greater than or equal to 8, then send 01b+Tn′8.

[0090] 5. Validation field. Using a parity check or other check, the result of the check is calculated and sent.

[0091] In this embodiment, the clock synchronization field, the reference temperature field, the temperature difference field, and the test field are collectively referred to as the data transmission field.

[0092] The coding protocol and rule in this embodiment defines the fault types and temperature sensor codes, thereby facilitating debugging. There will be no 0000000000b in the codestream, so loss of synchronization is unlikely to occur. There will be no 1111111111b in the codestream, so loss of synchronization is unlikely to occur. Transmission of a fault code takes a short time, so that a sensor malfunction has little effect on overall communication. The protocol explicitly defines the clock signal used by the slave module, and therefore can be used for a system with a low precision clock signal. Taking four temperature sensors as an example, in most cases, the protocol can save 8-12 bits of data transfer time. Even with large temperature differences, accurate transmission can still be realized.

[0093] Embodiment 3

[0094] To further reduce transmission time, improve data update rate (for example, in large energy storage systems that have two hundred battery banks, and each battery bank contains ten individual batteries connected in parallel, it takes a long time to transfer thousands of temperature values), detecting a failed battery as soon as possible and improving safety, this embodiment uses the circuit structure shown in FIG. 7.

[0095] FIG. 7, R21, R24, and Q22 constitute one signal modulation module 28, and R21a, R24a, and Q22a constitute another signal modulation module 28. Two signal modulation modules 28 are connected in parallel and controlled by slave controllers 21, respectively. If we ignore the resistance of Q22 and Q22a, then assuming that R21>R21a, the following four cases are possible:

[0096] 1. Q22 and Q22a are turned off, the total output current of the signal modulation modules 28, denoted as I0, is 0, and the voltage across R11 is 0.

[0097] 2. Q22a is off, Q22 is on, and the total output current of the signal modulation modules 28 is equal to the current on R21 and is denoted as I1.

[0098] 3. Q22a is on, Q22 is off, and the total output current of the signal modulation modules 28 is equal to the current on R21a and is denoted as I2.

[0099] 4. Q22a is on, Q22 is on, and the total output current of the signal modulation modules 28 is equal to the sum of the current on R21a and the current on R21, and is denoted as I3.

[00100] In this embodiment, since R21>R21a, then I0<I1<I2<I3. By selecting proper resistance values for R21 and R21a, four different resistance values can be obtained across R11 of the main module (as shown in FIG. 5). With this modulation scheme, four symbol coding can be realized, for example: I0 corresponds to 00b, I1 corresponds to 01b, I2 corresponds to 10b, and I3 corresponds to 11b. This type of character encoding can greatly improve the data rate.

[00101] The modulation scheme in this embodiment is simple, can be easily implemented, and is of low cost. Character encoding saves a lot of transmission time. In addition, the characters are very different from each other, so it is not easy to cause a bit error.

[00102] In this embodiment, a four-character transmission protocol and the following encoding rule are used.

[00103] 1. Measurement interval field.

[00104] 2. Clock field. The slave temperature detecting module 12 uses as a reference its own clock signal to serially send I3, I2, I1, and I0 to inform the master module 11 of the clock frequency and symbol level used by the slave temperature detecting module 12.

[00105] 3. Temperature reference field. The quaternary code Tmin is sent bit by bit at interval W. If all temperature sensors are short-circuited, then Tmin=0000q (quaternary system) and the temperature difference field is empty. If all temperature sensors are open, then Tmin=3333q (quaternary system) and the temperature difference field is empty. If some temperature sensors are open and other temperature sensors are short-circuited, in other words, there is no normal temperature sensor, then Tmin=0000q and the temperature difference field is not empty.

[00106] 4. Temperature difference field. The N temperature differences Tn' are sent sequentially according to the following coding rule: if the temperature difference is less than 16, then 2q+TN'2q is sent (TN'2q indicates a 2-bit quaternary number); if the temperature difference is 0, then send 30q; if the temperature sensor is open, then send 32q; if the temperature sensor is short-circuited, then send 31q; if the temperature difference is greater than or equal to 16, then send 1q+Tn'4q.

[00107] 5. Validation field. Using a parity check or other check, the result of the check is calculated and sent.

[00108] The protocol of this embodiment uses character coding, thereby achieving high transmission efficiency. There will be neither 00000q nor 33333q in the codestream, so loss of synchronization is unlikely to occur, reducing clock accuracy requirements. The sync field performs clock synchronization transmission and bit coding synchronously.

[00109] Embodiment 4

[00110] Taking temperature measurement as an example, this embodiment provides a daisy-chained two-wire temperature measurement system comprising: a master module configured to receive a temperature signal and a plurality of temperature detection slave modules configured to detect a temperature signal. The master module and a plurality of temperature detection slave modules are connected in series one after the other by a power wire to form a temperature control daisy chain. The slave temperature detection module modulates the detected temperature signal into a corresponding current signal and transmits the current signal through the power wire. The main module decodes the current signal in the power wire to obtain the corresponding temperature data.

[00111] In this embodiment, each of the plurality of temperature determination slave modules includes a temperature transmission upper interface and a temperature transmission lower interface that are connected to each other. The upper temperature transmission interface of the lower stage temperature detection slave module is connected to the lower temperature transmission interface of the upper stage temperature detection slave module through a power wire to directly transmit the temperature signal to the main module without the need for temperature signal processing by the upper stage temperature detection slave module.

[00112] The concept of daisy chaining in this embodiment refers to a daisy chain formed by connecting a plurality of daisy chains in series. In this embodiment, daisy chaining means that a plurality of temperature detection slave modules are connected in series one after another, including the first stage temperature detection slave module, the second stage temperature detection slave module, ..., etc., and transmit the detected temperature signals to the master module. .

[00113] The biggest advantage of the daisy chain structure in this implementation is that multiple devices can be connected by using a limited signal wire to share the same service without bus contention, blocking, and other problems. When a new temperature detection slave is to be added, it only needs to be connected to the tail of the daisy chain. Therefore, the daisy chain structure can be easily expanded.

[00114] In the prior art, a power wire is used to supply power and a communication wire is used to communicate. With a plurality of temperature detection slave modules, the complexity of the wire increases and it is prone to wire failure.

[00115] In this embodiment, the temperature detecting slave module encodes a temperature signal to change the wire current, so that the master module decodes the power wire current signal to obtain the corresponding temperature data, thereby realizing temperature signal transmission. The power wires are used to supply power and transmit the temperature signal at the same time, so there is no need for a communication wire for separate communication and no need for address coding. The signal is transmitted in current mode, which enhances noise immunity.

[00116] When the temperature determination slave module encodes the temperature signal, an appropriate unique number is added. Based on this number, the main unit can determine the source of the temperature signal when decoding the current signal. If the temperature signal is abnormal, a faulty temperature detection slave module can be detected.

[00117] As shown in FIG. 2 and 4, in this embodiment, the master module includes a power interface and a lower temperature transmission interface, and each of the plurality of temperature detecting slave modules comprises an upper temperature transmission interface and a lower temperature transmission interface.

[00118] The power interface is connected to the power supply, the lower temperature transmission interface is connected to the upper temperature transmission interface of the first stage temperature detection slave module through a power wire, and the upper temperature transmission interface of the lower stage power detection slave module is connected to the lower temperature detection slave module temperature transmission interface upper stage temperature via the power cable. The daisy chain connection mode facilitates expansion and does not require a main module communication interface.

[00119] A direct current (DC) voltage is input to the power interface. The recommended input power supply voltage is 12V. In some implementations, an anti-reverse protection diode may be provided to prevent the input power supply from being connected in reverse order, or a full bridge rectifier circuit may be provided to ignore the polarity of the power supply so that the power supply can be operated independently of the forward or reverse connection. .

[00120] In this embodiment, each of the plurality of temperature detection slave modules includes: a temperature sensor configured to receive a temperature signal; and a slave lower bus switch connected between the upper temperature transmission interface and the lower temperature transmission interface to control the conductivity of the lower stage temperature detection slave module.

[00121] The slave controller connected to the temperature sensor, the slave lower bus switch and the lower temperature transmission interface is configured to control the temperature sensor, the slave lower bus switch and the lower temperature transmission interface.

[00122] A signal modulation module connected between the upper temperature transmission interface and the slave controller is configured to modulate the temperature signal into a corresponding current signal.

[00123] In this embodiment, each of the plurality of temperature detection slave modules also includes: a voltage stabilization slave circuit connected between the upper temperature transmission interface and the lower temperature transmission interface to stabilize the input supply voltage and output the stabilized supply voltage. When the voltage fluctuates greatly, the output voltage stabilizes to provide a stable DC power supply to the slave controller.

[00124] FIG. 3 is a wiring diagram of the slave temperature detection module. FIG. 3 MCU_S represents the slave controller, and LDO represents the slave voltage regulation circuit. Resistor R24, switching transistor Q22, capacitor C21 and resistor R21 constitute the signal modulation module. R5 and RT make up the temperature sensor circuit. Resistor R22, capacitor C22, switching transistor Q21, resistor R23, and switching transistor Q22 constitute the slave lower bus switch. BUS+0 and BUS- constitute the upper temperature transmission interface, and BUS+1 and BUS- constitute the lower temperature transmission interface.

[00125] After energizing the upper temperature transfer bus, the power to the slave controller is turned on to start it. After the slave controller has been stable for a period of time, temperature sampling is activated. After the slave temperature detection module is powered on, the voltage of capacitor C22 and capacitor C21 remains at 0V. The DO pin of the slave controller outputs high to turn on the switching transistor Q22. The voltage of capacitor C22 cannot change abruptly, so the switching transistor Q21 remains off. The voltage of the capacitor C21 cannot change abruptly, and the resistor R21 instantaneously accepts the voltage of the upper temperature transfer interface, resulting in a large modulated current.

[00126] The DO terminal of the slave controller outputs a low level, and the switching transistor Q22 turns off, or at least the switching transistor Q22 turns on for a short time. The switching transistor Q21 remains off. When switching transistor Q22 turns on and off, a pulsed current is generated in the top rail. Since the lower switches of the upper stage temperature detection slave bus are turned on, temperature information can be transmitted to the upper temperature transmission bus by using pulse current, and the demodulation circuit of the main controller can directly recover the modulated temperature data.

[00127] When the temperature data is fully transferred, the DO pin of the slave controller remains in the high-level output state, the current of the resistor R21 gradually decreases to zero, the voltage of the capacitor C22 gradually increases, so that the switching transistor Q21 turns on, and the lower stage temperature detection slave module starts. In the meantime, the temperature detection slave unit can enter into a sleep state with reduced power consumption.

[00128] In this embodiment, the main module includes: a signal demodulation circuit configured to decode a power wire current signal to obtain corresponding temperature data; and a main controller connected to the signal demodulation circuit and the lower temperature transmission interface to control the conductivity of the lower temperature transmission interface.

[00129] In this embodiment, the main lower bus switch is connected between the lower temperature transfer interface and the main controller. In addition, a low-resistance resistor R is connected in series between the lower temperature transmission interface and the main lower bus switch, and a signal demodulation circuit is connected in parallel with the low-resistance resistor R and connected to the main controller.

[00130] In this embodiment, the signal demodulation circuit includes a low resistance resistor R, which is connected in series on the power wire and connected in parallel to the signal demodulation circuit, and the signal demodulation circuit samples and demodulates the voltage across the low resistance resistor.

[00131] When the current in the power wire changes, the voltage across the low-resistance resistor R changes, and the signal demodulation circuit performs decoding based on the voltage change to obtain the corresponding temperature data.

[00132] In this embodiment, the master module also includes a master lower bus switch connected to the power interface and the lower temperature transmission interface to control the conductivity of the temperature detection slave module.

[00133] In this embodiment, the main module also includes a main voltage regulation circuit connected to the power interface and the main controller and configured to stabilize the input supply voltage and output the stabilized supply voltage.

[00134] When there is a large change in the supply voltage, the output voltage stabilizes to provide a stable DC power supply to the main controller.

[00135] In this embodiment, in order to facilitate the storage and analysis of temperature data, the main module also includes a communication interface connected to the main controller and the upper computer for transmitting temperature data to the upper computer.

[00136] The wiring diagram of the main module in this embodiment is shown in FIG. 5. In FIG. 5 MCU_ M represents the main controller. Comparator COMP, resistor R11, resistor R12 and diode D11 make up a simple demodulation circuit. Resistor R10 and switching transistor Q11 constitute the lower bus switch. After the switching transistor Q11 is turned on, under the control of the main controller, a voltage is generated on the low-resistance resistor R11. After the current is generated in the slave module's modulation circuit, the current also flows through the resistor R11 to form a voltage. The demodulation circuit can compare these voltages to recover the temperature data signal.

[00137] Embodiment 5

[00138] As shown in FIG. 6, this embodiment provides a daisy-chained two-wire temperature measurement method including the following steps:

[00139] S1: The temperature detection slave module activates temperature sampling and encodes the temperature signal.

[00140] S2: The temperature detection slave module modulates the temperature signal into the corresponding current signal by the signal modulation module and sends the current signal to the power wire.

[00141] S3: The signal demodulation circuit demodulates the current signal to obtain the corresponding temperature data.

[00142] S4: Based on the temperature data, the master controller determines whether there is a faulty slave temperature detection module or an abnormal temperature.

[00143] In this embodiment, the main module receives a command from the communication interface of the upper computer and starts the temperature measurement process. The main controller turns on the lower bus switch and prepares to receive data.

[00144] In this embodiment, upon power-up, the temperature detection slave module starts operation, activates temperature sampling, and encodes the temperature signal. The slave temperature detection module sends the temperature signal to the power wire through the signal modulation module. The temperature signal passing through the power wire is converted by the signal demodulation block of the main unit into a change in the active component of the voltage, and then converted by the demodulation circuit into a serial signal, which will be received by the main controller of the main unit.

[00145] In this embodiment, the temperature detecting slave turns on the lower bus switch and activates the sleep mode after connecting the bus with the lower stage temperature detecting slave, so that the current stage temperature detecting slave is in a low power sleep state.

[00146] The above steps are repeated until the data transmission of all slave temperature detection modules is completed. The master controller turns off the lower bus switch and processes all temperature data, then determines whether there is a faulty slave temperature detection module or an abnormal temperature.

[00147] In this embodiment, the main module transmits the collected temperature data and fault information to the upper computer via the communication interface of the upper computer. This completes one temperature data collection process. During the entire measurement process, the slave modules turn on power in sequence and enter sleep mode after data transmission to enter a power-down state. When the measurement is completed, the master controller turns off the lower bus switch, and all slave temperature detection modules turn off to reduce power consumption. Consequently, the system has a low energy consumption throughout the measurement process.

[00148] Embodiment 6

[00149] This implementation option provides a method for locating a fault. FIG. 9 is a timing diagram of a two-wire daisy chain sensor system.

[00150] T0 represents a period of time in which the bus is off and controlled by the main controller. During this period of time, the master controller turns off the master lower switch, and all slave modules are in a power-off state.

[00151] T1 represents a time period for synchronization. During this period of time, the main controller is already turning on the main lower switch, and the power of the slave modules is turned on in sequence. The duration T1 is determined by the slave modules. During T1, the slave modules prepare at power-up to transmit data and sample the signal from the encoder. The duration T1 has an upper limit T1max.

[00152] T2 represents a period of time for data transmission. During this period of time, slave modules collect sensor data, process and transmit this data. The upper limit of the T2 duration is T2max.

[00153] This embodiment provides a method for transmitting data and locating a fault in a two-wire daisy-chain sensor system with N slave modules, comprising the following steps:

[00154] S1: turning on the main lower switch by the main unit, terminating the period T0, and activating the timing for T1, with n set to 1.

[00155] S2: If no data is received by the master within T1max, determine that n slaves fail to read and proceed to step SE.

[00156] S3: activation of the timing for T2 after receiving data by the main module, stop receiving all data and wait for the transmission to complete.

[00157] S4: if T2>T2max, determining that a data error occurs in the nth slave module, and proceeding to step SE.

[00158] S5: if there is a validation error in the data, go to step SE; if there is a fault in the data indicating an open or shorted sensor, go to step S6.

[00159] S6: Set n to n+1 and enable timing for T1.

[00160] S7: Go to step S2.

[00161] SE: if n=N+1, indicating that the data of all slave modules has been received and data transmission is completed, turning off the main lower switch by the master module; if n<N+1, determining that there is a communication failure in the nth slave module.

[00162] In conclusion, in the present invention, the master module and a plurality of sensor detection slave modules are connected in series one after the other by a power wire to form a daisy-chained sensor monitoring network, which simplifies expansion. The wire is shared for power supply and communication, in other words, only the power wire is used to supply power to the master module and a plurality of slave sensor detection and communication modules, which simplifies the wiring in the field. The signal is transmitted in current mode, so the protection against interference is enhanced and no address coding is required. In addition, the advantages of the present invention are low cost and low energy consumption.

[00163] In the present invention, a special daisy chain structure is used. The data of the lower stage sensor detection slave module is sent directly to the master module without being forwarded by the upper stage detection slave module. Each slave sensor detection module is configured to only sample, transmit data, and control the bottom bus switch, which imposes low requirements on the slave controller and facilitates low cost implementation.

[00164] In the present invention, a two-wire bus is used, and cable routing is convenient. This technical solution can also be used for other sensor control systems. Each Slave Sensor Detection Module can also be connected to multiple external sensors using one common data link, further reducing system cost and simplifying device installation.

[00165] The above embodiments are only used to explain the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they may nevertheless modify the technical solutions described in the above embodiments or make equivalent substitutions for some of their technical features without deviating from the respective technical solutions. from the essence and scope of technical solutions of embodiments of the present invention.

Claims (34)

1. A daisy-chained two-wire sensor measuring system, comprising: one or more slave modules connected to one or more sensors and configured to detect a sensor signal and modulate the detected sensor signal into a corresponding current signal; a master module cascading in series with the first slave module, the upper stage slave module, and the lower stage slave module of said one or more slave modules via a daisy chain wire to form a daisy chain sensor network, and connected to the upper computer via a communication wire; and wherein the daisy chain wire is configured to supply power and transmit a current signal received by the slave modules through modulation, the master module receiving and then decoding the current signal in the daisy chain wire to obtain the corresponding sensor data; wherein the slave upper interface of the lower stage slave module is connected to the slave lower interface of the upper stage slave module, or the slave upper interface of the first slave module is connected to the main lower interface of the main module; between the slave upper interface and the slave lower interface, a slave lower bus switch is connected to control the conduction of the lower stage slave module; the slave voltage stabilization circuit is connected between the slave upper interface and the slave controller and is configured to stabilize the voltage input by the daisy chain bus and output the stabilized voltage to the slave controller and the peripheral circuit of the slave controller to supply power, and is also configured to shield interference to the slave controller, caused by signal transmission when data is transmitted by the slave module; and a signal modulation circuit is connected between the slave upper interface and the slave controller, and is configured to modulate the sensor signal into a corresponding current signal and transmit the current signal to the master unit via a daisy chain wire; wherein the signal modulation circuit uses a light emitting diode to perform signal modulation and displays the working state of the slave module during data transmission; and wherein the slave module contains an internal sensor and an external sensor, a slave controller is connected to the internal sensor and the external sensor to detect the internal sensor and the external sensor, the internal sensor is configured to obtain the internal parameter of the slave module; and the external sensor includes, without limitation, one or more of a temperature sensor, an ultrasonic sensor, an acceleration sensor, a smoke sensor, a humidity sensor, a vibration sensor, a photosensitive sensor, or a proximity switch on a Hall sensor. 2. The daisy chain two-wire sensor measuring system according to claim 1, wherein the main module includes a power interface, a main bottom switch, a main bottom interface, a signal demodulation circuit, a main voltage stabilization circuit, a main controller, and a communication interface. 3. The daisy chain two-wire sensor measuring system according to claim 2, in which the power interface is connected to an external power source and the main voltage stabilization circuit, and the main voltage stabilization circuit is connected to the main controller and is configured to stabilize the input supply voltage and output the stabilized supply voltage to the main controller and the peripheral circuit of the main controller. 4. The daisy chain two-wire sensor measuring system according to claim 2, wherein the main bottom switch is connected to the main controller and is connected in series with the daisy chain wire, and controls the conductance of the slave top interface of the first slave module through the main bottom interface. 5. The daisy chained two-wire sensor measurement system of claim 2, wherein the signal demodulation circuit is connected to the main controller and configured to decode the current signal in the daisy chain wire to obtain the corresponding sensor data. 6. The daisy-chained two-wire sensor measurement system of claim 2, wherein the communication interface is connected to the upper computer and transmits sensor data to the upper computer. 7. The daisy chain two-wire sensor measuring system of claim 1, wherein the slave module comprises a slave top interface, a slave bottom interface, a reverse connection protection circuit, a slave voltage regulation circuit, a signal modulation circuit, a slave controller, and a slave bottom switch. 8. The method of daisy-chained two-wire sensor measurement using a daisy-chained two-wire sensor measuring system according to any one of paragraphs. 1-7 and includes the following steps: S1: initialization of the system, activation of sampling of the sensor signal and encoding of the collected sensor signal; S2: modulate the sensor signal into the corresponding current signal, and send the current signal to the daisy chain wire; S3: decoding the current signal from step S2 to obtain the corresponding sensor data; and S4: determining, based on the sensor data, whether there is a faulty slave module or abnormal sensor data; moreover, the data transmission and fault location of one slave module includes the following time periods: T0 represents a period of time in which the bus is off and is controlled by the master unit, wherein in this period of time the master unit turns off the master lower switch and all slave units are in a power-off state; T1 represents a period of time for synchronization, and in this period of time, the master unit already turns on the main lower switch, and the power of the slave units is sequentially turned on, and the duration of the period T1 is determined by the slave units; slave modules prepare for data transmission after power-up and sampling of the signal from the sensor for T1, with the upper limit of the duration of T1 being T1max; and T2 represents a period of time for data transmission, and in this period of time, the slave modules complete the acquisition of sensor data, process and transmit this data, while the upper limit of the duration of T2 is T2max; wherein the data transmission and fault location of the N slave modules include the following steps: S1: turning on the main lower switch by the main unit, terminating the period T0, and activating the timing for T1, with n set to 1; S2: if no data is received by the master within T1max, determining that n slaves fail to read and proceed to step SE; S3: activation of the timing for T2 after the main unit receives data, stop collecting all data and wait for the completion of data transmission; S4: if T2 > T2max, determining that a data error occurs in the nth slave module, and proceeding to step SE; S5: if there is a validation error in the data, go to step SE; if there is a fault in the data indicating an open or shorted sensor, go to step S6; S6: set n to n + 1 and activate timing for T1; S7: go to step S2 and SE: if n = N + 1, meaning that all slave modules receive data, and data transmission is completed, turn off the main lower switch by the master module; if n < N + 1, determining that there is a communication fault in the nth slave module.

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