JP3152324U - Current / voltage input recognition circuit - Google Patents

Abstract

An input recognition circuit for automatically recognizing an input current and voltage so that various measuring devices can be connected with good compatibility. A diode D1 for preventing reverse connection, a pull-down resistor R1, a current-voltage conversion reference resistor R2, and a current-voltage conversion reference resistor R2 connected to an input terminal are controlled. 20 mA switching relay circuit 2, and when a current is input from the input terminal, the voltage defined by the voltage drop of pull-down resistor R 1 and reverse connection prevention diode D 1 when received in the voltage input state. Is equal to or higher than a predetermined voltage, it is recognized that a current is input, the switching relay circuit 2 is turned on, a current is passed through the current-voltage conversion reference resistor R2, the current is converted into a voltage, and digital Convert and output. [Selection] Figure 1

Description

  The present invention relates to a circuit suitable for a telemeter system for centrally managing data collected by measuring various data in a wide range such as a factory or a management area, and in particular, from a portion requiring continuous monitoring to a predetermined range. The present invention relates to a current / voltage input recognition circuit which is suitable for a slave unit of a telemeter system that collects data by communication and recognizes input of a 4-20 mA signal or a 1-5 V signal from a sensor or the like, for example.

  2. Description of the Related Art Conventionally, many water treatment facilities and production sites for various products need to be manufactured while maintaining water quality, water flow, temperature, humidity, and the like within a predetermined range. In such a case, sensors for monitoring these environmental conditions, facilities for transmitting and receiving information from the sensors, and facilities for centralized monitoring are provided, and these facilities are used for remote monitoring. A telemeter system may be constructed.

  Nowadays, as a telemetering system for remote monitoring, a system for building a network by wireless communication is attracting attention, and an observation device for performing a predetermined measurement and an analog signal from the observation device are converted from analog to digital. A sensor network system including a CPU that generates a predetermined data signal and a wireless unit that wirelessly transmits the data signal is also known (see, for example, Patent Document 1).

JP 2007-122550 A

  In the conventional telemeter system as described above, a slave unit placed at a remote place receives an analog signal from a sensor or an external device and performs analog-to-digital conversion and outputs the analog signal, but the analog signal is 4-20 mA. Signals and 1-5V signals are often used.

  Generally, when analog-to-digital conversion of an analog signal, it is necessary to convert current to voltage. However, a slave unit with an analog input terminal supports only one of current input and voltage input. The actual situation is that the input is set by jumpers. Therefore, the conventional telemeter system has a problem that various measuring devices cannot be connected with good compatibility in the slave unit.

  Therefore, in view of the above technical problems, the present invention is a telemeter system child device that collects measurement data by connecting a child device capable of measuring a plurality of data to the parent device by predetermined wireless communication. This is a suitable circuit, and various measuring devices can be connected with good compatibility. For example, a current / voltage input capable of automatically recognizing a current / voltage input by a 4-20 mA signal or a 1-5 V signal. An object is to provide a recognition circuit.

  In order to solve the above technical problem, a current / voltage input recognition circuit according to the first aspect of the present invention includes a reverse connection prevention diode connected to an input terminal, a pull-down resistor, and a current-voltage conversion. And a switching relay circuit that controls energization of the reference resistor for current-voltage conversion. When current is input from the input terminal, pull-down resistor and reverse connection when received in the voltage input state If the voltage specified by the voltage drop of the prevention diode is equal to or higher than the specified voltage, it recognizes that a current is being input, turns on the switching relay circuit, and passes the current through the reference resistor for current-voltage conversion. The current is converted into a voltage and output.

  A current / voltage input recognition circuit according to a second aspect of the present invention includes a reverse connection prevention diode having an anode connected to an input terminal and a cathode connected to a protection circuit, and one end of which is the cathode of the reverse connection prevention diode. A pull-down resistor connected to the first node between the first node and the protection circuit, the other end of which is grounded, and a current connected to the second node between the first node and the protection circuit. A voltage conversion reference resistor and a switching relay circuit connected to the other end of the current-voltage conversion reference resistor. When a current is input from the input terminal, a pull-down resistor If the voltage specified by the voltage drop of the reverse connection prevention diode is equal to or higher than the predetermined voltage, it is recognized that the current is being input, the switching relay circuit is turned on, and the current-voltage change is detected. Current flows to use the reference resistor, and outputs by converting said current into a voltage.

  According to the current / voltage input recognition circuit of the present invention, various measuring devices and the like can be connected with good compatibility. For example, a current / voltage input by a 4-20 mA signal or a 1-5 V signal can be automatically recognized. Is possible.

1 is a configuration diagram of a current / voltage input recognition circuit according to a first embodiment of the present invention. FIG. It is a block diagram which shows the detailed structure of the subunit | mobile_unit to which the electric current / voltage input recognition circuit which concerns on the 1st Embodiment of this invention is applied. It is a conceptual diagram which shows the structure of the telemeter system using the subunit | mobile_unit to which the electric current / voltage input recognition circuit concerning the 1st Embodiment of this invention was applied.

  An embodiment of a current / voltage input recognition circuit suitable for a telemeter system of the present invention will be described with reference to the drawings. In addition, the telemeter system provided with the subunit | mobile_unit to which the electric current / voltage input recognition circuit which concerns on one Embodiment of this invention is applied is a factory, a farm, an apartment, etc. which produce various products, such as a foodstuff, a chemical | medical agent, a chemical product, and a semiconductor, for example. It is a system used in a building or the like, and is suitable for use in a relatively large-scale manufacturing facility that is automatically operated unattended on a predetermined site (hereinafter referred to as a management area).

  First, FIG. 1 shows and describes the configuration of a current / voltage input recognition circuit 1 according to an embodiment of the present invention. As shown in FIG. 1, the input terminal of the current / voltage input recognition circuit 1 is connected to one end of a resistor R3 via a reverse connection prevention diode D1. That is, the anode of the reverse connection preventing diode is connected to the input terminal, and the cathode is connected to the resistor R3. The other end of the resistor R3 is connected to the connection end of the diodes D2 and D3, and the connection end continues to the output terminal. A node N1 between the cathode of the reverse connection prevention diode D1 and the resistor R3 is connected to one end of the pull-down resistor R1, and the other end of the pull-down resistor R1 is grounded. A node N2 between the node N1 and the resistor R3 is connected to one end of the current-voltage conversion reference resistor R2, and the other end of the resistor R2 is connected to the 4-20 mA switching relay circuit 2. In this example, the resistance values of the resistors R1, R2, and R3 are 1 MΩ, 250Ω, and 1 KΩ, respectively. This is merely an example, and is not limited to this value.

  Here, the principle of automatically recognizing a current input by a 4-20 mA signal with the above configuration will be described. In the normal standby state, voltage input is set. When a current is input and received in a voltage input state, the terminal voltage becomes 5 V or more if it is 5 μA or more due to the pull-down resistor R1 (1 MΩ). However, when a voltage is applied, the input voltage is reduced by the voltage drop (referred to as VF) of the reverse connection prevention diode D1, so that the maximum is 5V-VF. Therefore, if a predetermined voltage (5 V in this example) is detected in the voltage input state, it can be considered that a current is almost input, and if the input current is in the range of 4-20 mA, the current input Can be determined to have been made. That is, according to the above principle, it becomes possible to automatically recognize a current input by a 4-20 mA signal.

  In such a configuration, when a current input by a 4-20 mA signal is made from a sensor (not shown) or an external device, the 4-20 mA switching relay circuit 2 is turned on. As a result, a current flows through the current-voltage conversion reference resistor R2, and the current can be converted into a voltage, digitally converted, and output. The voltage at this time is the product of the current flowing through the current-voltage conversion reference resistor R2 and the resistance value of the reference resistor (in this example, 250Ω). On the other hand, when a voltage input by a 1-5 V signal is made from a sensor (not shown) or an external device, the 4-20 mA switching relay circuit 2 is turned off, and the digital conversion is performed as it is. The resistor R3 and the diodes D2 and D3 following the latter stage constitute a commonly used input voltage protection circuit. When a 4-20 mA current is input, the voltage input state (the 4-20 mA switching relay circuit 2 is This is for protecting a digital conversion circuit (not shown) that follows the subsequent stage when the voltage increases in the OFF state) and when a voltage exceeding 1-5 V is input.

  Next, FIG. 2 shows and describes the circuit configuration of a slave unit in which the current / voltage input recognition circuit 1 of FIG. 1 is adopted. As shown in FIG. 2, the slave unit 10 includes a central processing unit (CPU) 11, a 4-20 mA digital conversion unit 12 including the current / voltage input recognition circuit 1, and an RS232C interface unit 13. A serial conversion unit 14, a memory 15 such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a wireless communication module 16, a power source 17, and an antenna 18. The 4-20 mA digital conversion unit 12 is connected to the sensor 21 and the external device 22, and the RS232C interface unit 13 is connected to the camera 23, the external device 24, and a setting personal computer (hereinafter referred to as a PC) 25. Yes. The setting PC 25 for setting the slave unit connected to the RS232C interface unit 13 may be a notebook personal computer or a dedicated electronic device.

  In such a configuration, the 4-20 mA digital conversion unit 12 is a circuit for receiving a standard 4-20 mA DC signal as an output signal of a measuring instrument or the like and converting it into digital data. The current / voltage input recognition circuit 1 shown in FIG. That is, the 4-20 mA digital conversion unit 12 can be directly connected to the sensor 21 or the like that outputs a 4-20 mA DC signal, or can be connected to an external device 22 such as various measuring devices to acquire data. Is possible. The input terminal for the 4-20 mA DC signal may be singular or plural. When a 4-20 mA DC signal from the sensor 21 or the like is input to the 4-20 mA digital converter 12, the current input is automatically recognized by the current / voltage input recognition circuit 1 in FIG. Will be output.

  The RS232C interface unit 13 functions as a signal input / output terminal for inputting / outputting data, and it is possible to set a communication setting or a function in an ad hoc mode by connecting a slave unit setting PC 25 or the like only to the slave unit. is there. For example, in a factory that requires strict temperature control, the temperature data from the temperature sensor is received by the 4-20 mA digital conversion unit 12, and a data signal about the temperature is wirelessly transmitted to the master unit and the personal computer via the CPU 11. In the case of automatic control, the slave unit wirelessly receives control data from a personal computer, and sends a control signal from the CPU 11 to an external device 24 such as an air conditioner connected to the RS232C interface unit 13 to control the temperature. Anyway. Further, a commercially available camera 23 capable of serial connection with RS232C is connected to the RS232C interface unit 13 to distribute still images and moving images, and to remotely control camera operations such as panning and zooming with a personal computer. It can also be done from the side.

  The CPU 11 is connected to a memory 15 for storing programs, data, and the like and temporarily storing measurement data, image data, and the like. The CPU 11 is connected via a serial conversion unit 14 that is a signal conversion unit. Connected to the wireless communication module 16.

  Various wireless LAN modules can be adopted as the wireless communication module unit 16, for example, IEEE802.11, IEEE802.11a, IEEE802.11b, IEEE802.11 by IEEE (Institute of Electrical and Electronics Engineers). 11g, IEEE802.11n, IEEE802.15.1 (Bluetooth (registered trademark)), IEEE 802.15.3 (UWB (Ultra-WideBand)), IEEE802.15.4 (ZigBee (registered trademark)), IEEE802.16 (WiMAX (registered trademark)) ), And a predetermined wireless communication method is selected according to the distance between the parent device and the child device described later, the type of data to be processed, and the like. .

  In the present embodiment, the wireless communication module 16 is a chip that creates a signal compliant with the ZigBee (registered trademark) standard, and can transmit and receive data via the antenna 18. The wireless communication module 16 employs a DSSS (Direct Sequence Spread Spectrum) modulation method using a predetermined frequency (for example, 2.4 GHz), and the wireless communication is performed by dividing the band into, for example, 16 channels. The ZigBee standard adopted by the wireless communication module 16 is compliant with IEEE 802.15.4, and encryption is also performed by the common key encryption algorithm AES (Advanced Encryption Standard).

  A power source 17 is connected to the CPU 11 and the like. The power source 17 may be a power supply means such as a power line, or a power supply means such as a solar battery, a dry battery, a storage battery, a fuel cell, or other uninterruptible power supply. Since the slave unit in the telemeter system of the present embodiment adopts the ZigBee (registered trademark) standard as described above, it is possible to reduce power consumption even during long-time operation, and independent solar cells, dry cells, etc. Even the power supply means will function.

  The wireless communication module 16 has been described as a single chip with reference to FIG. 2, but a circuit configuration including a CPU and a memory is also possible, and an interface unit with an external device is an RS232C. Alternatively, a wired LAN cable such as Ethernet (registered trademark), USB, or another connection method may be used.

  FIG. 3 shows a schematic configuration diagram of a telemeter system using a slave unit to which the current / voltage input recognition circuit 1 according to an embodiment of the present invention is applied. The slave unit 10 having the configuration as shown in FIG. 2 corresponds to the slave units 52 to 54 in FIG.

  For example, the slave units 52 to 54 are installed in the range of several tens of meters to 2,300 meters from the master unit 51, and are set to constantly transmit measurement data. In this embodiment, the parent device 51 and the child devices 52 to 54 are equipped with a communication module compliant with the ZigBee (registered trademark) communication standard, and can perform wireless communication using the 2.4 GHz band. In particular, by conforming to the ZigBee (registered trademark) standard, it becomes possible to operate with low power consumption, which is not possible with other wireless communication standards, and for example, a solar cell 65 or the like can be fed even to a handset that is difficult to sufficiently feed. It can also be operated without difficulty by means.

  The configuration of the master unit 51 will be described. The master unit 51 is connected to a personal computer 55 for centrally monitoring predetermined measurement data, and the measurement data from the slave units 52 to 54 is stored in the personal computer 55. In addition to being stored in the hard disk, the monitor 57 connected to the personal computer 55 displays the measurement data from the slave units 52 to 54. If an abnormality occurs, an alarm is displayed and a warning message is displayed. The situation can be communicated to the observer. A keyboard 58 for input is also connected to the personal computer 55, and a pointing device such as a mouse (not shown) is also connected. The parent device 51 and the personal computer 55 are installed in a place where a supervisor is present, such as a factory monitoring room or a business office. For example, the data received by the personal computer 55 is transmitted to the Internet as a communication network. For example, data can be transmitted to the monitoring center of the headquarters or the terminal 56 for maintenance or monitoring of the security company via 64.

  An application for monitoring measurement data from the slave units 52 to 54 is installed in the personal computer 55 connected to the master unit 51. With this application, basic settings, communication settings, and various slave unit function settings are set. Etc., and a warning screen or fault information display in a monitoring screen or abnormal situation is also executed. In the telemeter system of the present embodiment, images captured by the cameras 59 and 62 connected to the slave units 52 and 54 can be transmitted to the personal computer 55 and viewed on the monitor 57, and warning display and failure information display are displayed in the application. When performing, the image captured by these cameras 59 and 62 is configured to be displayed by clicking a predetermined button.

  The telemeter system of the present embodiment is configured such that the slave units 52 to 54 transmit different measurement data to the configuration on the master unit 51 side. In addition, the installation example of these subunit | mobile_units 52-54 is only an illustration, and can also install many more subunit | mobile_units, for example, can also install detectors, such as a water quality sensor, in several places. In the illustrated example, the topology is a star network, but the telemeter system of this embodiment can be a tree type or mesh type network by utilizing the features of the ZigBee (registered trademark) standard. is there.

  The slave unit 52 is a device capable of transmitting an image of the surveillance camera 59 in the management area. The surveillance camera 59 is connected to the RS232C terminal of the slave unit 52, and, for example, a stationary frame of about one frame is set every second. Image data can be transmitted from the slave unit 52 to the master unit 51. Surveillance camera 59 is assumed to be installed in a part that needs to ensure security such as entry prohibition except for related persons. For example, an image of a person entering or exiting a room or hallway from the ceiling or the like is transmitted to base unit 51. It functions to execute programs such as prompting a warning if there is an abnormality by image analysis.

  The subunit | mobile_unit 53 is connected to the measuring device 60, The temperature sensor 61 is attached to the measuring device 60, The temperature detection in the manufacturing process of a product is performed by these subunit | mobile_unit 53, the measuring device 60, and the temperature sensor 61. The temperature can be monitored. As a power source for the slave unit 53, a solar battery 65 is used in particular, and power can be supplied by sunlight even in places where it is not easy to route the power line. In particular, in a system compliant with the ZigBee (registered trademark) standard Since operation with low power consumption is guaranteed, the degree of freedom of installation location is increased. The measuring device 60 is a device that functions as an amplifier that converts the measurement data from the temperature sensor 61 into a 4-20 mA current signal, and wirelessly transmits the data to the parent device 51 side for each time interval set in the child device 53. .

  The handset 54 is a device for sending water quality data. A water quality probe 63 is attached to the peripheral portion of the water supply pipe 66, and the handset 54 takes in data of a 4-20 mA current signal from the water quality probe 63. Can do. The handset 54 is connected to the camera 62 in addition to the connection to the water quality probe 63, and the camera 62 continuously sends images of a portion of the water supply pipe 66 that can be transmitted through, for example, a glass material and monitored. It functions so as to notify the parent device 51 to the personal computer 55 via the child device 54 in the form of an image.

  Although about the subunit | mobile_unit 52-54 demonstrated to monitor the water quality and temperature in the system of FIG. 3, the data which can be measured are not limited to these, It can comprise so that various measurement data can be obtained. Further, the power source is not limited to the solar cell 65, and a dry cell, a storage battery, a fuel cell, or another uninterruptible power source can also be used. Further, in the above-described slave units 52 and 54, the cameras 59 and 62 are connected to send images, respectively, but it is also possible to collect sound with a microphone or the like and transmit voice data to the master unit 51.

  In the above-described embodiment, the ZigBee (registered trademark) standard is described as an example of the communication standard, but another wireless standard can be used for part or all of the communication part. Connections between peripheral devices such as measuring instruments, sensors, and cameras and the slave units can also be wireless communication.

1 current / voltage input recognition circuit 2 4-20 mA switching relay circuit R1 pull-down resistor R2 current-voltage conversion reference resistor R3 resistor D1 reverse connection prevention diode D2, D3 diode 11 CPU
12 4-20 mA digital conversion unit 13 RS232C interface unit 14 serial conversion unit 15 memory 16 wireless communication module 17 power supply 18 antenna 21 sensor 22 external device 23 camera 24 external device 25 setting PC
51 Master unit 52 to 54 Slave unit 55 Personal computer 56 Terminal 57 Monitor 58 Keyboard 59 Monitoring camera 60 Measuring instrument 61 Temperature sensor 62 Camera 63 Water quality probe 64 Internet 65 Solar cell 66 Water supply pipe

Claims (5)

A diode for preventing reverse connection connected to the input terminal;
A pull-down resistor;
A reference resistor for current-voltage conversion;
A switching relay circuit for controlling energization to the current-voltage conversion reference resistor;
If the voltage input state receives a current input from the input terminal and the voltage specified by the voltage drop of the pull-down resistor and the reverse connection prevention diode is not less than a predetermined voltage, , Recognizing that a current is input, turning on the switching relay circuit, passing a current through a current-voltage conversion reference resistor, converting the current into a voltage, and outputting the current Voltage input recognition circuit.   2. The current / voltage input recognition circuit according to claim 1, wherein the detected current input is a 4-20 mA DC signal.   The current / voltage input recognition circuit according to claim 1, further comprising a protection circuit configured by a resistor and a diode. A reverse connection prevention diode whose anode is connected to the input terminal and whose cathode is connected to the protection circuit, and one end of which is connected to the first node between the cathode of the reverse connection prevention diode and the protection circuit. A pull-down resistor having one end grounded, a current-voltage converting reference resistor having one end connected to a second node between the first node and the protection circuit, and the current-voltage converting reference A switching relay circuit connected to the other end of the resistor,
When a current is input from the input terminal, when the voltage is input, if the voltage defined by the voltage drop of the pull-down resistor and the reverse connection prevention diode is equal to or higher than a predetermined voltage, the current input is A current / voltage input recognition circuit, wherein the switching relay circuit is turned on, a current is passed through a reference resistor for current-voltage conversion, the current is converted into a voltage and output. .   5. The current / voltage input recognition circuit according to claim 4, wherein the detected current input is a 4-20 mA DC signal.