JPH02274086A - Two-wire bidirectional communication circuit of automatic meter inspecting system - Google Patents

Abstract

PURPOSE:To execute the bidirectional communication by dividing a detection terminal equipment side into two serial arms of a receiving side and a transmitting side, and also, controlling a signal power source switching circuit of a repeating installation side by a down-signal, and mutually reversing the directions of a current flowing to two DC arms at the time of transmission (up-signal) at the time of reception (down-signal). CONSTITUTION:The bidirectional communication of a down-signal and an up- signal brings currents i1, i2 flowing in the reverse directions to each other through a current loop 11 and 12 allowed to branch to two by a parallel circuit 10 to ON/OFF control by a down-signal 101 or an up-signal 102, and the respective receiving signals are generated. In such a way, the bidirectional communication can be executed without interfering with each other, and also, it is unnecessary that a current is allowed to flow to a photodiode 7A of a transmitting side photocoupler 7 at the time of receiving the down-signal, as well and it is set to an operable state, and therefore, the battery capacity for backup is suppressed to the necessary minimum and a meter inspecting terminal 2 can be miniaturized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an automatic meter reading system for a watt-hour meter, and relates to an automatic meter reading system for a power meter, which is formed between a meter reading terminal and a relay device connected via a two-wire transmission line. The present invention relates to a circuit that performs bidirectional communication by controlling on/off a current supplied from a single power source to a current loop using a down signal or an up signal.

[Conventional technology]

The automatic meter reading system is installed for each electricity consumer and monitors the amount of electricity used by i! This is an attempt to automatically read the meter of a watt-hour meter that measures watt-hours without having to rely on all hands. Data such as the amount of electricity used is stored in the meter-reading terminal on the watt-hour meter side, and this stored data is This is a system that calculates the amount of electricity used and electricity charges for each consumer by transmitting data to a computer on the power company side. A wire-type power distribution line is used to transfer signals between the meter reading terminal and the relay device. A current loop is formed that is controlled on and off in accordance with the meter reading terminal, and a signal from the relay device to the meter reading terminal side (called the lower multi-signal) and a signal from the meter reading terminal side to the relay device side (called the upper multi-signal) are formed. )
A signal power supply switching circuit system using a two-wire single power supply that performs bidirectional communication is known. Furthermore, this system includes a point-to-point connection form in which one meter reading terminal device is combined with one relay device, and a multi-drop connection form in which multiple meter reading terminal devices and one relay device are combined.

FIG. 3 is a connection diagram showing a conventional signal power switching circuit connected point-to-point, in which the relay device 1 and the meter reading terminal device (hereinafter also abbreviated as the terminal device) 2 are connected to two photocouplers 18, 19 and 6, respectively. .7t-equipped with phototransistors 18B, 7B and photodiodes 19A,
6A are connected in series to each other via two-wire transmission lines 3A and 3Bk, one end is connected to the single power supply 17 via a resistor 17A, and the other end is grounded, thereby creating a current loop consisting of one closed circuit. 60 is formed. Therefore, the photodiode 18A of the photocoupler 18 for lower multi-signal transmission
Alternatively, by applying a high potential or low potential signal to the photodiode 7A of the photocoupler 7 for transmitting an uplink signal and controlling on/off the current flowing to the current loop 60, the received signal is transmitted to the phototransistor 6B side of the photocoupler 6. An upstream reception signal is created on the phototransistor 19B side of the photocoupler 19.

[Problem to be solved by the invention]

In an automatic meter reading system, the meter reading terminal is always in a standby state where it can receive data, and it is required to send stored data to the computer via a relay device based on instructions from the convenience store of the electric power company. However, in the conventional device, since the current loop 60 is composed of one closed circuit, when trying to transmit a downlink signal from the photocoupler 18 side, the photodiode 7A of the uplink signal transmission photocoupler 7 on the meter reading terminal 2 side Phototransistor 7B' with full DC current supplied? If it is not turned on, it will not be possible to control the current loop on and off using the downstream signal. In addition, when transmitting all the upper signals from the photocoupler 7 side, the phototransistor 18Bt- of the photocoupler 18
Similarly, it is required to keep it in the on state. in general,
In consideration of commercial power outages, the meter reading terminal 2 is equipped with a storage battery as a backup power source. A problem arises in that the capacity of the storage battery must be increased. Also, even if either of the phototransistors 18B and 7B in the current loop fails, the current goes up.

There is also the problem that communication on both sides becomes impossible.

An object of the present invention is to obtain a bidirectional communication circuit consisting of a two-wire single power supply and having a simple configuration that allows bidirectional communication to occur without any interference.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, a current supplied from a single power supply to a current loop formed between a meter reading terminal and a relay device connected via a two-wire transmission line, Turns on/off by downstream signal or upper multi-signal 1υI
In a circuit that performs bidirectional communication by controlling J, a series arm consisting of a lower multi-signal receiving photocoupler arranged on the meter reading terminal side and a diode connected in series to the photodiode, and an upstream signal transmitting photocoupler and The series arms of the phototransistor and the diode connected in series are connected in parallel so that the directions of current flow are opposite to each other.
This parallel circuit is connected to a signal power switching circuit arranged on the relay device side via a two-wire transmission line, and the current supplied from the single power supply to the signal power switching circuit is switched and controlled by the lower multi-signal. It is assumed that a current loop is formed between two series arms in which the current direction is opposite to each other.

[Operation] In the above means, the flow directions of the two series arms provided on the meter reading terminal side are formed to be opposite to each other, and the signal is supplied from a single power source by a signal power source switching circuit provided in the relay device. By configuring the current to flow in opposite directions to the two series arms corresponding to the upper multi-signal and the lower multi-signal, υ allows the current loop to be controlled on and off by the lower multi-signal and the upper multi-signal. The current flows through the two series arms on the meter reading terminal side in opposite directions, allowing two-way communication without mutual interference, and making it possible for the meter reading terminal to receive information at all times. It is no longer necessary to supply DC current to the photodiode of the transmitting side photocoupler for storage, and it is possible to store 100% of backup power. The total capacity of the pond can be reduced to the minimum required capacity.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a connection diagram of a bidirectional communication circuit showing an embodiment of the present invention. In the figure, the downlink signal 10 is on the relay device 1 side.
A signal power supply switching circuit 15 is provided, which includes a transistor 4 that receives the down signal 101 through a resistor 21t, and an operational amplifier 5 that has a resistor 24. It will be done.

Further, on the meter reading terminal 2 side, a photocoupler 6 on the downlink signal 101 receiving side and a photocoupler 7 on the upstream signal transmission side are provided.
A parallel circuit 10 is formed by connecting the series arms of B and the diode 8 in parallel so that the directions of current flow are opposite to each other. One side is connected to the output side of the voltage follower 5, and the other side is connected to the transistor 4 and the single power supply 1.
7 through resistors 23 and 22 to form an output terminal 27 of the overload signal 112.

When a high-potential falling signal 101 is input to the switching circuit j5 configured as described above, the transistor 4 becomes conductive and at the same time, the voltage follower 5 receives a current of 1! from the single power supply 17! is supplied, so that current 11 flows through the series arm consisting of diode 9 and photodiode 6A and transistor 4.
Current loop 11 of the down signal flowing to the ground side via
is formed, the phototransistor 6B of the downlink signal receiving side photocoupler 6 becomes conductive, and the detection end of the downlink reception signal 111 connected to the single power supply 17 via the resistor 26 drops to the ground potential, so that the downlink reception signal 111 is output as a low potential signal. Furthermore, when the downlink signal 101 becomes a low potential, the transistor 4 is turned off and the output of the voltage follower 5 also becomes a low potential.
i, does not flow, and therefore the phototransistor 6B of the photocoupler 6 is also turned off, the voltage of the single power supply 17 is applied to the receiving end of the downlink signal 111, and a high potential downlink reception signal 111 is generated. The signal 101 is transmitted as a received signal 111 (with the high potential and low potential swapped).

On the other hand, in the transmission of No. 91-102 102, the down signal 101 is held at a low potential, the transistor 4 is off, and the output of the voltage follower 5 is at a low level, and the photodiode 7 AK of the transmitting side photocoupler 7 is inputted to all the up signal 102. It is done by At this time, since the transistor 4 is in the off state, the potential of the receiving end 27 of the high/low signal is held at the potential V of the single power source 17, and the output end of the voltage follower is in a grounded state with a low potential. . Then, when the high potential rising signal 102 is applied to the photodiode 7A and the phototransistor 7B is turned on, the resistor 22. Diode 8. A current loop 12 of the upstream signal grounded through the phototransistor 7B and the voltage follower 5 is formed, and the current 1. However, the potential at the output end 27 of the upstream signal becomes a low potential due to the potential drop of the resistor 22, and the upstream reception signal 112 of a low potential is output.

Furthermore, when the upstream transmission signal 102 becomes a low potential, the phototransistor 7B is turned off and the current 12 stops flowing, so the potential drop across the resistor 22 becomes zero, and therefore the output terminal 27 of the upstream reception signal is simply The potential of the power supply 17 increases, and a high potential upstream reception signal 112 is generated.

In this way, in the example circuit, the down signal and the up
Bidirectional communication of signals is achieved by passing currents i, , i, which flow in opposite directions through current loops 11 and 12 branched into two in a parallel circuit 10, into a downstream signal 1°1 or an upstream signal 10.
2 generates each received signal through on/off control, making it possible to perform two-way communication without mutual interference. Since there is no need to supply current to enable operation, the capacity of the backup storage battery can be reduced to the necessary minimum and the meter reading terminal 2 can be downsized.

FIG. 2 is a connection diagram on the relay device side showing a different embodiment of the present invention, in which the signal power switching circuit 35 is composed of two ICs (integrated circuits) 35A and 35B configured as a totem pole output circuit and a transistor 4. and the downlink signal 101
This differs from the previous embodiment in that the voltage is supplied to the transistor 4 via the circuit C35A and the resistor 21, and when the lower signal 101 is at a low potential, the transistor 4 is
is turned on and a current of 11 tl flows to the ground side, and at the same time C3
Since the output side of 5B has a high potential and supplies current 11, the downstream receiver signal 111 and the downstream signal 101 in FIG.
It differs from the previous embodiment in that both of the received signals 111 and 111 have a high potential or a low potential.
The convenience of being able to arbitrarily select whether the potential of the signal 112 is made to match that of the transmission signals 101 and 102 or to be inverted is provided.

In addition, the explanation of the embodiment is based on a point-to-point type device t-9'l in which a meter reading terminal and a relay device correspond to each other on a one-to-one basis.
Although described above, the present invention can be easily applied to multi-drop type circuits.

〔Effect of the invention〕

As mentioned above, this invention divides the detection terminal side into two series arms, the receiving side and the transmitting survey arm, and controls the signal power switching circuit on the relay device side with a downstream signal to direct the current flowing to the two DC arms. The signals are configured so that they are in opposite directions when transmitting (upper multiple signals) and when receiving (lower 9 signals). As a result, bidirectional communication of lower multiple signals and upstream signals is performed without mutual interference by controlling the on/off of currents flowing in the two series arms in opposite directions, so two-way communication can be performed in one closed circuit. A problem with conventional devices in which a communication current loop is formed is that downstream signals cannot be communicated unless direct current is constantly passed through the photodiode of the photocoupler for generating uplink signals, which is not used when communicating downlink signals. Therefore, it is possible to provide a two-wire bidirectional communication circuit for an automatic meter reading system that is capable of bidirectional communication without increasing the backup storage battery capacity and without complicating the configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit connection diagram showing a device according to an embodiment of the present invention, FIG. 2 is a connection diagram of main parts showing a different embodiment, and FIG. 3 is a connection diagram of main parts showing a conventional device. 1... Relay device, 2... Meter reading terminal, 3A, 3B.
... Two-wire transmission line, 4... Transistor, 5... Voltage follower, 6... Photocoupler (receiving side), 7.
...Photocoupler (transmission side), 1 leaf...Parallel circuit, 11
, 12°60...Current loop, 15.35...
Signal power supply switching circuit, 17-flit source, 35A, 35B
・4C (totem pole configuration), 101, 111...
Down signal, 102, 112... up signal. / 384 mu 3me L person sound <(2JR hair is small)

Claims (1)

[Claims] 1) Turn on and off the current supplied from a single power supply to the current loop formed between the meter reading terminal and the relay device connected via a two-wire transmission line by a downstream signal or an upstream signal.
In a circuit that performs two-way communication with OFF control, a series arm consisting of a downlink signal receiving photocoupler arranged on the meter reading terminal side and a diode connected in series with the photodiode, and an uplink signal transmission side photocoupler and its A series arm with a diode connected in series to a phototransistor is connected in parallel so that the direction of current flow is opposite to each other, and this parallel circuit is connected to a signal power source arranged on the relay device side via a two-wire transmission line. connected to the switching circuit, the current supplied from the single power supply to the signal power supply switching circuit is switched and controlled by the down signal, and a current loop is formed between the two series arms in which the directions of the currents are opposite to each other. A two-wire two-way communication circuit for an automatic meter reading system.