JPS60227592A - Current output terminal of multiplex transmission system - Google Patents

Abstract

PURPOSE:To attain centralized control of a load at the side of a central control unit by current-controlling the load based on control data received by each terminal, and returning monitoring data in the controlled state. CONSTITUTION:A central control unit 1 transmits signals consisting of a start signal, address data, control data, and a return standby signal, etc., to each terminal 3 in terms of time division. In each terminal 3 a signal processing circuit 5 compares address data of a transmission signal with its inherent address data. When they are coincident, control data is fetched, and fed to a constant current circuit 15 through a D/A convertor 6. Said circuit 15 transmits a current at the prescribed stage corresponding to the control data and supplies it to a load. Monitoring data in the controlled state of the load is returned to the unit 1 from the circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a current output terminal for a multiplex transmission system.

[Background technology] Conventionally, analog signals such as temperature, humidity, and pressure have been directly transmitted, for example, from 4 to 20 m, to control air conditioning equipment such as electric control valves.
Since the method was to convert the signal into a current signal of A and control it, centralized monitoring and control could not be easily performed.

1. Purpose of the Invention] The present invention has been provided in view of the above points, and provides a method for controlling a load by outputting a current corresponding to control data of a transmission signal transmitted from a central control device in a multiplex transmission system. The present invention provides a current output terminal device for a multiplex transmission system, which is intended to monitor the control state of a load.

[Disclosure of invention] Embodiments of the present invention will be described below with reference to the drawings.

Figure 3 shows a system block diagram of a multiplex transmission system, where 1 is a central control unit consisting of a microcomputer;
A plurality of terminal devices 3 . . . are connected to a central control device 1 of - via dedicated signal lines 2.

FIG. 4 shows the seven formats of transmission signals time-divisionally transmitted from the central control device 1 to each terminal device 3. As shown in the figure, a start signal, address data, control data,
It consists of a return standby signal, etc. In addition, each terminal 3
has a unique address. Thus, the transmission signal is time-divisionally transmitted from the central control device 1, and each terminal device 3 compares and judges the address data of the transmission signal and its own unique address data, and if the address data match, Control data following the address data is taken in, and the load 4 is controlled based on the control data. still,
The specific configuration and method for controlling this load 4 will be described later. In addition, the terminal device 3 sends back a return signal as monitoring data indicating the controlled state of the load 4 to the central control device 1 within the period of the return standby signal of the transmission signal, and the central control device 1 controls the load 4 using the return signal. The status can be monitored. Further, the load 4 is, for example, an air conditioning device such as an electric control valve.

Next, it will be explained in detail. FIG. 1 shows a block circuit diagram of the terminal device 3, and FIG. 2 shows a specific circuit diagram of the terminal device 3. As shown in FIG. Reference numeral 8 is a constant voltage circuit, which makes the output of the diode bridge DB non-polarized, which makes the power sent along with the transmission signal from the signal line 2, a constant voltage.
2, C3, transistor Q 2, Zener diode Z
It is composed of D, etc. 9 is an isolation circuit consisting of 7 automatic couplers, which electrically blocks the transmission signal. 5 is a signal processing circuit, and an isolation circuit 9
The transmission signal is input to the terminal 5IGN via the terminal 5IGN, and the address data of the transmission signal and the own address are compared and determined. If they match, the control data following the address data is fetched and the control data is sent to the terminals RDI to RD4. Output. 12
An address setting section is used to set a unique address for the terminal device 3, and is composed of dip switches. 6 is a D/A converter which inputs control data from the signal processing circuit 5 to terminals DB4 to DB7 and converts the digital signal of the control data into an analog signal. In other words, the D/A converter 6 outputs analog signals of several stages depending on the content of the control data. 1
3 is a latch circuit, and the control data of the terminals RD1 to RD4 is changed by the rising edge of the terminal RD5 of the signal processing circuit 5.
It is input to terminals DB4 to DB7 of the D/A converter 6, and also to the terminals of this latch circuit 13. - Control data is input to D3 as monitoring data for monitoring the state of the load 4. Furthermore, the monitoring data output from the terminal Qo''-Qs of the latch circuit 13 is transferred to the terminal IN1 of the signal processing circuit 5.
~4 is input. The signal processing circuit 5 outputs the monitoring data as a return signal from the terminal RET within the period of the return standby signal of the transmission signal.

An isolated circuit consisting of a 101 photo coupler electrically cuts off the above return signal and outputs it.

Reference numeral 11 denotes a return signal output circuit composed of transistors Q, 3Q, etc., which turns on the transistor Q by the return signal from the isolation circuit 10, shorts the output side of the diode bridge DB, and centrally controls the signal. The data is sent back to device 1. In this way, by isolating the central control device 1 side and the controlled equipment side using the isolation circuits 9 and 10, it is possible to prevent current and noise from flowing between the two sides. 14. is a local power supply on the terminal device 3 side, and AC 24V is supplied to the diode bridge DB. , 19 is a constant voltage circuit, which is composed of a capacitor C4Cs, a transistor Q5, Zener diodes ZD2 to ZD4, and the like. next,
The current output means will be described. The current output means is a resistor R
5~R3, capacitor C1, operational amplifier OP1. OP2
A constant current circuit 15 is constituted by a resistor R2, a transistor Q1, and an operational amplifier OP1, and a resistor R3,
Constant current circuit 16 with transistor Q7 and operational amplifier OP2
is configured. 7 is a 7-Ruse 7 circuit, consisting of a 2-channel selector 17 and a changeover switch SW. Toward, 7
Although the circuit 7 is specifically shown in FIG. 2, it is omitted from the block diagram of FIG. 1 for convenience of explanation.

Next, the operation will be explained. Incidentally, since the overall operation has been schematically explained, a description thereof will be omitted, and only the operation of the gist of the present invention will be explained. First, the signal processing circuit 5 takes in the control data following the address data, and inputs the control data to the terminals DB4 to DB7 of the D/A converter 6. DBO in D/A converter 6
A current value I corresponding to the digital signal of ~7 is sucked into the terminal A-0. Further, the resistor R3 of the constant current circuit 16 has V R
A current i of EF/R3 flows. Therefore, the potential at point A shown in FIG. 1 becomes V no -Rl (I +i), and the constant current circuit 15 outputs a current of (I 1i) R+/R2. Here, the control data of RD1 to 4 is 0.
If H (hexadecimal), I=0, so at this time iR, /
Also, FH (16
), then I=IF, so (I p +i)R+/
Each resistor R1 to R
Determine the constant of 3. Here, capacitor C1 is L/
This is to prevent sudden operation of the controlled device by worsening the X-ponse. Further, the diode D1 is provided to prevent damage to the circuit due to incorrect wiring. Therefore, the constant current circuit 15 operates in several stages (in this case, 1) according to the control data.
An analog current (4 to 20+nA) of 6 stages) is output, and this current is used to control the electric control valve of the air conditioner, which is the load 4. On the other hand, the control data for controlling the load 4 is input as the monitoring data of the load 4 to the latch circuit 13 and the signal processing circuit 5 as described above, and the return signal is sent from the terminal RET of the signal processing circuit 5 to the central control. It is sent back to device 1. Therefore, air conditioning equipment such as electric control valves can be controlled from the central control device 1, and furthermore, the control status of the equipment can be monitored by answering back (return signals) from the terminal device 3.

By the way, when the local power supply 14 is turned on, the output current value from the constant current circuit 15 is unknown, which causes an inconvenience. Therefore, a fail-safe circuit 7 is provided that sets the output current value from the constant current circuit 15 to a minimum value of 4 mA or a maximum value of 20+oA when the power is turned on. 7 Engineering - Rousse 7 Circuit 7
The 2 channel selector 17 that constitutes the C-MOS
4019 type is used, and the control terminals Ka,
By controlling Kb, 2 channels of data X1 to X
4. This is a data selector that switches between Yl and Y. The output terminal of the inverter G1 is connected to the control I terminal Kb of the 2-channel selector 17, and is connected to the control terminal Kb of the 2-channel selector 17.
The output terminal of G2 is connected to the other control terminal Ka. Now, in FIG. 2, when the local power supply 14 is turned on, the potential at point a is lower than the threshold voltage of the inverter G1 due to the delay in the charging time of the capacitor C6, which is determined from the time constant consisting of the resistor R4 and the capacitor C6. Therefore, the control terminal Ka of the 2-channel selector 17 is at the L level, and the other control terminal K is at the L level.
I(level) will be input to l).

Therefore, levels Y1 to Y are output to D1 to D of the two-channel selector 17. Therefore, switch S
If W is on the VDD side, H level is output to D1 to D,
If it is on the GND side, L level is output. Furthermore, since the output of the NOR date G3 is at the L level regardless of the output of the RD5 of the signal processing circuit 5, a rising edge is input to the STB of the D/A converter 6 and the CLOCK of the latch circuit 13.
At the same time, 2 channel selector 17, ~D,
The outputs of DB4 to DB7 . of the D/A converter 6 are respectively output.
The latch circuit 13 is input to -D3. Therefore, D
The output from the constant current circuit 15 is based on the output of the /A converter 6. If the switch SW is on the VDD side, 20[OA1 switch SW is
On the ND side, a current of 4+nA is output and the latch circuit 13 is connected. The input to -D3 is input to INI to IN4 of the signal processing circuit 5 through Qo-Q).

Thereafter, when the charging of the capacitor C6 progresses and the potential at point a becomes equal to or higher than the threshold voltage of the inverter G1, the control li of the 2-channel selector 17 is activated.
An H level is input to the control terminal Kb of the 2-channel selector 17 and a point b of the NOR gate G3. Therefore, R of the signal processing circuit 5 is connected to the 2-channel selector 17 through X1 to D.
Control data from DI to RD4 is output, and the D/A converter 6° latch circuit 13 is operated by the rising edge from RD5. In this way, when the local power supply 14 is turned on by the 7-Ruse 7 circuit 7,
The output current value of the current output type terminal device 3 becomes clear, and accordingly, the operation of the controlled equipment when the power is turned on becomes clear, and there is no danger. Further, since the output current value when the power is turned on can be set to a minimum value of 4+IIA or a maximum value of 20 mA using the switch SW, it is possible to select whether to close or open a controlled device, such as an electric damper, when the power is turned on.

[Effects of the Invention 1] As described above, the present invention transmits a transmission signal consisting of address data, control data, a return standby signal, etc. from a central control unit to a plurality of terminal devices via a signal line in a time-division manner, and the address data is In the matched terminal device, the load is controlled based on the control data following the address data, and a return signal based on the monitoring data of the controlled load is sent back to the central control unit within the period of the return standby signal of the transmission signal. In a multiplex transmission system, a signal processing circuit receives a transmission signal from a central control unit and outputs control data when it matches its own address, inputs monitoring data based on the control data, and outputs a return signal. and a D/A converter that converts the digital signal of control data from the signal processing circuit into an analog signal, and outputs a current of a magnitude corresponding to the analog signal from the D/A converter, and outputs a current corresponding to the amount of current. Since the terminal equipment is equipped with a current output means for controlling the load, the control data of the transmission signal transmitted from the central control unit to control the load is converted to D/A via the signal processing circuit. A current of a magnitude corresponding to this analog signal is output from the current output means to control the load, and is also output from the D/A converter depending on the content of the control data. The analog quantity can be varied in many stages, and therefore the load can be centrally controlled from the central control unit.The signal processing circuit also inputs monitoring data based on the control data and converts the return signal into a transmission signal. In order to return the signal to the central control unit within the period of the return standby signal, the central control unit is able to control and monitor the load.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the embodiment of the present invention, Fig. 2 is a specific circuit diagram of the same, Fig. 3 is a system configuration diagram of the multiplex transmission system of the above, and Fig. 4 is a transmission diagram of the same. This is the format of the signal. 1 is a medium heat control device, 2 is a signal line, 3 is a terminal device, 4 is a load, 5 is a signal processing circuit, and 6 is a D/A converter. Agent Patent Attorney Stone 1) Trap 7

Claims (1)

[Claims] (1) Transmission signals consisting of address data, control data, return standby signals, etc. are transmitted in a time-division manner from the central control unit to multiple terminal devices via signal lines, and in terminal devices whose address data matches, control continues after the address data. In a multiplex transmission system in which a load is controlled based on data and a return signal based on monitoring data of the controlled load is sent back to the central controller within a period of a return standby signal of the transmission signal, the central controller A signal processing circuit that receives a transmission signal from and outputs control data when it matches its own address, inputs monitoring data based on the control data, and outputs a return signal, and control data from the signal processing circuit. a D/A converter that converts the digital signal into an analog signal, and a current output means that outputs a current of a magnitude corresponding to the analog signal from the D/A converter and controls a load according to the amount of current. A current output terminal device for a multiplex transmission system, characterized in that the terminal device is equipped with the following.