CN201146521Y

CN201146521Y - RS-485 bus hub

Info

Publication number: CN201146521Y
Application number: CNU2007201961891U
Authority: CN
Inventors: 熊伟
Original assignee: Sanwang Communication Technology Co Ltdshenzhen
Current assignee: Sanwang Communication Technology Co Ltdshenzhen
Priority date: 2007-12-19
Filing date: 2007-12-19
Publication date: 2008-11-05
Anticipated expiration: 2017-12-19

Abstract

The utility model discloses a RS-485 bus hub, which comprises a power supply management unit, a signal convergent and distribution unit, a main device interface branch and at least two slave device interface branches, wherein, the main device interface branch and each slave device interface branch respectively comprises a device interface and a bus isolated location; in the main device interface branch, a main device interface is connected with the signal convergent and distribution unit by the bus isolated location; in the slave device interface branch, a slave device interface is connected with the signal convergent and distribution unit by the bus isolated location; the bus isolated location is responsible for the separating between ground potential between interfaces and power supply; the signal convergent and distribution unit is responsible for signal forwarding between the main device interface branch and the slave device interface branch so as to realize the function of line concentration; the power supply management unit is responsible for the power supply and the power up sequence of each module. The RS-485 bus hub of the utility model can be used for realizing the combining mode of RS-485 bus star type connection and daisy chain connection, which enlarges routing coverage area and interlinked equipment number, simplifies the routing process of the system, reduces engineering cost and improves the reliability of the system.

Description

RS-485 bus hub

[technical field]

The utility model relates to the serial communication data acquisition system, relates in particular to a kind of RS-485 bus hub.Be suitable for data acquisition, the RS-485 interface equipment engineering application in fields such as automation control.

[background technology]

The RS-485 interface is a kind of low-cost bus interface that can realize point-to-multipoint delivery, and in data acquisition, find broad application in fields such as automation control.Yet the RS-485 bus must be carried out apparatus interconnection with the wire laying mode that is similar to the daisy chain form, this performance difficulty not only for the more multiple spot acquisition system engineering of branch, and improved the cost of installation and maintenance.

Mainly there is following shortcoming in traditional wire structures:

1.RS-485 bus is subjected to the total line length of the restriction of differential signal transmission characteristics generally about 1200 meters, the area coverage that can connect up is very limited, has to adopt repeater in order to widen transmission range sometimes, has also strengthened the possibility that goes wrong in the wiring process.

2. all devices is shared same RS-485 bus.The short circuit of arbitrary equipment RS-485 port all can influence the operate as normal of whole system.

3. owing to RS-485 route bus more complicated, most engineering costs and time all are wasted in the wiring link in system.And the number that articulates of the length of the complexity of RS-485 route bus and bus and equipment has much relations, seems in large scale system especially by for outstanding.Adopt traditional wire structures to strengthen the difficulty of wiring undoubtedly.

4. because always there is the unbalanced problem of earth potential in geographical environment at a distance of between the equipment of certain distance.This factor that causes because of environment is difficult to comprehensive the solution, even causes whole system to start in the traditional wiring structure, make numerous RS-485 interface equipments operate as normal in a RS-485 network reliably.Even working properly, its number of devices generally also must be limited in 32.

[summary of the invention]

The technical problems to be solved in the utility model provides a kind of RS-485 bus hub, realize that by RS-485 bus hub the star-like connection of RS-485 bus is connected the mode that combines with daisy chain, improve the area coverage of wiring and the reliability of system, wiring process that simultaneously can also simplified system reduces engineering cost.

In order to solve the problems of the technologies described above, the technical solution adopted in the utility model is that a kind of RS-485 bus hub comprises that Power Management Unit, signal compile Dispatching Unit, host device interface branch road and at least 2 slave unit interface branch roads; Described host device interface branch road and every slave unit interface branch road comprise equipment interface and bus isolated location respectively; In the host device interface branch road, host device interface is compiled Dispatching Unit by the bus isolated location with signal and is connected; In slave unit interface branch road, the slave unit interface compiles Dispatching Unit by the bus isolated location with signal and connects; Described bus isolated location is responsible for earth potential and the isolated from power between each interface; Described signal compiles Dispatching Unit and is responsible for signal forwarding between the master-slave equipment interface branch road, realizes the line concentration function; Described Power Management Unit is responsible for the power supply power supply and the electrifying timing sequence of each module of RS-485 bus hub.

Above-described RS-485 bus hub; preferably be respectively arranged with the short circuit open loop protection circuit in described host device interface branch road and the slave unit interface branch road; the signal protection of described short circuit open loop protection circuit under short circuit or open-circuit condition avoids influencing the proper communication of other interface equipment.

Above-described RS-485 bus hub, preferably be respectively arranged with the port auto shut off circuit in described host device interface branch road and the slave unit interface branch road, the interface of described port auto shut off circuit automatic closing fault under the situation of this interface branch trouble is guaranteed the normal use of other interface.

The utility model compiles Dispatching Unit with many slave unit interface branch roads by signal with a host device interface branch road and is connected, compile Dispatching Unit by signal and realize signal forwarding between the master-slave equipment interface branch road, realize the line concentration function, changed traditional RS-485 bus and must carry out the wire laying mode of apparatus interconnection with the daisy chain form, can be connected the mode that combines with daisy chain by star-like connection, improve the area coverage of wiring and the number of devices of interconnection, and the wiring process of simplified system, reduce engineering cost.The utility model all is provided with the earth potential be responsible between each interface and the bus isolated location of isolated from power in host device interface branch road and slave unit interface branch road, solved the unbalanced problem of earth potential between the equipment, has improved the reliability of system effectively.

The utility model will further improve the reliability of system as in host device interface branch road and slave unit interface branch road short circuit open loop protection circuit and port auto shut off circuit being set respectively.

[description of drawings]

Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.

Fig. 1 is the theory diagram of the utility model RS-485 bus hub embodiment 1.

Fig. 2 is the schematic diagram of the utility model RS-485 bus hub embodiment 2 large-scale work attendance gate control system cabling scenarios.

Fig. 3 is the utility model RS-485 bus hub embodiment 3 multi-service RS-485 control system cabling scenario schematic diagrames.

[embodiment]

As shown in Figure 1, the utility model RS-485 bus hub embodiment comprises that Power Management Unit, signal compile Dispatching Unit, host device interface branch road and many slave unit interface branch roads.Host device interface branch road and every slave unit interface branch road all comprise equipment interface, bus isolated location, short circuit open loop protection circuit and port auto shut off circuit respectively.In the host device interface branch road, host device interface is compiled Dispatching Unit with signal and is connected by bus isolated location, short circuit open loop protection circuit, port auto shut off circuit.In every slave unit interface branch road, the slave unit interface compiles Dispatching Unit with signal and connects by bus isolated location, short circuit open loop protection circuit, port auto shut off circuit.

Power Management Unit is responsible for the power supply power supply and the electrifying timing sequence of each module, and power unit receives and exchanges 110V, 220V, direct current 220V, and 110V, 48V, 24V, 12V, the input of 5V power supply, output+5V power supply adopts isolation technology to supply with each module.Control the electrifying timing sequence of each chip simultaneously and guarantee steady operation.

Host device interface is responsible for being connected RS-485 bus main control equipment and slave unit respectively with the slave unit interface.Employing standard RS-485 chip for driving, different according to selected chip producer and model can be realized 32,128,256 point device driving forces.

The bus isolated location is responsible for realizing earth potential and the isolated from power between each port.Adopt DC/DC isolated from power and light lotus root Signal Isolation Technology, realize signal and the dual isolation of power supply.

The short circuit open loop protection circuit is responsible for realizing the signal protection of each interface under the short circuit open-circuit condition avoided influencing the proper communication of other interface equipment.Because the minimum judgement threshold of RS-485 chip for driving is 200mV, when interface was in short circuit and open-circuit condition, the input of RS-485 chip for driving will be less than 200mV, and the output of RS-485 chip for driving is with instability at this moment.The short circuit open loop protection circuit adopts the operational amplifier of high input impedance to realize the voltage signal follow circuit, by the collection respectively to two differential signals of RS-485, judges whether corresponding interface exists short circuit or open circuit situation.When short circuit or open circuit situation occurring, at once the interface input signal is changed to 1 signal by force, with the labile state of avoiding being brought by short circuit and open circuit.

The port auto shut off circuit adopts timer that the signal that each interface receives is grown 0 input, specification interface fault when long-time 0 signal appears in interface (long 1 signal itself does not influence other interface communication), simultaneously the port auto shut off circuit adopts burst counter that the signal that each interface receives is counted, when the very frequent specification interface serious interference of pulse signal within a short period of time appears in interface.This moment, port auto shut off circuit drive end was opened the data transmit-receive passage of this road interface, guaranteed the operate as normal of other passage, and sent corresponding end mouth alarm indication, made things convenient for the user to safeguard.The port auto shut off circuit recovers this interface data transceiver channel again automatically after fault and interference disappearance.

Signal compiles Dispatching Unit and is responsible for signal forwarding between the principal and subordinate interface, realizes the line concentration function.

The whole system workflow is, the request of giving an order of master control RS-485 equipment, and signal enters the host device interface of hub, and signal compiles Dispatching Unit to be responsible for this command request is distributed to each slave unit interface.After corresponding slave unit sent echo message, this echo message entered hub through RS-485 slave unit interface, and signal compiles Dispatching Unit to be responsible for this echo message is transmitted a main equipment by the RS-485 host device interface.

Large-scale work attendance gate control system cabling scenario shown in Figure 2 has solved the defective that prior art exists:

1. adopt hub-and-spoke configuration to connect the RS-485 bus, the wiring area coverage improves (being generally several sq-kms) greatly under the situation of effectively utilizing interface.

2. each port all has short-circuit protection function, and can be operated in shutdown mode.To large-scale work attendance gate control system,, effectively raise the reliability of whole system simultaneously by sharing the load that access controller to eight port not only can reduce single RS-485 bus.When the short circuit of arbitrary controller RS-485 port, only can influence its place RS-485 bus system, can not influence the operate as normal of the RS-485 system of other interfaces connections.

3.RS-485 it is simple and clean soon that the system wiring process becomes, thereby effectively reduced the expense and the time of engineering.

Exist 3000V to isolate between each port.For the wiring problem of bringing by environmental problem, only need significant regional the connection with independent port of problem focused on, solve the wiring problem that earth potential brings effectively.

Multi-service RS-485 control system cabling scenario shown in Figure 3 also has the following advantages: work attendance gate control system, managing system of car parking and dining room meal sale system are connected up respectively, and be installed in different RS-485 bus hub slave computer interfaces respectively, share same upper computer control system main frame.For system host, all systems help all devices is carried out centralized control and saves engineering cost just as being articulated on the RS-485 bus.Owing to adopted photoelectric isolation technology and bus cutting techniques between each port of RS-485 bus hub, make the user to treat each port system simultaneously as designing each system separately.When a certain port device goes wrong, the system that other port connects will can not be affected.Effectively solved different system centralized control problem.

As mentioned above, the utlity model has following beneficial effect:

1) circuit is realized simple, with low cost. 2) but each RS-485 interface driving arrangement 255 (relevant with selected chip) platform, along with increasing of equipment interface, single system can carry to be established Standby quantity will constantly increase. 3) wiring is adopted daisy chain and is connected the connection mode that combines, the worker Journey is implemented flexible. 4) the wiring scope expands to 1200 in the situation that does not add relaying Rice is the circular scope of radius. 5) total interface all has short circuit open-circuit-protection and isolated location, Effectively avoid earth potential, the uncertain factors such as signal interference improve greatly to the impact of bus The engineering success rate. 6) the port auto shut off circuit is so that any one interface breaks down can not Affect the normal operation of other port, greatly strengthened Systems balanth, reduced system Maintenance cost.

Claims

1. a RS-485 bus hub is characterized in that, comprises that Power Management Unit, signal compile Dispatching Unit, host device interface branch road and at least 2 slave unit interface branch roads; Described host device interface branch road and every slave unit interface branch road comprise equipment interface and bus isolated location respectively; In the host device interface branch road, host device interface is compiled Dispatching Unit by the bus isolated location with signal and is connected; In slave unit interface branch road, the slave unit interface compiles Dispatching Unit by the bus isolated location with signal and connects; Described bus isolated location is responsible for earth potential and the isolated from power between each interface; Described signal compiles Dispatching Unit and is responsible for signal forwarding between the master-slave equipment interface branch road, realizes the line concentration function; Described Power Management Unit is responsible for the power supply power supply and the electrifying timing sequence of each module of RS-485 bus hub.

2. RS-485 bus hub according to claim 1; it is characterized in that; be respectively arranged with the short circuit open loop protection circuit in described host device interface branch road and the slave unit interface branch road; the signal protection of described short circuit open loop protection circuit under short circuit or open-circuit condition avoids influencing the proper communication of other interface equipment.

3. RS-485 bus hub according to claim 1, it is characterized in that, be respectively arranged with the port auto shut off circuit in described host device interface branch road and the slave unit interface branch road, the interface of described port auto shut off circuit automatic closing fault under the situation of this interface branch trouble is guaranteed the normal use of other interface.