A can-based distributed control system for fire alarm (1)

With the development of economic construction, fire alarm control system sizing requirements, in order to adapt to the needs of the market, the authors use CAN field bus technology, the design of a distributed fire alarm control system, the system structure is flexible, easy to use, can meet the needs of large, medium and small businesses of all sizes of fire alarm and fire control requirements.

CAN (Controller Area Network) is the controller area network — an effective support for distributed control and real-time control of serial communication network, because of its high performance, high reliability, and unique design, more and more people's attention, its bus specification has been ISO International Organization for Standardization (ISO) as an international standard, and is recognized as the most promising one fieldbus. This article describes the composition of the MCP2551 MCP2510 and CAN field bus in distributed fire alarm control system.

1. system composition and working principle

This article by CAN-fieldbus-based distributed fire alarm control system network structure as shown in Figure 1, each node in the node controller AT89C51-chip, MCP2510 MCP2551 for bus controller, as bus transceiver, which, unlike the console workstations connected nodes is called a centralized machine, the other regions.

In the concentration, the so-called console workstation, is a PC machine, single-chip through external serial interface for the exchange of information with the console workstation. Distribution in various areas of machines in different geographic locations, independent implementation of a complete tasks. In this system, an area of the machine through a specially designed detector bus can connect smoke, photosensitive, heat, fire detector, you can use adapter control such as sprinkler valves, shutter, and other firefighting equipment and a variety of sound and light alarm device, the probe bus device known as a front end device. Utilization CAN communications technology, the networking of regional machine management staff in the central computer can observe various parts, ease of management and inspection, ready to be aware of the regional machine running properly and that there is no alarm occurs, you can enable all regions to interact through information, machine for resource sharing, joint control. Each machine is a basic alarm control unit, its functionality and use exactly the same time, they are from the region on the acquisition of detectors, such as a warning to appear, in the start area for fire-fighting equipment, through the CAN bus will send alarm signal, set machine set machine and then decide you need starting from other relevant regional machine jurisdiction of fire fighting equipment, and through the can bus to issue joint command. In addition, due to the CAN bus is based on the text of the node on the bus can be Plug and play, and system scalability is better; and that additions CAN bus in addition to centralized computer other than a node that does not cause any other node.

Figure 1 MCP2510 is Microchip companies to simplify the can bus interface application specifically designed for an independent CAN controller chip that supports the CAN Protocol 2.0A/2.0B, maximum programmable baud rate to 1Mbps; MCP2551 is the Microchip company-tolerant of high speed CAN bus transceiver chip, support the operating speed of 1Mbps, can connect up to 112 node, suitable for 12V and 24V system, pin properties are fully compatible with MCP2510.

2 hardware circuit and SPI interface technology

Figure 2 is this system nodes CAN communicate with hardware circuit diagrams, schematics, bus controller MCP2510 and bus transceiver MCP2551 directly connected, because their PIN is fully compatible, in addition, considering the system bus speed is relatively low, so that the slope of the MCP2551 resistance input pin RS vacant, select minimum slope, so that both will minimal RFI suppression, and simplifies circuit design.

The following points describe MCP2510 interface with AT89C51.

Figure 2 nodes CAN communicate with the hardware interface circuit

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