Abstract

With productivity and the continuous development of science and

technology, people's daily lives and production activities of a large number of the use of automated control, not only saving human resources, but a large degree of improved production efficiency, further promote the rapid development of productive forces, and constant enrich people's lives.

Early automatic control system relies on the relay - Contactor to achieve, and its features are: simple structure, low cost, anti-interference capability, can achieve centralized control and remote control, but the introduction of fixed wiring, versatile and flexible of the poor and by the switch contacts, the low frequency contacts easily damaged, poor reliability.

1969, a programmable logic controller PLC (Programmable Logic Controller), its features are: a logic control, timing, counting, and other functions, intuitive programming language used ladder diagram language, software changes convenience, versatility and flexibility good.

At present, the major PLC programmable controller is a small, low-cost, standardized, high-speed, intelligent, high-capacity, in the direction of the network, and computer technology, formation of industrial control systems, distributed Control Systems DCS (Distributed Control System), fieldbus control system FCS (Field bus Control System), the PLC will enable more powerful, more reliable, more convenient to use, a wider scope.

The design is based on the storage of vehicles PLC management systems, LED used two vehicles in the garage to show that the actual number. The use of two light sensor to monitor vehicle access and complete count, the two vehicles entered the house through the sensor and a digital display, two

vehicles going through the sensor by a digital display, but only after a sensor vehicles will not count.

In order to prevent accidents counting error, the system used repeatedly checking procedures to enhance the reliability of the system.

First of all, pay attention to control the distance between the two sensors, access to the garage with the certification procedures for the vehicles, through the sensor when people do not count; Secondly, the introduction of the logical interlocked, and counting would start by counting lock, a Canadian Counting will have to lock pulse by pulse count, so in order to ensure reliability; Finally, a reduction of the processing time to avoid vehicles in the vicinity of sensors for counting from the wrong campaign.

Key words: PLC Sensor Vehicles Reliability