Design of electronic clock printed circuit board using Prote199se

Abstract: In the design and development process of printed circuit boards, the layout of components and the routing of components on the printed circuit board are the most important performance indicators of the printed circuit board design performance. The electronic clock circuit printed circuit board developed by the AT89C51 single-chip microcomputer has clear circuit functions, and the circuit has the functions of testing real-time temperature and recording time and date, which has a certain degree of comprehensiveness. Therefore, in this article, the electronic clock printed circuit board circuit is used as the analysis carrier of Prote199se to analyze the important steps and key technologies in the design of printed circuit boards.
Keywords: printed circuit board; component layout; automatic wiring; process; electronic clock

0 Introduction
In view of the development trend of modern electronic products, the function of the circuit board has an increasingly obvious impact on the performance of the entire electronic product. Therefore, it is very important to design a circuit board that meets the process requirements and meets the normal working performance of the product. Combined with the author's many years of experience in teaching and researching electronic professional courses, combined with single-chip microcomputer development and circuit board design, this article will specifically explain the important steps and precautions for the design of the electronic clock circuit board of a typical single-chip microcomputer product developed by Prote199se software.

1 Precautions and steps for designing circuit schematics using Prote199se software
The schematic is the most basic foundation for realizing circuit functions. The circuit schematic reflects the electrical connection relationship of various electronic components. In the design process of electronic products, the drawing of the schematic is the basis for drawing PCB. The schematic is also the basis for engineering and technical personnel to install and debug the product. Therefore, in the design and drawing process of the schematic, it is necessary to strictly follow the drawing steps and process requirements of the schematic. In the process of drawing the schematic, it is necessary to strictly follow the basic process requirements such as top-down, from left to right, and signal flow. The layout of components is carried out according to the functional modules of the circuit. All connections should be structured as much as possible. The overall drawing requires a complete structure, beautiful and easy to read. For the schematics of more complex products, the design thinking of hierarchical circuits can be adopted. In this way, the structure of the circuit is clear and meets the basic requirements of schematic design. In the drawing of the electronic clock schematic, considering the complexity of the circuit, the design adopts the overall circuit schematic consisting of three sub-circuits: single-chip control circuit, time display circuit, date and temperature display circuit. In the subcircuit, in order to enhance the readability of the schematic diagram and the convenience of wiring, a large number of network labels are used as the electrical connection method of the components in the circuit schematic diagram. The overall schematic diagram of the designed electronic clock circuit and the schematic diagram of the time display circuit of one of the subcircuits are shown in Figures 1 and 2 respectively.

2. Define the appropriate package for components and check the electrical rules
Component package refers to the outer frame and solder joint position represented by the component placed in the electronic circuit board. Different components can share the same component package, and the same component can also have different packages. Generally, after the schematic diagram is drawn, the appropriate package definition is made for each component according to the actual requirements. Generally speaking, the common standard package library provided in the software can meet the design requirements of general products. In modern printed circuit board design and development companies, there is generally a standard package library built within the company. Printed circuit board designers are required to be familiar with the package form of common devices. For uncertain packages, actual measurement and self-built packages can be used to solve them. The form of the package directly determines the installability of the circuit board, so it must be carefully analyzed and treated with caution when defining it.

The last step of schematic design is to check the electrical rules. It is mainly for the software to automatically analyze whether there are multiple network names for the same network in the circuit schematic; whether there are floating unconnected input signals; whether there are errors such as duplicate component names that do not comply with electrical rules. What needs to be emphasized here is that the check of electrical rules cannot replace the verification of whether the schematic drawing is correct. The correctness of the schematic requires the drafter to have skilled drawing skills and a high sense of responsibility.

3 Manual layout of all components in the electronic clock printed circuit board
In the layout of the components of the electronic clock printed circuit board, the first thing to be determined is the position of the annotated Chinese characters such as year, month, day, week, room temperature, and degree. This will make the display of the digital tube easy to read. Secondly, considering the placement of the digital tubes in each corresponding position, in this process, it is necessary to pay attention to the correspondence between the annotated Chinese characters to avoid confusion in the display.
On this basis, the position of the four LEDs can be determined. The four LEDs are designed to display the hours, minutes, and seconds of the clock. The placement must be accurate, neat and beautiful. Then the position of each interface can be determined, and then the position of special components such as temperature sensors and relays can be considered. Determine the position of the microcontroller and the components that constitute the minimum system of the microcontroller, and finally consider other components. The overall layout requires consideration of the performance of normal operation, the beauty of the overall PCB, and the layout of components in accordance with the modular design concept. The rationality and processability of the manual layout directly determine the performance of the printed circuit board and the direction of the copper film line on the printed circuit board. As a printed circuit board developer, you must accumulate layout experience in actual engineering design and summarize the layout ideas and methods.

4 Use the automatic wiring function of the software to wire and adjust the electronic clock PCB.
Prote199se has a very complete automatic wiring function. It can simulate artificial intelligence to support the wiring function of 32-layer circuit boards. When wiring with the automatic wiring function of the application software, you must first set the rules for automatic wiring so that the software can complete automatic wiring under the established rules. Prote199se supports the setting of multiple practical rules such as safety distance, wiring angle, wiring layer, wiring topology technology, line width, etc. In the process of use, you must make reasonable settings according to the design requirements and actual conditions and make local adjustments according to the wiring effect. After the automatic routing is completed, the designer needs to make local adjustments and modifications to the PCB, add necessary annotations, etc. to ensure the realization of the circuit board diagram function. The completed PCB of the electronic clock circuit board is shown in Figure 3.

5 Conclusion
As a typical single-chip microcomputer product, the electronic clock circuit has a certain degree of complexity and comprehensiveness. The development and design process widely involves the design ideas and methods of hierarchical circuit schematics, the definition of each component package in the circuit board, and the inspection of the electrical rules of the schematic. In the design part of the PCB of the circuit board, the general principles of manual layout and automatic wiring are mainly discussed and analyzed, which has a certain guiding significance and demonstration role for the circuit board design of general electronic products.