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Daquan knowledge of electronic components: PCB layout elements

    One. Circuit board design steps.

    In general,booster cables the basic circuit board design process can be divided into three steps.

    (1). Circuit diagram of the design: the design of the main circuit diagram is PROTEL099 schematic design system (Advanced Schematic) to draw a circuit diagram. In this process, to take full advantage PROTEL99 offer a variety of schematic drawing tools,battery clip a variety of editing functions, to achieve our purpose, that get a correct and fine circuit schematic.

    (2). Generate network table: the table is a circuit diagram network design (SCH) and the printed circuit board design (PCB) as a bridge between, tow rope it is the soul of the board automatically. Netlist can be obtained from the circuit schematics, printed circuit boards can also be extracted from it.

    (3). Printed circuit board design: the design of printed circuit boards mainly for PROTEL99 Another important part of the PCB for the purposes of,ratchet tie dowm in this process, we provide the power through PROTEL99 circuit board layout to achieve to complete the difficult and so on.

    II. Draw a simple circuit.

   2.1 The schematic design process according to the following schematic design process to complete.

   (1) the design drawings the size of Protel 99 / Schematic, the first idea of a good part drawings, design drawings, good size. Size is based on schematic drawings of the size and complexity of the, and set the appropriate paper size is the first step in the schematic design is good.

   (2) Set Protel 99/Schematic set Protel 99/Schematic design environment design environment, including setting the size and type of grid, the cursor type, etc., most of the parameters can also use the system default values.

   (3) rotating part of the user according to the needs of circuit, remove the part from the parts library onto the drawing, and place the number of parts, spare parts package to define and set and so on.

   (4) the use of Protel 99/Schematic schematic layout provides a variety of tools, components used on the drawings with electrical wires meaning, symbols connected to form a complete schematic.

   (5) adjust the line will initially draw a good schematic for further adjustments and modifications to make the schematic more beautiful.

   (6) report output provided by Protel 99/Schematic various reporting tools generate various reports, the most important statements of the network table, the table through the network for the subsequent preparation of circuit board design.

   (7) Save the file and print out the final step is to save the file and print output.

SCM control panel design principles to follow the following principles:

   (1) the layout of the components, the components should be as much as possible about each other there was not * recently, for example, clock generator, crystal oscillator, CPU's clock input are easy to produce noise in the time they should be placed near more. For those prone to device noise, low current circuit, high current circuit switching circuit, as far as possible away from the logic control circuit microcontroller and memory circuits (ROM, RAM), if possible, these circuits can be made of other circuit boards, it is a good anti-jamming, to improve the availability * of the circuit.

   (2) as the critical components, such as ROM, RAM and other chip decoupling capacitors next to install. In fact, the printed circuit board traces, pin connection and wiring and so may contain large inductance effects. Large inductance Vcc traces may cause severe switching noise spikes. Prevent switching noise spikes Vcc go online the only way is to be placed between the VCC and the power to the electronic one 0.1uF decoupling capacitors. If the circuit board using surface mount components, chip capacitors can be used directly bear * the components in the Vcc pin fixed. It is best to use ceramic capacitors, this is because the capacitor has a low static losses (ESL) and high frequency impedance, this capacitor other media on the temperature and time stability is also very good. Do not use tantalum capacitors, because the impedance at high frequencies it is higher. Decoupling capacitor in place to note the following:

   In the printed circuit board power input jumper around 100uF electrolytic capacitor, if the volume permitting, large capacity a number is better.

   In principle, each integrated circuit chips are to be placed next to a 0.01uF ceramic capacitor, if the circuit board placed no less than the gap is too small, you can chip about every 10 to place a 1 to 10 of tantalum capacitors.

   The weak anti-interference ability, when the current changes off the components and large RAM, ROM and other storage devices, power lines should be (Vcc) and ground access between the decoupling capacitors.

   Capacitance of the lead is not too long, especially not with a high frequency bypass capacitor leads.

   (3) In the SCM control system, there are many types of ground, in a systematic manner, the shield, the logic, the analog ground, etc., whether the layout is reasonable ground, the board will determine the anti-jamming capability. Ground and ground in the design, it should consider the following questions:

   Logic and analog ground to separate the wiring, can not be combined, to their respective ground were connected with the corresponding power supply ground. In the design, analog ground should be bold, and try to increase the terminal area with the ground. In general, the input and output of the analog signal, preferably between the microcontroller circuit isolation via optocouplers.

   Logic circuits in the design of printed circuit version, the ground shall constitute a closed form, to improve the circuit's noise immunity.

   Should be coarse ground. If the ground is very thin, then the ground resistance will be greater, resulting in ground potential with the current changes, resulting in signal level instability, leading to decline in anti-interference circuit. In the wiring space permitting, to ensure that the width of the main ground at least 2 ~ 3mm above the ground pin devices should be around 1.5mm.
 

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iande Weida Electrical Appliance Tools Co.Ltd. professionally manufacture booster cables , battery clip, tow rope,ratchet tie down.