PCB 被动组件的隐藏特性解析 传统上，EMC一直被视为「黑色魔术（black magic）」。其实，EMC是可以藉由数学公式来理解的。不过，纵使有数学分析方法可以利用，但那些数学方程式对实际的EMC电路设计而言，仍然太过复杂了。幸运的是，在大多数的实务工作中，工程师并不需要完全理解那些复杂的数学公式和存在于EMC规范中的学理依据，只要藉由简单的数学模型，就能够明白要如何达到EMC的要求。本文藉由简单的数学公式和电磁理论，来说明在印刷电路板（PCB）上被动组件（passivecomponent）的隐藏行为和特性，这些都是工程师想让所设计的电子产品通过EMC标准时，事先所必须具备的基本知识。导线和PCB走线导线（WIRE）、走线（trace）、固定架……等看似不起眼的组件，却经常成为射频能量的最佳发射器（亦即，EMI的来源）。每一种组件都具有电感，这包含硅芯片的焊线（bond WIRE）、以及电阻、电容、电感的接脚。每根导线或走线都包含有隐藏的寄生电容和电感。这些寄生性组件会影响导线的阻抗大小，而且对频率很敏感。依据LC 的值（决定自共振频率）和PCB走线的长度，在某组件和PCB走线之间，可以产生自共振（self-resonance），因此，形成一根有效率的辐射天线。在低频时，导线大致上只具有电阻的特性。但在高频时，导线就具有电感的特性。因为变成高频后，会造成阻抗大小的变化，进而改变导线或PCB 走线与接地之间的EMC 设计，这时必需使用接地面（ground plane）和接地网格（ground grid）。导线和PCB 走线的最主要差别只在于，导线是圆形的，走线是长方形的。导线或走线的阻抗包含电阻R和感抗XL = 2πfL，在高频时，此阻抗定义为Z = R + j XL j2πfL，没有容抗Xc = 1/2πfC存在。频率高于100 kHz以上时，感抗大于电阻，此时导线或走线不再是低电阻的连接线，而是电感。一般而言，在音频以上工作的导线或走线应该视为电感，不能再看成电阻，而且可以是射频天线。
上传时间： 2013-11-16
上传用户：极客
用途：测量地磁方向，测量物体静止时候的方向，测量传感器周围磁力线的方向。注意，测量地磁时候容易受到周围磁场影响，主芯片HMC5883 三轴磁阻传感器特点（抄自网上）： 1，数字量输出：I2C 数字量输出接口，设计使用非常方便。 2，尺寸小: 3x3x0.9mm LCC 封装，适合大规模量产使用。 3，精度高：1－2 度，内置12 位A/D,OFFSET, SET/RESET 电路，不会出现磁饱和现象，不会有累加误差。 4，支持自动校准程序，简化使用步骤，终端产品使用非常方便。 5，内置自测试电路，方便量产测试，无需增加额外昂贵的测试设备。 6，功耗低：供电电压1.8V, 功耗睡眠模式-2.5uA 测量模式-0.6mA 连接方法： 只要连接VCC，GND，SDA，SDL 四条线。 Arduino GND -> HMC5883L GND Arduino 3.3V -> HMC5883L VCC Arduino A4 (SDA) -> HMC5883L SDA Arduino A5 (SCL) -> HMC5883L SCL (注意，接线是A4，A5，不是D4,D5) 源程序： #include <WIRE.h> #include <HMC5883L.h> HMC5883Lcompass; voidsetup() { Serial.begin(9600); WIRE.begin(); compass = HMC5883L(); compass.SetScale(1.3); compass.SetMeasurementMode(Measurement_Continuous); } voidloop() { MagnetometerRaw raw = compass.ReadRawAxis(); MagnetometerScaled scaled = compass.ReadScaledAxis(); float xHeading = atan2(scaled.YAxis, scaled.XAxis); float yHeading = atan2(scaled.ZAxis, scaled.XAxis); float zHeading = atan2(scaled.ZAxis, scaled.YAxis); if(xHeading < 0) xHeading += 2*PI; if(xHeading > 2*PI) xHeading -= 2*PI; if(yHeading < 0) yHeading += 2*PI; if(yHeading > 2*PI) yHeading -= 2*PI; if(zHeading < 0) zHeading += 2*PI; if(zHeading > 2*PI) zHeading -= 2*PI; float xDegrees = xHeading * 180/M_PI; float yDegrees = yHeading * 180/M_PI; float zDegrees = zHeading * 180/M_PI; Serial.print(xDegrees); Serial.print(","); Serial.print(yDegrees); Serial.print(","); Serial.print(zDegrees); Serial.println(";"); delay(100); }
上传时间： 2014-03-20
上传用户：tianyi223
一种很有用的搜寻算法，对开发1-WIRE很有用
标签： 算法
上传时间： 2014-08-13
上传用户：我干你啊
此程序为 单片机开发过程中，1—WIRE总线方式数字温度传感器的控制显示程序。供参考
上传时间： 2014-01-03
上传用户：362279997
The CC1000 RF transceiver is very easy to interface with a microcontroller. The chip is configured using a three-WIRE bus, comprising of PCLK, PDATA and PALE signals.
标签： microcontroller transceiver configured The
上传时间： 2014-01-04
上传用户：c12228
This text surrounds the development of the electric power SCADA system exactly, aiming at the present condition of the our country electric power charged barbed WIRE net currently, according to the oneself at the e- lectric power protect the profession after the electricity in seven years of development, design and adjust to try the experience on the scene from following severals carry on the treatise:Is the emergence to the system of SC- ADA and developments to introduce first Carry on the introduction elucidation to applied present condition and the development foregrounds of various terminal equipments communication agreement(rules invite) the next in order Then is the elucidation to the windows the bottom according to the mfc the plait distance environment an- d VC++6.0 plait distance softwares Carry on the more detailed treatise to the realization of the procedure struct- ure frame and the source code again End is the applied case example give examples.
标签： the development surrounds electric
上传时间： 2014-10-28
上传用户：liuchee
Universal Serial Bus (USB) is a communications architecture that gives a personal computer (PC) the ability to interconnect a variety of devices using a simple four- WIRE cable. The USB is actually a two-WIRE serial communication link that runs at either 1.5 or 12 megabits per second (mbs). USB protocols can configure devices at startup or when they are plugged in at run time. These devices are broken into various device classes. Each device class defines the common behavior and protocols for devices that serve similar functions. Some examples of USB device classes are shown in the following table
标签： communications architecture Universal computer
上传时间： 2015-12-08
上传用户：stvnash
water temperature control system uses the Single Chip Microcomputer to carry on temperature real-time gathering and controling. DS18B20, digitized temperature sensor, provides the temperature signal by "a main line". In -10～+85℃ the scope, DS18B20’s inherent measuring accuracy is 0.5 ℃. The water temperature real-time control system uses the electricity nichrome WIRE carring on temperature increiseament and operates the electric fan to realize the temperature decrease control. The system has the higher measuring accuracy and the control precision, it also can complete the elevation of temperature and the temperature decrease control.
标签： temperature Microcomputer real-tim control
上传时间： 2015-12-10
上传用户：nairui21
// This program accesses a SPI EEPROM using polled mode access. The F06x MCU // is configured in 4-WIRE Single Master Mode, and the EEPROM is the only // slave device connected to the SPI bus. The read/write operations are // tailored to access a Microchip 4 kB EEPROM 25LC320. The relevant hardware // connections of the F06x MCU are shown here:
标签： configured accesses program EEPROM
上传时间： 2014-01-18
上传用户：liglechongchong
// This program accesses a SPI EEPROM using polled mode access. The F06x MCU // is configured in 4-WIRE Single Master Mode, and the EEPROM is the only // slave device connected to the SPI bus. The read/write operations are // tailored to access a Microchip 4 kB EEPROM 25LC320. The relevant hardware // connections of the F06x MCU are shown here:
标签： configured accesses program EEPROM
上传时间： 2016-04-12
上传用户：qb1993225
