PCB 被動組件的隱藏特性解析 傳統上，EMC一直被視為「黑色魔術（black magic）」。其實，EMC是可以藉由數學公式來理解的。不過，縱使有數學分析方法可以利用，但那些數學方程式對實際的EMC電路設計而言，仍然太過復雜了。幸運的是，在大多數的實務工作中，工程師并不需要完全理解那些復雜的數學公式和存在于EMC規范中的學理依據，只要藉由簡單的數學模型，就能夠明白要如何達到EMC的要求。本文藉由簡單的數學公式和電磁理論，來說明在印刷電路板（PCB）上被動組件（passivecomponent）的隱藏行為和特性，這些都是工程師想讓所設計的電子產品通過EMC標準時，事先所必須具備的基本知識。導線和PCB走線導線（wire）、走線（trace）、固定架……等看似不起眼的組件，卻經常成為射頻能量的最佳發射器（亦即，EMI的來源）。每一種組件都具有電感，這包含硅芯片的焊線（bond wire）、以及電阻、電容、電感的接腳。每根導線或走線都包含有隱藏的寄生電容和電感。這些寄生性組件會影響導線的阻抗大小，而且對頻率很敏感。依據LC 的值（決定自共振頻率）和PCB走線的長度，在某組件和PCB走線之間，可以產生自共振（self-resonance），因此，形成一根有效率的輻射天線。在低頻時，導線大致上只具有電阻的特性。但在高頻時，導線就具有電感的特性。因為變成高頻后，會造成阻抗大小的變化，進而改變導線或PCB 走線與接地之間的EMC 設計，這時必需使用接地面（ground plane）和接地網格（ground grid）。導線和PCB 走線的最主要差別只在于，導線是圓形的，走線是長方形的。導線或走線的阻抗包含電阻R和感抗XL = 2πfL，在高頻時，此阻抗定義為Z = R + j XL j2πfL，沒有容抗Xc = 1/2πfC存在。頻率高于100 kHz以上時，感抗大于電阻，此時導線或走線不再是低電阻的連接線，而是電感。一般而言，在音頻以上工作的導線或走線應該視為電感，不能再看成電阻，而且可以是射頻天線。
上傳時間： 2013-11-16
上傳用戶：極客
用途：測量地磁方向，測量物體靜止時候的方向，測量傳感器周圍磁力線的方向。注意，測量地磁時候容易受到周圍磁場影響，主芯片HMC5883 三軸磁阻傳感器特點（抄自網上）： 1，數字量輸出：I2C 數字量輸出接口，設計使用非常方便。 2，尺寸小: 3x3x0.9mm LCC 封裝，適合大規模量產使用。 3，精度高：1－2 度，內置12 位A/D,OFFSET, SET/RESET 電路，不會出現磁飽和現象，不會有累加誤差。 4，支持自動校準程序，簡化使用步驟，終端產品使用非常方便。 5，內置自測試電路，方便量產測試，無需增加額外昂貴的測試設備。 6，功耗低：供電電壓1.8V, 功耗睡眠模式-2.5uA 測量模式-0.6mA 連接方法： 只要連接VCC，GND，SDA，SDL 四條線。 Arduino GND -> HMC5883L GND Arduino 3.3V -> HMC5883L VCC Arduino A4 (SDA) -> HMC5883L SDA Arduino A5 (SCL) -> HMC5883L SCL (注意，接線是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); }
上傳時間： 2014-03-20
上傳用戶：tianyi223
一種很有用的搜尋算法，對開發1-wire很有用
標簽： 算法
上傳時間： 2014-08-13
上傳用戶：我干你啊
此程序為 單片機開發過程中，1—wire總線方式數字溫度傳感器的控制顯示程序。供參考
上傳時間： 2014-01-03
上傳用戶：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.
標簽： microcontroller transceiver configured The
上傳時間： 2014-01-04
上傳用戶：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.
標簽： the development surrounds electric
上傳時間： 2014-10-28
上傳用戶：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
標簽： communications architecture Universal computer
上傳時間： 2015-12-08
上傳用戶：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.
標簽： temperature Microcomputer real-tim control
上傳時間： 2015-12-10
上傳用戶：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:
標簽： configured accesses program EEPROM
上傳時間： 2014-01-18
上傳用戶：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:
標簽： configured accesses program EEPROM
上傳時間： 2016-04-12
上傳用戶：qb1993225
