鎖定放大是微弱信號檢測的重要手段。基于相關檢測理論，利用開關電容的開關實現鎖定放大器中乘法器的功能，提出開關電容和積分器相結合以實現相關檢測的方法，并設計出一種鎖定放大器。該鎖定放大器將微弱信號轉化為與之相關的方波，通過后續電路得到正比于被測信號的直流電平，為后續采集處理提供方便。測量數據表明鎖定放大器前級可將10-6 A的電流轉換為10-1 V的電壓，后級通過帶通濾波器級聯可將信號放大1×105倍。該方法在降低噪聲的同時，可對微弱信號進行放大，線性度較高、穩定性較好。
Abstract:
Lock-in Amplifying（LIA）is one of important means for weak signal detection. Based on cross-correlation detection theory， switch in the swithched capacitor was used as multiplier of LIA， and a new method of correlation detection was proposed combining swithched capacitor with integrator. A kind of LIA was designed which can convert the weak signal to square-wave， then DC proportional to measured signal was obtained through follow-up conditioning circuit， providing convenience for signal acquisition and processing. The measured data shows that the electric current（10-6 A） can be changed into voltage（10-1 V） by LIA， and the signal is magnified 1×105 times by cascade band-pass filter. The noise is suppressed and the weak signal is amplified. It has the advantages of good linearity and stability.
設計了一種基于PIC16C71單片機的數字水溫配制閥。該配制閥采用NTC熱敏電阻作溫度傳感器，與固定電阻組成簡單分壓電路作為水溫測量電路，利用PIC16C71單片機內置的8位A/D轉換器把熱敏電阻上的模擬電壓轉換為數字量，PIC16C71單片機控制直流電機驅動混水閥調節冷熱水的混合比例實現水溫調節。給出了控制電路圖，對水溫測量電路的參數選擇和測溫精度作了詳細討論。實驗和分析表明，選用阻值較大的NTC熱敏電阻和分壓電阻可較好地解決熱敏電阻因功耗較大造成的熱擊穿問題。
Abstract:
A digital valve for controlling water temperature based on PIC16C71 was presented in this paper.A bleeder circuit which consisted of a NTC thermistor as temperature sensor and a fixed resistance was designed as water temperature measuring circuit.The analog voltage on the thermistor was converted into digital signal by a 8-bit A/D converter embedded in PIC16C71. Based on the digital signal， the MCU PIC16C71 drived the valve by a DC motor to adjust the water temperature through adjusting the proportion of hot water and cold water.The circuit diagram of controller was given，the principle，the component parameters and the accuracy of measuring temperatures were also dissertated in detail. It was found by experiment and analysis that thermal breakdown of thermistor caused by high power could be solved by selecting thermistor and fixed resistance with high impedance value.
The PCA9549 provides eight bits of high speed TTL-compatible bus switching controlledby the I2C-bus. The low ON-state resistance of the switch allows connections to be madewith minimal propagation delay. Any individual A to B channel or combination of channelscan be selected via the I2C-bus, determined by the contents of the programmable Controlregister. When the I2C-bus bit is HIGH (logic 1), the switch is on and data can flow fromPort A to Port B, or vice versa. When the I2C-bus bit is LOW (logic 0), the switch is open,creating a high-impedance state between the two ports, which stops the data flow.An active LOW reset input (RESET) allows the PCA9549 to recover from a situationwhere the I2C-bus is stuck in a LOW state. Pulling the RESET pin LOW resets the I2C-busstate machine and causes all the bits to be open, as does the internal power-on resetfunction.
the calculator s usage!
after you have inputed 2 operators,choose + - * / function!
But the only situation I did t deal with is that
when you choos + fuction ,and the operaters signs is like this
-A+B,just turn it to B-A!
The XML Toolbox converts MATLAB data types (such as double, char, struct, complex, sparse, logical) of any level of nesting to XML format and vice versa.
For example,
>> project.name = MyProject
>> project.id = 1234
>> project.param.a = 3.1415
>> project.param.b = 42
becomes with str=xml_format(project, off )
"<project>
<name>MyProject</name>
<id>1234</id>
<param>
<a>3.1415</a>
<b>42</b>
</param>
</project>"
On the other hand, if an XML string XStr is given, this can be converted easily to a MATLAB data type or structure V with the command V=xml_parse(XStr).
Implement the following integer methods:
a) Method celsius returns the Celsius equivalent of a Fahrenheit calculation
celsius = 5.0 / 9.0 * ( fahrenheit - 32 )
b) Method fahrenheit returns the Fahrenheit equivalent of a Celsius the calculation
fahrenheit = 9.0 / 5.0 * celsius + 32
c) Use the methods from parts (a) and (b) to write an application either to enter a Fahrenheit temperature and display the Celsius or to enter a Celsius temperature and display the Fahrenheit equivalent.
用AVR單片機設計的MP3播放器
功能：
MP3 Player
IDE ATA interface
FAT 32 with long file name support
USB interface
On board power supply (input from 7v to 20v DC)
Bootloader firmware upgradeable via USB port
Infrared bi-directional interface
Remote Control
Back light graphic LCD
worked with only 2x AA batteries
In sleep mode sink less than 1uA (2.5mA in active mode)
5 buttons for easy navigation
Long range (more than 20 feets)
LED 線陣顯示裝置, 分為 LED 線性旋轉顯示主機和圖文錄入器兩部分。主機用直流電機帶動由紅綠 LED 組成的線陣旋轉, 同時線陣按照時序依次切換顯示狀態, 在固定區域利用視覺暫留效果形成 16×16 點陣, 用以顯示圖文;圖文錄入器用 HMI 觸控屏作為人機交互界面, 實現圖文錄入和回放功能。主機與圖文錄入器通過無線通信方式進行信息交互,可由圖文錄入器控制主機切換不同工作任務, 以及改變線陣顯示內容。The LED linear array display device is divided into two parts:the one is the main unit used to display content,and the other one is used to input the contents.The main unit is driven by a DC motor to rotate the linear array composed by red and green light emitting diodes.At the same time,the 16×16 dot matrix that switching the display state according to the time sequence on the main unit displays pictures and texts in the fixed area,by using the visual temporary effect.The HMI touch screen is used as human machine interface to realize the function that input and playback pictures and texts.The two parts of the device communicate with each other through wireless communication.The image and text input controller can control the main unit to switch different tasks and change the content of linear array displayed.
Agenda■Motor Types Overview■BLDC Motor Applications■Comparison of DC to Brushless DC Motors■Hall Sensors■Six-Step Commutation■Sensorless Commutation with Back-EMFVector Motor Control basicsClosed-Loop Speed Control■Introduction to BLDC Motor Control Evaluation Kit■SummaryAll the popular motor types have their specific applications, and all can be controlled with microcontrollers.We wll talk about Brushless DC motors as it is the fast growing motor type today.Motors used in modern Air conditioners, home appliances, tools, even electric bikes are all going to Brushless DC.
