為了解決磁放大器性能測試過程中，需要對其供給不同數值恒定電流的問題，設計了一種基于DAC7512和單片機的數控恒流源系統。該系統采用AT89C51作為主控器件，將計算機發送的電流控制字命令轉換為D/A轉換器控制字，通過模擬SPI通信接口，寫D/A控制字到DAC7512，從而控制其輸出相應數字電壓值，經差動縮放電路、電壓/電路變換電路和功率驅動電路，最后輸出恒定電流。實驗結果表明，恒流源輸出電流調節范圍為-45~+45 mA、精度為±0.1 mA，分辨率達0.024 4 mA，具有應用靈活，外圍電路簡單，可靠性高的特點。該數控直流恒流源也可為相關產品的測試系統研發提供參考。
Abstract:
In order to solve the need to supply different values constant current for the magnetic amplifier in testing process， numerical control constant current source system was designed based on DAC7512 chip and microcontroller technology. The system used the AT89C51 as the main chip， which can convert the current control word from computer into to D/A control words. And the system wrote D/A control word into the DAC7512 chip to control the Output voltage value by the SPI communication interface， which can Output corresponding constant current figures by scaling circuit， the V/I converter and power drive circuit. Experimental results show that the current source Output current adjustment range is -45~+45mA， accuracy is ± 0.1mA， and resolution ratio is 0.024 4mA
介紹了一種基于MSP430系列單片機和ADXL203加速度傳感器的數字式傾角儀，它不僅可以實現水平度檢測，而且可以測量00～3600范圍內的任意傾角，分辨率可達O．1。。此外，由于該傾角儀輸出為數字結果，因此它也可以與其他的數字設備結合起來，組合成一個功能更加強大的儀器。該數字傾角儀可廣泛應用于建筑、機械、道路、橋梁、石油、煤礦和地質勘探等各種需要測量重力參考系下傾角的場合。關鍵詞：MSP430F133單片機；力敏傳感器；ADXL203加速度計；角度測量
Abstract：This paper presents a new style digital inclinometer which is developed on the basis of the MSP430F133 MCU and the ADXL203 dual axis aeeelerometer．This inclinometer not only can test levelness，but also can measure any angle between 0。and 360。with an accuracy of 0．1 O．In addition，its Output is a digital result，which makes it possible to integrate itself with other digital devices to form a more functional unit．This inclinometer can be widely used in any construction site，oil field，coal-mine or geologic survey and SO on where it will provide the working people with convenience to measure any angles．Key words：MSP430F133 MCU；force sensor；ADXL203 accelerometer；angle measurement
The SN65LBC170 and SN75LBC170 aremonolithic integrated circuits designed forbidirectional data communication on multipointbus-transmission lines. Potential applicationsinclude serial or parallel data transmission, cabledperipheral buses with twin axial, ribbon, ortwisted-pair cabling. These devices are suitablefor FAST-20 SCSI and can transmit or receivedata pulses as short as 25 ns, with skew lessthan 3 ns.These devices combine three 3-state differentialline drivers and three differential input linereceivers, all of which operate from a single 5-Vpower supply.The driver differential Outputs and the receiverdifferential inputs are connected internally to formthree differential input/Output (I/O) bus ports thatare designed to offer minimum loading to the buswhenever the driver is disabled or VCC = 0. Theseports feature a wide common-mode voltage rangemaking the device suitable for party-lineapplications over long cable runs.
FEATURES400 MSPS internal clock speedIntegrated 10-bit DAC32-bit tuning wordPhase noise ≤ –120 dBc/Hz @ 1 kHz offset (DAC Output)Excellent dynamic performance>75 dB SFDR @ 160 MHz (±100 kHz offset) AOUTSerial I/O control1.8 V power supplySoftware and hardware controlled power-down48-lead TQFP/EP packageSupport for 5 V input levels on most digital inputsPLL REFCLK multiplier (4× to 20×)Internal oscillator; can be driven by a single crystalPhase modulation capabilityMultichip synchronization
The PCA9536 is an 8-pin CMOS device that provides 4 bits of General Purpose parallel
Input/Output (GPIO) expansion for I2C-bus/SMBus applications and was developed to
enhance the NXP Semiconductors family of I2C-bus I/O expanders. I/O expanders provide
a simple solution when additional I/O is needed for ACPI power switches, sensors,
push buttons, LEDs, fans, etc.
The PCA9534 is a 16-pin CMOS device that provide 8 bits of General Purpose parallel
Input/Output (GPIO) expansion for I2C-bus/SMBus applications and was developed to
enhance the NXP Semiconductors family of I2C-bus I/O expanders. The improvements
include higher drive capability, 5 V I/O tolerance, lower supply current, individual I/O
configuration, 400 kHz clock frequency, and smaller packaging. I/O expanders provide a
simple solution when additional I/O is needed for ACPI power switches, sensors,
push buttons, LEDs, fans, etc.
The CAT25128 is a 128−Kb Serial CMOS EEPROM device internally organized as 16Kx8 bits. This features a 64−byte page write buffer and supports the Serial Peripheral Interface (SPI) protocol. The device is enabled through a Chip Select (CS) input. In addition, the required bus signals are clock input (SCK), data input (SI) and data Output (SO) lines. The HOLD input may be used to pause any serial communication with the CAT25128 device. The device featuressoftware and hardware write protection, including partial as well as full array protection.
The CAT823, CAT824, and CAT825 provide basic reset and monitoring functions for the electronic systems. Each device monitors the system voltage and maintains a reset Output until that voltage reaches the device’s specified trip value and then maintains the reset Output active condition until the device’s internal timer, after a minimum timer of 140ms; toallow the systems power supply to stabilize.
The PAM2862 is a continuous mode inductivestep-down converter, designed for driving singleor multiple series connected LEDs efficientlyfrom a voltage source higher than the LEDvoltage. The device operates from an inputupply between 6V and 30V and provides anexternally adjustable Output current of up to 1A.Depending upon supply voltage and externalcomponents, this can provide up to 24 watts ofOutput power.
