新型便携式电子秤设计

本文研究了一种利用变极距电容式传感器实现质量-电量转换、以PIC16F877单片机为信息处理核心的便携式电子秤,论述了仪器的测量原理,介绍了减少变极距电容式传感器质量称量误差的自校准方法,给出了仪器原理框图、单片机单元硬件电路和仪器程序流程图.     

基于PIC单片机的矿用甲烷传感器的设计

针对传统的甲烷传感器测量精度低、稳定性差、缺乏智能性等问题,介绍了一种智能甲烷传感器的设计方案。该传感器采用多个甲烷气敏元件,以PIC16F877单片机为控制核心,采用C语言进行程序设计。通过单片机控制甲烷传感器,实现对井下甲烷浓度实时采集、处理,并当所测甲烷浓度超过设定的报警上、下限时自动报警,使矿工能够及时脱离危险,是煤矿传感器设计的首选器件。     

智能型1∶1电动助力车控制系统的研究

为提高我国电动自行车厂家的市场竞争力,研制出一款新颖的智能型1∶1助力车。在详细阐述1∶1电动助力车的实现原理及其方案的基础上,提出采用经特殊设计的速度传感器和扭矩传感器采集人力脚踩速度和扭矩,并利用PIC16C712单片机作为信号处理与中心控制单元,以完成对人力脚踩输出功率的计算,并根据该功率的大小控制直流驱动电机的输出,实现真正意义上的1∶1助力。此外,为提高使用性能和安全性能,PIC16C712单片机还能够对该车的工作状况进行实时监测和控制。经测试表明：该车完全符合有关的1∶1技术标准,与同类车相比,该车在可靠性、使用性和性价比等方面呈现出明显的优势。     

智能型1∶1电动助力车控制系统的研究

 为提高我国电动自行车厂家的市场竞争力，研制出一款新颖的智能型1∶1助力车。在详细阐述1∶1电动助力车的实现原理及其方案的基础上，提出采用经特殊设计的速度传感器和扭矩传感器采集人力脚踩速度和扭矩，并利用PIC16C712单片机作为信号处理与中心控制单元，以完成对人力脚踩输出功率的计算，并根据该功率的大小控制直流驱动电机的输出，实现真正意义上的1∶1助力。此外，为提高使用性能和安全性能，PIC16C712单片机还能够对该车的工作状况进行实时监测和控制。经测试表明：该车完全符合有关的1∶1技术标准，与同类车相比，该车在可靠性、使用性和性价比等方面呈现出明显的优势。     

一种基于PIC16F877的温度显示报警装置的设计与实现

本文使用铂热电阻PT100作为温度测量传感器,采用三线制桥式电路将非电量的温度信号转换为电压信号,并通过集成A/D转换技术的单片机PIC16F877完成数据采集、处理、显示,实现了对温度的精确测量报警.     

基于PIC16F877单片机的公交车智能投币机设计

介绍应用PIC单片机对硬币进行鉴别的原理及其在公交车智能投币机系统中的具体实现。系统采用电涡流传感器对%硬币进行信号检测收集,使用PIC16F877作为设计的核心数字信号处理部分,在软件方面使用速度加权算法,目标是硬币的正确辨识率达到98%以上。     

PIC16C66单片机在多费率电能表设计中的应用

文章介绍了以Microchip公司的PIC16C66单片机为CPU的多费率电能表接口设计。该表用ADE7755作为计量芯片，采用液晶显示并具有RS－485接口和红外通讯两种通讯方式。     

基于CIS的微小流量实时测量系统研究

本文针对微小流量的特点,用接触式图像传感器CIS采集透射光携带的液位信号,用可编程逻辑器件GAL产生CIS的驱动时序．以PIC16F877单片机作控制核心,对图像作二值化处理。可以实时测得微小流量。整个测量系统结构简单,性能可靠。     

基于PIC单片机的静电测量仪设计

以静电传感器测量原理为基础,介绍了基于PIC单片机技术的静电测量自动控制系统的程序设计原理,该系统可以实现静电测量、数据分析处理以及静电的消除等功能.为静电测量提供了一种新型实时静电测量仪的设计模型.     

一种单片机在直流电动机调速系统中的利用

介绍一种单片机(如89C51型)在直流电动机转速控制系统中的应用、实现方法以及硬件结构等。直流电动机转速控制系统采用了霍尔元器件测量电动机的转速,用此种单片机对直流电动机的转速进行了控制,用DAC0832芯片实现输出模拟电压值来控制直流电动机的转速。     

Voltage and frequency control of parallel operated synchronous generator and induction generator with STATCOM in micro hydro scheme

Parallel operation of synchronous and induction generators in micro hydro scheme is presented. The synchronous generator has an exciter, which provides a fixed excitation to produce normal rated terminal voltage at full resistive load. On the other hand, the induction generator has neither exciter nor speed controller. Static compensator (STATCOM) is connected to the common bus for terminal voltage and frequency control. A resistive dump load is connected across the DC link capacitor of STATCOM through a chopper to control active power. Simulink model is developed to perform transient analysis of the proposed scheme. Experimental results are presented to compare with the simulation results. It is found that connection of an induction generator in parallel with the synchronous is much simpler than connecting two synchronous generators in parallel.     

Novel Readout Electronics for Thickness Shear-Mode Liquid Sensors Compensating for Spurious Conductivity and Capacitances

In this paper, a readout circuit for a thickness shear-mode (TSM) resonator is presented which can be used for sensing applications in liquids such as viscosity sensing. The system features compensation of both spurious capacitances and conductances in parallel to the resonator. This allows measurements even in conductive liquids without the need for an elaborate sealing of the sensor. The influence of the spurious elements is determined by means of two orthogonal synchronous detectors and eliminated by active compensation using voltage-controlled amplifiers (VCAs). Furthermore, the circuit is robust against possible phase errors. The basic concept is discussed in detail, and a readout circuit is developed. A prototype is presented, and sample results are given, demonstrating the feasibility of the approach     

基于PIC单片机的胶印机墨斗电机控制系统设计

以四色胶印机墨斗为平台,以PIC18F2580单片机为控制核心,设计了一套完整的直流电机闭环调速控制系统。详细设计了系统硬件电路,着重设计了与操作台和PC机通讯的CAN通讯接口电路、电机控制与驱动电路、电机位置闭环反馈电路和电机PWM调速电路,编写了系统的C语言驱动程序。经实验和实际环境下的运行证明,该系统具有良好的驱动性能、调速性能和抗电磁干扰性能,有利于降低成本,有利于国产胶印机的自动化、智能化进程,有良好的市场应用前景。     

Novel portable electrical detection system for DNA SENSOR application

A novel, portable, electrical detection system was constructed for DNA sensor application to detect DNA hybridisation. The read-out circuit consists of an analogue circuit and a digital circuit. The analogue circuit with an IC MAX038 generates a sine wave with a constant frequency (10?kHz), which serves as the input for the DNA sensor. The DNA sensor consists of active and reference sensors. DNA hybridisation between the DNA probe and the target sequences causes changes in the conductance of the conductive membrane (DNA/MWCNTs) on the sensor surface, which lead to changes in the amplitude of the sine wave from the sensor output compared with that of the reference signal output (input sine wave). We used a digital circuit with a microprocessor (PIC33FJ256MC710) to determine the change in the amplitude of the sine wave signal of the sensor. From these digital data, the difference in the amplitudes of the active and reference sensors was calculated and displayed on the liquid crystal display. Measurement results show that the portable electrical detection system can detect DNA target concentrations as low as 0.16?µM. The detection of the amplified polymerase chain reaction sample and the reproducibility of the DNA sensor results were also determined using the designed readout circuit. The proposed electrical detection system is suitable for DNA sensor application.     

Synchronous Demodulator for Autonomous Sensors

In this paper, a novel differential synchronous demodulator is presented that uses the on-off switching characteristic of the power supply in autonomous systems as the control signal for demodulation. The proposed circuit, which uses only an op amp and a double-pole double-throw switch, can be useful in sensor nodes for sensor networks or distributed data-acquisition systems involving ac sensors or impedance measurements. Three prototype demodulators have been implemented using op amps with different power-bandwidth characteristics, and their common-mode rejection ratio (CMRR), nonlinearity, and initial transient were characterized. The working of the circuit when supplied by a piezoelectric energy converter is also verified.     

医学超声内镜中同步编码激励技术的设计与实现

为了提高医学超声内镜系统中的探测深度、分辨率及成像质量,在超声内镜成像系统中采用编码激励技术,首次将普遍用于开关电源电路设计中的"半桥"电路引入超声内镜编码激励电路.在只有正电压电源供电的情况下产生正负高压激励脉冲,利用电机转动的编码信号,设计了基于CPLD的同步编码激励电路,在保证与超声内镜主机FPGA同步的基础上,简化了超声内镜系统内信号的传递.实验中,同步编码激励电路发射的编码激励信号与理论码型一致,通过人体体模实验,获得的回波波形幅度达1.0Vpp,噪声20×10-3VPP~30×10-3Vpp,信噪比高达34 dB,波形与仿真结果一致.     

Conversion of Fluid Thermal Parameters into Frequency and Time by Means of Thermistors

A versatile direct converter of fluid thermal parameters into frequency and time is described. The circuit is based on a complementary multivibrator, the frequency of which is controlled by the temperature-sensitive current generator. Temperature-to-time (?-T) and temperature-to-frequency (?-f) conversion is obtained by simple rearranging of passive circuit elements. The linearizing conditions and sensitivity for various probe configurations are given. In battery telemetering systems, the circuit is economical in power supply consumption due to the very small mark-to-space ratio of output pulses. The sensitivity as well as the transducer Rmax/Rmin ratio are considerably increased in comparison with other direct thermistor converters. With the positive temperature coefficient (PTC) thermistor probe, the frequency change can be about three decades in the temperature range of 30°C, which represents the highest obtained sensitivity of ?-T/f converters. The circuit is also successfully applied with self-heated miniature bead thermistors as a sensor when it represents the linearized air speed-to-time converter within the range of 0-3.6 m/s.     

Autonomous excitation of induction generators

This paper treats the autonomous induction generator as a two-phase oscillator and compares it with another one, the very simple and well-known LC resonant circuit. As a result, an original explanation of the excitation process of the induction generator is presented. Furthermore, it is shown that the autonomous induction generator could be excited without capacitors by switching, in a suitable way, its resistive load in and out in the stator circuit