Singlechipmicrocomputerandthedevelopmentof.doc

Single chip microcomputer and the development of the temperature and humidity sensor
Born in the 1970 s single chip microcomputer, and experience the SCM, MCU, SOC three phases.
(1) SCM namely Single Chip computer stage, main is to seek out the monolithic forms of the embedded system best system structure. "Innovation mode" success, laid the SCM and general computer completely different development road.
(2) MCU namely Micro Controller (Micro Controller Unit) stage, the main technological development direction is: expanding meet embedded application, the object system requirements of various peripheral circuit and interface circuit, dash forward show its object the intelligent control ability.
(3) MCU is embedded system independent development way, to a key factor to the development of MCU stage, is to seek application system on a chip in the maximization of the solution; Therefore, special MCU development natural form the SOC tendency. With microelectronics technology, IC design, EDA tools development, based on the single chip microcomputer application system SOC design can have larger development.
Temperature is a basic physical quantities, everything in nature is closely related with the process of temperature. The temperature sensor is the earliest development, the most widely used kind of sensor. From 17 th century people began to use temperature measuring. The temperature sensor there are four main types: thermocouple, thermal resistance, resistance temperature detector (RTD) and temperature sensor IC. IC temperature sensor and including analog output and digital output two types. Contact temperature sensor detection part and the tested object has a good contact, and calls the thermometer. The thermometer through the transmission or convection reach thermal equilibrium, thus make the thermometer and value can be measured directly says the temperature of the objects. General measurement precision. In a certain temperature range, the thermometer can also be measuring objects of internal temperature distribution. But for sports body, small target or heat capacity is very small objects will produce larger measurement error, commonly used a thermometer have two-metal thermometer, glass liquid thermometer, pressure type thermometer, resistance thermometers, thermistors and temperature difference electric dipole, etc. Contactless temperature sensor sensitive components and tested object each other is not contact, again say non-contact highlighted.it table. This instrument can be used to measure movement object, small goals and heat capacity small or temperature change quickly (transient) the surface temperature of the object, also can used for the measurement of the temperature distribution.
1.AT89S52 devices profile
The main performance: and MCS-51 SCM products compatible, and 8 K bytes in the system programmable Flash memory, 1000 time period, and the static integration.it operation: 0 Hz ~ 33 Hz, level 3 encryption program memory, 32 programmable I/O mouth line, three 16 timer/counters, eight interrupt source, full-duplex UART serial channel, low power dissipation power lost mode, and free after power off interrupt can wake up, the watchdog timer, double data pointer, off the identifier.
Functional characteristics description: AT89S52 devices is a low power, high-performance CMOS 8-bit microcontrollers, with 8 K in system programmable Flash memory. Atmel company use high-density nonvolatile technology manufacturing, and industry 80 C51 product instructions and pin fully compatible. Chip Flash allow program memory in the system programmable, also suitable for conventional programming console. In a single chip, with clever 8 bits CPU and in the system programmable Flash, make AT89S52 devices for many embedded control system to provide high flexible application, super efficient solution. AT89S52 devices has the following standard function: 8 k bytes Flash, 256 bytes RAM, 32 bit I/O mouth line, the watchdog timer, two data pointer, three 16 timer/counter, a 6 vector level 2 interrupt structure, full-duplex serial mouth, within crystals of timely clock circuit. In addition, AT89S52 devices can be down to 0 Hz series static logic operation, support two software can choose power saving mode. Idle mode, the CPU to stop working, and allow RAM, timer/counter, serial ports, interrupt continue to work for. Power lost protection ways, a RAM content being saved, has been frozen, SCM all work stop, until the next an interrupt or hardware reset so far.
2.Integrated temperature sensorAD590
Integrated temperature sensor AD590 to, its temperature resolution for the 0.3 degrees Celsius. The analog signal is output AD590 to, when the temperature of 0 degrees, output current 273.2 microamps, and current variation and temperature variation in a linear relationship, temperature, and once every change, the output current change 1 microamps, the temperature sensor of working temperature range is-30 degrees-150 degrees. If use AD590 to make the temperature sensor, sensor peripheral circuit is simple, just put sampling resistance and AD590 to link and then to amplify the signal, and then using voltage comparator compared to output voltage, voltage comparator output signals can be directly as PLC the input signal.
3.Humidity sensor
There are many ways of measuring the air humidity, its principle is based on certain material from the surrounding air absorb water caused by physical or chemical properties of the change, indirectly from the material of water quantity and the surrounding air humidity. Capacitive and resistive and wet go up wet type according to its original susceptibility were macromolecule material moisture absorption after the dielectric constant and resistivity and volume change and humidity measurement
Solution a: the HOS-201 wet sensors. HOS-201 wet sensor for high humidity sensor switches, it's the job of the voltage of ac 1 V the following, frequency for frequency 50 HZ ~ 1 KHZ, humidity measurement range of 0 ~ 100% RH, working temperature range is 0 ~ 50 ℃, impedance in 75% RH (25 ℃) for 1 M Ω. The sensor is used to switch the sensor, not on the wideband range detection humidity, therefore, mainly for the judgment or under more than e. humidity level. However, the sensor to a certain range, have a good use of the linear, and can be effectively using the linear characteristics.
Scheme ii: the HS1100 / HS1101 humidity sensor. HS1100 / HS1101 capacitance sensor, in a circuit of equivalent to a capacitor, it has the capacity as the air humidity increases while. Do not need to complete interchangeability of calibration, high reliability and long-term stability, fast response time, patent design of solid polymer structure, the top contact (HS1100) and lateral contact (HS1101) two kinds of packaging products, apply to linear output voltage and frequency output two circuit, is suitable for making automatic assembly line of the plugin and automatic assembly process, etc.
Relative humidity at 1%-100% RH range; The capacity to change by 16 pF 200 pF, the error is not more than plus or minus 2% RH; Response time less than 5 S; The temperature coefficient is 0.04 pF / ℃. Visible is higher accuracy.
A comprehensive comparison of scheme and scheme ii, plan one although meet the precision and the requirements of the measure humidity range, but its limited to certain scope, have a good use of the linear, and can be effectively using the linear characteristics. And still do not have in this design system of temperature-30 to 50 ℃ request, so we chose this design as the second scheme humidity sensor.
4.MC14433 A/D converter
MC14433 is three and A half double integral type of the A/D converter, with high precision, good anti-jamming performance advantages, its shortcoming is conversion rate low, about 1-10 times/SEC. Without the requirement of high speed switching occasions, for example, in low speed data acquisition system, is widely used. MC14433A a/D converter and domestic product 5 G14433 are all the same, can be interchanged.
5.The research significance
The collection of temperature and humidity monitoring in daily life has a wide range of USES, the temperature and humidity monitor based on this and design, the biggest advantage is that it can display the current temperature and humidity measurement, and the current temperature and preset temperature carries on the comparison, more than when the current temperature and humidity preset temperature alarm, realize the historical data monitoring, collection and analysis purposes. The temperature and humidity monitoring alarm low power consumption, can use the minimal resource for different temperature for high precision measurement, reliable performance, convenient operation information, complex work through software programming to complete, easy to get results, in actual use for the ideal effect. This design has realized to the real-time control of the temperature, flexible control precision and reliability, high, can meet the product preliminary test the requirements of the aging. In the processing of constant temperature and heating temperature, formed a complete set of control plan, can transplantation for constant temperature, heating the house and equipment many aspects. Therefore, this design research results and the design idea can be good in other design transplantation, did it and the actual good union, with strong practical significance.