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Understanding the principle of thermistor is the premise of applying thermistor well. Thermistor is a kind of temperature-sensitive semiconductor element, whose main feature is that its resistance will change greatly with the change of external environment temperature. The dependence of resistance value on temperature is called resistance-temperature characteristic. Thermistors are divided into two categories according to temperature coefficient: positive temperature coefficient thermistors and negative temperature coefficient. Due to different characteristics, applications are also different.
Positive temperature coefficient thermistor is abbreviated as PTC (abbreviation of positive temperature coefficient). When it exceeds a certain temperature (Curie temperature), its resistance value increases step by step with the increase of temperature. Its principle is to introduce trace rare earth elements, such as La and Nb. The resistivity can be reduced to below10Ω by adding ceramic materials. Cm is a good semiconductor ceramic material. This material has a large temperature coefficient of positive resistance, and its resistivity can be increased by 4~ 10 orders of magnitude in the temperature range of tens of degrees above Curie temperature, that is, the so-called PTC effect is produced.
What kinds of PTC thermistors are widely used at present? PTC thermistor for constant temperature heating
? Low-voltage heating PTC thermistor
? PTC thermistor for air heating
? PTC thermistor for overcurrent protection
? PTC thermistor for overheating protection
? PTC thermistor for temperature sensing
? PTC thermistor for delayed start-up
Negative temperature coefficient is abbreviated as NTC (abbreviation of negative temperature coefficient), and its resistance decreases with the increase of temperature. Mainly made of manganese, cobalt, nickel, copper and other metal oxides through ceramic technology. These metal oxide materials have semiconductor characteristics because they are completely similar to semiconductor materials such as germanium and silicon in conductivity. The temperature coefficient of NTC thermistor is -2%~-6.5%, which can be widely used in temperature measurement, temperature compensation, surge current suppression and other occasions.
Main parameters of NTC negative temperature coefficient:
Zero power resistance value rt (ω)
Rated zero power resistance R25(ωω)
Material constant (thermal sensitivity index) b value (k)
Temperature coefficient of zero power resistor (αT)
Application design:
* Electronic thermometer, electronic calendar, electronic clock temperature display, electronic gifts;
* heating and cooling equipment, heating thermostat;
* Automobile electronic temperature measurement and control circuit;
* temperature sensor, temperature instrument;
* Medical electronic equipment, electronic toilet equipment;
* Mobile phone batteries and charging equipment.
Main application characteristics of MCS-5 1 single chip microcomputer (turn)
MCS-5 1 Single Chip Microcomputer is a product introduced by INTE Company of America 1980. Compared with MCS-48 single chip microcomputer, it has more advanced structure and stronger functions, and more circuit units and instructions are added on the original basis, and the number of instructions reaches 1 1, MCS-565438. MCS-5 1 series or its compatible single chip microcomputer is still the mainstream product of application, and the training materials of colleges and universities are still represented by MCS-5 1 single chip microcomputer for theoretical basic learning. We also systematically explained this representative model.
MCS-5 1 series single-chip computers mainly include 803 1, 805 1 and 875 1, and their main functions are as follows:
8-bit CPU
4 kbyte program memory (ROM)
128 byte data memory (RAM)
32 input/output port lines
1 1 1 instructions, mostly single-byte instructions.
2 1 special register
2 programmable timers/counters
5 interrupt sources, 2 priorities
Full duplex serial communication port
The addressing space of the external data memory is 64kB.
The addressing space of the external program memory is 64kB.
Logical operation bit addressing function
Dual in-line 40-lead DIP package
+5V single power supply
MCS-5 1 is a generation of "famous machines" with its typical structure, perfect centralized management of bus special registers, numerous logical bit operation functions and rich control-oriented instruction systems, which laid the foundation for the development of other single-chip computers in the future. It is precisely because of its superior performance and perfect structure that many subsequent manufacturers have followed or referred to its architecture. Many world-famous electrical companies have enriched and developed MCS-5 1 single-chip computers, and famous semiconductor companies such as Philips, Dallas and ATMEL have introduced MCS-5 1 single-chip computers. Even Winbond Company of Taiwan Province Province in China has developed a variety of single-chip microcomputers compatible with C5 1 (people used to call them MCS-5 1 for short, unless otherwise specified, both of them refer to MCS-5 1 series single-chip microcomputers).
In recent years, C5 1 has developed rapidly. Intel, the originator of C5 1, was busy developing PCs and high-end microprocessors, so it didn't have time to continue developing its own single-chip microcomputer, but was developed by other manufacturers, the most typical of which were Philips and ATML. Philips mainly improves performance, and develops high-speed I/O port and A/D converter on the original basis. PWM (pulse width modulation), WDT and other enhanced functions, and the functions of low voltage, micro power consumption, extended serial bus (I2C) and control network bus (CAN) need to be improved.
Philips has made a lot of contributions to the development of low power consumption, high speed and enhanced functions of C5 1. At the beginning, it was mainly used to develop C5 1 single chip microcomputer, and their 83Cxx and 87Cxx series omitted parallel expansion bus, which was suitable for economical single chip microcomputer control of household appliances.
The AT89Cxx series single chip microcomputer compatible with C5 1 introduced by ATMEL company perfectly combines Flash EEPROM with 80C5 1 kernel, and still adopts the overall structure and instruction system of C5 1. Flash's erasable program memory can effectively reduce the development cost, so that the single chip microcomputer can be reused many times.
Siemens also followed the core of C5 1 and successively introduced C500 series single-chip computers. On the premise of maintaining compatibility with C5 1 instruction, the performance of its products has been further improved, especially in anti-interference, electromagnetic compatibility and communication control bus function. Its products are often used in harsh working environments. But also applicable to the fields of communication and home appliance control.
Winbond Company in Taiwan Province Province has also developed a series of single-chip microcomputers compatible with C5 1, and their products usually have rich functional characteristics, and they also occupy a certain share in the market with high quality and low price.
The following table is the main classification and functional characteristics of 80C5 1 series single chip microcomputer:
Description of I/O port timer/counter interrupt source serial communication port on-chip RAM and on-chip ROM of a series of typical chips
5 1 series 80C3 1 4x8 bits 2x 16 bits 5 1 128 bytes None
80C5 1 4x8-bit 2x 16-bit 5 1 128-byte 4kB mask ROM
87C5 1 4x8-bit 2x 16-bit 5 1 128-byte 4kBEPROM
89C5 1 4x8-bit 2x 16-bit 5 1 128 bytes 4kBEEPROM
52 series 80C32 4x8 bits 2x 16 bits 1 256 bytes None
80C5 1 4x8-bit 2x 16-bit 6 1 256 bytes 8kB shielded ROM.
87C52 4x8 bit 2x 16 bit 6 1 256 bytes 4kBEPROM
89C52 4x8-bit 2x 16-bit 6 1 256 bytes 4kBEEPROM
805 1 is the representative product of MCS-5 1 series single chip microcomputer, which integrates powerful central processor, including hardware multiplier and divider, 2 1 special control register, 4kB program memory, 128 byte data memory, 4 groups of 8-bit parallel ports and 2/kloc-0.
MCS-5 1 has a relatively large addressing space, and the address line width reaches 16, that is, the addressing range of external data memory and program memory reaches 2 16=64kB, which is relatively large for single chip microcomputer control, and it also has the ability to access I/O ports. In addition, MCS-5 1 adopts modular structure, which can easily add or delete a new product with pin and instruction compatibility. So as to facilitate the serialization of products.
Because MCS-5 1 integrates almost perfect 8-bit central processing unit with powerful processing function, the central processing unit integrates convenient and flexible special registers, hardware addition, subtraction, multiplication, division, Boolean processors and various logic operations and transfer instructions, which provides great convenience for application.
The instruction system of MCS-5 1 is almost perfect, including comprehensive data transmission instructions, perfect arithmetic and logic operation instructions, convenient logic operation and control instructions, and the programming is quite flexible and convenient.
The working frequency of MCS-5 1 single chip microcomputer is 2- 12MHz. When the oscillation frequency is 12MHz, the period of a machine is 1us, which should be said to be relatively fast.
805 1 integrates all kinds of perfect interrupt sources, and users can control and use its functions very conveniently, which expands its application scope and can meet most application occasions.
MCS-5 1 integrates all the main components of microcomputer on one chip, which greatly shortens the data transmission distance, improves the reliability and runs faster. As a microchip microcomputer, the layout and structure of each functional part in the chip have been optimized, the anti-interference ability has been strengthened, and the work is relatively stable. Therefore, in the industrial measurement and control system, the use of single chip microcomputer is the most ideal choice. Single chip microcomputer is a typical embedded system and the best equipment for low-end control system.
The development environment of MCS-5 1 is low and the software resources are very rich. Books and development software introducing its functions and characteristics can be seen everywhere. You only need to equip a PC (personal computer-there is basically no requirement for computer configuration) and a simulation programmer to realize product development. Most of the early development software used DOS version. With the popularity of Windows software, almost all of them now use the Windows version. And the variety of software is dazzling. Among many kinds of single-chip computers, C5 1 has the richest environmental resources, which brings great convenience to users of C5 1.
Knowing this, I think you will do it! I hope it helps you!