1) separated amplifier is made by separating the amplifier from the sensor, using special integrated circuit and mixed installation process. Because the sensor has the characteristics of subminiature and diversity, the amplifier has more functions. Therefore, this model adopts terminal station connection mode and can be used for AC and DC power supply. It has the function of on-off delay, can set the switch between light and sound, can control six output States, and has two output modes: contact and level.
2) The built-in amplifier integrates the amplifier with the sensor, and is made of special integrated circuit and surface mount technology, and works with DC power supply. Its response speed (0. 1ms and 1ms) can detect narrow and high-speed moving objects. Changing the polarity of power supply can switch between bright and dark motion, and self-diagnosis and stable working area indicator light can be set. It has two output modes of voltage and current, which can prevent mutual interference and is very convenient for system installation.
3) Built-in power supply is integrated by amplifier, sensor and power supply device, using application specific integrated circuit and surface mount technology. Generally, AC power supply is used, which is suitable for replacing contact travel switch in production site and can be directly used in high voltage control circuit. You can also set a self-diagnosis stable work area indicator light, and the output is equipped with SSR solid-state relay or relay normally open and normally closed contacts to prevent mutual interference, which can be closely installed in the system. After the modulation pulse generated by the oscillation circuit passes through the reflection circuit, the light pulse is emitted by the light emitting tube GL. When the measured object enters the action range of the optical receiver, the reflected light pulse enters the phototransistor DU. In the receiving circuit, the optical pulse is demodulated into an electrical pulse signal, amplified by an amplifier, synchronously gated and shaped, and then the interference is eliminated by digital integration or RC integration. Finally, the driver is triggered to output the photoelectric switch control signal with delay (or without delay).
Generally, photoelectric switches have good return error characteristics, so even if the detected object shakes in a small range, it will not affect the output state of the driver, thus keeping it in a stable working area. At the same time, the self-diagnosis system can also display the light receiving state and stable working area, so as to monitor the working situation of photoelectric switch at any time. MGK series photoelectric switch is the product of the development of modern microelectronics technology and the upgraded product of HGK series infrared photoelectric switch. Compared with the previous photoelectric switch, it has its own remarkable characteristics:
It has the functions of self-diagnosis and indication of stable working area, and can inform whether the working state is reliable in time;
Opposite, reflective and specular photoelectric switches all have the function of preventing mutual interference and are convenient to install;
Setting the ES external synchronization (external diagnosis) control terminal can check whether the photoelectric switch works normally before operation. It can accept the interrupt or detection instruction of computer or programmable controller at any time, and the appropriate combination of external diagnosis and self-diagnosis can make the photoelectric switch intelligent;
The response speed is fast. The response speed of the high-speed photoelectric switch can reach 0. 1ms, and it can carry out 300,000 detection operations per minute, which can detect tiny objects moving at high speed.
Adopt special integrated circuit and advanced SMT surface mounting technology, with high reliability;
Small size (the minimum is only 20×3 1× 12mm), light weight, simple installation and debugging, and short-circuit protection function. Detection distance: The detection distance of retro-reflective and specular-reflective photoelectric switches refers to the maximum distance that can be stably detected without effective shielding on the optical axis. The detection distance of reflective photoelectric switch is the maximum distance that can stably detect standard detection objects.
Return distance: Return distance refers to the difference between action distance and reset distance. Expressed by the ratio of detection distance, it is generally below 20% of detection distance.
Response time: the time from the effective light reception of the light receiver to the output action is called response time.
Reset application time: the time from the initial effective shading of the optical receiver to the output reset is called reset application time.
Dark open: Shadow action. It means that the output transistor will turn on the output when the speed of light entering the optical receiver decreases to a certain program or is completely blocked.
Lighting action: turning on the light, also called light receiving action. It means that when the beam entering the receiver increases to a certain amount, the output transistor is turned on and has an output.
External synchronous input function: In general, all photoelectric switches with external diagnostic input function generally have external synchronous function.
In other words, it can be used to check whether the sensor detection is normal before work. At work, this attribute can also be used to accept operation or interrupt instructions issued by the control system at any time. If the previous output is connected in series with the latter external synchronous input, functions such as AND gate can be realized. 1) photoelectric switch can be used in various applications, avoiding strong light sources and generally working stably when the ambient illumination is high. However, direct pointing of the optical axis of the sensor to strong light sources, such as sunlight and incandescent lamps, should be avoided. When the angle between the optical axis of the sensor (light receiver) and the strong light source cannot be changed, a light shielding plate or a long light shielding tube can be installed around the sensor.
2) Prevent mutual interference. MGK series new photoelectric switches usually have the function of automatically preventing mutual interference, so there is no need to worry about mutual interference. However, when several groups of opposed HGK series infrared photoelectric switches are installed side by side, adjacent groups and mutual interference should be prevented. The most effective way to prevent this kind of interference is to cross the projector and the receiver. When there are more than two groups, the distance between the groups becomes wider. Of course, it is also a good idea to use models with different frequencies.
An effective way to prevent the mutual interference of HGK series reflective photoelectric switches is to open the interval. Moreover, the farther the detection distance is, the larger the interval should be, and the specific interval should be determined according to the debugging situation. Of course, models with different operating frequencies can also be used.
3) Influence of mirror angle: When the measured object is shiny or meets a smooth metal surface, the reflectivity is generally high, similar to a mirror. At this time, the projector and the measured object should be installed at an included angle of10 ~ 20, so that its optical axis is not perpendicular to the measured object to prevent misoperation.
4) Eliminate the influence of background objects: When using reflective diffusion projector and receiver, sometimes the photoelectric switch may be unstable because the detected object is close to the background object, and the photoelectric switch or the background is smooth and other objects with high reflectivity. So you can use a projector and receiver with limited distance instead, or you can remove the background by staying away from it, moving it, painting it dark black, or trying to make it rough and gloomy.
5) Use of self-diagnosis function: During installation or use, due to the influence of the table top or background and the vibration during use, problems such as slight deviation of optical axis, lens pollution, dust accumulation, external noise, and out-of-range ambient temperature sometimes occur. These problems may make the photoelectric switch deviate from the stable working area. At this time, the self-diagnosis function of photoelectric switch can be used to make it send out a notice through a stable green indicator light to remind users to adjust in time. Switching power supply is a kind of power supply which uses modern power electronics technology to control the time ratio of switching tube on and off and maintain stable output voltage. Switching power supply generally consists of pulse width modulation (PWM) control IC and MOSFET. Compared with linear power supply, the cost of switching power supply and linear power supply increases with the increase of output power, but the growth rate is different. At a certain output power point, the cost of linear power supply is higher than that of switching power supply, which is called cost inversion point. With the development and innovation of power electronics technology, switching power supply technology is also constantly innovating, and this cost reversal point is increasingly moving to the low output power end, which provides a broad development space for switching power supply.
High frequency switching power supply is its development direction. High-frequency switching power supply makes it smaller, and makes it enter a wider range of applications, especially in the high-tech field, which promotes the miniaturization and portability of high-tech products. In addition, the development and application of switching power supply is of great significance to saving energy, saving resources and protecting the environment. The power electronic devices used in switching power supply are mainly diodes, IGBT and MOSFET. Silicon controlled rectifier has a small number of applications in the input rectifier circuit and soft start circuit of switching power supply. GTR is difficult to drive and its switching frequency is low, so it is gradually replaced by IGBT and MOSFET.
Three conditions:
1. switch: power electronic devices work in the switch state, not the linear state.
2. High frequency: Power electronic devices work at high frequency, not at low frequency close to power frequency.
3.DC: the switching power supply outputs DC instead of alternating current.
Switching power supply generally has three working modes: constant frequency variable pulse width mode, constant frequency variable pulse width mode and variable frequency variable pulse width mode. The former working mode is mostly used for DC/ AC inverter power supply or DC/DC voltage conversion; The latter two working modes are mostly used for switching regulated power supply. In addition, the output voltage of switching power supply has three working modes: direct output voltage mode, average output voltage mode and amplitude output voltage mode. Similarly, the former working mode is mostly used for DC/ AC inverter power supply or DC/DC voltage conversion; The latter two working modes are mostly used for switching regulated power supply.
According to the connection mode of switching devices in the circuit, the switching power supplies widely used at present can be roughly divided into three categories: series switching power supplies, parallel switching power supplies and transformer switching power supplies. Among them, transformer switching power supply (hereinafter referred to as transformer switching power supply) can be further divided into: push-pull, half-bridge, full-bridge and so on; According to the excitation of transformer and the phase of output voltage, it can be divided into forward excitation, flyback excitation, single excitation and double excitation. If divided by purpose, it can be divided into more categories.
Classification of switching power supply:
In the field of switching power supply technology, people are developing related power electronic devices and switching frequency conversion technology at the same time. The two promote each other, pushing the switching power supply to develop in the direction of light, small, thin, low noise, high reliability and anti-interference with an annual growth rate of more than two digits. Switching power supplies can be divided into two categories: AC /DC and DC/DC. The DC/DC converter has been modularized, and the design technology and production technology have matured and standardized at home and abroad, and have been recognized by users. However, due to its own characteristics, the modularization of AC/DC has encountered more complicated technical and technological manufacturing problems in the process of modularization. The structure and characteristics of two types of switching power supplies are described below.
disembark
Switching power supply will produce more interference than linear power supply. Electrical equipment sensitive to * * * mode interference shall be grounded and shielded. According to EMC restrictions such as ICE 1000, EN6 1000, FCC, etc., the switching power supply should adopt EMC electromagnetic compatibility measures, so the switching power supply should generally be equipped with EMC electromagnetic compatibility filters. For example, HA series switching power supply based on LEED Huafu technology can meet the above electromagnetic compatibility requirements only if its FG terminal is connected to the ground or user chassis.
protective circuit
Switching power supply must have protection functions such as over-current, overheating, short circuit, etc. Therefore, switching power supply module with complete protection functions should be preferred in design, and the technical parameters of its protection circuit should match the working characteristics of electrical equipment to avoid damaging electrical equipment or switching power supply.
development trends
The development direction of switching power supply is high frequency, high reliability, low power consumption, low noise, anti-interference and modularization. Because the key technology of light, small and thin switching power supply is high frequency, major foreign switching power supply manufacturers are committed to developing new high-intelligence components, especially to improve the loss of secondary rectifier devices, and apply them to power ferrite (Mn? Zn) materials should be innovated in science and technology to improve high magnetic properties and high magnetic flux density (Bs) at high frequency, and miniaturization of capacitors is also the key technology. The application of SMT technology in switching power supply has made great progress. Components are arranged on both sides of the circuit board to ensure the light, small and thin switching power supply.
The high frequency of switching power supply will inevitably innovate the traditional PWM switching technology. The soft switching technology of ZVS and ZCS has become the mainstream technology of switching power supply, which greatly improves the working efficiency of switching power supply. For the high reliability index, American switching power supply manufacturers reduce the stress of devices by reducing the operating current and junction temperature, which greatly improves the reliability of products.
Modularization is the general trend of switching power supply development. Modular power supply can be used to form a distributed power supply system, which can be designed as N+ 1 redundant power supply system to realize capacity expansion in parallel. Aiming at the disadvantage of high noise of switching power supply, if we simply pursue high frequency, its noise will increase. Theoretically, the use of partial resonance conversion circuit technology can realize high frequency and reduce noise, but there are still technical problems in practical application of partial resonance conversion technology, and a lot of work needs to be done in this field to make this technology practical. The switching voltage stabilizing system LTM460 1AHVMPV has PLL and output tracking functions, and is specially designed for demanding military and aviation applications. LTM460 1AHVMPV has been tested in the temperature range of -55℃ to 125℃. The device is packaged in15mm x15mm x 2.8mm military plastic land grid array (LGA) and weighs only1.7g.. This compact LGA package can be used in high-power DC/DC solutions because its thermal resistance is lower than that of ball grid array (BGA) packages of similar size. LTM460 1AHVMPV are all made of silicon chips from Lingerlite Company. After rigorous internal testing, demanding high-reliability applications have component-level reliability and industry-leading performance.
LTM460 1AHVMPV is a synchronous DC/DC buck regulator with built-in inductor, which supports power components and compensation circuits. The device works in the input power supply range of 4.5V to 28V, and the output voltage range is adjusted from 0.6V to 5V ... This DC/DC micro-module regulator can provide continuous load current of 12A (peak value is 14A), and can also realize current sharing up to 48A in parallel. Its efficiency is up to 92%. DC/DC micro-module voltage regulators such as LTM460 1AHVMPV can simplify the design and structure of power supply, and only need large input and output capacitors and a resistor to set the output voltage.
LTM460 1AHVMPV DC/DC micro-module voltage regulator LGA package allows surface mount assembly and can be handled and assembled like all surface mount ics. In addition, its flat design allows devices to be soldered on the back of the printed circuit board, thus freeing up valuable circuit board space for advanced digital integrated circuits. LTM460 1AHVMPV has the self-protection ability of output overvoltage and short circuit. Buy in bulk in units of 1 0,000 tablets at a price of $40.25 per tablet.
Performance summary: LTM460 1AHVMPV
Complete 12A DC/DC power supply system; Parallel connection can make the current as high as 48A.
Ultra-thin15mm x15mm x 2.8mm high reliability plastic LGA package.
The testing temperature range is -55℃ to 125℃
Guaranteed to start at -55℃
The input voltage range is 4.5V to 28V；; Proximity switches with an output of 0.6V to 5V are also called contactless travel switches. It can not only complete stroke control and limit protection, but also be a non-contact detection device, which can be used to detect the size and speed of parts, as well as the automatic connection of frequency conversion counter, frequency conversion pulse generator, liquid level control and machining program. It is characterized by reliable work, long service life, low power consumption, high repositioning accuracy, high working frequency and adaptability to harsh working environment.
Performance characteristics:
Among all kinds of switches, there is an element-displacement sensor, which has the ability to "sense" the approach of objects. Proximity switch uses the sensitive characteristics of displacement sensor to close the object to control the switch on and off.
When something moves towards the proximity switch and approaches a certain distance, the displacement sensor will "sense" it and the switch will act. This distance is usually called "detection distance". Different proximity switches have different detection distances.
Sometimes the detected objects move to the proximity switch one by one and leave one by one at a certain time interval, and so on. Different proximity switches have different response abilities to detected objects. This response characteristic is called "response frequency".
Because displacement sensors can be made according to different principles and methods, and different displacement sensors have different "sensing" methods for objects, the common proximity switches are as follows:
1, eddy current proximity switch
This kind of switch is sometimes called inductive proximity switch. It uses conductive objects to generate eddy currents when they approach the proximity switch that generates electromagnetic fields. This eddy current is reflected on the proximity switch, which changes the internal circuit parameters of the switch, thus identifying whether there is a conductive object approaching, and then controlling the on-off of the switch. The object that the proximity switch can detect must be a conductor.
2. Capacitive proximity switch
The measurement of this kind of switch is usually one plate of the capacitor and the other plate is the shell of the switch. During measurement, the housing is usually grounded or connected to the equipment housing. When something moves close to the switch, whether it is a conductor or not, the dielectric constant of the capacitor will always change due to its proximity, so that the capacitance will change and the state of the circuit connected to the probe will also change, so that the switch can be controlled to be turned on or off. The detection object of the proximity switch is not limited to conductor, insulating liquid or powder, etc.
3. Hall proximity switch
Hall element is a magnetic sensitive element. Switches made of Hall elements are called Hall switches. When a magnetic object moves close to the Hall switch, the Hall element on the detection surface of the switch changes the internal circuit state of the switch due to the Hall effect, so that the presence of a nearby magnetic object can be recognized, and then the switch can be controlled to be turned on or off. The detection object of the proximity switch must be a magnetic object.
4, photoelectric proximity switch
Switches made by photoelectric effect are called photoelectric switches. The light-emitting device and photoelectric device are installed in the same probe according to a certain direction. When a reflecting surface (the detected object) approaches, the photoelectric device will output a signal after receiving the reflected light, thus "sensing" that an object is approaching.
5, thermoelectric proximity switch
Switches made of elements that can sense temperature changes are called thermoelectric proximity switches. In this switch, a thermoelectric device is installed on the detection surface of the switch. When an object with different ambient temperatures approaches, the output of the thermoelectric device changes, so that the approach of the object can be detected.
6. Other types of proximity switches
When the distance between the observer or the system and the wave source changes, the frequency of the approaching wave will shift, which is called Doppler effect. Sonar and radar are made by the principle of this effect. Ultrasonic proximity switch and microwave proximity switch can be made by using Doppler effect. When an object approaches, the reflected signal received by the proximity switch will produce Doppler frequency shift, so that whether the object approaches or not can be identified.
Main uses:
Proximity switches are widely used in aviation, aerospace, aerospace technology and industrial production. In daily life, such as hotels, restaurants, garages, automatic doors, automatic air heaters have applications. In terms of security and anti-theft, anti-theft devices composed of various proximity switches are usually installed in important places such as data files, accounting, finance, museums, treasury and so on. In measurement technology, such as length and position measurement; In control technology, such as the measurement and control of displacement, velocity and acceleration, a large number of proximity switches are also used.
Select precautions:
In general industrial production sites, eddy current proximity switches and capacitive proximity switches are usually selected. Because these two proximity switches have low environmental requirements. When the measured object is a conductive object or an object that can be fixed on a metal object, eddy current proximity switch is generally selected because of its high response frequency, good anti-environmental interference performance, wide application range and low price. If the measured object is nonmetal (or metal), liquid level height, powder height, plastic, tobacco, etc. Capacitive proximity switches should be selected. This switch has low response frequency, but good stability. Environmental factors should be considered during installation. If the object is made of magnetic conductive material or magnetic steel is buried in the object to be measured in order to distinguish the object moving with it, the Hall proximity switch should be selected, which has the lowest price.
When the environmental conditions are good and there is no dust pollution, the photoelectric proximity switch can be used. The photoelectric proximity switch has little effect on the measured object when it works. Therefore, it is widely used in demanding fax machines and tobacco machinery.
In the anti-theft system, automatic doors usually use pyroelectric proximity switches, ultrasonic proximity switches and microwave proximity switches. Sometimes, in order to improve the reliability of identification, the above proximity switches are often used in combination.
No matter which proximity switch you choose, you should pay attention to the requirements of working voltage, load current, response frequency, detection distance and other indicators. Switchgear is a kind of electrical equipment. The outside line first enters the main control switch in the cabinet, and then enters the sub-control switch, and each branch is set as needed. Such as instruments, automatic control, motor magnetic switch, various AC contactors, etc. There are also high-voltage and low-voltage switchgear and high-voltage buses, such as power plants. , and some have low cycle load shedding protection main equipment.
General classification:
1, low-voltage draw-out switchgear
2. AC low-voltage distribution cabinet
3. Metal armored detachable switch cabinet
4. Low-voltage fixed separation switchgear
5, high voltage capacitor cabinet
6, high voltage switchgear switch socket type:
Type 86 switch: The most common switch socket has a square shape with an external dimension of 86 mm× 86 mm This type of switch is often called Type 86 switch, which is an international standard. Many developed countries are equipped with type 86 switch, which is also the most commonly used switch in engineering and home improvement in most parts of China.
1 18 type switch: 1 18 type switch generally refers to a horizontal bar switch. 1 18 switches are generally freely combined: different functional modules are combined in a frame, which is widely used in Chongqing, Hubei, Guangxi and other places. 1 18 switches are generally divided into small boxes, medium boxes and large boxes in the electrician list. The length is 1 18MM, 154MM, 195MM, and the width is generally 74MM, 1 108. More flexible, can change colors according to their own needs and preferences, easy to assemble and disassemble, free style.
120 switch: The common modules of 120 are based on 1/3, that is, three 1/3 standard modules can be installed on a vertical standard panel. The module is divided into 1/3, 2/3, 1 bit by size. The height of 120 fingerboard is 120mm, which can be matched with functional components of one unit, two units or three units.
The 120 switch comes in two sizes. One is single connection, 74mm× 120mm, which can be equipped with one, two or three sets. One is double connection, 120mm× 120mm, which can be configured with four units, five units or six units.
146 switch: twice as wide as ordinary switch socket. For example, for some four-position switches and ten-hole sockets, the panel size is generally 86mm× 146mm or similar, and the center distance of installation holes is 120.6㎜. Note: Only long film boxes can be installed.