Circuit board test points
The purpose of setting test points is to test whether the components on the circuit board meet the specifications and solderability. For example, if you want to check the resistance of a circuit board, the simplest method is to measure it with a multimeter You can know both ends. In the early days when traditional plug-in (DIP) was used on the circuit board, the solder pins of the parts were indeed used as test points. Because the solder pins of the traditional parts are strong enough, they are not afraid of needle sticks, but there are often probes. The misjudgment situation of poor contact occurs, because after the general electronic parts are subjected to wave soldering or SMT tin eating, a residual film of solder paste flux is usually formed on the surface of the solder, and the resistance of this film Very high, which often causes poor contact of the probes, so the test workers of the production line were often seen at that time, often blowing desperately with an air spray gun, or wiping these places that need to be tested with alcohol.If you want to order PCB product, please check and custom your order online.In fact, the test points after wave soldering will also have the problem of poor contact with the probe. Later, after the prevalence of SMT, the situation of test misjudgment has been greatly improved, and the application of test points has also been greatly endowed, because SMT parts are usually very fragile and cannot withstand the direct contact pressure of test probes. Use test points It is not necessary to let the probe directly contact the part and its soldering feet, which not only protects the part from injury, but also greatly improves the reliability of the test indirectly, because the number of misjudgments becomes less. However, with the evolution of technology, the size of circuit boards is getting smaller and smaller. It is already difficult to squeeze so many electronic parts on a small ground board. Therefore, the problem of occupying circuit board space at test points is often found in The tug of war between the design side and the manufacturing side, but this topic will be discussed later.The appearance of the test point is usually round, because the probe is also round, which is easier to produce, and it is easier to bring the adjacent probes closer together, so that the needle implant density can be increased. Circuit board test pointsBasically, the purpose of setting test points is to test whether the components on the circuit board meet the specifications and solderability. For example, if you want to check the resistance of a circuit board, the easiest way is to take a multimeter. It can be known by measuring its two ends. However, there is no way for mass production factories to allow you to slowly measure whether each resistance, capacitance, inductance, and even IC circuit on each board is correct with an electric meter, so there is a so-called ICT (In -Circuit-Test) The emergence of automated testing machines that use multiple probes (commonly referred to as "Bed-Of-Nails" fixtures) to simultaneously contact all parts on the board that need to be measured, Then, through program control, the sequence is mainly used, and the side by side method is used to measure the characteristics of these electronic parts in sequence. Generally, it takes only 1-2 minutes to test all the parts of the general board, depending on the number of parts on the circuit board. However, the more parts, the longer the time.But if these probes are allowed to directly touch the electronic parts on the board or their solder pins, it is very likely that some electronic parts will be crushed, but it is counterproductive, so smart engineers invented "test points" at both ends of the parts An additional pair of small round points are drawn without a mask, which allows the test probe to touch these small points without directly touching the electronic parts being measured. PCB test point gold finger There are some inherent limitations in the use of needle beds for circuit testing, such as:1. The minimum diameter of the probe has a certain limit, and a needle with a too small diameter is easily broken and damaged. 2. Needles cannot be implanted next to some high parts. If the probe is too close to the high part, there is a risk of damage to the high part. In addition, because the part is relatively high, it is usually necessary to open a hole in the test fixture needle bed seat to avoid the needle implantation. 3. The distance between the needles is also limited, because each needle must come out of a hole, and the rear end of each needle also needs to be welded with a cable. If the adjacent hole is too small, except for the needle and the needle There will be the problem of contact short circuit, and the interference of the cable is also a big problem. 4. Test points for all parts that are increasingly difficult to accommodate on the circuit board. As the board is getting smaller and smaller, the number of test points has been repeatedly discussed, and now there have been some methods to reduce test points, such as Net test, Test Jet, Boundary Scan, JTAG, etc.; there are other test methods Want to replace the original needle bed test, such as AOI, X-Ray, but at present each test seems to be unable to replace ICT 100%. About the ICT's needle implantation ability, the cooperating jig manufacturer should be asked, that is, the minimum diameter of the test point and the minimum distance of the adjacent test point. Usually there will be a desired minimum value and the minimum value that the ability can achieve, but there are Manufacturers of large scale will require that the distance between the minimum test point and the minimum test point should not exceed how many points, otherwise the fixture will be easily damaged. These are the most critical issues that must be kept in mindWanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 11:20
Circuit board test method
The test is a measurement with experimental nature, that is, a combination of measurement and test. The test means is instrumentation. Because test and measurement are closely related, in actual use, it is often not strict to distinguish between test and measurement. The basic task of the test is to obtain useful information. Through the use of special instruments and equipment, the design of reasonable experimental methods and the necessary signal analysis and data processing, in order to obtain information related to the measured object. The final result of the test is to input the displayed information into the information processing library for control.If you want to order PCB product, please check and custom your order online.Circuit board test process Detection before power-on: After soldering a circuit board, when checking whether the circuit board can work normally, usually not directly supply power to the circuit board, but follow the steps below to ensure that there is no problem at each step and then power on late: 1. Whether the connection is correct: check whether the board connection is correct according to the schematic diagram, and check one by one according to the circuit diagram of the circuit diagram; 2. Check the installation of the components: whether the diode polar capacitor and the chip are installed correctly. Check whether the soldering of each device has virtual soldering.3. Check the power supply interface and other short circuits: Check whether there is a short circuit between the power supply and each level. Protection circuits such as resettable fuses should be added to the circuit design. The power supply part can be designed with 0Ω resistance, and the front line of the power supply is not welded to prevent the chip of the back unit from being burned abnormally. Detection after power on: Check the following steps after power on:、1. Observation of power-on: Do not rush to measure electrical indicators after power-on, but observe whether the circuit has abnormal phenomena, such as smoke, abnormal smell, touch the outer package of the integrated circuit, whether it is hot, etc. If an abnormal phenomenon occurs, turn off the power supply immediately, and then check the power supply after troubleshooting. 2. Static test: Check whether the level status reaches the expectation step by step, and gradually restore the welding 0Ω resistance. The debugging sequence of the sub-circuit is generally carried out according to the signal flow direction, and the output signal of the circuit that has been debugged before is used as the input signal of the subsequent stage to create conditions for the final unified adjustment. 3. Dynamic test: gradually add external input and output signals to debug various parts of the system. This step requires joint debugging with software. Test method of circuit board 1. Manual visual inspection:Use a magnifying glass or calibrated bai microscope, and use the visual inspection of the operator to confirm that the circuit board is unqualified and determine when correction operation is required. It is the most traditional and the most important detection method. Its main advantages are low upfront costs and no test fixtures, and its main disadvantages are human subjective errors, high long-term costs, discontinuous defect detection, and difficulty in data collection. At present, due to the increase in the output of PCBs and the reduction in the spacing of wires on the PCB and the volume of components, this method has become less and less feasible. 2. Online testing (ICT, In Ciruit Testing)ICT finds manufacturing defects and tests analog, digital and mixed-signal components through the inspection of electrical performance to ensure that they meet specifications. There are Bed of Nails Tester and Flying Probe Tester ) Wait for several test methods. The main advantages of ICT are low test cost per board, strong digital and functional test capabilities, fast and thorough short-circuit and open-circuit testing, programming firmware, high defect coverage, and easy programming. The main disadvantages are the need for test fixtures, programming and debugging time, the high cost of making fixtures, and the difficulty of using them3. Functional TestingThe functional system test is to use special test equipment at the middle and end of the production line to comprehensively test the functional modules of the circuit board to confirm the quality of the circuit board. Functional testing can be said to be the earliest automatic testing principle. It is based on a specific board or a specific unit and can be completed with various devices. There are final product test (Final Product Test), the latest solid model (Hot Mock-up) and "stacked" test ('Rack and Stack' Test) and other types. Functional testing usually does not provide footsteps for process improvement and Deep-level data such as component-level diagnostics, and requires special equipment and a specially designed test process to write functionsThe test procedure can be complicated, so it is not suitable for most circuit board production lines.4. Automatic optical detectionAlso known as automatic visual inspection, it is based on the principle of optics, using a variety of technologies such as image analysis, computer and automatic control to detect and process defects encountered in production, which is a relatively new method of confirming manufacturing defects. AOI is usually used before and after reflow and before electrical testing to improve the pass rate in the electrical processing or functional testing phase. At this time, the cost of correcting defects is much lower than the cost of conducting after the final test, often reaching a dozen times.5. Automatic X-ray Inspection (AXI, Automatic X-ray Inspection)AXI makes use of the difference in X-ray absorption rate of different substances to see through the parts to be detected and find defects. It is mainly used to detect defects such as ultra-fine pitch and ultra-high-density circuit boards and bridging, chip dropping, and misalignment during the assembly process. It can also use its tomography technology to detect internal defects in IC chips. It is currently the only way to test the soldering quality and blocked solder balls of Ball Grid Array (BGA). In the latest AXI system for circuit board assembly, the latest products of companies such as Feinfocus, Phoenix Xray, etc. can not only perform 2D perspective inspection, but also provide 3D inspection through the sample side tilt, "side-view" X-ray information. Its main advantages are the ability to detect BGA welding quality and embedded components, and no fixture cost; the main disadvantages are slow speed, high failure rate, difficulty in detecting reworked solder joints, high cost, and long program development time.6. Laser detection systemIt is the latest development of PCB testing technology. It uses a laser beam to scan the printed board, collect all measurement data, and compare the actual measurement value with the preset qualified limit value. This technology has been confirmed on the light board, and is being considered for assembly board testing, and the speed is sufficient for mass production lines. Fast output, without requiring fixtures and visual uncovered access are its main advantages; high initial cost, and maintenance and use problems are its main disadvantages.From the above 6 commonly used PCB inspection methods, it can be found that AOI automatic optical inspection equipment, like any vision-based inspection system, can only detect faults that can be seen with vision, and can only detect defects such as short circuits and open circuits. Use electrical test method to solve. Compared with the primitive visual detection method of human naked eye, AOI is an automated detection method, and its detection efficiency is much higher and its reliability is much more stable.7. Needle bed methodThis method bai is connected to each detection point on the electric circuit board by a probe with a spring. The spring makes each probe have a pressure of 100-200g, to ensure that each detection point is in good contact, such a probe is arranged together is called a "needle bed". Under the control of the inspection software, the inspection points and inspection signals can be programmed, and the inspector can get the information of all the inspection points. In fact, only those probes that need to be tested are installed. Although the needle bed test method may be used to test both sides of the circuit board at the same time, when designing the circuit board, all the detection points should be on the soldering surface of the circuit board. Needle bed tester equipment is expensive and difficult to maintain. The needles are selected in different arrangements according to their specific application.A basic general-purpose grid processor consists of a drilled board with a pin center spacing of 100, 75, or 50 mils. Pins act as probes and make direct mechanical connections using electrical connectors or nodes on the circuit board. If the pads on the circuit board match the test grid, a vinegar film that is perforated according to the specifications will be placed between the grid and the circuit board to facilitate the design of specific probes. Continuity detection is achieved by accessing the end point of the grid (which has been defined as the x-y coordinate of the pad). Since every network on the circuit board is tested for continuity. In this way, an independent test is completed. However, the proximity of the probe limits the effectiveness of the needle bed test.8.ObservationThe circuit board is small in size and complex in structure, so professional observation instruments must also be used to observe the circuit board. In general, we use a portable video microscope to observe the structure of the circuit board. Through the video microscope camera, you can clearly see the microstructure of the circuit board from the microscope. In this way, it is easier to design and test the circuit board. 9. Flying probe testThe flying probe tester does not depend on the pin pattern installed on the fixture or bracket. Based on this system, two or more probes are mounted on a tiny magnetic head that can move freely on the x-y plane, and the test points are directly controlled by CADI Gerber data. The dual probes can move within 4mil of each other. The probes can move independently, and there is no real limit to how close they are to each other. The tester with two arms that can move back and forth is based on the measurement of capacitance. The circuit board is pressed tightly on the insulating layer of a metal plate, which is used as another metal plate of the capacitor. If there is a short circuit between the lines, the capacitance will be larger than at a certain point. If there is an open circuit, the capacitance will become smaller.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 11:16
Vacuum cleaner circuit board
The vacuum cleaner can be divided into vertical, horizontal and portable according to the structure. The working principle of the vacuum cleaner is to use the electric motor to drive the blades to rotate at high speed, generating negative air pressure in the sealed casing to suck the dust. In September 2012, the output of household vacuum cleaners in my country was 7.405 million units.If you want to order PCB product, please check and custom your order online.Working principle of vacuum cleaner The working principle of the vacuum cleaner is that the vacuum cleaner motor rotates at high speed and sucks air from the suction port to generate a certain vacuum.The dust enters the dust filter bag in the dust box through the floor brush, takeover, handle, hose, and main suction pipe, and the dust is left in In the dust filter bag, the filtered air passes through a layer of filter sheet to enter the motor.This layer of filter sheet is a protective barrier to prevent the dust bag from breaking into the motor and the air entering the motor flows out through the motor. Because it is worn out, another filter is added before it flows out of the vacuum cleaner.The finer the filter material, the cleaner the air can be filtered, but the poorer the air permeability, which affects the amount of air drawn by the motor and reduces the efficiency of the vacuum cleaner. But for users, comfort and cleanliness is the main thing.Its air permeability is low, so it is made into a wave shape to increase the air permeability area. Some of this filter material can also be washed repeatedly. Any filter material has a "life", that is, the micropores of the filter material have been blocked by small particles of dust after long-term use. Therefore, the paper dust bag is more ideal than A=πR2. It is disposable after use, hygienic and convenient. After the cloth filter bag is cleaned, the fibers will harden, which will affect the filtering effect and ventilation effect. SMS three-layer composite filter material is washable, but the permeability is slightly lower.The basic structure of the vacuum cleaner is divided into five parts according to function:1. Power part: vacuum cleaner motor and governor. The governor is divided into hand control and machine control.Motor: There are copper wire motor and aluminum wire motor.Copper wire motor has the advantages of high temperature resistance, long life and long single operation time, but the price is higher than aluminum wire;The aluminum wire motor has the characteristics of low price, but the temperature resistance is poor, the melting point is low, and the life is not as long as the copper wire.Speed governor: manual control is generally used for damper adjustment (as shown);The machine control type is power-type hand-held button or infrared adjustment.2. Filtration system: dust bag, front filter and rear filter. According to different filter materials, they are divided into: paper, cloth, SMS, HEPA (HEPA high efficiency filter material).3. Functional part: take-up and pay-off mechanism, dust full indicator, button or slide switch.4. Protection measures: dust-free bag protection, high vacuum protection, anti-interference protection (soft start), overheat protection, anti-static protection.5. Accessories: handle and hose, take over, floor brush, flat suction, round brush, bed brush, sofa suction, hook, strap.6. Vacuuming principle: the fan impeller of the vacuum cleaner is driven by the motor at high speed, and the air in the impeller is discharged out of the fan at high speed, and at the same time, the air in the suction part is continuously replenished into the fan. This may wish to form a higher pressure difference with the outside world. The dust and dirt of the suction nozzle are sucked into the dust suction part with the air, and leak through the leaker to collect the dust and dirt in the dust cylinder.7. The original of the vacuum cleaner: Most vacuum cleaners are equipped with an assembled brush head for cleaning floors and carpets. The suction vacuum cleaner will also be equipped with a series of cleaning brushes and suction nozzles to clean corners, curtains, sofas and gaps.8. Throat: All suction-type vacuum cleaners will be equipped with a hard throat, used to connect the soft throat and accessories for cleaning.9. Electric brush: The cleaning head of the internal vacuum cleaner is a special accessory for hybrid vacuum cleaners.10. Round brush head: also small suction nozzle, can do 360* rotation, easy to clean furniture, fine mesh fabric, etc.11. Flat nozzle: It is also called slit nozzle, it is a slender, flat hard nozzle. It is especially suitable for cleaning walls, radiant heaters, corners and shallow and narrow places.12. Dust sweeping brush: made of long and soft mane, suitable for cleaning curtains, walls, etc.The vacuum cleaner is mainly composed of three parts: dust raising, dust suction and dust filtering, and generally includes a series excited commutator motor, a centrifugal fan, a dust filter (bag) and a dust attachment. The power of general vacuum cleaners is 400-1000W or higher, and the power of portable vacuum cleaners is generally 250W and below. The vacuum cleaner can remove dust, mainly because its "head" is equipped with an electric exhaust fan. There is a wind impeller on the rotating shaft of the extractor fan. After being energized, the extractor will produce high suction and pressure at 500 revolutions per second. Under the effect of suction and pressure, the air is discharged at a high speed, and the air in the suction part of the fan is constantly The air in the fan is replenished, resulting in an instantaneous vacuum inside the vacuum cleaner, and a negative pressure difference is formed with the outside atmospheric pressure. Under the effect of this pressure difference, the air containing dust is sucked in. Dust and other debris sequentially enter the dust filter bag through the carpet or floor brush, long tube, elbow, hose, and hose joint. Dust and other debris stay in the dust filter bag. After the air is purified by the filter, it is discharged from the rear of the body.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 11:10
Circuit board impedance
In a circuit with resistance, inductance, and capacitance, the impediment to alternating current is called impedance. The impedance is usually expressed by Z. Impedance is composed of resistance, inductive reactance and capacitive reactance, but they are not simply added together. The unit of impedance is ohm. In direct current, the effect of an object on current obstruction is called resistance. All substances in the world have resistance, but the difference in resistance value.If you want to order PCB product, please check and custom your order online. Substances with very low resistance conduct good conductors, such as metals, etc.; substances with extremely high resistance conduct conductors, such as wood and plastics. There is also a conductor between the two called a semiconductor, and a superconductor is a substance whose resistance value is almost zero. However, in the field of alternating current, in addition to resistance inducting current, capacitance and inductance will also interfere with the flow of current. This effect is enough to make reactance, which means resistance to current. Their unit of measurement is ohms as the resistance, and its value is related to the frequency of the alternating current. The higher the frequency, the capacitive reactance, the inductance, the capacitance and the inductance, and the phase angle. There is a relationship between the vectors. Will say: resistance is the sum of resistance and reactance on the vector. For a specific circuit, the impedance is not constant, but changes with frequency. In a series circuit of resistance, inductance and capacitance, the impedance of the circuit is generally larger than the resistance. That is, the impedance is reduced to the minimum. In the parallel circuit of inductance and capacitance, the impedance increases to the maximum value at resonance, which is the opposite of the series circuit. In addition, from the overall view of the electronics industry, PCB circuit boards are the most prone to problems in tin plating, and are the key link that affects impedance. Because the tin plating of circuit boards, it is now popular to use chemical tin plating technology for tin plating However, as a recipient of the electronics industry, we have been contacting and observing the electronics or electronic processing industry for more than 10 years, and there are not many enterprises that can do chemical tin plating (for PCB or electronic tin plating) in China. The chemical tin plating process is a rising star in China, and the technical level of various enterprises is uneven... For the electronics industry, according to industry surveys, the most fatal weakness of electroless tin plating is easy to discolor (both easily oxidized or deliquesced), poor solderability leads to difficult soldering, high impedance leads to poor conductivity or unstable overall board performance 1. Yi Chang tin must cause PCB circuit short circuit to burn or catch fire. Later, when the entire social production industry developed to a certain extent, many later participants often belonged to plagiarism. In fact, a considerable number of companies themselves did not have R&D or pioneering capabilities. Therefore, many products and their users’ electronic products (circuit boards) The bottom of the board or the overall electronic product) performance is poor, and the main reason for the poor performance is because of the impedance problem, because when the unqualified chemical tin plating technology is in use, it is actually the tin plated on the PCB circuit board. Not really pure tin (or pure metal element), but a tin compound (that is, it is not a metal element at all, but a metal compound, oxide or halide, which is more directly a non-metallic substance) or tin It is a mixture of compounds and tin metal, but it is difficult to find by naked eyes alone. And because the main circuit of the PCB circuit board is copper foil, the tinned layer is on the solder joint of the copper foil, and the electronic component is soldered on the tinned layer through solder paste (or solder wire). In fact, the solder paste is in It is metal tin (that is, a metal element with good conductivity) that is welded between the electronic component and the tin plating layer in the molten state, so it can be simply pointed out that the electronic component is connected to the copper foil on the bottom of the PCB board through the tin plating layer, so The purity of the tin coating and its impedance are the key; but, before we plug in the electronic components, when we directly use the instrument to detect the impedance, in fact, the two ends of the instrument probe (or called test lead) also contact the bottom of the PCB board first The tin coating on the surface of the copper foil communicates with the copper foil on the bottom of the PCB. Therefore, tin plating is the key, the key that affects the impedance and the performance of the entire PCB, and it is also the key that is easily overlooked. As we all know, except for the elemental metal, its compounds are electrical poor conductors or even non-conductive (again, this is also the key to the distribution capacity or distribution capacity in the circuit), so there is such a conductive rather than conductive in tin plating Tin compounds or mixtures, their ready-made resistivity or future oxidation, the resistivity after electrolysis caused by moisture, and their corresponding impedance are quite high (which has affected the level or signal transmission in digital circuits), and The characteristic impedance is also inconsistent. So it will affect the performance of the circuit board and the whole machine. Therefore, as far as the current social production phenomenon is concerned, the coating material and performance on the bottom of the PCB board are the most important and direct reasons that affect the characteristic impedance of the entire PCB board. However, due to its aging with the coating layer and electrolysis due to moisture Variability, so the anxiety effect of its impedance becomes more recessive and volatile, the main reason for its concealment is: the first cannot be seen by the naked eye (including its changes), and the second cannot be measured constantly because it has The variability changes with time and environmental humidity, so it is always easy to be ignored. Or pass the cause wrong. Therefore, after knowing the cause of high impedance, solving the plating problem is the key to the impedance problem.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 11:00
Oxygen machine circuit board
Oxygen machine, also known as oxygen generator or oxygen generator, industrial oxygen machine uses air as raw material, without any auxiliary materials, using pressure swing adsorption method to separate oxygen and nitrogen in the air, and filter out harmful substances in the air, thus To provide you with 90% purity oxygen to meet their respective needs, installation and operation costs are lower than bottled or liquefied oxygen.The household oxygen machine produces oxygen-enriched air by filtering the nitrogen molecules in the air. It has the advantages of small volume and small power consumption, but the generated oxygen concentration is reduced, which does not have a good therapeutic effect, but it can be used for health care. To achieve good results, it is suitable for household use and not suitable for industrial oxygen production. It is common in vehicle-mounted oxygen generators.If you want to order PCB product, please check and custom your order online.Working principle of oxygen machine Oxygen production mechanism The principle of oxygen uses molecular sieve technology, which has a stable oxygen production concentration and maximizes the needs of oxygen inhalers. In addition to oxygen cylinders, the oxygen production principles of other oxygen generators are roughly divided into 4 categories: Molecular sieve oxygen generatorThe molecular sieve oxygen generator adopts advanced PSA (pressure swing adsorption) air separation oxygen production technology, which is based on the difference in the adsorption capacity of oxygen and nitrogen in the air by the attractant (zeolite molecular sieve) to achieve the separation of oxygen and nitrogen, which can be directly from the air Extracting high-purity oxygen is the only oxygen generator with international and national standards. The new machine's oxygen concentration at the factory should be 90%. It must have a cumulative timing function and an oxygen concentration status monitoring system. The sound produced at the maximum flow rate does not exceed 60 decibels.Electronic oxygen generatorThe electronic oxygen generator uses the process of oxidation and reduction of oxygen in the air in the solution. It does not produce dangerous hydrogen like electrolyzed water. The operation is relatively quiet, and the requirements during handling and use are very strict. Never tilt or turn it upside down, otherwise the solution will flow into the oxygen delivery tube and be sprayed into the nasal cavity, which will cause serious damage to the user.Oxygen-rich membrane oxygen generatorOxygen-enriched membrane oxygen generators produce oxygen-enriched air through the filtration of nitrogen molecules in the air by the membrane, which has the advantages of small volume and small power consumption, but the generated oxygen concentration is low and does not have a good therapeutic effect. Car oxygen generator.Chemical oxygen generatorThe chemical agent oxygen generator uses reasonable chemical formulas to generate oxygen in specific occasions through chemical reactions between the agents, which can meet the urgent needs of some consumers, but the equipment is simple, the operation is cumbersome, the use cost is high, and it cannot be used continuously. Not suitable for long-term home use.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 10:55
Electric water heater circuit board
Electric water heater is to point to the water heater that USES electricity as energy to undertake heating. It is one of the three water heaters with gas water heater and solar water heater. Electric water heater can be divided into water storage type by heating power size (also called positive displacement type or heat storage type), namely hot type, rapid heat type (also called half water storage type) 3 kinds.Water heater and ordinary speed dual-mode electric water heater, although similar size, but the internal structure, speed water heater and water storage type electric water heater than just smaller, more power, so the heating speed is faster than water storage type electric water heater, but it is hot in the spring and autumn are not reached, preheating, namely needs to wait for, and dual-mode electric water heater in the spring, summer, autumn three seasons namely thermal model are available, and that is hot.If you want to order PCB product, please check and custom your order online.Electric water heaterWater storage type electric water heater is divided into open type and enclosed type again two kinds. Early water storage type electric water heater is open type more or open type, its structure is simple, volume is not big, rely on the pressure that hangs in gao Gao to gush, water flow is lesser, but the price is lower, suit to the population is little, domestic circumstance is not very rich, do the family that bath USES only to buy. Because open type electric water heater does not have to the pressure function of interior design, cannot supply water to other conduit much, the function is limited. The inner bladder of enclosed electric water heater is sealed, water pressure inside cistern is very big, its inner bladder can bear pressure, reason can supply water more, can be used at shower already, also can be used at tub bath, still can be used at washing clothes, wash vegetables, the price is relatively more expensive, be in commonly 1000 Yuan or so. Water storage type electric water heater can automatically keep constant temperature and heat preservation, can still supply hot water when power failure. The electric water heater on domestic market basically is closed water heater of water of water storage type, it need not divide a room to install, do not produce harmful gas, clean sanitation, and can adjust temperature conveniently.Enclosed water heaters work simply by using an electric heating tube that provides heat to the water after it is energized. The tank shall store hot water and bear a pressure of 0.6mpa (about 6kg/cm2), and the shell shall be insulated. The first difference between the products is reflected in the heating tube, there are immersion type, that is, direct contact with the water to be heated, or isolation type. The heating tube has 1.2, 1.5 and 2.5KW power to choose from. The heating tube is controlled by a thermostat that sets the required temperature and keeps the water temperature in the tank constant, adjustable from 40℃ to 75℃.Timing product series of time control system can bring maximum energy savings, coupled with time-sharing meters, can save a lot of electricity costs.Some products also have a large LCD screen, single-key shuttle operation interface and real-time fault monitoring functions. Electric water heater must be installed with a pressure relief valve to ensure overpressure relief. In order to minimize heat loss, a polyurethane or high density foam insulation layer is used between the shell and the inner tank.According to the different installation mode, electric water heater can be divided into horizontal wall hanging, vertical wall hanging, groove under the type (under the stage type), common floor type and integrated floor installation. Floor type capacity is larger, usually for collective or industrial use; Wall hanging small capacity also groove type (under the stage type) varieties, their inlet and outlet pipe joint is located in the upper end rather than the lower end, so should be near the ground position wall installation.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 10:41
Electric blanket circuit board
Electric blanket, also known as electric mattress, is a contact electric heating appliance, it will be specially made, insulation performance up to the standard of flexible cable electric heating elements in the shape of a coil woven or sewed into the blanket, when the power is generated heat. It is mainly used for people to increase the temperature of the bed to achieve the purpose of heating. It can also be used for desiccant of bedding.It has a history of more than 100 years for its low power consumption, adjustable temperature, convenient use and wide use. At present, a new type of radiation-free electric blanket has been awarded the national patent. Pregnant women, children and the elderly can safely use the radiation-free electric blanket.If you want to order PCB product, please check and custom your order online.Electric blanket implementation principleUsed in thermostat blanket. The yarn core is woven with glass fiber or polyester yarn, which is wound with flexible flexible electrothermal alloy wire (or foil strip), covered with a layer of nylon heat-sensing layer or special plastic heat-sensing layer, and then wrapped with a copper alloy signal wire outside the heat-sensing layer, and coated with a layer of heat-resistant resin on the outside. When the temperature at any point of the electric blanket exceeds the predetermined value, the sensible heat layer on the corresponding electric heating wire there will change from the insulator into a good conductor, so that the control circuit will be closed and the electric blanket will be cut off to achieve the purpose of temperature control and safety protection.General type electric blanket with no signal linear electric heating element is adopted. If the temperature control is to be realized, there are generally two types of temperature control elements: one is the overheating safety thermostat. Each electric blanket needs about 8 ~ 9 pieces, which are connected in series with the electric heating element to play a role of safety protection; The other is a thermostat controller, located at the head of a bed or at hand, that regulates temperature. The thermostatic controller is only needed for the electric blanket with a signal wire heating element.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 10:34
Electric iron circuit board
Electric irons are tools for flattening clothes and cloth, and their power is generally between 300 and 1000W. Its type can be divided into: ordinary type, thermostat type, steam spray type, etc. The common type electric iron is simple in structure, cheap in price, convenient in manufacture and maintenance.Adjustable electric iron can automatically adjust the temperature within the range of 60-250 ℃ and automatically cut off the power supply. It can be ironed at the appropriate temperature according to different clothing materials, which saves energy compared with ordinary type. Steam atomizing electric irons have both the function of temperature-regulating and steam generating. Some of them are also equipped with atomizing devices to avoid the trouble of artificial water spraying. The wetting of clothing materials is more even and the ironing effect is better.If you want to order PCB product, please check and custom your order online.Electric iron principleEarly irons were made of cast iron and were shaped like a bucket in which charcoal was burned, hence the name "iron". Europeans have been ironing their own clothes since the 17th century. They use a heavy "flat iron" to heat clothes in a fire or on a hot metal plate before ironing them. This gave rise to all sorts of problems, such as the tendency to scorch clothes by making the iron too hot. The anxiety was also expressed when the iron was not quite hot enough to begin ironing. Sometimes the iron handle was made very hot. This means that people often injure themselves while ironing. New York inventor Henry W. See changed all that yesterday. He invented the first practical electric iron in 1882.It contains a wire element. When an electric current passes through it, the wire heats up, just like in a traditional electric furnace.The temperature of the tool from electric energy to heat energy is determined by its own power and the length of the electrification time. With large wattage and long electrification time, the fast heating temperature will be high; conversely, the slow heating temperature will be low. The heating element of electric iron includes mica skeleton heating element and metal tube heating element. The electric iron made of mica skeleton heating element has the advantages of simple structure, easy manufacture, uniform heating and convenient maintenance. Its disadvantages are that the electric heating wire is exposed to the air, oxidizes quickly at high temperature, has a short life, is easily affected by humid air and has poor insulation performance. Electric irons made of metal tube heating elements have good mechanical strength, long life, high thermal efficiency, good moisture-proof performance, safety and reliability, but the manufacturing process is complex.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 10:26
Circuit board of air purifier
Air purifier is also called the machine, the air cleaner, fresh air purifier, refers to the adsorption and decomposition or transformation of various air pollutants (generally include PM2.5, dust, pollen, peculiar smell, formaldehyde, decoration pollution, such as bacteria, allergens, etc.), effectively increase the air cleanliness of products, mainly divided into residential, commercial, industrial, building.There are many different technologies and media in the air purifier, enabling it to provide users with clean and safe air.Common air purification technologies include: adsorption technology, negative (positive) ion technology, catalytic technology, photocatalyst technology, super-structured light mineralization technology, HEPA high efficiency filtration technology, electrostatic dust collection technology, etc.The main materials include photocatalyst, activated carbon, synthetic fiber, HEPA high efficiency material, anion generator, etc.Existing air purifiers are mostly composite, that is, a variety of purification technologies and materials at the same time.If you want to order PCB product, please check and custom your order online.How the air purifier works?Air purifier is mainly composed of motor, fan, air filter screen system, its working principle is: the machine inside the motor and fan to make indoor air circulation flow, the air pollution through the air in the machine filter after the various pollutants removal or adsorption, some models of air purifier in outlet with anion generator (anion generator while working in the high pressure dc negative high voltage), the air ionization, produce a large number of negative ions, is the breeze fan out, form a negative ion airflow, achieve the goal of clean, purify air.Purification Principle of passive adsorption filter type (Filter type)The main principle of passive air purifier is: use fan to pump air into the machine and filter the air through the built-in filter, which can filter dust, peculiar smell, poisonous gas and kill some bacteria.And the filter is mainly divided into: particulate filter and organic filter.The particle filter net is divided into coarse effect filter net, and fine particle filter net.The quality of fans and filters of such products determines the effect of air purification. The location of machines and indoor layout will also affect the purification effect.Active purification principle (strainless type)Active principle and principle of passive air purification of air purifier fundamental difference is that the active air purifier get rid of the limitation of the fan and mesh, not passively waiting for indoor air is pumped into the purifier filter purification, but effective and active purification sterilization factors that are released into the air, the characteristics of the spread through the air, to reach every corner of the indoor no dead Angle of air purification.There are mainly silver ion technology, negative ion technology, low-temperature plasma technology, photocatalyst technology and net ion group ion technology in the market to purify sterilization factors. The biggest defect of such products is the problem of excessive ozone release.Dual purification (active purification + passive purification)The essence of this kind of purifier is to combine the technologies of passive purification with those of active purification.Wanna know PCB knowledge? Check and read for more.
PCB Project ⋅ 04/28/2021 10:21
Air conditioner circuit board
An air conditioner is an air conditioner. Refers to the use of artificial means, the building or structure of the ambient air temperature, humidity, flow rate and other parameters for adjustment and control of equipment.Generally, it includes several parts such as cold source/heat source equipment, cold and hot medium transmission and distribution system, terminal device and other auxiliary equipment. Mainly includes, refrigeration host, water pump, fan and pipeline system.The terminal unit is responsible for the specific treatment of the air state by using the heat and cold transferred to make the air parameters of the target environment meet certain requirements.If you want to order PCB product, please check and custom your order online.Composition of air conditioningThe structure of air conditioning includes: compressor, condenser, evaporator, four-way valve, one-way valve capillary assembly, etc.The compressorThe working process of an intertooth volume pair specified in an air conditioning compressor. The side of the female screw and the male screw are compressed to meet each other. This side is called the high pressure area. Instead, the screw turns to a side that diverges from each other, and the volume between the teeth expands and is in the inspiratory stage, known as the low pressure area. These two areas are separated by a contact line between the tooth surfaces of the female screw and the male screw. It can be approximately considered that the plane in which the two screw axes are located is the interface between high and low pressure zones.Compression refrigerants, such as freon, become liquid. Then it is cooled by the endothermic phenomenon of the liquid changing into the gaseous state at atmospheric pressure.The density of air is very small. You take a syringe for an injection. Fill a syringe with air, plug the outlet with your hand, and push the syringe to compress the air. A gas can be compressed by a third of its volume with a needle. The condenserCompressor suction from the evaporator working medium low pressure steam, after pressure into the condenser, cold high pressure of the liquid condensed in the condenser, the throttle valve throttle, become low pressure liquid, into the evaporator, the evaporator of heat to evaporate and become a low pressure steam, thus complete the refrigeration cycle. For some applications, the gas must pass through a long tube, usually coiled into a solenoid, to allow the heat to escape into the surrounding air. Heat-conducting metals such as copper are often used to transport steam. In order to improve the efficiency of the condenser, heat sinks are often attached to the pipes to accelerate the heat dissipation. A radiator fin is a flat plate made of good heat-conducting metal.The evaporatorThe evaporator is the tube that's inside the chamber, and it's covered with fins. A device for concentrating or precipitating grains from a solution by heating. It is mainly composed of heating chamber and evaporation chamber. The heating chamber provides the heat needed to evaporate the liquid, causing it to boil and vaporize; The evaporation chamber completely separates the gas-liquid two phases. The vapor produced in the heating chamber contains a large amount of liquid foam. When the vapor chamber is in a larger space, the liquid can be separated from the vapor by condensing or defaming apparatus.Four-way valveFour-way valve, hydraulic valve term, is a control valve with four oil ports. Four-way valve is the indispensable parts in refrigeration equipment, its working principle is that when the power is solenoid coil, pilot valve on the right side of the compression spring driven her left shift, high pressure gas entering into the right side piston cavity after the capillary (1), on the other hand, the left side of the piston chamber gas discharge, due to the existence pressure difference on both ends of the piston, the piston and the slide valve left shift, the exhaust pipe with the takeover, outdoor two root over are interlinked, form a refrigeration cycle.Working principle of air conditioningAir conditioning is divided into single cooling air conditioning and air conditioning, the working principle is the same, the refrigerant commonly used before air conditioning is freon. The characteristic of freon is that when it changes from gas to liquid, it releases a lot of heat. And when you go from a liquid to a gas, you absorb a lot of heat. Air conditioning is designed on this principle.The compressor compresses the gaseous refrigerant into the gaseous refrigerant of high temperature and high pressure, and then sends it to the condenser (outdoor machine) for heat dissipation to become the liquid refrigerant of normal temperature and high pressure, so what the outdoor machine blows out is the hot air.And then to the capillary, into the evaporator (indoor machine), because the evaporator refrigerants from capillary reached space suddenly increases, pressure decreases, and the liquid will vaporize refrigerants, into a gaseous cryogenic refrigerants, to absorb a lot of heat, the evaporator will become cold, indoor machine of the fan will indoor air blows from the evaporator, so indoor machine out of the cold wind is blowing; The water vapor in the air will condense into water drops when it meets the cold evaporator and flows out along the water pipe, which is why the air conditioner will give water.When heating, there is a component called the four-way valve, so that the refrigerant flow direction in the condenser and evaporator and the opposite of the refrigeration, so when the heating is cold air blowing outside, indoor machine blowing is hot air.In fact, I learned from junior high school physics that when you liquefy (a gas to a liquid) you have to expel heat and when you vaporize (a liquid to a gas) you have to absorb heat.Working principle of environmental protection air conditioning:With circulating pump continuously put out of the water in the tank, and through the cloth evenly spray water system on the evaporation filter layer, outdoor hot air into the evaporative cooling medium, CELdek in evaporative cooling medium (special material of the honeycomb filter layer, let the cooling effect is more ideal, Sweden's high-tech patent products) and water in heat exchange, due to water evaporation heat and cool the cool and refreshing, clean by low noise fan pressurized air into indoor, make indoor to outdoor hot air, so as to achieve the aim of indoor temperature.Wanna know PCB knowledge? 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PCB Project ⋅ 04/28/2021 10:07