• Home
  • Tutorials
  • Ten Daily Electronic Common Sense-Section 143

    What are the challenges of implementing embedded processor peripheral design based on SOPC Builder?

    1. Embedded processor interface
    2. System processor and peripherals
    3. Avalon specification
    4. SOPC Builder tool can realize the interconnection strategy of switching network
    5. External memory interface and Avalon interface
    6. User-defined peripherals
    7. Simplify Multi-Master Processor Designs

    What are the classifications of detonation sensors?

    According to the different detection methods of the vibration frequency of the engine cylinder, the knock sensor can be divided into two types: resonance type and non-resonance type.
    According to the structure of the deflagration sensor, it can be divided into piezoelectric type, magnetostrictive type and spark plug seat metal pad type.

    What are the design and wiring principles for a two-layer printed board?

    • Loops or guard lines should be placed as close as possible to high-risk signal lines so that the RF energy can fully return to the source. Power and ground returns must be in parallel with each other to provide decoupling capacitance for switching energy injection into each element of the power distribution system. In order to realize such a topological relationship, wiring may be difficult. However, this is very beneficial to the electromagnetic compatibility of the PCB.
    •Use a grid structure for power and ground planes to reduce the inductance of the RF return path. The smaller the grid, the better the effect.
    • In fact, there is no real EMl-compliant double-layer printed circuit board. The distance between the ground plane on the bottom of the board and the signal lines on the top layer is very large, and the double-layer board should be regarded as two single-layer boards. Use various techniques to ensure that the RF return path is physically close to all high-risk signal lines.

    What is a GPRS module?

    GPRS (General Packet Radio Service, General Packet Radio Service) is a new bearer service developed on the existing GSM system.
    Various applications based on this business are also flourishing, mainly used in wireless data transmission, wireless POS machines, security, lottery machines, smart meter reading, wireless fax, small switches, wireless advertising, wireless media, medical monitoring, railway Terminals, smart home appliances, vehicle monitoring and other fields.
    GPRS communication is more suitable for sudden, frequent, and small data transmission. Also suitable for occasional large data transfers.

    What is the working principle of the OTL circuit?

    Complementary symmetrical power amplifier is also called OTL circuit (push-pull power amplifier without output transformer).
    The main advantage of this circuit is that it eliminates the need for bulky input and output transformers. And the frequency response is wide, the distortion is small, and the output power is large. It is conducive to miniaturization and integration, and has a wide range of applications.
    From the perspective of push-pull and waveform synthesis, the working principle of this circuit is basically the same as that of a Class B push-pull power amplifier.

    What are the basic requirements for electrode materials for thermocouples?

    1. In the range of temperature measurement, the thermoelectric properties are stable. Does not change with time, has sufficient physical and chemical stability, and is not easy to oxidize or corrode;
    2. The temperature coefficient of resistance is small, the conductivity is high, and the specific heat is small;
    3. The thermoelectric potential generated during temperature measurement is large, and the relationship between thermoelectric potential and temperature It has a linear or nearly linear single-value function relationship;
    4. The material has good reproducibility and high mechanical strength. The manufacturing process is simple and the price is cheap.

    What is IEC 62026?

    IEC 62026 is a controller electrical interface standard for low-voltage switchgear and control equipment, passed in June 2000. it includes:
    IEC 62026-1: General requirements.
    IEC 62026-2: Actuator Sensor Interface (AS-i), supported by German Siemens.
    IEC 62026-3: Device Network (Device Network, DN), supported by American Rockwell Corporation.
    IEC 62026-4: LonTalk, the communication protocol of Lonworks (Local OperatingNetworks) bus, has been cancelled.
    IEC 62026-5: Intelligent Distributed System (Smart Distributed System, SDS), supported by American Honeywell Company.
    IEC 62026-6: Serial Multiplexed Control Bus (Serial Multiplexed Control Bus, SMCB), supported by American Honeywell Company.

    Briefly describe the pin function of the 100V flyback isolation controller – LT3748?

    • VIN (1PIN): input voltage terminal. This terminal supplies current to the internal start-up circuit and generates a reference voltage for the feedback circuit at RFB terminal. A bypass capacitor must be placed at this terminal.
    • EN/UVLO (3P1N): enable/undervoltage latch terminal. Connect a resistor divider to the VlN terminal, and adjust a minimum input voltage to the LT3748 to make it work. If the voltage drops by 0.5v, the inflow of quiescent current is less than 1, which is lower than 1 at this time. 223V but higher than 5V, it can also drive quiescent current, but cannot adjust the INTVCC terminal to supply power to the gate drive circuit. Above 1.223V, all internal circuits start to work. The SS terminal sources 5 吣 current. When EN/UVL0 drops to l. Below 223V, 2.49A current is given from this terminal, providing an adjustable window as an undervoltage latch.
    • INTVCC (5PIN): gate drive bias voltage terminal. This terminal supplies current to the gate drive circuit of LT3748, INTVCC must also add a bypass capacitor. This end should also be connected to VlN, if the third winding is not used, and ‰≤20V. If a third winding is used, the INTVCC voltage will be lower than the input voltage.
    • GATE (6PIN): The gate drive output terminal of the N-channel MOSFET. Level between INTVCC and GND.
    • SENSE (7PIN): Current detection input terminal. For the control loop, Kelvin connect this terminal to the positive voltage terminal of the switch current sense resistor, at the source of the N-channel MOSFET, the negative terminal of the sense resistor to GND close to the IC.
    • GND (8PIN, 9PIN), IC common terminal.
    • SS (10P1N): soft start terminal. This terminal delays start and clamps the VC terminal voltage. The soft start period is set by an external capacitor. When the voltage reaches 0.65V, the switch starts to work.
    • VC (11PIN): Compensation terminal. For the internal error amplifier, an external RC series network is connected to GND to compensate the amplifier of the switching regulator, and a 100pF capacitor is connected in parallel to help eliminate noise.
    • TC (12PIN): output voltage compensation. Connect an external resistor to GND to generate a current, which is proportional to the absolute temperature, and this current is sourced into the RREF node. c=0.55V/RTc.
    • RREF (14PIN): The resistance input terminal of the external reference. The resistance at this end is 6.04kf2, and when choosing the ratio of the resistor divider, the range of this value can be from 5.76 to 6.34k. Q, the resistor should be placed next to the LT3748.
    • RFB (16P1N): External feedback resistor input terminal. This terminal is connected to the external power MOSFET switch on the primary side of the transformer. The ratio of the resistance to the ReEF resistance should be twice the internal bandwidth to determine the output voltage. The average current through this resistance is about 2009A in the flyback mode, and the resistance is also tight. Placed against the LT3748.

    What are the fault characteristics of electronic components?

    Although there are a large number of electronic components inside electrical equipment, their failures are regular.

    1. Characteristics of resistance damage Resistance is the most numerous component in electrical equipment, but it is not the component with the highest damage rate. Open circuit is the most common type of resistance damage, it is rare for the resistance value to become large, and it is very rare for the resistance value to become small. The common ones are carbon film resistors, metal film resistors, wire wound resistors and insurance resistors. The first two resistors are the most widely used, and their damage characteristics are that the damage rate of low resistance value (below 100Ω) and high resistance value (above 100kΩ) is relatively high, and the resistance value of intermediate resistance (such as hundreds of ohms to tens of thousand ohms) There is very little damage; the second is that when the low-resistance resistor is damaged, it is often burnt and blackened, which is easy to find, while there are few traces when the high-resistance resistor is damaged. Wirewound resistors are generally used for high current limiting, and the resistance is not large. When the cylindrical wirewound resistor burns out, some will turn black or the surface will burst and crack, and some will have no trace. Cement resistors are a type of wirewound resistors, which may break when burned out, otherwise there will be no visible traces. When the fuse burns out, some surfaces will blow off a piece of skin, and some will have no traces, but they will never be burnt and blackened. According to the above characteristics, when checking the resistance, you can focus on it and quickly find out the damaged resistance.
    2. Characteristics of electrolytic capacitor damage Electrolytic capacitors are widely used in electrical equipment and have a high failure rate. The damage of electrolytic capacitors has the following manifestations: one is complete loss of capacity or smaller capacity; second is slight or severe leakage; third is loss of capacity or smaller capacity with leakage. The methods for finding damaged electrolytic capacitors are:
      (1) Look: Some capacitors will leak when they are damaged, and there will be a layer of oil stains on the surface of the circuit board under the capacitor and even on the surface of the capacitor. This kind of capacitor must not be used again; continue to use;
      (2) Touch: Some electrolytic capacitors with serious leakage will heat up after starting up, and even burn your hands when you touch them with your fingers. This kind of capacitor must be replaced;
      (3) There is an electrolyte inside the electrolytic capacitor. Long-term baking will dry out the electrolyte and reduce the capacitance. Therefore, it is necessary to focus on checking the capacitors near the heat sink and high-power components. The closer they are, the more likely they will be damaged. The greater the sex.
    3. Second, the characteristics of damage to semiconductor devices such as triodes. 2. The damage of triodes is generally caused by PN junction breakdown or open circuit, among which breakdown and short circuit are the majority. In addition, there are two damage manifestations: one is the deterioration of thermal stability, which is normal when starting up, and soft breakdown occurs after working for a period of time; the other is the deterioration of the characteristics of the PN junction, measured with a multimeter R×1k, All PN junctions are normal, but they cannot work normally after being put on the machine. If you use R×10 or R×1 low-range measurement, you will find that the forward resistance of the PN junction is larger than the normal value. Measurement 2. The triode can be measured on the road with a pointer multimeter. The more accurate method is: set the multimeter to R×10 or R×1 (generally use R×10, and then use R×1 when it is not obvious) in the road test. 2. The forward and reverse resistance of the PN junction of the triode, if the forward resistance is not too large (relative to the normal value), and the reverse resistance is large enough (relative to the forward value), it indicates that the PN junction is normal, otherwise it is doubtful and needs to be soldered Next test again. This is because the peripheral resistances of diodes and triodes in general circuits are mostly hundreds or thousands of ohms, and the influence of peripheral resistances on PN junction resistance can be basically ignored by using a multimeter to measure on the road with a low resistance value.
    4. The characteristics of integrated circuit damage The internal structure of the integrated circuit is complex and has many functions. If any part is damaged, it will not work normally. There are also two types of damage to integrated circuits: complete damage and poor thermal stability. When it is completely damaged, it can be removed, and compared with the normal integrated circuit of the same type, the forward and reverse resistance of each pin to the ground can be measured, and one or several pins can always be found to have abnormal resistance values. For those with poor thermal stability, the suspected integrated circuit can be cooled with anhydrous alcohol when the equipment is working. If the failure time is delayed or no longer occurs, it can be determined. Usually it can only be ruled out by replacing a new integrated circuit.

    Capacitor detection method and experience:

    1. Detection of fixed capacitors: A detects small capacitance below 10pF because the capacity of fixed capacitors below 10pF is too small. Measuring with a multimeter can only qualitatively check whether there is leakage, internal short circuit or breakdown. When measuring, you can choose the R×10k block of the multimeter, and use the two test leads to connect the two pins of the capacitor arbitrarily, and the resistance should be infinite. If the measured resistance value (the pointer swings to the right) is zero, it means that the capacitor is damaged by leakage or internal breakdown. B Detect whether the 10PF ~ 001μF fixed capacitor is charged, and then judge whether it is good or bad. The multimeter selects the R×1k block. The β values of the two triodes are both above 100, and the penetration current should be small. 3DG6 and other types of silicon transistors can be used to form composite tubes. The red and black test leads of the multimeter are respectively connected to the emitter e and collector c of the composite tube. Due to the amplification effect of the composite triode, the charging and discharging process of the measured capacitor is amplified, and the pendulum of the pointer of the multimeter is increased, so that it is easy to observe. It should be noted that during the test operation, especially when measuring a small capacity capacitor, it is necessary to repeatedly switch the pins of the capacitor under test to touch points A and B, so that the swing of the pointer of the multimeter can be clearly seen. C For the fixed capacitance above 001μF, the R×10k block of the multimeter can be used to directly test whether the capacitor has a charging process and whether there is an internal short circuit or leakage, and the capacity of the capacitor can be estimated according to the amplitude of the pointer swinging to the right.
    2. Detection of electrolytic capacitors: A Because the capacity of electrolytic capacitors is much larger than that of ordinary fixed capacitors. Therefore, when measuring, the appropriate range should be selected for different capacities. According to experience, under normal circumstances, the capacitance between 1 and 47μF can be measured with R×1k gear, and the capacitance larger than 47μF can be measured with R×100 gear. B Connect the red test lead of the multimeter to the negative pole, and the black test lead to the positive pole. At the moment of first contact, the pointer of the multimeter deflects to the right by a large degree (for the same electric resistance, the larger the capacity, the larger the swing), and then gradually turn to the left. , until it stops at a certain position. The resistance at this time is the forward leakage resistance of the electrolytic capacitor, which is slightly larger than the reverse leakage resistance. Practical use experience shows that the leakage resistance of electrolytic capacitors should generally be above several hundred kΩ, otherwise, it will not work normally. In the test, if there is no charging phenomenon in the forward and reverse directions, that is, the hands of the watch do not move, it means that the capacity has disappeared or the internal circuit is broken; if the measured resistance value is very small or zero, it means that the capacitor has a large leakage or has been broken down. Can no longer be used. C? For electrolytic capacitors with unknown positive and negative signs, the above method of measuring leakage resistance can be used to identify them. That is, first measure the leakage resistance arbitrarily, remember its size, and then exchange the test leads to measure a resistance value. The one with the larger resistance value in the two measurements is the positive connection method, that is, the black test lead is connected to the positive pole, and the red test lead is connected to the negative pole. D? Use a multimeter to block electricity, use the method of positive and negative charging to the electrolytic capacitor, and estimate the capacity of the electrolytic capacitor according to the size of the pointer swinging to the right.
    3. Detection of variable capacitors: A. Gently rotate the shaft by hand, it should feel very smooth, and it should not feel loose or tight or even stuck. When the loading shaft is pushed forward, backward, up, down, left, right, etc., the shaft should not be loose. B Use one hand to rotate the rotating shaft, and the other hand to lightly touch the outer edge of the moving piece group, and there should be no looseness. Variable capacitors with poor contact between the rotating shaft and the moving piece cannot be used any longer. C Put the multimeter in the R×10k block, connect the two test leads to the moving piece and the lead-out end of the fixed piece of the variable capacitor with one hand, and slowly rotate the rotating shaft a few times with the other hand, the pointer of the multimeter should be Do not move at infinity. In the process of rotating the shaft, if the pointer sometimes points to zero, it means that there is a short circuit point between the moving piece and the fixed piece; if it encounters a certain angle, the reading of the multimeter is not infinite but a certain resistance value appears, indicating that the variable capacitor is moving. There is a leakage phenomenon between the sheet and the fixed sheet.


    DISQUS: 0