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    What constitutes a remote frame?

    A long-range frame is composed of 6 different bit fields: frame start, arbitration field, control field, CRC field, response field and frame end.

    What are the common CAN bus network link failures?

    CAN-H and CAN-L are short-circuited to the positive and negative poles respectively at a certain point;
    The CAN-H and CAN-L of a certain node are respectively disconnected;
    Short circuit at a certain point between CAN-H and CAN-L;
    CAN-H and CAN-L are short-circuited to positive and negative poles at the same time.

    What are the humidity measurement methods?

    Dual pressure method, dual temperature method, saturated salt method in static method, dew point method, wet and dry bulb method, using sensor measurement.

    How do you compare the performance of fuses and circuit breakers?

    Now compare the protection performance and other characteristics of fuses and circuit breakers, and the circuit breakers are described in two categories: non-selective type and selective type.

    1. Fuse:
      (1) The main advantages and characteristics of fuses: ①Good selectivity. The rated current of the fuse link of the upper and lower fuses only needs to meet the requirements of the national standard and IEC standard that the overcurrent selection ratio is 1.6:1. That is to say, the rated current of the superior fuse link is not less than 1.6 times the value of the lower level, and it is considered that the upper and lower levels can selectively cut off the fault current. ②Excellent current-limiting characteristics and high breaking capacity. ③ relatively small size. ④The price is cheaper.
      (2) The main shortcomings and weaknesses of the fuse: ①The fuse must be replaced after the fault is blown. ②Single protection function, only one section of overcurrent inverse time characteristic. Overloads, short circuits and ground faults are all protected against this. ③ When one-phase fusing occurs, it will lead to adverse consequences of two-phase operation for three-phase motors. Of course, it can be compensated by a fuse with an alarm signal, and a fuse of one phase can disconnect three phases. ④ Remote control cannot be realized, it needs to be combined with electric knife switch and switch to be possible.
    2. Non-selective circuit breaker:
      (1) Main advantages and features: ①After the fault is disconnected, it can be manually reset. There is no need to replace components, unless repairs are required after breaking the large short-circuit current. ② Two-stage protection functions of long-time delay release and instantaneous current release with inverse time-limit characteristics. They are respectively used as overload and short circuit protection, each performing its own duties. ③Remote control can be realized when there is an electric operating mechanism.
      (2) Main shortcomings and weaknesses: ① It is difficult to realize selective cut-off between upper and lower non-selective circuit breakers. When the fault current is large, it is easy to cause the instantaneous disconnection of the upper and lower circuit breakers. ②The relative price is slightly higher. ③The breaking capacity of some circuit breakers is small. If a circuit breaker with a small rated current is installed close to a large-capacity transformer, the breaking capacity will be insufficient. Now there are products with high breaking capacity, but the price is higher.
      3 selection type circuit breaker:
      (1) Main advantages and characteristics: ① It has the above-mentioned advantages of non-selective circuit breakers. ② It has multiple protection functions, including long-time delay, instantaneous, short-time delay and ground fault (including zero-sequence current and residual current protection) protection. Respectively realize overload, open circuit delay, large short-circuit current instantaneous action and ground fault protection. The protection sensitivity is extremely high, it is convenient to adjust various parameters, and it is easy to meet various protection requirements of distribution lines. In addition, it can have cascade protection function, which has better selective action performance. ③Most of today’s products have intelligent features. In addition to protection functions, they also have power measurement and fault records. And a communication interface to realize centralized monitoring and management of power distribution devices and systems.
      (2) Main problems: ①The price is very high, so it should only be used at the head end of distribution lines and branch lines in particularly important places. ② Larger size.

    How to output a fixed voltage rectified power supply?

    The rectified power supply is a DC power supply that converts alternating current into direct current by using a rectifier composed of rectifying elements and some other electrical components.
    Because of its simple equipment composition, convenient use and maintenance, stable and reliable working performance, no noise, and high efficiency, it is widely used.
    Its disadvantage is that the ripple factor of the current is relatively large.
    According to the number of phases of the AC power used, there are two types of rectified power supplies: single-phase and three-phase;
    For single-phase, it can be divided into half-wave and full-wave;
    From the rectification components used, there are two categories: controllable (output DC voltage adjustable) and uncontrollable (output DC voltage not adjustable).

    What are the advantages of silicon photocells?

    Silicon photovoltaic cells have the advantages of stable performance, wide spectral range, good frequency characteristics, high conversion efficiency and high temperature radiation resistance. Thus the most attention, the most widely used.

    What is the basic concept of interruption?

    When the CPU is processing a certain information. If an emergency occurs suddenly in the outside world at this time and the CPU is requested to temporarily stop the current work, and turn to deal with the emergency. After the CPU handles the emergency, it returns to the place where it was interrupted and continues the original work. This process of temporarily stopping processing information in the microcontroller is called an interrupt.
    The combination of all program software that realizes the interrupt function is called the interrupt system. Setting up the interrupt system can make the microcontroller have the ability to deal with external asynchronous events. It has greatly improved its work efficiency and flexibility in dealing with problems.
    The request source used to request the CPU to generate an interrupt is called an interrupt source. A microcontroller’s interrupt system generally allows multiple interrupt sources. When several interrupt sources request interrupts to the CPU at the same time, there is a problem of which interrupt source request the CPU responds to first.
    Usually, the CPU prioritizes the most urgent interrupt request sources according to the priority of the interrupt sources. In other words, the CPU stipulates that each interrupt source has a priority, and the interrupt request with the highest priority is always processed first. Interrupt requests that are temporarily unresponsive are suspended.
    When the CPU is processing an interrupt request, another interrupt source request with higher priority occurs. Then the CPU can temporarily suspend the execution of the processing program for the original interrupt source, and process the interrupt request with higher priority. After the processing is completed, return to the original low-priority interrupt processing service routine. This process is called interrupt nesting. Such an interrupt system is called a multi-level interrupt system. An interrupt system without interrupt nesting function is called a single-level interrupt system.

    What is the basic form of the bleeder Resistors circuit?

    The basic form of the bleeder resistor circuit is a resistor with a relatively large resistance (usually hundreds of kiloohms) connected in parallel across a capacitor.

    The early combinational logic circuit design was based on manual design. How to design by Boolean algebraic simplification?

    Step 1: convert the logical proposition described in the text into a truth table:
    First, the causality of events is analyzed to identify input and output variables. Generally, the cause of the event is always defined as the input variable, and the result caused by the event is defined as the output variable.
    Secondly, define the meaning of the logic state, that is, determine that 0 and 1 represent two different states of the input and output variables respectively.
    Finally, a truth table is presented in terms of causality.
    Step 2: Write the logical expression from the truth table and simplify it. The simplified form should depend on the selected gate circuit.
    Step 3: Draw a logic diagram and finally convert it into a circuit.

    What are the power management solutions for portable media players?

    1. Design Challenge
    2. Innovative solutions
    3. Multimedia processor dynamic power management technology
    4. The latest development of PMP power management technology and digital control power management


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