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    What are the most commonly used control technologies?

    There are three most commonly used control technologies. That is, continuous conduction mode average current control Boost PFC, CCM/DCM boundary control Boost PFC and current clamp control Boost PFC.

    FPGA/CPLD chips are special ASIC chips.In addition to the characteristics of ASIC, what advantages do they have?

    1. With the continuous improvement of the VISI process, a single chip can accommodate millions of transistors. The scale of FPGA/CPLD chips is also increasing, and the number of single-chip logic gates has reached millions. The functions it can achieve are getting stronger and stronger, and it can also achieve system integration.
    2. FPGA/CPLD chips are 100% tested before leaving the factory, and designers do not need to bear the risk and cost of casting. Designers only need to complete the final functional design of the chip through the relevant software and hardware environment in their own laboratory. Therefore, the capital investment of FPGA/CPLD is small, which saves a lot of potential costs.
    3. The user can repeatedly program, erase, use or use different software to achieve different functions without the peripheral circuit not moving. Therefore, using FPGA/PLD trial production samples can occupy the market at the fastest speed. There are various input tools and simulation tools in the FPGA/CPLD software package, as well as a full line of products such as layout design tools and programmers. Circuit designers can complete the circuit input, compilation, optimization, simulation, and finally the production of the chip in a very short time. When the circuit has a small amount of changes, it can show the advantages of FPGA/CPLD. When circuit designers use FPGA/CPLD for circuit design, they do not need to have deep knowledge of specialized ICs. FPGA/CPLD software is easy to learn and use, which enables designers to concentrate more on circuit design and bring products to the market quickly.

    How to divide based on policy VLAN?

    To divide VLANs based on matching policies means to configure the MAC addresses and IP addresses of terminals on the switch and associate them with VLANs.
    Only qualified terminals can join the specified VLAN. After the terminal that meets the policy is added to the specified VLAN, it is strictly forbidden to modify the IP address or MAC address, otherwise the terminal will be withdrawn from the specified VLAN.  
    This division method has high security. After the VLAN is successfully divided based on the MAC address and IP address, users are prohibited from changing the IP address or MAC address.
    Compared with other VLAN division methods, VLAN division based on the combination policy of MAC address and IP address is the VLAN division method with the highest priority.

    What is passive PFC technology?

    Passive PFC technology uses passive components to improve input power factor. Reduce current harmonics to meet standard requirements.

    What is the lead antenna?

    Steering antenna, also known as Yagi antenna, is an antenna widely used in meter wave and decimeter wave.
    The lead antenna is a tightly coupled parasitic oscillator end-fire array, which consists of an active oscillator (usually a half-wave oscillator, such as element 1), a reflective oscillator (slightly longer than the active oscillator, such as element 0) and several lead elements. The direction device (slightly shorter than the active oscillator, such as units 2-N) is formed.
    Except that the active oscillator is connected to the signal source or receiver through the feeder, the other oscillators are passive oscillators.

    Does the CPU respond properly to interrupts generated by peripherals?

    Whether the CPU can normally respond to interrupts generated by peripherals depends entirely on the VIC.

    What is the power supply design specification?

    1. The full voltage input range is AC90~265V.
    2. The input voltage is AC90~265V.
    3. The power factor is greater than 0.9.
    4. The output current is 350mA.
    5. The LED load voltage is DCl2.

    What are the triggering methods for interrupts?

    There are two types of interrupt triggers: edge-triggered and level-triggered.
    Among them, edge trigger is divided into rising edge trigger and falling edge trigger. Level trigger is divided into high level trigger and low level trigger.

    The technical parameters of the А/D converter reflect its performance characteristics. What are the main indicators?

    Resolution Accuracy Conversion Time Power Sensitivity Range.

    How to remove the Integrated Circuits(ICs) block?

    During circuit maintenance, it is often necessary to disassemble the integrated circuit from the printed circuit board. Due to the many and dense pins of the integrated circuit, it is difficult to disassemble, and sometimes the integrated circuit and the circuit board are damaged. Several effective integrated circuit disassembly methods are summarized here for your reference.
    Solder suction and disassembly method: use a tin absorber to disassemble the integrated block, which is a common professional method. The tool used is an ordinary electric soldering iron for suction and welding, and the power is above 35W. When removing the manifold, just place the heated dual-purpose soldering iron tip on the pins of the manifold to be removed. After the tin of the solder joints is melted, it is sucked into the fine tin container, and the integrated block can be removed after the solder of all the pins is sucked.
    Medical hollow needle disassembly method: Take a few medical 8-12 gauge hollow needles. When in use, it is advisable that the inner diameter of the needle head just covers the pins of the integrated block. When disassembling, use a soldering iron to melt the solder on the pins, and cover the pins with needles in time. Then remove the soldering iron and rotate the needle, wait for the solder to solidify and pull out the needle. This way the pin is completely separated from the printed board. After doing this for all pins, the integrated block can be easily removed.
    Soldering iron and brush with disassembly method: This method is simple and easy to implement, as long as there is an electric soldering iron and a small brush. When dismantling the integrated block, first heat the electric soldering iron. After reaching the melting temperature, the solder on the pins is melted, and then use a brush to remove the melted solder. In this way, the pins of the integrated block can be separated from the printed board. This method can be carried out separately or in columns. Finally, use sharp tweezers or a small “one” screwdriver to pry off the integrated block.
    Add solder melting and disassembly method: This method is a trouble-free method, as long as you add some solder to the pins of the integrated block to be disassembled. Connect the solder joints of each column of pins to facilitate heat transfer and facilitate disassembly. When disassembling, use a soldering iron to heat each column of pins, and pry it with sharp tweezers or a small “one” screwdriver. The two columns of pins are heated alternately until they are removed. Generally, each column of pins can be removed by heating twice.
    Multi-strand copper wire tin absorption and disassembly method: It is to use multi-strand copper-core plastic wire, remove the plastic outer skin, and use multi-strand copper-core wire (short wire can be used). Before use, put the rosin alcohol solution on the multi-strand copper core wire, and put the multi-strand copper core wire on the integrated block pins for heating after the electric iron is heated. In this way, the solder on the pins will be absorbed by the copper wire, and the part that absorbs the solder can be cut off. Repeat this several times to remove all the solder on the pins. The braided wire in the shielded wire can also be used if possible. As long as the solder is sucked, the integrated block can be removed by gently prying it with tweezers or a small “one” screwdriver.


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