aa alkaline battery.Capacitor and resistor parallel LED circuit design, characteristics and working principle of lightning protection grounding resistor

　　Electronic enthusiasts provide you with the capacitor-resistance parallel LED circuit design, the characteristics and working principle of the lightning protection grounding resistor. LED is a constant voltage component, that is, once it is turned on, it changes with the current, and the voltage on it changes very little. The moment the capacitor is powered on, it is equivalent to a short circuit. Therefore, when a capacitor is used to reduce the voltage to drive an LED, the LED will bear a large impact current at the moment of power-on, which may affect the life of the LED at best, or burn the LED immediately at worst. Therefore, it is not advisable to use capacitor voltage reduction to drive LED. If it is actually used, a current-limiting resistor must be connected in series with the circuit. Characteristics and working principle of lightning protection grounding resistor:

　　Construction method of lightning protection grounding

　　Lightning protection grounding projects include the installation of grounding devices, lightning protection down conductors and lightning protection strips. The standard used for construction is "Code for Construction and Acceptance of Grounding Devices in Electrical Installation Projects" (GB50169-92)

　　1. Lightning protection grounding device

　　1. According to the size and position requirements of the design drawing, weld and connect the two main structural bars in the bottom plate, and weld them with the relevant steel bars in the pile platform and column (use two vertical structures to connect up and down at different elevations), and connect the two The main ribs are marked with paint to facilitate lead-out and inspection.

　　2. All welding joints should be full and have sufficient mechanical strength. There should be no defects such as slag inclusions, meat bites, cracks, false welds, pores, etc. After the coating on the welding joints is clean, apply asphalt for anti-corrosion treatment, and use matching When welding, the welding length requirements are:

　　Galvanized flat steel shall be no less than 2 times its width and at least 3 edges shall be welded.

　　The welding length of galvanized round steel is 6 times its diameter and should be welded on both sides.

　　When galvanized round steel is connected to galvanized flat steel, its length is 6 times the diameter of the round steel.

　　3. After each construction is completed, the quality inspection department should be promptly requested to conduct inspection and acceptance of concealed projects. Only those that pass the inspection can be concealed, and at the same time, the acceptance records of concealed projects should be kept.

　　2. Installation of lightning protection grounding down conductors

　　When building steel bars are used as down conductors, the cross-section of the steel bars must meet the design requirements.

　　The connection of the steel bars must meet the requirements of the specification. If the submerged arc welding process is used in the construction, no treatment is required. Otherwise, a grounding jumper must be performed, and the overlap length should not be less than 6 times the diameter of the spanning steel bar.

　　3. Lightning protection belt

　　The lightning protection belt of this project uses 25&TImes;4 hot-dip galvanized flat steel.

　　1. Bracket installation:

　　During the construction of civil roof structures, pre-buried supports should be used. All brackets must be solid, with full mortar, level and vertical. The spacing between brackets should not be greater than 1.5m and should be evenly spaced. The allowable deviation is 30mm. The distance between the brackets on both sides of the corner should not be greater than 250mm from the center of the corner. The horizontality of the row of brackets should be 3/1000 per 2m inspection section, but the total length deviation should not be greater than 10mm.

　　2. Installation of lightning protection belts

　　Straighten the galvanized flat steel.

　　When installed, the lightning protection wire should be straight and firm, without any ups and downs or bends. The distance from the building should be consistent. The allowable deviation of the straightness is 3/1000 for every 2m inspection section, but the total length deviation should not be greater than 10mm.

　　The bend of the lightning protection wire shall not be less than 90°, and the bending radius shall not be less than 2.5 times the diameter of the galvanized flat iron.

　　Lightning protection spans should be made at the deformation joints of buildings.

　　4. Electrical grounding construction methods

　　At present, according to the "Residential Design Code" (GB50096-1999), the grounding system mainly adopts TT, TN-C-S or TN-S grounding method, and the total equipotential bonding is carried out.

　　1. For the grounding system of high/low voltage power transformation and distribution room equipment, a horizontal grounding ring belt 300mm above the ground should be set up around the room. The specifications should be in accordance with the design requirements.

　　2. Switch cabinets, power distribution panels (boxes), power transformers and various electrical equipment, metal shells that may be charged due to damaged insulation, independently installed metal brackets and transmission mechanisms for electrical use, and grounding holes of sockets should all Reliably connect with a dedicated grounding (pE line) branch line. The pE line should be connected to the grounding device and grounded repeatedly.

　　3. When the protective wire (pE wire) is made of the same material as the phase wire, the minimum cross-section of the pE wire should comply with the requirements in the table below. When the pE wire uses a single-core insulated wire, according to the mechanical strength requirements, the cross-section should not be less than: Mechanically When protected, it is 2.5mm2, and when there is no mechanical protection, it is 4mm2.

　　List of minimum cross-sections of pE lines

　　Phase wire core wire cross-section S (mm2) pE wire minimum cross-section S (mm2)

　　S≤16S

　　16≤S≤3516

　　S》35S/2

　　d. All exposed grounding points and test points should be painted with red paint and have signs indicating their uses.

　　e. The automatic fire alarm system, building equipment automatic monitoring system (BMS) and other weak current equipment rooms use special grounding wires, which are introduced into the control room through the grounding device.

　　5. Ground resistance test

　　The ground resistance tester model is ZC29B-2, and the instrument must be professionally measured. Before testing, first adjust the pointer of the galvanometer to zero, then place the magnification standard rod at the maximum magnification, shake it slowly, and adjust the measurement dial at the same time to make the galvanometer zero. Accelerate and shake to about 120r/min, then adjust to balance, read the scale on the dial, and multiply by the magnification to get the measured resistance value. Note that the wiring length of the current probe is 40m and the wiring length of the potential detection is 20m.

　　Capacitor and resistor parallel LED circuit design:

　　The acceleration effect of resistors and capacitors in series circuits with LED lights after resistors and capacitors are connected in parallel

　　The resistor is connected in series with the LED to divide the voltage, otherwise the LED will be damaged if the current is too high. The function of the capacitor is to pass AC and block DC. If there is no capacitor in this circuit, the LED will emit light after power is turned on, and the brightness will change from dark to light in a process that takes a long time. If a capacitor and a resistor are connected in parallel, since the voltage of the capacitor does not change suddenly, all the voltage is applied to the LED when power is first turned on, and the LED will emit light very brightly in a short period of time, and then due to the capacitor's The charging current becomes smaller and smaller, and the LED's work is carried out by the resistor.

　　LED circuit parallel capacitor

　　Surge absorption, anti-interference, filtering, soft start, AC anti-flash

　　Soft start: delay, slowly increase voltage, protect LED

　　Surge absorption: If the capacitor is used to reduce voltage and has a surge effect, it can prevent the high voltage of the pulse at the moment of access to the circuit from damaging the LED.

　　AC anti-flash: Our usual alternating current has a somewhat inductive nature due to its long wires. When the plug or switch is turned on, it is actually a

　　The process of repeated on and off can easily produce higher voltage and damage the LED.

　　Many universal chargers are damaged when plugged into the circuit and unplugged. Very few batteries actually break after being fully charged.

　　LED is a constant voltage component, that is, once it is turned on, the voltage on it changes very little with the current. The moment the capacitor is powered on, it is equivalent to a short circuit. Therefore, if a capacitor is used to reduce the voltage to drive an LED, the LED will bear a large impact current at the moment of power-on, which may affect the life of the LED at best, or burn the LED immediately at worst. Therefore, it is not advisable to use capacitor voltage reduction to drive LED. If it is actually used, a current-limiting resistor must be connected in series with the circuit. Under the premise that the voltage is high enough, it is of course better to use them in series as much as possible, because the equivalent resistance of the LEDs increases after series connection, and the inrush current is smaller. The current-limiting resistor in series can be reduced accordingly, thereby improving the efficiency of the circuit. In addition, the total current after series connection is the current of one LED. The series capacitance is the smallest, the inrush current is the smallest, and the withstand voltage can also be reduced accordingly. Also please note: Do not group multiple LEDs in parallel and then connect them in series, because even LEDs of the same model have very different volt-ampere characteristics. After connecting them in parallel, LEDs with low voltage will have a large current, and LEDs with high voltage will have a small current. The current flowing through them is uneven. The correct approach is to group multiple LEDs in series and then connect a current limiting resistor in series, and then connect them in parallel to connect to the power supply.

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