Questions about the resistance of the LED indicator

When the power supply is 220V AC, the resistance in series should be greater than 100K, generally between 100K and 200K. If the resistance value is too small, the resistor is required to be powerful, and it is easy to burn out the LED.

If you use a high-brightness LED, the resistance value can be large. to reduce the power dissipation of the resistor.

Practice has proved that 200K for ordinary LEDs and 430K for high-brightness LEDs can be used as a status indication for general small equipment.

To protect the LED, it is best to connect one 1N4007 diode in the forward direction or one diode in parallel at both ends of the LED.

You mean that each voltage is indicated by an LED:

Suppose you. 48v

Pick up. White light, white light on-voltage is around the right and right, let's say the current is 20 mA, so you connect the series resistance. r=

Kilohm. 24V connection. Blue.

Lamp. The blue on-voltage is also there.

Left and right, also set the current to 20 mA

then r=(kiloohms, you can choose;

12V green light.

Lamp. The green light is on-voltage.

Left and right, also set the current to 20 mA

Then r=(ohm, you can choose 510 ohms.) 5V green light.

Lamp. The green light is on-voltage.

Left and right, also set the current to 20 mA

Then r=(165 ohms, you can choose 220 ohms.)

It is best not to exceed 20 milliamps of the current of the lamp, you can use the current of 10 milliamps to calculate, and it is not much brighter than flowing through 20 milliamps than flowing through 10 milliamps, so it is okay for you to use 10 milliamps to calculate, that is, your resistance can be appropriately larger.

Engineers, especially electronic R&D engineers, will select some basic electronic components and chips when developing circuit projects, and combine them to form a complete project schematic scheme through different circuit theories. For example.

For the mobile phone charger project, after reviewing the design plan, the engineer will select the AC-DC power supply chip, QC fast charging protocol chip, rectifier bridge, MOS tube, synchronous rectifier chip, PWM control chip, high-frequency transformer, diode, resistor, capacitor and varistor to design a detailed circuit schematic;

In the inverter air conditioning project, after reviewing the design plan, the engineer will select the IPM power module, 32-bit M0 core microcontroller, LDO power chip, electrolytic capacitor, MOS tube, temperature and humidity sensor, LCD display, infrared receiving tube, diode, transistor, chip resistor and chip capacitor to design a detailed circuit schematic;

For industrial motor control projects, after reviewing the design scheme, engineers will select motor driver chips, MOS tube gate driver chips, DSP processors, Hall sensors, operational amplifiers, ADC acquisition chips, TVS transient suppression diodes, clock chips, LED lights, power transistors, Schottky diodes, resistors, capacitors and fuses to design detailed circuit schematics;

Electronic components and chips.

Engineers use resistors in the circuit schematics of these various projects, mainly because resistors can perform more functions in the circuit, such as:

Current limiting: In the LED driver circuit, the 68K resistor connected in series acts as the current limiting function;

Voltage division: In the two resistor series circuits composed of 10K resistor A and 47K resistor B, the resistor A that is connected in series is the voltage divider function of resistor B;

Sampling: In the current acquisition circuit, the resistance with a low resistance value of 4m acts as the sampling function of the current;

Filtering: In the RC filter circuit, the 22K resistor connected in parallel acts as a filtering function;

Isolation: In the analog AGND and digital DGND circuits, the GND of the power supply will be connected together through the 0 resistor, and the 0 resistance that is connected is the charging isolation function;

This is related to the voltage and the voltage drop of the LED light. The circuit of the LED lamp is an LED connected in series with a resistor, and then the power supply voltage on both sides. There are several parameters involved:

1) The voltage drop of LED, this is a fixed value, and it will not change after leaving the factory, such as 2V; Here we assume vh; There is also a minimum luminous current, which here we assume is IH

2) The power supply voltage on both sides is provided by you externally, here we assume that it is vi;

3) The power dissipation p of the resistor, the resistor has a power dissipation value, generally 0805 package is, 0603 package is 1 8W, 0402 package is 1 16W.

Then let's calculate the minimum resistance required: r=u 2 p=(vi-vh) 2 p;

Then calculate the maximum allowable resistance: r=u ih=(vi-vh) ih;

This question is too broad, there are 10,000 kinds of LED lights, there are 10,000 possibilities.

<>1. LED lamp plus resistance in order to reduce current.

2. LED light.

It is not necessary to add resistance, if the power supply is constant current, you can use the resistor. Because LED nonlinear components, very sensitive to voltage, can not be controlled by voltage, mainly in the way of current to control the brightness of LED lights, plus resistance is only a current limit, in fact, the resistance will affect the efficiency of LED lights, small power LED lights can ignore the loss on the resistance, and high power LED lights are directly powered by constant current power supply.

<>1. LED lamp plus resistance in order to reduce current.

2. LED lamps do not have to add resistance, if the power supply is constant current, you can use resistors. Because LED nonlinear components, very sensitive to voltage, can not be used in the voltage way to control the sail quietly, mainly in the way of current to control the brightness of the LED lamp, the resistance is only the current limit, in fact, the resistance will affect the efficiency of the LED lamp, the small power LED lamp can ignore the loss on the resistance, and the high power LED lamp is directly powered by a constant current hail source.

The first thing that can be determined is that there is absolutely resistance, as long as it is not a superconductor, even a copper wire is resistant. LED is a type of diode with a small forward resistance and a large reverse resistance.

1. It is related to its temperature;

2. It is related to whether the solder joints of the gold wire welding are corrected;

3. It is related to the resistance value of the chip itself.

How to find the appropriate resistance of LED lamp, first of all, we must determine the rated working voltage and current of the lamp beads, and then configure the resistance value according to the actual maximum voltage of power supply.

When the LED light heats up, the resistance becomes smaller. Because semiconductor materials have a negative temperature coefficient, the higher the temperature, the lower the resistance. This is different from other metal conductors.

There are resistances, but the resistance of normal LED lamps does not have a unified value, most of the LED lamp power supplies are switching power supplies, and the resistance of the input end of the switching power supply is very large, all of which are above one trillion ohms. LED lamp bead is a semiconductor device, there is forward resistance and reverse resistance, it is a nonlinear component, the resistance value, with the multimeter measurement gear change.

Generally light-emitting 2113 diodes.

The current is 5,30mA.

1. Connect the 200 ohm resistor, the current is 1A, be careful that your eyes have glue, choose to wait for the LED to be burned at 70 200 ohms, of course not, use a series of ordinary LEDs to do the indicator 43 47K, 2W 3W resistor. The current is generally 5mA (the resistance of the high-brightness LED connection is 110 150K, 1 2W), and the current is generally 2mA), and the lamp should be connected in reverse parallel with the IN4007 or IN4007LED.

2. Of course, this is the most ideal value, including the fluctuation of the power grid, the resistance is best between 1 50,000 and 1 60,000 euros, and a series of resistors together is the best, if a resistance is divided into 220V voltage, the heat dissipation is not very good.

3. The brightness of different colors can be increased or decreased by 30k 50k according to their preference, but not less than 150k, otherwise it burns out or is not used for a long time, and the current limit resistance power should be large enough, generally use 1 2w or more resistors, and it is better to connect two resistors in series.

The current limiting resistance of the 220V LED power indicator can be used with a 240K resistor, of course, a 330K resistor can also be used, but the resistance of the resistance is too large, and the indicator light is not too bright.

150k resistor. The indicator light effect is obvious and not dazzling. There is no need to connect other electronic components in series, which increases cost and power consumption. At this point, the LED current is milliampere. No fever for a long time.

The series connection is more than 10K resistor, and a slightly larger one such as about 120K can also be used. The current of LED lamps is usually about 2mA, because it is energized all year round, the heat of the resistor is not small.

Do you think it's military or aerospace, you can look at the circuit that is hot and boils water quickly, you can get a more than 100k one, what diode is used? Draw a snake then put legs on it.