Calculate the power of the block for the LED strip. LED resistor resistance calculator

Connecting LEDs is not a difficult task. To connect correctly, it is enough to know a school physics course and follow a number of rules.

The main parameter of any LED is current, not voltage, as many believe. The LED must be powered with a stabilized current, the value of which is always indicated by the manufacturer on the packaging or in the datasheet.

The LED current is limited by a resistor - this is the cheapest option. But there is also a more “advanced” one - use . In fact, the use of resistors is a relic of the past, because today there are plenty of drivers for every taste and color and at the most attractive prices. For example, the cheapest ones are possible. The drivers provide a stable current to the LEDs regardless of changes in the voltage at its input.

The correct connection of the LED to the driver is as follows: first you need to connect the LED to the driver, only after that we turn on the driver.

There are several types:

Let's remember Ohm's law:

R - resistance - measured in Ohms

U - voltage- measured in volts (V)

I - current measured in amperes (A)

Example of calculating a resistor for an LED:

Let's say the power supply produces 12 V: Vs=12 V

LED - 2 V and 20 mA

20 mA=0.02 A.

R=10/0.02=500 Ohm

10 V is dissipated into resistance (12-2)

Let's calculate the resistance power:

P=10*0.02 A=0.2 W

Required resistor - R=500 Ohm and P=0.2 W

Calculation of a resistor for an LED when connecting LEDs in series

The minus of the LED is connected to the plus of the next one. This way you can connect ad infinitum. When the voltage drop across the LED is multiplied by the number of diodes in the circuit. Those. if we have 5 LEDs with a rated current of 700 mA and a voltage drop of 3.4 Volts, then we need a driver for 700 mA 3.4 * 5 = 17 V

We have looked at what drivers can be selected, and now we will return directly to how to calculate the resistor for an LED with such connections.

Above we looked at the calculation of a resistor for an LED (one). For a series connection, the calculation is similar, but it must be taken into account that the voltage drop across the resistor is smaller. If “on fingers”, then the total voltage drop across the LEDs Vl=3*2=6V is subtracted from the power source. Provided that our source produces 12V, then 12-6 = 6V.

R=6/0.02=300 Ohm.

Р=6*0.02=0.12W

Those. we need a 300 ohm and 0.125 watt resistor.

The characteristics of the LED and power supply are similar to the previous example.

Calculation of a resistor for an LED in parallel connection

When the plus of the LED is connected to the plus of the other, the minus to the minus. With this connection, the current is summed, but the drop remains unchanged. Those. if we have 3 LEDs of 700 mA and a drop of 3.4 V, then 0.7 * 3 = 2.1A, then we will need a driver with parameters of 4-7 V and at least 2.1A.

The calculation of the resistor for the LED in this case is similar to the first case.

Calculation of a resistor for an LED in a series-parallel connection

Interesting connection. With this arrangement of diodes, several serial chains are connected in parallel. You need to know that the number of LEDs in the chains must be equal. The driver is selected taking into account the voltage drop on one circuit and the product of the current by the number of circuits. Those. 3 serial circuits with parameters 12V and 350 mA are connected in parallel, the voltage remains 12V, and the current is 350 * 3 = 1.05A. For long-term operation of the chips, we need an LED driver with 12-15V and a current of 1050mA.

The calculation of the resistor for the LED in this case will be as follows:

The resistor is similar when connected in series, however, it is worth considering that the consumption from the power source will increase three times (0.2+0.2+0.2=0.06A).

When connecting LEDs through a resistor, you need a stabilized power source, because When the voltage changes, the current flowing through the diode will also change.

There is another way to connect LEDs - parallel-series with cross connection. but this is a rather complex topic in calculations, so I will not reveal it here. If necessary, of course, I will describe it, but I think this is only needed by a narrow circle of specialists.

You can find many online calculators on the Internet that will immediately calculate resistors for you. But you shouldn’t blindly believe them, but rather double-check, following the saying: “If you want to do it well, do it yourself.”

Video on the correct calculation of resistors for LEDs

When connecting low-power LEDs, a quenching resistor is most often used. This is the simplest connection scheme, which allows you to obtain the required brightness without using expensive ones. However, despite its simplicity, to ensure optimal operation it is necessary to calculate the resistor for the LED.

LED as a nonlinear element

Let's consider a family of current-voltage characteristics (volt-ampere characteristics) for LEDs of various colors:

This characteristic shows the dependence of the current passing through the light-emitting diode on the voltage applied to it.

As can be seen in the figure, the characteristics are nonlinear. This means that even with a small change in voltage of a few tenths of a volt, the current can change several times.

However, when working with LEDs, they usually use the most linear section (the so-called working region) of the current-voltage characteristic, where the current does not change so sharply. Most often, manufacturers indicate in the LED characteristics the position of the operating point, that is, the voltage and current values ​​at which the declared brightness is achieved.

The figure shows typical operating point values ​​for red, green, white and blue LEDs at 20 mA. Here you can notice that leds of different colors with the same current have different voltage drops in the working area. This feature should be taken into account when designing circuits.

The characteristics presented above were obtained for light-emitting diodes connected in the forward direction. That is, the negative pole of the power supply is connected to the cathode, and the positive pole is connected to the anode, as shown in the picture on the right:

The complete current-voltage characteristic looks like this:

Here you can see that reverse switching is pointless, since the LED will not emit, and if a certain reverse voltage threshold is exceeded, it will fail as a result of breakdown. Emission occurs only when turned on in the forward direction, and the intensity of the glow depends on the current passing through the LED. If this current is not limited by anything, then the led will go into the breakdown region and burn out. If you need to install a working LED or not, then an article detailing all the methods will be useful to you.

How to choose a resistor for a single LED

To limit the current of the light-emitting diode, you can use a resistor connected as follows:

Now we determine which resistor is needed. To calculate the resistance, the formula is used:

where U supply is the supply voltage,

U pad - voltage drop across the LED,

I is the required LED current.

In this case, the power dissipated by the resistor will be proportional to the square of the current:

For example, for the Cree C503B-RAS red LED, the typical voltage drop is 2.1 V at 20 mA. With a supply voltage of 12 V, the resistance of the resistor will be

From the standard range of E24 resistances, we select the closest nominal value - 510 Ohms. Then the power dissipated by the resistor will be

Thus, a quenching resistor with a nominal value of 510 Ohms and a dissipation power of 0.25 W will be required.

It may seem that at low supply voltages you can connect LEDs without a resistor. This video clearly shows what will happen to a light-emitting diode turned on in this way at a voltage of only 5 V:

The LED will work at first, but after a few minutes it will simply burn out. This is caused by the nonlinear nature of its current-voltage characteristic, as discussed at the beginning of the article.

Never connect an LED without a quenching resistor, even at low supply voltage. This leads to its burnout and, at best, to an open circuit, and at worst, to a short circuit.

Calculation of a resistor when connecting several LEDs

In a series connection, one resistor is used, which sets the same current to the entire LED chain. It should be taken into account that the power source must provide a voltage greater than the total voltage drop across the diodes. That is, when connecting 4 LEDs with a drop of 2.5 V, a source with a voltage of more than 10 V will be required. The current will be the same for all. The resistance of the resistor in this case can be calculated using the formula:

where is the supply voltage,

- the sum of the voltage drops across the LEDs,

- consumption current.

So, 4 green Kingbright L-132XGD LEDs with a voltage of 2.5 V and a current of 10 mA with a 12 V supply will require a resistor

At the same time, it must dissipate power

When connected in parallel, each light-emitting diode is limited by its own resistor. In this case, you can use a low-voltage power supply, but the current consumption of the entire circuit will be the sum of the currents consumed by each LED. For example, 4 yellow BL-L513UYD LEDs from Betlux Electronics with a consumption of 20 mA each will require a current of at least 80 mA from the source when connected in parallel. Here, the resistance and power of resistors for each “resistor-led” pair are calculated in the same way as when connecting a single LED.

Please note that both series and parallel connections use the same power supply. Only in the first case will you need a source with a high voltage, and in the second - with a high current.

You cannot connect several LEDs in parallel to one resistor, because either they will all burn very dimly, or one of them may open a little earlier than the others, and a very large current will flow through it, which will disable it.

Programs for calculating resistance

With a large number of connected LEDs, especially if they are connected both in series and in parallel, manually calculating the resistance of each resistor can be problematic.

The easiest way in this case is to use one of the many programs for calculating resistance. The online calculator on the website cxem.net is very convenient in this regard:

It includes a small database of the most common LEDs, so you don't have to manually enter the voltage and current drop values, just enter the supply voltage and select the desired light-emitting diode from the list. The program will calculate the resistance and power of resistors, and also draw a connection diagram or circuit diagram.

For example, this calculator was used to calculate the resistor for three XLamp MX3s at a supply voltage of 12 V:

The program also has a very useful function: it will tell you the color coding of the required resistor.

Another simple program for calculating resistance, widespread on the Internet, was developed by Sergei Voitevich from the portal ledz.org.

Here you manually select the method of connecting the LEDs, voltage and current. The program does not require installation, just unpack it to any directory.

Conclusion

A quenching resistor is the simplest current limiter for an LED circuit. The current, and therefore the intensity of the glow and the durability of the LED, depend on its selection. However, it should be remembered that at high currents, significant power will be released on the resistor, so it is better to use drivers to power high-power LEDs.

LED is a semiconductor element, which is used for lighting. Used in lanterns, lamps, lamps and other lighting devices. The principle of its operation is that when current flows through a light-emitting diode, photons are released from the surface of the semiconductor material, and the diode begins to glow.

Reliable LED operation depends on current flowing through it. If the values ​​are too low, it simply will not shine, and if the current value is exceeded, the characteristics of the element will deteriorate, even to the point of destruction. At the same time they say that the LED has burned out. In order to eliminate the possibility of failure of this semiconductor, it is necessary to select it in a circuit with a resistor included in it. It will limit the current in the circuit to optimal values.

For the radio element to operate, power must be supplied to it. According to Ohm's law, the greater the resistance of a circuit segment, the less current flows through it. A dangerous situation arises if more current flows in the circuit than it should, since each element cannot withstand the greater current load.

LED resistance is nonlinear. This means that when the voltage applied to this element changes, the current flowing through it will change nonlinearly. You can verify this if you find the volt-ampere characteristic of any diode, including light-emitting diodes. When power is applied below the opening voltage of the p-n junction, the current through the LED is low and the element does not work. Once this threshold is exceeded, the current through the element rapidly increases and it begins to glow.

If power supply connect directly to the LED, the diode will fail, since it is not designed for such a load. To prevent this from happening, you need to limit the current flowing through the LED with a ballast resistance, or lower the voltage on a semiconductor that is important to us.

Let's consider the simplest connection diagram (Figure 1). The DC power source is connected in series through a resistor to the desired LED, the characteristics of which must be known. This can be done on the Internet by downloading a description (information sheet) for a specific model, or by finding the desired model in reference books. If it is not possible to find a description, you can approximately determine the voltage drop across the LED by its color:

• Infrared - up to 1.9 V.
• Red – from 1.6 to 2.03 V.
• Orange – from 2.03 to 2.1 V.
• Yellow – from 2.1 to 2.2 V.
• Green – from 2.2 to 3.5 V.
• Blue – from 2.5 to 3.7 V.
• Purple – 2.8 to 4 V.
• Ultraviolet - from 3.1 to 4.4 V.
• White – from 3 to 3.7 V.

Figure 1 – LED connection diagram

The current in the circuit can be compared to the movement of liquid through a pipe. If there is only one flow path, then the current strength (flow rate) in the entire circuit will be the same. This is exactly what happens in the circuit in Figure 1. According to Kirchhoff’s law, the sum of the voltage drops across all elements included in a circuit flowing one current is equal to the EMF of this circuit (in Figure 1 indicated by the letter E). From this we can conclude that the voltage dropping across the current-limiting resistor should be equal to the difference between the supply voltage and its drop across the LED.

Since the current in the circuit must be the same, the current obtained through both the resistor and the LED is the same. For stable operation of a semiconductor element, increasing its reliability and durability, the current through it must be of certain values ​​indicated in its description. If a description cannot be found, you can take the approximate value of the current in the circuit as 10 milliamps. After determining this data, you can already calculate the resistor value for the LED. It is determined by Ohm's law. The resistance of a resistor is equal to the ratio of the voltage drop across it to the current in the circuit. Or in symbolic form:

R = U(R)/I,

where, U (R) is the voltage drop across the resistor

I – current in the circuit

Calculation of U (R) on a resistor:

U (R) = E – U (Led)

where, U (Led) is the voltage drop across the LED element.

Using these formulas you will get the exact value of the resistor resistance. However, the industry produces only standard resistance values, the so-called rating series. Therefore, after the calculation, you will have to select the existing resistance value. You need to select a slightly larger resistor than what was calculated, this way you will have protection against accidental excess voltage in the network. If it is difficult to select an element that is close in value, you can try connecting two resistors in series or in parallel.

If you choose a resistance with less power than needed in the circuit, it will simply fail. Calculating the power of a resistor is quite simple; you need to multiply the voltage drop across it by the current flowing in this circuit. Then you need to select a resistance with a power not less than the calculated one.

Calculation example

We have a supply voltage of 12V, a green LED. It is necessary to calculate the resistance and power of the current-limiting resistor. The voltage drop across the green LED we need is 2.4 V, the rated current is 20 mA. From here we calculate the voltage dropping across the ballast resistor.

U (R) = E – U (Led) = 12V – 2.4V = 9.6V.

Resistance value:

R = U (R)/ I = 9.6V/0.02A = 480 Ohm.

Power value:

P = U (R) ⋅ I = 9.6V ⋅ 0.02A = 0.192 W

From a number of standard resistances we select 487 Ohms (E96 series), and the power can be selected at 0.25 W. This resistor must be ordered.

If you need to connect several LEDs in series, you can also connect them to the power source using only one resistor, which will suppress excess voltage. Its calculation is carried out using the above formulas, however, instead of one forward voltage U (Led), you need to take the sum of the forward voltages of the required LEDs.

If you need to connect several light-emitting elements in parallel, then for each of them you need to calculate its own resistor, since each of the semiconductors may have its own forward voltage. The calculations for each circuit in this case are similar to the calculation of one resistor, since they are all connected in parallel to the same power source, and its value for calculating each circuit is the same.

Calculation steps

To make the correct calculations, you must do the following:

1. Finding out the forward voltage and current of the LED.
2. Calculation of the voltage drop across the desired resistor.
3. Calculation of resistor resistance.
4. Selection of resistance from the standard range.
5. Calculation and selection of power.

You can do this simple calculation yourself, but it’s easier and more time-efficient to use a calculator to calculate a resistor for an LED. If you enter such a query into a search engine, you will find many sites offering automated calculations. All the necessary formulas are already built into this tool and work instantly. Some services also immediately offer a selection of elements. You will only need to choose the most suitable calculator for calculating LEDs, and thus save your time.

The online LED calculator is not the only way to save time in calculations. The calculation of transistors, capacitors and other elements for various circuits has long been automated on the Internet. All that remains is to competently use the search engine to solve these problems.

LEDs are the optimal solution for many lighting problems at home, office and production. Pay attention to Ledz lamps. This is the best ratio of price and quality of lighting products; using them, you do not have to make calculations and assemble lighting equipment yourself.

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Currently, LED strips are becoming popular; due to their flexibility and variability in size, it is possible to create unique and varied lighting. If previously this type of lighting was installed exclusively by craftsmen, now, knowing the power of the LED strip, almost anyone can do this.

This type of backlight is distinguished by low power consumption of LED strip and high luminous fluxes, which allows you to achieve the desired effect without overpaying for electricity. Another advantage of this lighting technology is its ease of installation. In order to install the backlight on the desired object, so to speak, “with your own hands,” you definitely need to understand how the electricity consumption of an LED strip is calculated and what you need to know for its accurate calculations.

How does the design of an LED strip affect energy consumption?

First, let's look a little at the device of the LED strip, since it is this that affects the amount of electricity with which it operates, and therefore its power. So, an LED strip is a flexible strip in which the light source, LEDs, are on the same side and located at the same distance from each other. Electricity consumption depends on the size of the LEDs; we’ll talk about it in more detail below. On the same side there are controls. The reverse side, most often, is an adhesive base for fixing lighting objects to the surface.

The power of an LED strip is affected not only by its design, but also by other indicators. Here are the main ones that are required for power consumption calculations:

• type (type) of the product;
• size of individual light-emitting diodes;
• overall size, footage.

You can find out all these indicators on the product packaging; for this you need to know the main positions in which the data we need to calculate the power is entered. So, we can read the size of the diodes themselves, the type of product, the footage (standard footage is 5 meters), the number of elements per meter on the box. As a rule, the type of product is indicated in the first place of marking.

This is usually followed by numbers that indicate the area of ​​the LED in millimeters. It is logical to assume that the larger the LED, the higher the power consumption, and this is true. That is, if a product has a light-emitting diode measuring 5 * 5 mm, then its energy consumption is greater than that of a tape with elements measuring 3.5 * 2.8 mm. Information about the size of the luminous elements can be found by looking at the numbers indicated on the marking, immediately after the type (, SMD 3528).

The marking also indicates the number of LEDs per meter. Strips come with the following number of luminous elements: 30, 60, 72, 120 for SMD 5050 products and 60,120 and 240 for, respectively. Naturally, more elements consume more energy, which increases the power of the LED strip.

An example of LED strip labeling from the domestic manufacturer ERA. Length - 5 meters. There are 30 LEDs per meter. Brightness in lumens and other parameters.

Why are calculations needed?

Many people want to know how to correctly calculate energy consumption, since there are no backlights designed for use in specific objects. The buyer himself decides where to place which device. Often installation is also carried out independently, without resorting to the services of specialists. However, not all consumers are aware of the need to take into account how much the LED strip consumes and not everyone understands why they need to calculate power consumption.

For effective use and correct selection of this type of lighting, it is necessary to calculate the power of the LED strip. That is, you should find out the amount of electricity consumed for the entire product. By making the calculation, you will extend its service life and be able to correctly select the auxiliary elements necessary for the operation of the equipment (power supply and control panel or controller).

Unfortunately, when purchasing, you cannot always get all the necessary information from the seller. Or worse, they will give you a recommendation that will only harm you. To avoid such situations, there is no better solution than being able to calculate the required indicator yourself.

Correct calculations will allow you to save energy and provide high-quality lighting for the objects you need. If earlier spotlights and incandescent lamps in chandeliers and lampshades were used to create a play of light in the interior, today it is possible to save money and live in a beautifully lit room. Correct calculation of consumption will undoubtedly affect electricity bills.

Modern lighting using LED strips allows you to organize such beautiful lighting

When choosing all the additional elements for installing LED strip lighting, you need to know its power. To connect the backlight, you will need a power supply that connects to the device and a controller if you use an RGB device. Remember that for an LED strip that consumes, for example, 14 W, choose a 20 W power supply. That is, it must be selected in such a way that its power exceeds the total consumed. This is done in order to ensure safe use and prevent the possibility of LEDs burning out.

Consumption calculation

Anyone can make consumption calculations, and often they don’t even need a calculator. But in order to calculate, you will need some information. So, in order to know how to calculate the power of an LED strip of the required footage, you need to know the following parameters:

• footage, what length you will need;
• number of LEDs per meter (SMD 5050 – 30, 60, 72, 120; SMD 3528 – 60, 120, 240);
• electricity consumption per meter (measured in W).

Depending on the type of product and the number of light-emitting diodes that will be used per meter, the power consumed by this segment of electricity depends. How many LEDs are there per meter of strip, as well as the type of product, as mentioned earlier, can be found out upon purchase. The most common types, which are used both in interiors and for advertising lighting, are single-color devices - SMD 5050, SMD 3528. The power parameters for them are indicated in the tables.

Parameters in table form for 1 meter for SMD 5050

Parameters in table form for 1 meter for SMD 3528

As an example, we will calculate the power for 72 LEDs per meter for a product of 5 meters.

We look at the table for the power consumption for this number of LEDs and multiply by the footage.

Calculation example: 15(W)*5(m)=75(W/m)

We get - the power consumption of the LED strip for 5 meters of this type of product with 72 diodes is 75 W. Having made such simple calculations, we found out the power consumption we needed so much.

If you decide to use this type of lighting (backlight), then you made the right choice. But remember that calculating the electricity consumption is necessary and quite simple. Even if they calculate it for you when purchasing, do not be lazy and be sure to calculate it yourself, this will help to avoid possible disappointments in the future.

Video

We present to your attention an interesting video to consolidate the knowledge gained. The author of the video, based on the elementary Ohm's law (physics, grade 7), shows how to make all the necessary calculations.

Results

Summarizing the above, we recall that the main parameter when installing the tape is the power consumption of electricity. To calculate, you only need to know two parameters: the footage of the tape you use and the power consumption per 1 meter, which in turn depends on the number of LEDs and the type of product.

Of course, we are not addressing only drivers, but even those who ride as passengers in a car can guess why a gearbox is needed. Primitive - for acceleration, gaining speed and driving. In first gear we get powerful traction, and the car starts moving and we get acceleration. We won't accelerate in first gear.

On the last one, everything is exactly the opposite, minimum thrust, but maximum speed. On a flat road, when we accelerated, traction is not needed, only speed is needed. But if on a viscous dirt road, then for the same speed you will need more traction. The heavy surface increases the resistance of the bumper and to overcome it, we reduce the gears. You can’t drive through the garden at fifth speed after rain - you’ll stall instantly.

Now let’s move on to the images - we compare light bulbs with wires to the road (wire) and the ground (lamp). Voltage is thrust, current is speed. It is clear that speed is always needed, but it can be set by thrust.

In order for the current to overcome the resistance, voltage is needed, and in exactly the right amount. If the voltage is higher, the current will not flow faster; accordingly, it will drop. What is the difference between a Zhiguli and an SUV on a flat road at a speed of 60 km/h? No! And at the same speed, but on a viscous primer? Huge. Mercedes has much more traction. If you do not control the current, the load will constantly draw voltage until it crashes. Accordingly, you need to find a limiter that will provide just enough voltage (thrust) to be enough to overcome the current resistance. And a resistor acts as such a limiter in diode lighting.

Why do LEDs need a resistor?

And again, before calculating the resistor resistance for LEDs, a few words on hardware.

Since the most popular light bulbs in our country are still those with incandescent filaments, everyone knows that to turn them on you need direct contact with the power source (switch, socket, etc.). A light bulb can only burn out when the tungsten filament bursts, and this happens when the voltage increases (we don’t take a good shake into account). In this case, the thread itself is the resistor through which the current flows.

An LED, as a complex semiconductor, is far from the same as an incandescent lamp. This is a current device that picks up voltage on its own and is designed for a certain maximum voltage. For example, if an LED is designed for a voltage of 1.8V, but 1.9V is supplied, then it burns out. In simple terms, a battle begins between the crystals and the power source - who will win. If the ice lamp forcibly reduced the voltage in a weak source, it continues to work, but if it didn’t work, it burned out. The purpose of the resistor in this case is to attenuate the power supply and help reduce the voltage on the crystals.

VIDEO: How a resistor works

Why does each LED need its own resistor?

There are 2 options for connecting resistors:

• sequentially;
• parallel.

When switched on in series, all the light bulbs are in one circuit through which current flows at the same speed. Here, only one resistor is enough, which initially reduces the source voltage and then the process proceeds cyclically.

Parallel connection for LEDs is the worst option. There are no absolutely identical copies, and each one has slightly different voltage parameters. When connected in parallel, the current needed by all LEDs will be taken by the one with the lowest voltage. And since there is a lot of current, it burns out instantly. It’s the turn of the next one with the lowest voltage, and literally within a few minutes we have a pile of burnt-out ice bulbs, albeit with a resistor.

When the calculation of the resistor for the LED is made, they are connected only in series - one after the other.

Each box with ice lamps indicates the voltage, but not the power supply, but the one they need to work.

The voltage indicated on the LED is approximate. It is necessary to calculate the resistor.

In order to determine the voltage across the resistor, you can use an online calculator (at the end of the article) or subtract from the power supply the one indicated on the light bulb. To determine the current, divide the resulting difference by the resistance.

On some sites you can find statements that blue and green ice lamps do not need resistors, since it is already built into them with a resistance of 20 ohms. Needed! In any case, this is an LED - a current device that picks up voltage on its own, and such resistance is not enough to weaken the power source.

If it is not possible to connect the lamps in series, you can ring each one separately and select those that are as close to each other as possible. Let's say right away that this is very unreliable. Yes, such lighting will last not a day, but longer, but you can basically forget about the declared 50 thousand hours.

A resistor, like a personal “nutritionist”, is needed by all LEDs.

Varieties

It is in our open spaces that you can find only 3 types:

• 12V - limiting when a specified threshold is reached;
• car - in case you decide to do some easy tuning and connect LEDs as backlight;
• snag is more of an auxiliary tool for identifying problems on the network.

How to correctly calculate voltage and resistance

For lighting technicians, this is a one-and-done task, but for everyone else, we suggest using an online service that calculates parameters based on the rated operating current.

Please note that the data obtained in the calculator will be approximate; accordingly, choose the standard denomination that is closest in value.

You don’t have to touch the calculator for LEDs if the resistor is variable or trimmer.

How to connect

Regardless of which resistor is chosen - trimmer, variable or constant, there is no difference in how it is connected. It has no polarity. The main task is internal resistance and power dissipation. If the power is exceeded, the resistor burns out. So calculate correctly and use it with pleasure.

VIDEO: Calculation of resistor for LEDs