Series connection of LEDs. Correct LED activation Serial connection of LEDs to the driver
In the diagram we see a traditional series connection of LEDs connected to a battery.
This connection assumes that the LEDs glow equally brightly. But here the resistor “interferes” with us.
Let's look at a slightly different example. Namely, let's take an LED driver and connect it to three serial LEDs.
As a result of the fact that the current strength in the closed circuit is the same, then the same current I 1 =I 2 =I 3 will flow through each diode. A connection without a resistor using a driver also ensures the same brightness, and the difference in voltage drop across the diodes does not matter meanings. It is reflected only in the magnitude of the potential difference between points 1 and 2.
Calculation of a driver for serial connection of LEDs
The series connection of LEDs described above can raise big questions about the choice of the driver itself. Using the calculation algorithm below, you can always calculate the driver yourself, depending on the selected connection.
Let's say we need to power three LEDs connected in series with a current of 700 mA.
The voltage drop (fictional) at this current is 3.2 to 3.4 V.
Minimum voltage U min =3*3.2=9.6 V
Maximum voltage U max =3.4*3=10.2 V
The power consumed by the LEDs will be: P=10.2*0.7=7.14 W.
Total: our driver must have:
Output current 700 mA
Output voltage 10.2V +- 5%
Output power no less than 7.2 W
This is all! As you can see. no problem. I will not consider calculating the resistor in the absence of a driver. These are relics of the past. Any manufacturer already produces LED drivers for every taste and color. Moreover, their cost is negligible. And the efficiency of the “box” is much greater than that of a simple resistor.
Pros and cons of daisy-chaining LEDs
There is one big plus - cheapness in design.
There are at least two disadvantages to a serial connection:
- If at least one LED fails, the entire chain will naturally go out. Here, however, you can find another plus... If the diode short-circuits, the circuit will not break and the rest of the chips will continue to work.
- If there are a lot of LEDs, then low-voltage power supply is extremely difficult to implement. And this is already a problem. Especially if you need to have safety first.
Video on serial connection of LEDs
For those who are too lazy to read a lot of books, we suggest watching a simple video on the topic: “serial connection of LEDs.” From it you will quickly gain information on how to correctly connect diodes with such a connection.
Today, LEDs are manufactured in various wattages. A wide variety of power supplies are suitable for them. It should also be taken into account that the connection of the model depends on the type of device driver (if any). Nowadays, you can find good and bad LED switching schemes. To understand this issue in more detail, you need to look at models of different capacities.
Connection to 5 V network
In a 5 V network, the LEDs (diagram shown below) are most often connected in series order. In this case, much depends on the nominal resistance in the network. If this parameter exceeds 10 Ohms, then it is more advisable to use switching power supplies.
At the same time, a pass-through capacitor will help cope with electromagnetic interference in the circuit. In this case, it is better to connect LEDs with linear resistors. In turn, open analogues can withstand a maximum resistance of 13 Ohms. To increase the conductivity of the LED, system modulators are used.
If we consider models with contact drivers, then controllers must be selected separately for them. Most often they are used with a special amplifier. In this case, the threshold voltage will be at 6 V. In order to solve the problem with negative polarity in the network, many experts recommend using operational amplifiers.
Connection to 12 V network
Connecting LEDs to 12 volts can be done either in series or in parallel. If we consider the first option, then it is more advisable to select switching type power supplies. You should also know that you can connect LEDs to 12 volts without amplifiers. However, if more than three pieces are installed, then they must be provided. Models with resonant drivers should only be connected to low-impedance amplifiers.
If we consider parallel connection of LEDs, then in this case it is important to select two open resistors for the circuit. In this case, the first of them must be installed in front of the amplifier. Its current carrying capacity must be at least 3 A. At the same time, the threshold voltage parameter in the device should not be allowed below the level of 4 A. As a rule, the negative resistance of models of this type is small. At the same time, maintaining linearity is achieved through the use of high-quality drivers.
LEDs in 220 V network
What features does connecting LEDs have in this case? 220V usually provides for a sequential order. Power supplies in this case are mainly used of the step-down type. To prevent an increase in frequency, connecting LEDs to a 220V network must be done with operational amplifiers.
It should also be taken into account that their sensitivity depends on the types of filters. In order to minimize magnetic interference, experts advise installing low-impedance filters. In this case, a lot depends on the LED driver. If we consider the analog type, then it will require a rotary regulator. To cope with nonlinear distortions in this situation, low-frequency adapters are used. They are usually installed near amplifiers.
Diagram of connecting devices to a computer
LEDs can be connected to a computer in different ways. As a rule, capacitors for this purpose are used only of the phase type. In this case, open resistors can be used, but they must withstand a threshold voltage of at least 5 V. Additionally, you should pay attention to the frequency of the LED.
If we consider standard models, they are connected to power supplies through amplifiers. In this case, resistors must be located at the end of the circuit. If we consider high-power LEDs, then they will require an integrated amplifier. In this case, drivers with high coverage are welcome. The conductivity of the device depends solely on the power of the power supply. In this case, the direct connection of the LED occurs through a surge protector.
Connection to low frequency power supply
LEDs (the diagram is shown below) can only be connected to a low-frequency power supply in a DC network. In this case, resistors are used of the open type. In this case, the minimum power of the LED must be 5 V. An amplifier for it can be selected as an operational type. If we consider models with drivers, they are often soldered together with feed-through capacitors.
In this case, the conductivity parameter is closely related to their capacitance. To enhance the sensitivity of the device, many experts advise using broadband converters. In this case, adapters for combating interference are not suitable. However, it makes sense to install different filters. Additionally, it should be noted that the regulators in the circuit can be used of both rotary and push-button types.
Connecting LEDs to a high-frequency power supply
LEDs are connected to high-frequency power supplies only through an auxiliary adapter. In this case, the type of driver plays an important role. If we consider single-pole models, they are distinguished by a high conductivity parameter. In this case, the negative resistance in the circuit should be kept at 10 ohms. If only one LED is connected, then an operational amplifier is not necessary.
Otherwise, it is better to install it to solve nonlinear distortion problems. Additionally, it should be taken into account that electrode drivers are not suitable for connection to high-frequency power supplies. This is primarily due to the high sensitivity of such devices. In this situation, the LEDs will burn out quite quickly. In this case, power regulators will not help.
Serial connection
The LEDs are connected in series using zener diodes. Finding them in stores today is quite easy. They are usually installed on a special magnetic grid. To fix them on the board you will have to use a blowtorch. It should also be taken into account that the power supply must have a powerful amplifier. In this case, many experts recommend installing resistors of the pectron type.
At the same time, they must withstand a nominal resistance level of at least 4 ohms. In turn, the load parameter is welcomed at around 20 A. The problem with magnetic interference can be solved by installing an output filter. To increase the sensitivity of the device, both variable and static capacitors are used. They differ quite a lot in size. In this regard, this issue must be approached individually each time.
Circuits with capacitive capacitors
Connecting high-power LEDs with capacitive capacitors, at first glance, is quite simple. However, in this situation, it is necessary to first take into account the power of the resistors. It is also important to remember that the parameters of LED drivers can vary quite a lot. In this regard, it is necessary to select capacitors for the device very carefully. First of all, the power supply directly to which the amplifier is connected is evaluated. If we consider modifications with a threshold voltage of 20 V, then in this case one capacitor can be used.
Otherwise, two of them are installed to solve problems with nonlinear distortion. In turn, the sensitivity of the device can always be adjusted using the controller. The drivers themselves are most often used of the pulse type. In turn, various modulators can be installed. Problems with polarity should not arise in this case. As a result, with a 20 V power supply, the threshold current must be maintained at 3 A. In this case, the frequency may fluctuate depending on voltage surges in the network.
Using snubber capacitors
Connecting LEDs with damping capacitors requires the use of 15 V power supplies. In this case, resistors are used only of the open type. As a result, the negative resistance parameter in the circuit does not exceed 30 Ohms. It should also be taken into account that LEDs can only be used at low power. The capacitors are installed directly near the power supplies. In this case, amplifiers are not required for normal operation of the device.
Due to the high sensitivity of the models, their threshold voltage is at least 15 V. Moreover, the maximum load depends on the power of the LEDs. Drivers for models are usually selected of the latitudinal type. Solving the problem with negative polarity in such a situation can be quite simple. Filters for this purpose should be installed behind amplifiers. Also in this case, integral tetrodes will help solve the problem.
Application of absorption filters
Filters of this type are most suitable for 20 V LEDs. Moreover, with pulse blocks they are not able to work with power. Additionally, it should be taken into account that they do not solve problems with nonlinear distortions. In turn, filters can stabilize frequency quite quickly. Due to this, problems with sensitivity in such models are very rare.
LEDs with wave receivers
LEDs of this type are usually connected directly to power supplies. In this case, amplifiers in the network are not required. However, in this case it is important to remember the type of resistor. If it is used open, filters will have to be installed. Additionally, it should be taken into account that these receivers are ideal for serial connection of LEDs. In this case, parallel connection can provoke nonlinear distortions. The sensitivity of the device will depend on the input voltage parameter.
LEDs with magnetic drivers
LEDs with magnetic drivers are usually connected in series order. At the first stage, it is very important to evaluate their power. Additionally, the negative resistance parameter in the circuit should be taken into account. If we consider low-power models, they are connected to power supplies through an amplifier. Otherwise, it is better to use surge protectors.
In this case, absorption modifications can lead to magnetic interference. How to solve problems with increased frequency in this case? Experts recommend using single-channel resistors. In this case, you can select a wide variety of modulators for the circuit.
The thing is that this lighting is not only quite powerful, but also cost-effective. LEDs are semiconductor diodes in an epoxy shell.
Initially they were quite weak and expensive. But later very bright white and blue diodes were released into production. By that time, their market price had decreased. On this moment There are LEDs of almost any color, which is the reason for their use in various fields of activity. These include lighting of various rooms, backlighting of screens and signs, use on road signs and traffic lights, in the interior and headlights of cars, in mobile phones, etc.
Description
LEDs consume little electricity, as a result of which such lighting is gradually replacing previously existing light sources. In specialized stores you can purchase various items based on LED lighting, ranging from a regular lamp and LED strip to what they all have in common is that they require a current of 12 or 24 V to connect them.
Unlike other light sources that use a heating element, this one uses a semiconductor crystal that generates optical radiation when exposed to current.
To understand the circuits for connecting LEDs to a 220V network, you must first say that it cannot be powered directly from such a network. Therefore, to work with LEDs, you need to follow a certain sequence of connecting them to a high voltage network.
Electrical properties of LED
The current-voltage characteristic of an LED is a steep line. That is, if the voltage increases even slightly, the current will increase sharply, which will cause the LED to overheat and subsequently burn out. To avoid this, it is necessary to include a limiting resistor in the circuit.
But it is important not to forget about the maximum permissible reverse voltage of LEDs of 20 V. And if it is connected to a network with reverse polarity, it will receive an amplitude voltage of 315 volts, that is, 1.41 times more than the current one. The fact is that the current in the 220-volt network is alternating, and it will initially go in one direction, and then back.
In order to prevent the current from moving in the opposite direction, the LED switching circuit should be as follows: a diode is connected to the circuit. It will not allow reverse voltage to pass through. In this case, the connection must be parallel.
Another scheme for connecting an LED to a 220 volt network is to install two LEDs back-to-back.
As for mains power with a quenching resistor, this is not the best option. Because the resistor will release strong power. For example, if you use a 24 kOhm resistor, the power dissipation will be approximately 3 W. When a diode is connected in series, the power will be halved. The reverse voltage on the diode should be 400 V. When two counter LEDs are turned on, you can install two two-watt resistors. Their resistance should be half as much. This is possible when there are two crystals in one package different colors. Usually one crystal is red, the other green.
In the case when a 200 kOhm resistor is used, the presence of a protective diode is not required, since the reverse current is small and will not cause destruction of the crystal. This scheme for connecting LEDs to the network has one drawback - the low brightness of the light bulb. It can be used, for example, to illuminate a room switch.
Due to the fact that the current in the network is alternating, this allows you to avoid wasting electricity on heating the air using a limiting resistor. A capacitor copes with this task. After all, it passes alternating current and does not heat up.
It is important to remember that both half-cycles of the network must pass through the capacitor in order for it to pass alternating current. And since the LED conducts current only in one direction, it is necessary to place a regular diode (or an additional LED) counter-parallel to the LED. Then he will miss the second half-period.
When the circuit for connecting the LED to a 220-volt network is turned off, voltage will remain on the capacitor. Sometimes even the full amplitude is 315 V. This threatens with an electric shock. To avoid this, you need to provide, in addition to the capacitor, a high-value discharge resistor, which, if disconnected from the network, will instantly discharge the capacitor. During normal operation, an insignificant current flows through this resistor, which does not heat it up.
To protect against pulsed charging current and as a fuse, we install a low-resistance resistor. The capacitor must be special, which is designed for a circuit with an alternating current of at least 250 V, or 400 V.
The sequential LED switching scheme involves installing a light bulb from several LEDs connected in series. For this example, one counter diode is sufficient.
Since the voltage drop across the resistor will be less, the total voltage drop across the LEDs must be subtracted from the power source.
It is necessary that the installed diode be designed for a current similar to the current passing through the LEDs, and the reverse voltage must be equal to the sum of the voltages on the LEDs. It is best to use an even number of LEDs and connect them back-to-back.
There can be more than ten LEDs in one chain. To calculate the capacitor, you need to subtract the amount of the LED voltage drop from the amplitude voltage of the 315 V network. As a result, we find out the number of voltage drops across the capacitor.
LED connection errors
- The first mistake is when you connect an LED without a limiter, directly to the source. In this case, the LED will fail very quickly due to lack of control over the current value.
- The second mistake is connecting LEDs installed in parallel to a common resistor. Due to the scattering of parameters, the brightness of the LEDs will be different. In addition, if one of the LEDs fails, the current of the second LED will increase, which may cause it to burn out. So when a single resistor is used, the LEDs must be connected in series. This allows you to leave the current the same when calculating the resistor and adding up the LED voltages.
- The third mistake is when LEDs, which are designed for different currents, are switched on in series. This causes one of them to burn weakly, or, on the contrary, to wear out.
- The fourth mistake is using a resistor that does not have enough resistance. This will cause the current flowing through the LED to be too high. Some of the energy, when the current voltage is too high, is converted into heat, resulting in overheating of the crystal and a significant reduction in its service life. The reason for this is defects in the crystal lattice. If the current voltage increases further and the pn junction heats up, this will lead to a decrease in the internal quantum efficiency. As a result, the brightness of the LED will decrease and the crystal will be destroyed.
- The fifth mistake is turning on the LED at 220V, the circuit of which is very simple, in the absence of reverse voltage limitation. The maximum allowable reverse voltage for most LEDs is approximately 2V, and the reverse half-cycle voltage affects the voltage drop, which is equal to the supply voltage when the LED is off.
- The sixth reason is the use of a resistor whose power is insufficient. This provokes strong heating of the resistor and the process of melting the insulation that touches its wires. Then the paint begins to burn and destruction occurs under the influence of high temperatures. This is because the resistor dissipates only the power for which it was designed.
Power LED connection circuit
To connect high-power LEDs, you need to use AC/DC converters that have a stabilized current output. This will help eliminate the need for a resistor or LED driver IC. At the same time, we will be able to achieve simple connection of LEDs, comfortable use of the system and reduced cost.
Before connecting high-power LEDs to the mains, make sure that they are securely connected to the current source. Do not connect the system to a power supply that is live, otherwise it will damage the LEDs.
LEDs 5050. Characteristics. Connection diagram
Low-power LEDs also include surface LEDs. They are most often used to illuminate buttons on a mobile phone or for decorative LED strips.
LEDs 5050 (case size: 5 by 5 mm) are semiconductor light sources, the forward voltage of which is 1.8-3.4 V, and the forward current per crystal is up to 25 mA. The special feature of SMD 5050 LEDs is that their design consists of three crystals, which allow the LED to emit multiple colors. They are called RGB LEDs. Their body is made of heat-resistant plastic. The diffusion lens is transparent and filled with epoxy resin.
In order for 5050 LEDs to last as long as possible, they must be connected to the resistance ratings in series. For maximum reliability of the circuit, it is better to connect a separate resistor to each chain.
Schemes for switching on flashing LEDs
A flashing LED is an LED in which an integral flashing frequency is built in. Its flash frequency ranges from 1.5 to 3 Hz.
Despite the fact that the flashing LED is quite compact, it contains a semiconductor generator chip and additional elements.
As for the voltage of the flashing LED, it is universal and can vary. For example, for high-voltage it is 3-14 volts, and for low-voltage it is 1.8-5 volts.
Accordingly, the positive qualities of a flashing LED include, in addition to the small size and compactness of the light signaling device, also a wide range of permissible current voltage. In addition, it can emit different colors.
In certain types of flashing LEDs, about three multi-colored LEDs are built in, which have different flash frequencies.
Flashing LEDs are also quite economical. The fact is that electronic circuit turning on the LED is made on MOS structures, thanks to which a flashing diode can replace a separate functional unit. Due to their small size, flashing LEDs are often used in compact devices that require small radio elements.
In the diagram, flashing LEDs are indicated in the same way as regular ones, the only exception is that the arrow lines are not just straight, but dotted. Thus, they symbolize the blinking of the LED.
Through the transparent body of the flashing LED you can see that it consists of two parts. There, on the negative terminal of the cathode base there is a light-emitting diode crystal, and on the anode terminal there is a generator chip.
All components of this device are connected using three golden wire jumpers. To distinguish a flashing LED from a regular one, just hold the transparent housing up to the light. There you can see two substrates of the same size.
On one substrate there is a crystal cube of a light emitter. It consists of a rare earth alloy. In order to increase the luminous flux and focusing, as well as to form the radiation pattern, a parabolic aluminum reflector is used. This reflector in a flashing LED is smaller in size than in a regular one. This is due to the fact that in the second half of the case there is a substrate with an integrated circuit.
These two substrates are connected to each other using two golden wire jumpers. As for the body of the flashing LED, it can be made of either light-diffusing matte plastic or transparent plastic.
Due to the fact that the emitter in a flashing LED is not located on the axis of symmetry of the housing, for the functioning of uniform illumination it is necessary to use a monolithic colored diffuse light guide.
The presence of a transparent body can only be found in flashing LEDs of large diameter, which have a narrow radiation pattern.
The flashing LED generator consists of a high-frequency master oscillator. Its operation is constant, and the frequency is about 100 kHz.
Along with the high-frequency generator, a divider based on logical elements also functions. He, in turn, carries out high frequency division up to 1.5-3 Hz. The reason for the combined use of a high-frequency generator with a frequency divider is that for the low-frequency generator to operate, it is necessary to have a capacitor with the largest capacitance for the timing circuit.
Bringing the high frequency to 1-3 Hz requires the presence of dividers on logic elements. And they can be used quite easily in a small space of a semiconductor crystal. On the semiconductor substrate, in addition to the divider and the master high-frequency oscillator, there is a protective diode and an electronic switch. A limiting resistor is built into flashing LEDs, which are designed for voltages from 3 to 12 volts.
Low Voltage Flashing LEDs
As for low-voltage flashing LEDs, they do not have a limiting resistor. When reversing the power supply, a protective diode is required. It is necessary in order to prevent the microcircuit from failure.
In order for the operation of high-voltage flashing LEDs to be long-lasting and uninterrupted, the supply voltage should not exceed 9 volts. If the current voltage increases, the power dissipation of the blinking LED will increase, which will lead to heating of the semiconductor crystal. Subsequently, due to excessive heat, the blinking LED will begin to degrade.
When it is necessary to check the serviceability of a flashing LED, in order to do this safely, you can use a 4.5 volt battery and a 51 ohm resistor connected in series with the LED. The resistor power must be at least 0.25 W.
LED installation
LED installation is very important question for the reason that it is directly related to their viability.
Since LEDs and microcircuits do not like static and overheating, parts must be soldered as quickly as possible, no more than five seconds. In this case, you need to use a low-power soldering iron. The temperature of the tip should not exceed 260 degrees.
When soldering, you can additionally use medical tweezers. The LED is clamped closer to the body with tweezers, which creates additional heat removal from the crystal during soldering. To prevent the LED legs from breaking, they should not be bent too much. They must remain parallel to each other.
In order to avoid overload or short circuit, the device must be equipped with a fuse.
Smooth LED switching circuit
The scheme for smoothly turning on and off the LEDs is popular among others; car owners who want to tune their cars are interested in it. This circuit is used to illuminate the interior of a car. But this is not its only use. It is used in other areas as well.
A simple LED soft-start circuit should consist of a transistor, a capacitor, two resistors and LEDs. It is necessary to select current-limiting resistors that can pass a current of 20 mA through each chain of LEDs.
The circuit for smoothly turning on and off the LEDs will not be complete without a capacitor. It is he who allows it to be collected. The transistor must be a pnp structure. And the collector current should not be less than 100 mA. If the LED smooth switching circuit is assembled correctly, then using the example of car interior lighting, the LEDs will switch on smoothly in 1 second, and after the doors are closed, they will switch off smoothly.
Alternately turning on the LEDs. Scheme
One of the lighting effects using LEDs is their alternate switching on. It is called running fire. This circuit operates on autonomous power supply. For its design, a conventional switch is used, which supplies power voltage alternately to each of the LEDs.
Let's consider a device consisting of two microcircuits and ten transistors, which together make up the master oscillator, control and indexing itself. From the output of the master oscillator, the pulse is transmitted to the control unit, also known as a decimal counter. Then the voltage goes to the base of the transistor and opens it. The anode of the LED is connected to the positive of the power source, which leads to a glow.
The second pulse forms a logical one at the next output of the counter, and a low voltage appears at the previous one and closes the transistor, causing the LED to go out. Then everything happens in the same sequence.
Quite often we have to face this question - how to connect LEDs to 220 V, or simply to the electrical network AC voltage. As such, directly connecting the diode directly to the network does not carry any meaning. Even when using certain schemes, we will not get the desired effect.
If we need to connect an LED to a constant voltage network, then this problem can be solved very simply - we install a limiting resistor and forget about it. The LED worked in the forward direction and will continue to work.
If we need to use a 220 V network for LED connections, then it will already be affected by reverse polarity. This can be clearly seen by looking at the graph of a sinusoid, where each half-cycle of the sinusoid tends to change its sign to the opposite one. 
In this case, we will not get a glow in this half-cycle. In principle, it’s okay))), but the LED will fail very quickly.
In general, the quenching resistor should be chosen based on the design voltage condition of 310 V. Explaining why this is so is a tedious task, but it’s worth just remembering this, because The effective voltage value is 220 V, and the amplitude already increases by the root of two from the effective value. Those. this way we get the applied forward and reverse voltage to the LED. The resistor is selected at 310V of reverse polarity in order to protect the LED. We will see below how protection can be carried out.
How to connect LEDs to 220 V using a simple circuit using resistors and a diode - option 1
The first circuit operates on the principle of reverse half-cycle cancellation. The vast majority of semiconductors are negative about reverse voltage. To block it we need a diode. As a rule, in most cases diodes of the IN4004 type are used, designed for voltages greater than 300 V. 
Connecting LED using a simple circuit with a resistor and diode - option 2
Another simple circuit shows how to connect LEDs to 220 V AC voltage is not much more complicated and can also be classified as a simple circuit. 
Let's consider the principle of operation. With a positive half-wave, the current flows through resistors 1 and 2, as well as the LED itself. In this case, it is worth remembering that the voltage drop across the LED will be the opposite for a conventional diode - VD1. As soon as the negative half-wave of 220 V “enters” the circuit, the current will flow through a conventional diode and resistors. In this case, the direct voltage drop across VD1 will be opposite to the LED. It's simple.
With a positive half-wave of the mains voltage, current flows through resistors R1, R2 and LED HL1 (in this case, the forward voltage drop across LED HL1 is the reverse voltage for diode VD1). With a negative half-wave of the mains voltage, current flows through diode VD1 and resistors R1, R2 (in this case, the forward voltage drop across diode VD1 is the reverse voltage for LED HL1).
Calculation part of the scheme
Rated mains voltage:
U S.NOM = 220 V
The minimum and maximum network voltage is accepted (experienced data):
U S.MIN = 170 V
U C.MAX = 250 V
The HL1 LED with the maximum permissible current is accepted for installation:
I HL1.DOP = 20 mA
Maximum calculated peak current of LED HL1:
I HL1.AMP.MAX = 0.7*I HL1.ADP = 0.7*20 = 14 mA
Voltage drop across LED HL1 (experienced data):
Minimum and maximum effective voltage on resistors R1, R2:
U R.RMS.MIN = U S.MIN = 170 V
U R.RMS.MAX = U C.MAX = 250 V
Calculated equivalent resistance of resistors R1, R2:
R EQ.CALC = U R.AMP.MAX /I HL1.AMP.MAX = 350/14 = 25 kOhm
P R.MAX = U R.RMS.MAX 2 /R EQ.CALC = 2502/25 = 2500 mW = 2.5 W
Estimated total power of resistors R1, R2:
P R.CALC = P R.MAX /0.7 = 2.5/0.7 = 3.6 W
A parallel connection of two MLT-2 type resistors having a total maximum permissible power is accepted:
P R.ADOP = 2 2 = 4 W
Calculated resistance of each resistor:
R CALC = 2*R EQ.CALC = 2*25 = 50 kOhm
The nearest higher standard resistance of each resistor is taken:
R1 = R2 = 51 kOhm
Equivalent resistance of resistors R1, R2:
R EKV = R1/2 = 51/2 = 26 kOhm
Maximum total power of resistors R1, R2:
P R.MAX = U R.RMS.MAX 2 /R EQ = 2502/26 = 2400 mW = 2.4 W
Minimum and maximum peak current of LED HL1 and diode VD1:
I HL1.AMP.MIN = I VD1.AMP.MIN = U R.AMP.MIN /R EQ = 240/26 = 9.2 mA
I HL1.AMP.MAX = I VD1.AMP.MAX = U R.AMP.MAX /R EQ = 350/26 = 13 mA
Minimum and maximum average current of LED HL1 and diode VD1:
I HL1.AVG.MIN = I VD1.AVG.MIN = I HL1.ACTIVE.MIN /K F = 3.3/1.1 = 3.0 mA
I HL1.SR.MAX = I VD1.SR.MAX = I HL1.ACTIVE MAX /K F = 4.8/1.1 = 4.4 mA
Diode reverse voltage VD1:
U VD1.REV = U HL1.PR = 2 V
Design parameters of diode VD1:
U VD1.CALC = U VD1.REV /0.7 = 2/0.7 = 2.9 V
I VD1.CALC = U VD1.AMP.MAX /0.7 = 13/0.7 = 19 mA
A VD1 diode of type D9V is accepted, which has the following basic parameters:
U VD1.ADOP = 30 V
I VD1.DOP = 20 mA
I 0.MAX = 250 µA
Disadvantages of using a diagram for connecting LEDs to 220 V according to option 2
The main disadvantages of connecting LEDs using this scheme are the low brightness of the LEDs due to the low current. I HL1.SR = (3.0-4.4) mA and high power on resistors: R1, R2: P R.MAX = 2.4 W.
Option 3 for connecting LEDs to a 220 V AC electrical network
With a positive half-cycle, current flows through resistor R1, the diode and the LED. When negative, no current flows, because In this case, the diode is switched in the reverse direction. 
The calculation of the circuit parameters is similar to the second option. Whoever needs it will count and compare. The difference is small.
Disadvantages of connecting using option 3
If the most “inquisitive minds” have already done the math, they can compare the data with the second option. Those who are too lazy will have to take their word for it. The disadvantage of this connection is also the low brightness of the LED, because the current flowing through the semiconductor is only I HL1.SR = (2.8-4.2) mA.
But with this scheme we get a noticeable reduction in the power of the resistor: P R1.MAX = 1.2 W instead of 2.4 W obtained earlier.
Connecting a 220 V LED using a diode bridge - option 4
As you can see in the graphic picture, in this case we use resistors and a diode bridge to connect to 220.
In this case, the current will flow through 2 resistors and the LED with both positive and negative half-waves of the sinusoid due to the use of a rectifier bridge on diodes VD1-VD4.
U VD.CALC = U VD.REV /0.7 = 2.6/0.7 = 3.7 V
I VD.CALC = U VD.AMP.MAX /0.7 = 13/0.7 = 19 mA
Diodes VD1-VD4 type D9V are accepted, having the following basic parameters:
U VD.ADP = 30 V
I VD.ADP = 20 mA
I 0.MAX = 250 µA
Disadvantages of the connection scheme according to option 4
However, with this scheme we will get a noticeable increase in the brightness of the LED: HL1: I HL1.SR = (5.9-8.7) mA instead of (2.8-4.2) mA
In principle, these are the most common circuits that show us how to connect LEDs to 220 V using a conventional diode and resistors. For ease of understanding, calculations have been provided. Not for everyone, maybe understandable, but whoever needs it will find it, read it and understand it. Well, if not, then a simple graphic part will be enough.
How to connect an LED to 220 V using a capacitor
Above we looked at how easy it is, using only diodes and resistors, to connect any LED to a 220 V network. These were simple diagrams. Now let's look at more complex ones, but better in terms of implementation and durability. For this we need a capacitor.
The current limiting element is a capacitor. In the diagram - C1. The capacitor must be designed to operate with a voltage of at least 400 V. After charging the latter, the current through it will be limited by a resistor. 
Connecting an LED to a 220 V network using the example of a backlit switch
Nowadays you won’t surprise anyone with a switch with integrated LED lighting. Having disassembled it and figured it out, we will get another way, thanks to which we can connect any LED to a 220 V network. 
All illuminated switches use a resistor rated at least 20 kOhm. The current in this case is limited to about 1A. When connected to the network, this LED will glow. At night it can be easily distinguished on the wall. The reverse current in this case will be very small and will not damage the semiconductor. In principle, such a circuit also has a right to exist, but the light from such a diode will still be negligibly small. And whether the game is worth the candle is not clear.
Video on connecting an LED to a 220 V network
Well, at the end of this entire long post, let’s watch a video on the topic: “how to connect LEDs to 220 V.” For those who are too lazy to read everything.
Previous articles have described various LED connection issues. But you can’t write everything in one article, so you’ll have to continue this topic. Here we will talk about different ways to turn on LEDs.
As stated in the mentioned articles, i.e. the current through it must be limited using a resistor. How to calculate this resistor has already been described, we will not repeat it here, but, just in case, we will present the formula again.
Picture 1.
Here Upit. - supply voltage, Upad. - voltage drop across the LED, R - resistance of the limiting resistor, I - current through the LED.
However, despite all the theory, the Chinese industry produces all kinds of souvenirs, key rings, lighters, in which the LED is turned on without a limiting resistor: just two or three disk batteries and one LED. In this case, the current is limited by the internal resistance of the battery, the power of which is simply not enough to burn out the LED.
But here, in addition to burnout, there is one more unpleasant property - the degradation of LEDs, which is most characteristic of white and blue LEDs: after some time, the brightness of the glow becomes very insignificant, although the current flows through the LED is quite sufficient, at the nominal level.
This is not to say that it does not shine at all, the glow is barely noticeable, but this is no longer a flashlight. If at the rated current degradation occurs no earlier than after a year of continuous glow, then at an increased current this phenomenon can be expected in half an hour. This inclusion of the LED should be called bad.
Such a scheme can only be explained by the desire to save on one resistor, solder, and labor costs, which is apparently justified given the massive scale of production. In addition, a lighter or keychain is a disposable item, cheap: if the gas runs out or the battery runs out, the souvenir is simply thrown away.
Figure 2. The scheme is bad, but it is used quite often.
Very interesting things happen (by accident, of course) if you connect an LED to a power supply with an output voltage of 12V and a current of at least 3A using this circuit: a blinding flash occurs, a fairly loud bang and smoke is heard, and a suffocating smell remains. This brings to mind this parable: “Is it possible to look at the Sun through a telescope? Yes, but only twice. Once with the left eye, once with the right.” By the way, connecting an LED without a limiting resistor is the most common mistake made by beginners, and I would like to warn you about it.
To correct this situation and extend the life of the LED, the circuit should be slightly changed.
Figure 3. Good diagram, correct.
This is the scheme that should be considered good or correct. To check whether the value of resistor R1 is indicated correctly, you can use the formula shown in Figure 1. We will assume that the voltage drop across the LED is 2V, the current is 20mA, the supply voltage is 3V due to the use of two AA batteries.
In general, there is no need to try to limit the current to the maximum permissible level of 20 mA; you can power the LED with a lower current, well, at least 15...18 milliamps. In this case, there will be a very slight decrease in brightness, which the human eye, due to the characteristics of the device, will not notice at all, but the service life of the LED will increase significantly.
Another example of poor inclusion of LEDs can be found in various flashlights, which are already more powerful than key fobs and lighters. In this case, a certain number of LEDs, sometimes quite large, are simply connected in parallel, and also without a limiting resistor, which again acts as the internal resistance of the battery. Such flashlights quite often end up in repair precisely because the LEDs burn out.
Figure 4. Very bad switching circuit.
It would seem that the situation can be corrected by the circuit shown in Figure 5. Just one resistor, and things seemed to be getting better.
Figure 5. This is a little better.
But even such inclusion will help little. The fact is that in nature you simply cannot find two identical semiconductor devices. This is why, for example, transistors of the same type have different gains, even if they are from the same production batch. Thyristors and triacs are also different. Some open easily, while others are so difficult that they have to be abandoned. The same can be said about LEDs - it is simply impossible to find two absolutely identical, much less three or a whole bunch.
A note on the topic. In DataSheet on LED assembly SMD-5050 (three independent LEDs in one housing) switching shown in Figure 5 is not recommended. They say that due to the variation in the parameters of individual LEDs, there may be a noticeable difference in their glow. And it would seem, in one building!
LEDs, of course, do not have any gain, but they do have such an important parameter as forward voltage drop. And even if the LEDs are taken from the same technological batch, from the same package, then there simply will not be two identical ones. Therefore, the current for all LEDs will be different. The LED whose current will be the highest, and sooner or later exceeds the rated one, will burn out first.
Due to this unfortunate event, all possible current will flow through the two surviving LEDs, naturally exceeding the rated one. After all, the resistor was designed “for three,” for three LEDs. An increased current will cause increased heating of the LED crystals, and the one that turns out to be “weaker” will also burn out. The last LED also has no choice but to follow the example of his comrades. This is how a chain reaction turns out.
In this case, the word “burn” simply means breaking the circuit. But it may happen that in one of the LEDs there is simply a short circuit, shunting the other two LEDs. Naturally, they will definitely go out, although they will remain alive. With such a malfunction, the resistor will heat up intensely and eventually, perhaps, burn out.
To prevent this from happening, the circuit needs to be slightly changed: for each LED, install its own resistor, as shown in Figure 6.
Figure 6. This is how LEDs will last a very long time.
Here everything is as required, everything is according to the rules of circuit design: the current of each LED will be limited by its own resistor. In such a circuit, the currents through the LEDs are independent of each other.
But this inclusion does not cause much delight, since the number of resistors is equal to the number of LEDs. I would like there to be more LEDs and fewer resistors. How to be?
The way out of this situation is quite simple. Each LED must be replaced with a chain of LEDs connected in series, as shown in Figure 7.
Figure 7. Parallel connection of garlands.
The price for such an improvement will be an increase in supply voltage. If only three volts are enough for one LED, then even two LEDs connected in series cannot be lit by such voltage. So what voltage will be needed to turn on a garland of LEDs? Or in other words, how many LEDs can be connected to a power source with a voltage of, for example, 12V?
Comment. Hereinafter, the name “garland” should be understood not only as a Christmas tree decoration, but also as any LED lighting device in which the LEDs are connected in series or parallel. The main thing is that there is more than one LED. Garland, it’s a garland in Africa too!
To answer this question, simply divide the supply voltage by the voltage drop across the LED. In most cases, this voltage is assumed to be 2V in calculations. Then it turns out 12/2=6. But we must not forget that some part of the voltage must remain for the quenching resistor, at least 2 volts.
It turns out that only 10V remains for the LEDs, and the number of LEDs will become 10/2=5. In this state of affairs, in order to obtain a current of 20mA, the limiting resistor must have a nominal value of 2V/20mA = 100 Ohm. The resistor power will be P=U*I=2V*20mA=40mW.
This calculation is quite fair if the direct voltage of the LEDs in the garland, as indicated, is 2V. It is this value that is often taken in calculations as some average. But in fact, this voltage depends on the type of LEDs and the color of the glow. Therefore, when calculating garlands, you should focus on the type of LEDs. The voltage drops for different types of LEDs are given in the table shown in Figure 8.
Figure 8. Voltage drop across LEDs of different colors.
Thus, with a power supply voltage of 12V, minus the voltage drop across the current-limiting resistor, a total of 10/3.7 = 2.7027 white LEDs can be connected. But you can’t cut a piece from an LED, so you can only connect two LEDs. This result is obtained if we take the maximum voltage drop value from the table.
If we substitute 3V in the calculation, then it is quite obvious that it is possible to connect three LEDs. In this case, each time you will have to painstakingly recalculate the resistance of the limiting resistor. If real LEDs turn out to have a voltage drop of 3.7V, or maybe higher, three LEDs may not light up. So it's better to stop at two.
It doesn’t matter in principle what color the LEDs will be, it’s just that when calculating you will have to take into account different voltage drops depending on the color of the LED. The main thing is that they are designed for one current. It is impossible to assemble a series garland of LEDs, some of which have a current of 20 mA, and the other part of which have a current of 10 milliamps.
It is clear that at a current of 20mA, LEDs with a rated current of 10mA will simply burn out. If you limit the current to 10 mA, then the 20 milliamp ones will not light up brightly enough, much like in a switch with an LED: you can see it at night, but not during the day.
To make their lives easier, radio amateurs develop various calculator programs that make all kinds of routine calculations easier. For example, programs for calculating inductances, filters various types, current stabilizers. There is such a program for calculating LED garlands. A screenshot of such a program is shown in Figure 9.
Figure 9. Screenshot of the program “Calculation_resistance_of_resistor__Ledz_”.
The program works without installation on the system, you just need to download it and use it. Everything is so simple and clear that no explanation is required for the screenshot. Naturally, all LEDs must be the same color and with the same current.
Limiting resistors are, of course, good. But only when it is known that this garland will be powered by a constant voltage of 12V, and the current through the LEDs will not exceed the calculated value. But what if there is simply no source with a voltage of 12V?
This situation may arise, for example, in a truck with a 24V on-board voltage. A current stabilizer, for example, “SSC0018 - Adjustable current stabilizer 20..600mA” will help to get out of such a crisis situation. Its appearance is shown in Figure 10. Such a device can be purchased in online stores. The asking price is 140...300 rubles: it all depends on the imagination and arrogance of the seller.
Figure 10. SSC0018 Adjustable Current Stabilizer
Specifications stabilizer are shown in Figure 11.
Figure 11. Technical characteristics of the current stabilizer SSC0018
The SSC0018 current stabilizer was originally developed for use in LED lamps, but can also be used for charging small batteries. Using the SSC0018 device is quite simple.
The load resistance at the output of the current stabilizer can be zero; you can simply short-circuit the output terminals. After all, stabilizers and current sources are not afraid of short circuits. In this case, the output current will be rated. If you set 20mA, then that’s what it will be.
From the above we can conclude that a DC milliammeter can be “directly” connected to the output of the current stabilizer. Such a connection should be started from the largest measurement limit, because no one knows what current is regulated there. Next, simply rotate the trimming resistor to set the required current. In this case, of course, do not forget to connect the SSC0018 current stabilizer to the power supply. Figure 12 shows the SSC0018 circuit diagram for powering LEDs connected in parallel.
Figure 12: Connections for powering LEDs connected in parallel
Everything is clear here from the diagram. For four LEDs with a current consumption of 20mA for each, the output of the stabilizer must be set to 80mA. In this case, the input of the SSC0018 stabilizer will require a voltage slightly greater than the voltage drop across one LED, as mentioned above. Of course, a higher voltage will do, but this will only lead to additional heating of the stabilizer chip.
Comment. If, to limit the current using a resistor, the voltage of the power supply must exceed the total voltage on the LEDs slightly, only two volts, then for normal operation of the SSC0018 current stabilizer this excess must be slightly higher. No less than 3...4V, otherwise the stabilizer control element simply will not open.
Figure 13 shows the connection of the SSC0018 stabilizer when using a garland of several LEDs connected in series.
Figure 13. Power supply of a serial garland through the SSC0018 stabilizer
The figure is taken from the technical documentation, so let's try to calculate the number of LEDs in the garland and the constant voltage required from the power supply.
The current indicated in the diagram, 350 mA, allows us to conclude that the garland is assembled from powerful white LEDs, because, as was said just above, the main purpose of the SSC0018 stabilizer is lighting sources. The voltage drop across the white LED is within 3...3.7V. For calculation, you should take the maximum value of 3.7V.
The maximum input voltage of the SSC0018 stabilizer is 50V. We subtract from this value the 5V required for the operation of the stabilizer itself, leaving 45V. With this voltage you can “illuminate” 45/3.7=12.1621621... LEDs. Obviously this needs to be rounded to 12.
The number of LEDs may be less. Then the input voltage will have to be reduced (the output current will not change, and 350mA will remain as it was adjusted), why supply 50V to 3 LEDs, even powerful ones? Such mockery can end in failure, because powerful LEDs are by no means cheap. Anyone who wants to, and they will always be found, can calculate for themselves what voltage is required to connect three powerful LEDs.
The adjustable current stabilizer SSC0018 device is quite good. But the whole question is, is it always necessary? And the price of the device is somewhat confusing. What could be the way out of this situation? Everything is very simple. An excellent current stabilizer is obtained from integrated voltage stabilizers, for example, the 78XX or LM317 series.
To create such a current stabilizer based on a voltage stabilizer, you will need only 2 parts. Actually, the stabilizer itself and one single resistor, the resistance and power of which can be calculated by the StabDesign program, a screenshot of which is shown in Figure 14.
Figure14. Calculation of a current stabilizer using the StabDesign program.
The program does not require any special explanation. In the Type drop-down menu, select the stabilizer type, set the required current in the In line and press the Calculate button. The result is the resistance of resistor R1 and its power. In the figure, the calculation was carried out for a current of 20 mA. This is for the case when the LEDs are connected in series. For parallel connection The current is calculated in the same way as shown in Figure 12.
The LED garland is connected instead of the resistor Rн, symbolizing the load of the current stabilizer. It is even possible to connect just one LED. In this case, the cathode is connected to the common wire, and the anode to resistor R1.
The input voltage of the considered current stabilizer is in the range of 15...39V, since a 7812 stabilizer with a stabilization voltage of 12V is used.
It would seem that this is where the story about LEDs can end. But there is more LED strips, which will be discussed in the next article.
