The most correct connection of several LEDs is in series. Now I will explain why.

The fact is that the determining parameter of any LED is its operating current. It is the current through the LED that determines what the power (and therefore the brightness) of the LED will be. It is the excess of the maximum current that leads to an excessive increase in the temperature of the crystal and failure of the LED - rapid burnout or gradual irreversible destruction (degradation).

Current is the main thing. It is indicated in the technical characteristics of the LED (datasheet). And depending on the current, the LED will have one voltage or another. Voltage can also be found in the reference data, but it is usually indicated in the form of a certain range, because it is secondary.

Serial connection

When LEDs are connected in series, the same current flows through them. The number of LEDs does not matter, it could be just one LED, or it could be 20 or even 100 pieces.

For example, we can take one 2835 LED and connect it to a 180mA driver and the LED will operate normally, delivering its maximum power. Or we can take a garland of 10 of the same LEDs, and then each LED will also work in normal passport mode (but the total power of the lamp, of course, will be 10 times greater).

Below are two LED switching circuits, pay attention to the difference in voltage at the driver output:

So to the question of how the LEDs should be connected, serial or parallel, there can only be one correct answer - of course, serial!

The number of LEDs connected in series is limited only by the capabilities of the driver itself.

Ideal driver can endlessly increase the voltage at its output to provide the required current through the load, so an infinite number of LEDs can be connected to it. Well, real devices, unfortunately, have a voltage limit not only from above, but also from below.

Here is an example of a finished device:

We see that the driver is able to regulate the output voltage only within the range of 64...106 volts. If to maintain a given current (350 mA) you need to raise the voltage above 106 volts, then it’s a bummer. The driver will output its maximum (106V), and what the current will be is no longer dependent on it.

And, conversely, you cannot connect too few LEDs to such an LED driver. For example, if you connect a chain of 10 LEDs connected in series to it, the driver will not be able to lower its output voltage to the required 32-36V. And all ten LEDs will most likely just burn out.

The presence of a minimum voltage is explained (depending on the circuit design) by limitations on the power of the output control element or by exceeding the limiting generation modes of the pulse converter.

Of course, drivers can be for any input voltage, not necessarily 220 volts. Here, for example, is a driver that converts any source permanent voltage (power supply) from 6 to 20 volts into a 3 A current source:

That's all. Now you know how to turn on an LED (one or more) - either through a current-limiting resistor or through a current-setting driver.

How to choose the right driver?

Everything is very simple here. You only need to choose according to three parameters:

1. output current;
2. maximum output voltage;
3. minimum output voltage.

Output (operating) current of the LED driver- this is the most important characteristic. The current should be equal to the optimal current for LEDs.

For example, we had 10 full-spectrum LEDs at our disposal for:

The rated current of these diodes is 700 mA (taken from the reference book). Therefore, we need a 700 mA current driver. Well, or a little less to extend the life of the LEDs.

Driver maximum output voltage must be greater than the total forward voltage of all LEDs. For our phytoLEDs, the forward voltage is in the range of 3...4 volts. We take it to the maximum: 4V x 10 = 40V. Our driver must be able to output at least 40 volts.

How to connect an LED to 12 volts? Just as easy as 9:00. The LEDs are connected to via a limiting resistor. The whole problem lies in the correct calculation of the resistance for the LED.

LEDs 12 volts

At connecting the LED to 12 volts First we find out what kind of LED we need to connect. As a rule, conventional LEDs have a voltage drop of 2 volts (blue and white LEDs have 4 volts each). You also need to know the operating current of the LED. This is usually 10 or 20 mA. We will assume that we have a red LED that requires 2 volts of power and a current of 20 mA.

If the voltage drop on the LED is 2 volts with a 12 volt supply, we are left with 10 volts, which we need to extinguish with a resistor. We need to calculate its resistance.

R=U/I

We get 10 / 0.02 = 500 ohms. We find the nearest higher value of the resistor value in series E24 (the most common) - 510 ohms. That's not all. For reliable operation of this circuit, it is necessary to calculate the power of the resistor. Power is voltage times current.

P=U*I

Those. the voltage dropping across the resistor (10 V) is multiplied by the current flowing through it (0.02 A) and we get 10 * 0.02 = 0.2 W or 200 mW. The standard larger resistor value is 0.25 W. All.

If we, for example, want to connect two LED to 12 volts, then everything is almost the same.

The only difference will be that the two LEDs will drop not 2, but 2 * 2 = 4 volts. That. 12 -4 = 8 volts will remain for the resistor. Then everything is the same. Resistor resistance R = 8 / 0.02 = 400 ohms. The nearest higher value for E24 is 430 ohms. Power 8 * 0.02 = 0.16 W. The nearest higher value is the same as in the previous example - 0.25 W. It's simple. By the way, where to place the resistor does not matter. On the anode or cathode side, or in the case of multiple LEDs, between them.
And don't shine

An LED is a diode that lights up when current flows through it. In English, an LED is called a light emitting diode, or LED.

The color of the LED glow depends on the additives added to the semiconductor. For example, impurities of aluminum, helium, indium, and phosphorus cause a glow from red to yellow. Indium, gallium, nitrogen makes the LED glow from blue to green. When a phosphor is added to a blue crystal, the LED will glow white. Currently, the industry produces LEDs in all colors of the rainbow, but the color does not depend on the color of the LED housing, but on the chemical additives in its crystal. An LED of any color can have a transparent body.

The first LED was manufactured in 1962 at the University of Illinois. In the early 1990s, bright LEDs appeared, and a little later, super bright ones.
The advantages of LEDs over incandescent light bulbs are undeniable, namely:

* Low power consumption - 10 times more economical than light bulbs
* Long service life - up to 11 years of continuous operation
* High durability - not afraid of vibrations and shocks
* Wide variety of colors
* Ability to operate at low voltages
* Environmental and fire safety - no toxic substances in LEDs. LEDs do not heat up, which prevents fires.

LED markings

Rice. 1. Design of 5 mm indicator LEDs

An LED crystal is placed in the reflector. This reflector sets the initial scattering angle.
The light then passes through the epoxy resin housing. It reaches the lens - and then it begins to scatter on the sides at an angle depending on the design of the lens, in practice - from 5 to 160 degrees.

Emitting LEDs can be divided into two large groups: visible LEDs and infrared (IR) LEDs. The former are used as indicators and illumination sources, the latter - in remote control devices, infrared transceiver devices, and sensors.
Light-emitting diodes are marked with a color code (Table 1). First, you need to determine the type of LED by the design of its housing (Fig. 1), and then clarify it by color markings in the table.

Rice. 2. Types of LED housings

LED colors

LEDs come in almost every color: red, orange, amber, amber, green, blue and white. Blue and white LED are a little more expensive than other colors.
The color of LEDs is determined by the type of semiconductor material from which it is made, and not by the color of the plastic of its housing. LEDs of any color come in a colorless housing, in which case the color can only be found out by turning it on...

Table 1. LED markings

Multicolor LEDs

A multicolor LED is designed simply; as a rule, it is red and green combined into one housing with three legs. By changing the brightness or the number of pulses on each crystal, you can achieve different glow colors.

LEDs are connected to a current source, anode to positive, cathode to negative. The negative (cathode) of an LED is usually marked with a small cut of the body or a shorter lead, but there are exceptions, so it is better to clarify this fact in the technical characteristics of a particular LED.

In the absence of these marks, the polarity can be determined experimentally by briefly connecting the LED to the supply voltage through the appropriate resistor. However, this is not the best way to determine polarity. In addition, in order to avoid thermal breakdown of the LED or a sharp reduction in its service life, it is impossible to determine the polarity “at random” without a current-limiting resistor. For quick testing, a resistor with a nominal resistance of 1k ohms is suitable for most LEDs as long as the voltage is 12V or less.

A word of warning: do not aim the LED beam directly at your own eye (or a friend’s eye) at close range, as this can damage your vision.

Supply voltage

The two main characteristics of LEDs are voltage drop and current. Typically, LEDs are designed for a current of 20 mA, but there are exceptions, for example, quad-chip LEDs are usually designed for 80 mA, since one LED housing contains four semiconductor crystals, each of which consumes 20 mA. For each LED, there are permissible values ​​of supply voltage Umax and Umaxrev (for direct and reverse switching, respectively). When voltages above these values ​​are applied, an electrical breakdown occurs, as a result of which the LED fails. There is also a minimum value of the supply voltage Umin at which the LED glows. The range of supply voltages between Umin and Umax is called the “working” zone, since this is where the LED operates.

Supply voltage - this parameter is not applicable for the LED. LEDs do not have this characteristic, so you cannot connect LEDs to a power source directly. The main thing is that the voltage from which the LED is powered (through a resistor) is higher than the direct voltage drop of the LED (the forward voltage drop is indicated in the characteristics instead of the supply voltage and for conventional indicator LEDs it ranges on average from 1.8 to 3.6 volts).
The voltage indicated on the LED packaging is not the supply voltage. This is the amount of voltage drop across the LED. This value is necessary to calculate the remaining voltage that has not “dropped” on the LED, which takes part in the formula for calculating the resistance of the current-limiting resistor, since it is this that needs to be adjusted.
A change in the supply voltage of just one tenth of a volt for a conventional LED (from 1.9 to 2 volts) will cause a fifty percent increase in the current flowing through the LED (from 20 to 30 milliamps).

For each LED of the same rating, the voltage suitable for it may be different. By switching on several LEDs of the same rating in parallel and connecting them to a voltage of, for example, 2 volts, we risk, due to the variation in characteristics, quickly burning some copies and under-illuminating others. Therefore, when connecting an LED, it is necessary to monitor not the voltage, but the current.

The current value for the LED is the main parameter, and is usually 10 or 20 milliamps. It doesn't matter what the tension is. The main thing is that the current flowing in the LED circuit corresponds to the nominal value for the LED. And the current is regulated by a resistor connected in series, the value of which is calculated by the formula:

R
Upit— power source voltage in volts.
Upfall— direct voltage drop across the LED in volts (indicated in the specifications and usually around 2 volts). When several LEDs are connected in series, the voltage drops add up.
I— maximum forward current of the LED in amperes (indicated in the specifications and is usually either 10 or 20 milliamps, i.e. 0.01 or 0.02 amperes). When several LEDs are connected in series, the forward current does not increase.
0,75 — reliability coefficient for the LED.

We should also not forget about the power of the resistor. Power can be calculated using the formula:

P— resistor power in watts.
Upit— effective (effective, root-mean-square) voltage of the power source in volts.
Upfall— direct voltage drop across the LED in volts (indicated in the specifications and usually around 2 volts). When several LEDs are connected in series, the voltage drops add up. .
R— resistor resistance in ohms.

Calculation of the current-limiting resistor and its power for one LED

Typical LED Characteristics

Typical parameters of a white indicator LED: current 20 mA, voltage 3.2 V. Thus, its power is 0.06 W.

Also classified as low-power are surface-mounted LEDs (SMD). They illuminate the buttons on your cell phone, the screen of your monitor if it is LED-backlit, they are used to make decorative LED strips on a self-adhesive base, and much more. There are two most common types: SMD 3528 and SMD 5050. The first contain the same crystal as the indicator LEDs with leads, that is, its power is 0.06 W. But the second one has three such crystals, so it can no longer be called an LED - it’s an LED assembly. It is common to call SMD 5050 LEDs, but this is not entirely correct. These are assemblies. Their total power is, respectively, 0.2 W.
The operating voltage of an LED depends on the semiconductor material from which it is made; accordingly, there is a relationship between the color of the LED and its operating voltage.

Table of LED voltage drop depending on color

By the magnitude of the voltage drop when testing LEDs with a multimeter, you can determine the approximate color of the LED glow according to the table.

Serial and parallel connection of LEDs

When connecting LEDs in series, the resistance of the limiting resistor is calculated in the same way as with one LED, simply the voltage drops of all LEDs are added together according to the formula:

When connecting LEDs in series, it is important to know that all LEDs used in the garland must be of the same brand. This statement should be taken not as a rule, but as a law.

To find out what is the maximum number of LEDs that can be used in a garland, you should use the formula

* Nmax – maximum permissible number of LEDs in a garland
* Upit – Voltage of the power source, such as a battery or accumulator. In volts.
* Upr - Direct voltage of the LED taken from its passport characteristics (usually ranges from 2 to 4 volts). In volts.
* With changes in temperature and aging of the LED, Upr may increase. Coeff. 1.5 gives a margin for such a case.

With this calculation, “N” can have a fractional form, for example 5.8. Naturally, you cannot use 5.8 LEDs, so you should discard the fractional part of the number, leaving only the whole number, that is, 5.

The limiting resistor for sequential switching of LEDs is calculated in exactly the same way as for single switching. But in the formulas one more variable “N” is added - the number of LEDs in the garland. It is very important that the number of LEDs in the garland is less than or equal to “Nmax” - the maximum allowable number of LEDs. In general, the following condition must be met: N =

All other calculations are carried out in the same way as calculating a resistor when the LED is turned on individually.

If the power supply voltage is not enough even for two LEDs connected in series, then each LED must have its own limiting resistor.

Parallel connection of LEDs with a common resistor is a bad solution. As a rule, LEDs have a range of parameters, each requiring slightly different voltages, which makes such a connection practically unworkable. One of the diodes will glow brighter and take on more current until it fails. This connection greatly accelerates the natural degradation of the LED crystal. If LEDs are connected in parallel, each LED must have its own limiting resistor.

A series connection of LEDs is also preferable from the point of view of economical consumption of the power source: the entire serial chain consumes exactly as much current as one LED. And when they are connected in parallel, the current is as many times greater as the number of parallel LEDs we have.

Calculating the limiting resistor for series-connected LEDs is as simple as for a single one. We simply sum up the voltage of all LEDs, subtract the resulting sum from the voltage of the power supply (this will be the voltage drop across the resistor) and divide by the current of the LEDs (usually 15 - 20 mA).

What if we have a lot of LEDs, several dozen, and the power supply does not allow connecting them all in series (there is not enough voltage)? Then we determine, based on the voltage of the power source, how many maximum LEDs we can connect in series. For example, for 12 volts, these are 5 two-volt LEDs. Why not 6? But something must also drop at the limiting resistor. Here we take the remaining 2 volts (12 - 5x2) for calculation. For a current of 15 mA, the resistance will be 2/0.015 = 133 Ohms. The closest standard is 150 Ohms. But we can now connect as many of these chains of five LEDs and a resistor each as we like. This method is called a parallel-series connection.

If there are LEDs of different brands, then we combine them in such a way that in each branch there are LEDs of only ONE type (or with the same operating current). In this case, it is not necessary to maintain the same voltages, because we calculate our own resistance for each branch.

Next, we will consider a stabilized circuit for switching on LEDs. Let's touch on the manufacture of a current stabilizer. There is a KR142EN12 microcircuit (a foreign analogue of LM317), which allows you to build a very simple current stabilizer. To connect an LED (see figure), the resistance value R = 1.2 / I is calculated (1.2 is the voltage drop in the stabilizer) That is, at a current of 20 mA, R = 1.2 / 0.02 = 60 Ohms. The stabilizers are designed for a maximum voltage of 35 volts. It’s better not to overextend them and supply a maximum of 20 volts. With this switching on, for example, a white LED of 3.3 volts, it is possible to supply a voltage to the stabilizer from 4.5 to 20 volts, while the current on the LED will correspond to a constant value of 20 mA. With a voltage of 20V, we find that 5 white LEDs can be connected in series to such a stabilizer, without worrying about the voltage on each of them, the current in the circuit will flow 20mA (the excess voltage will be extinguished at the stabilizer).

Important! A device with a large number of LEDs carries a lot of current. It is strictly forbidden to connect such a device to an active power source. In this case, a spark occurs at the connection point, which leads to the appearance of a large current pulse in the circuit. This pulse disables LEDs (especially blue and white). If the LEDs operate in dynamic mode (constantly turning on, off and blinking) and this mode is based on the use of a relay, then a spark should be prevented from occurring at the relay contacts.

Each chain should be assembled from LEDs of the same parameters and from the same manufacturer.
Also important! Changing the ambient temperature affects the current flow through the crystal. Therefore, it is advisable to manufacture the device so that the current flowing through the LED is not 20 mA, but 17-18 mA. The loss of brightness will be insignificant, but a long service life will be ensured.

How to power an LED from a 220 V network.

It would seem that everything is simple: we put a resistor in series, and that’s it. But you need to remember one important characteristic of the LED: the maximum permissible reverse voltage. For most LEDs it is about 20 volts. And when you connect it to the network with reverse polarity (the current is alternating, half a cycle goes in one direction, and the second half in the opposite direction), the full amplitude voltage of the network will be applied to it - 315 volts! Where does this figure come from? 220 V is the effective voltage, but the amplitude is (root of 2) = 1.41 times greater.
Therefore, in order to save the LED, you need to place a diode in series with it, which will not allow reverse voltage to pass through to it.

Another option for connecting an LED to a 220V power supply:

Or put two LEDs back-to-back.

The option of power supply from the mains with a quenching resistor is not the most optimal: significant power will be released through the resistor. Indeed, if we use a 24 kOhm resistor (maximum current 13 mA), then the power dissipated across it will be about 3 W. You can reduce it by half by connecting a diode in series (then heat will be released only during one half-cycle). The diode must have a reverse voltage of at least 400 V. When you turn on two counter LEDs (there are even those with two crystals in one housing, usually of different colors, one crystal is red, the other is green), you can put two two-watt resistors, each with twice the resistance less.
I’ll make a reservation that by using a high-resistance resistor (for example, 200 kOhm), you can turn on the LED without a protective diode. The reverse breakdown current will be too low to cause destruction of the crystal. Of course, the brightness is very low, but for example, to illuminate a switch in the bedroom in the dark, it will be quite enough.
Due to the fact that the current in the network is alternating, you can avoid unnecessary waste of electricity on heating the air with a limiting resistor. Its role can be played by a capacitor that passes alternating current without heating. Why this is so is a separate question, we will consider it later. Now we need to know that in order for a capacitor to pass alternating current, both half-cycles of the network must pass through it. But the LED only conducts current in one direction. This means that we place a regular diode (or a second LED) counter-parallel to the LED, and it will skip the second half-cycle.

But now we have disconnected our circuit from the network. There is some voltage left on the capacitor (up to the full amplitude, if we remember, equal to 315 V). To avoid accidental electric shock, we will provide a high-value discharge resistor parallel to the capacitor (so that during normal operation a small current flows through it without causing it to heat up), which, when disconnected from the network, will discharge the capacitor in a fraction of a second. And to protect against pulsed charging current, we will also install a low-resistance resistor. It will also play the role of a fuse, instantly burning out in the event of an accidental breakdown of the capacitor (nothing lasts forever, and this also happens).

The capacitor must be for a voltage of at least 400 volts, or special for alternating current circuits with a voltage of at least 250 volts.
What if we want to make an LED light bulb from several LEDs? We turn them all on in series; one counter diode is enough for all of them.

The diode must be designed for a current no less than the current through the LEDs, and the reverse voltage must be no less than the sum of the voltage across the LEDs. Better yet, take an even number of LEDs and turn them on back-to-back.

In the figure, there are three LEDs in each chain; in fact, there may be more than a dozen of them.
How to calculate a capacitor? From the amplitude voltage of the 315V network, we subtract the sum of the voltage drop across the LEDs (for example, for three white ones this is approximately 12 volts). We get the voltage drop across the capacitor Up=303 V. The capacity in microfarads will be equal to (4.45*I)/Up, where I is the required current through the LEDs in milliamps. In our case, for 20 mA the capacitance will be (4.45*20)/303 = 89/303 ~= 0.3 µF. You can place two 0.15 µF (150 nF) capacitors in parallel.

The most common mistakes when connecting LEDs

1. Connect the LED directly to the power source without a current limiter (resistor or special driver chip). Discussed above. The LED quickly fails due to poorly controlled current.

2. Connecting LEDs connected in parallel to a common resistor. Firstly, due to the possible scatter of parameters, the LEDs will light up with different brightness. Secondly, and more importantly, if one of the LEDs fails, the current of the second will double, and it may also burn out. If you use one resistor, it is more advisable to connect the LEDs in series. Then, when calculating the resistor, we leave the current the same (for example, 10 mA), and add up the forward voltage drop of the LEDs (for example, 1.8 V + 2.1 V = 3.9 V).

3. Switching on LEDs in series, designed for different currents. In this case, one of the LEDs will either wear out or glow dimly, depending on the current setting of the limiting resistor.

4. Installation of an insufficient resistance resistor. As a result, the current flowing through the LED is too high. Since part of the energy is converted into heat due to defects in the crystal lattice, it becomes too much at high currents. The crystal overheats, as a result of which its service life is significantly reduced. With an even greater increase in current due to heating of the pn-junction region, the internal quantum efficiency decreases, the brightness of the LED drops (this is especially noticeable for red LEDs) and the crystal begins to catastrophically collapse.

5. Connecting the LED to an alternating current network (eg 220 V) without taking measures to limit the reverse voltage. For most LEDs, the maximum permissible reverse voltage is about 2 volts, while the reverse half-cycle voltage when the LED is locked creates a voltage drop across it equal to the supply voltage. There are many different schemes that eliminate the destructive effects of reverse voltage. The simplest one is discussed above.

6. Installation of an insufficient power resistor. As a result, the resistor becomes very hot and begins to melt the insulation of the wires touching it. Then the paint on it burns, and eventually it collapses under the influence of high temperature. A resistor can safely dissipate no more than the power for which it is designed.

Flashing LEDs

A flashing LED (MSD) is an LED with a built-in integrated pulse generator with a flash frequency of 1.5 -3 Hz.
Despite its compact size, the flashing LED includes a semiconductor generator chip and some additional elements. It is also worth noting that the flashing LED is quite universal - the supply voltage of such an LED can range from 3 to 14 volts for high-voltage ones, and from 1.8 to 5 volts for low-voltage units.

Distinctive qualities of flashing LEDs:

Small sizes
Compact light signaling device
Wide supply voltage range (up to 14 volts)
Different emission color.

Some versions of flashing LEDs may have several (usually 3) multi-colored LEDs built in with different flash frequencies.
The use of flashing LEDs is justified in compact devices where high demands are placed on the dimensions of radio elements and power supply - flashing LEDs are very economical, since the electronic circuit of the MSD is made on MOS structures. A flashing LED can easily replace an entire functional unit.

The conventional graphic designation of a flashing LED on circuit diagrams is no different from the designation of a conventional LED, except that the arrow lines are dotted and symbolize the flashing properties of the LED.

If you look through the transparent body of the flashing LED, you will notice that it consists of two parts. A light-emitting diode crystal is placed on the base of the cathode (negative terminal).
The generator chip is located on the base of the anode terminal.
Three gold wire jumpers connect all parts of this combined device.

It is easy to distinguish an MSD from a regular LED by its appearance, looking at its body in the light. Inside the MSD there are two substrates of approximately the same size. On the first of them there is a crystalline cube of a light emitter made of a rare earth alloy.
To increase the luminous flux, focus and shape the radiation pattern, a parabolic aluminum reflector (2) is used. In an MSD it is slightly smaller in diameter than in a conventional LED, since the second part of the housing is occupied by a substrate with an integrated circuit (3).
Electrically, both substrates are connected to each other by two gold wire jumpers (4). The MSD housing (5) is made of matte light-diffusing plastic or transparent plastic.
The emitter in the MSD is not located on the axis of symmetry of the housing, so to ensure uniform illumination, a monolithic colored diffuse light guide is most often used. A transparent body is found only in large-diameter MSDs with a narrow radiation pattern.

The generator chip consists of a high-frequency master oscillator - it operates constantly; its frequency, according to various estimates, fluctuates around 100 kHz. A logic gate divider works together with the RF generator, which divides the high frequency to a value of 1.5-3 Hz. The use of a high-frequency generator in conjunction with a frequency divider is due to the fact that the implementation of a low-frequency generator requires the use of a capacitor with a large capacity for the timing circuit.

To bring the high frequency to a value of 1-3 Hz, dividers are used on logic elements, which are easy to place on a small area of ​​the semiconductor crystal.
In addition to the master RF oscillator and divider, an electronic switch and a protective diode are made on the semiconductor substrate. Flashing LEDs, designed for a supply voltage of 3-12 volts, also have a built-in limiting resistor. Low-voltage MSDs do not have a limiting resistor. A protective diode is necessary to prevent failure of the microcircuit when the power supply is reversed.

For reliable and long-term operation of high-voltage MSDs, it is advisable to limit the supply voltage to 9 volts. As the voltage increases, the power dissipation of the MSD increases, and, consequently, the heating of the semiconductor crystal increases. Over time, excessive heat can cause the flashing LED to rapidly degrade.

You can safely check the serviceability of a flashing LED using a 4.5-volt battery and a 51-ohm resistor connected in series with the LED, with a power of at least 0.25 W.

The serviceability of the IR diode can be checked using a cell phone camera.
We turn on the camera in shooting mode, catch the diode on the device (for example, a remote control) in the frame, press the buttons on the remote control, the working IR diode should flash in this case.

In conclusion, you should pay attention to such issues as soldering and mounting of LEDs. These are also very important issues that affect their viability.
LEDs and microcircuits are afraid of static, incorrect connection and overheating; soldering of these parts should be as fast as possible. You should use a low-power soldering iron with a tip temperature of no more than 260 degrees and soldering should take no more than 3-5 seconds (manufacturer’s recommendations). It would be a good idea to use medical tweezers when soldering. The LED is taken with tweezers higher to the body, which provides additional heat removal from the crystal during soldering.
The LED legs should be bent with a small radius (so that they do not break). As a result of the intricate bends, the legs at the base of the case must remain in the factory position and must be parallel and not stressed (otherwise the crystal will get tired and fall off the legs).

Although LEDs (lights) have been used in the world since the 60s, the question of how to connect them correctly is still relevant today.

Let's start with the fact that all LEDs operate exclusively on direct current. For them, the polarity of the connection, or the location of the plus and minus, is important. If the connection is incorrect. the LED will not work.

How to determine LED polarity

LED polarity can be determined in three ways:

N.B. Although in practice the latter method is sometimes not confirmed.

Be that as it may, it should be noted that if you briefly (1-2 seconds) do not connect the LED correctly, then nothing will burn out and nothing bad will happen. Since the diode itself works in one direction, but not in the opposite direction. It can burn out only due to increased voltage.

The nominal voltage for most LEDs is 2.2 - 3 volts. LED strips and modules that operate at 12 volts or more already contain resistors in the circuit.

How to connect an LED to 12 volts

Connecting the LED directly to 12 volts is prohibited; it will burn out in a split second. A limiting resistor (resistance) must be used. The resistor size is calculated using the formula:

R= (Upit-Upad)/0.75I,

where R is the resistance value of the resistor;

Upit and Upad – supply voltage and falling voltage;

I – passing current.

0.75 — reliability coefficient for the LED (constant value)

For greater clarity, let's look at the example of connecting one LED to a 12 volt car battery.

In this case:

• Upit - 12 volts (car battery voltage)
• Updrop - 2.2 volts (LED supply voltage)
• I - 10 mA or 0.01 A (current of one LED)

Using the above formula, we get R=(12-2.2)/0.75*0.01 = 1306 Ohm or 1.306 kOhm

The closest standard resistor value is 1.3 kiloohms

That's not all. It is necessary to calculate the required minimum resistor power.

But first, let's determine the actual current I (it may differ from that indicated above)

Formula: I = U / (Rres. + Rlight)

• Rlight - LED resistance:

Upd.nom. / Inom. = 2.2 / 0.01 = 220 Ohm,

It follows from this that the current in the circuit

I = 12 / (1300 + 220) = 0.007 A

The actual LED voltage drop will be:

And finally, the power is:

P = (Up. - Up.)² / R = (12 -1.54)²/ 1300 = 0.0841 W).

You should take a little more power than the standard size. In this case, 0.125 W is better.

So, in order to correctly connect one LED to 12 volts (car battery), you will need to insert a resistor into the circuit with a resistance 1.3 kOhm and power 0.125 W.

The resistor can be connected to any leg of the LED.

If you had a bad grade in math at school, there is a simpler option. When purchasing LEDs at a radio store, ask the seller which resistor you will need to insert into the circuit. Don't forget to indicate the voltage in the circuit.

How to connect an LED to 220V

The dimension of resistance in this case is calculated in a similar way.

The initial data is the same. LED consumption 10 mA and voltage 2.2 volts.

Only the supply voltage is 220 volts AC.

R = (Upit.-Up.) / (I * 0.75)

R = (220 - 2.2) / (0.01 * 0.75) = 29040 Ohm or 29,040 kOhm

The closest nominal value resistor is 30 kOhm.

Power is calculated using the same formula.

First, we determine the actual current consumption:

I = U / (Rres.+ Rlight)

Rlight = Upnom. / Inom. = 2.2 / 0.01 = 220 Ohm,

and from this it follows that the current in the circuit will be:

I = 220 / (30000 + 220) = 0.007 A

Thus the real LED voltage drop will be:

Upd.light = Rlight * I = 220 * 0.007 = 1.54 V

And finally the resistor power:

P = (Up. - Up.)² / R = (220 -1.54)² / 30000 = 1.59 W)

The resistance power should be at least 1.59 W, preferably a little more. The nearest higher standard value is 2 W.

So, to connect one LED to a voltage of 220 volts, we need to place a resistor with a nominal value of 30 kOhm and power 2 W.

BUT! Since in this case the current is alternating, the LED will light only in one half-phase, that is, it will blink very quickly, at approximately 25 flashes per second. The human eye does not perceive this and it will seem that the light is usually on. But in fact, it will still miss reverse breakouts, although it only works in one direction. To do this, you need to put a reverse directional diode in the circuit in order to balance the network and protect the LED from premature failure.

LEDs are semiconductor devices that convert electric current into direct light radiation.

How to connect an LED through a resistor or directly, and most importantly, to make such a connection safe to use and durable - these are the main issues that are considered in order to ensure the performance of any light-emitting diodes.

Independent determination of LED polarity is carried out using several simple methods:

• through measurements;
• based on the results of a visual assessment;
• when connected to a power source;
• in the process of familiarization with technical documentation.

The most common options for determining the polarity of light-emitting diodes include the first three methods, which must be performed in compliance with standard technology.

Using Test Devices

In order to determine the LED polarity as accurately as possible, the probes are connected directly to the diode, after which the tester readings are monitored. When “infinite” resistance is displayed on the scale, the probe wires change places.

If the tester shows any indicators of the final value when measuring the resistance of the light-emitting diodes being tested, then you can be sure that the device is connected in compliance with the type of polarity, and the data on the location of the “plus” and “minus” are accurate.

Checking LEDs with a multimeter

Visual polarity detection

Despite the many types of designs currently existing, the most widely used are light-emitting diodes enclosed in a cylindrical housing D from 3.5 mm.

The most powerful super-bright diodes have planar flat leads marked “+” and “-”.

Devices in a cylindrical housing have a pair of electrodes inside that differ in area. It is the cathode part of light-emitting diodes that is distinguished by a larger electrode area and the presence of a characteristic bevel on the “skirt”.

Surface mount LEDs have a special bevel or “key” that indicates the cathode or negative polarity.

Connecting to a power source

Transferring power from constant voltage elements is one of the most obvious options for determining diode polarity, requiring the use of a special unit with progressive voltage regulation, or a traditional battery. After connection, the voltage gradually increases, which causes the LED to glow and indicates the correct polarity is determined.

Connecting diodes to power

To check the functionality of the light diode, it is imperative to connect a current-limiting resistor with a resistance of 680 ohms.

Assembly steps

When independently assembling and subsequently testing light-emitting diodes in operating mode, it is advisable to use this sequence:

• determine the technical characteristics reflected in the accompanying documentation;
• draw up a connection diagram taking into account the voltage level;
• calculate the power consumption of the electrical circuit;
• select a driver or power supply with optimal power;
• calculate the resistor at a stabilized voltage;
• determine the polarity of the LED source;
• solder wires to LED outputs;
• connect the power source;
• fix the diode on the radiator.

The process of testing light-emitting diodes involves connecting the assembled structure to an electrical network and measuring the current consumed.

The star is installed on the radiator using heat-conducting paste, and the wires should be soldered with a fairly powerful soldering iron, which is due to the natural absorption of heat by aluminum from the contact area and the solder.

Power supplies

To connect the LED, special power supplies are used, developed in accordance with established requirements and standards. During the design process, you will need to determine the power factor, energy efficiency and ripple level.

The main feature of modern power supplies is the presence of a built-in power factor corrector, and devices for indoor lighting are characterized by increased requirements for the level of current ripple.

LED connection diagrams

If the power source in the form of light-emitting diodes is intended to be used in outdoor lighting, then the protection ratings of such a device should be IP-67 over a wide temperature range.

LED power supplies under current stabilization conditions provide constant output current values ​​over a wide range. If the source for an LED lamp has voltage stabilization, then a constant voltage of the output type is generated under current load conditions, but not more than the maximum permissible values. Some modern devices have combined stabilization.

How to connect an LED

Ensuring the functionality of light-emitting diodes requires not only the presence of a power source, but also strict adherence to the connection diagram.

K 1.5 V

The operating voltage of light-emitting diodes, as a rule, exceeds 1.5 V, so ultra-bright LEDs need a power source of at least 3.2-3.4 V. When connecting, a voltage converter is used in the form of a blocking generator using a resistor, transistor and transformer .

We power the LED to 1.5 watts

The use of a simplified circuit, devoid of a stabilizer, allows for continuous operation of light-emitting diodes until the voltage in the battery drops to 0.8 V.

K 5V

Connecting an LED to a battery with a rated current of 5 V involves connecting a resistor with a resistance in the range of 100-200 Ohms.

Parallel connection of LEDs

If a 5 volt connection is necessary to install a pair of diodes, then a limiting type resistor with a resistance of no more than 100 Ohms is connected to the electrical circuit in series.

K 9 V

The Krona battery has a relatively small capacity, so this power source is very rarely used to connect sufficiently powerful LEDs. According to the maximum current, which does not exceed 30-40 mA, three light-emitting diodes having an operating current of 20 mA are most often connected in series.

K 12 V

The standard algorithm for connecting diodes to a 12 V battery includes determining the type of unit, finding the rated current, voltage and power consumption, as well as connecting to the terminals with mandatory polarity. In this case, the resistor is placed on any part of the electrical circuit.

The contacts in the areas where light-emitting diodes are connected are securely sealed, and after a routine performance check they are insulated with special tape.

K 220 V

When using, the current that will flow through the light diode is necessarily limited, which will prevent overheating and failure of the light-emitting device. It is also necessary to reduce the level of reverse LED voltage to prevent breakdown.

Connection diagram for LEDs to 220 volts

Limiting the current level under alternating voltage conditions is accomplished by resistors, capacitors, or inductors. Powering the diode at a constant voltage requires the use of resistors only.

Powering LEDs from 220 V with your own hands

The driver for 220 V diode light sources is an integral part of assembling a safe and durable device, and it is quite possible to make such a device yourself. In order for light-emitting diodes to operate from a traditional network, it will be necessary to reduce the voltage amplitude, reduce the current, and also convert alternating voltage to constant values. For this purpose, a divider with a resistor or capacitive load, as well as stabilizers, is used.

Connecting LED strip to 220 V

A reliable homemade driver for 220 V diode light sources can be an elementary switching power supply that does not have galvanic isolation. The most important advantage of this scheme is its simplicity of execution, complemented by reliability of operation.

However, when performing the assembly yourself, you must be extremely careful, since a feature of this circuit is the complete absence of restrictions on the output current.

Of course, the LEDs will draw the standard 1.5 A, but the contact of hands with bare wires will provoke an increase to 10 A or more, which is very noticeable.

The standard circuit of the simplest 220V LED driver is based on three main stages, represented by:

• voltage divider on resistance indicators;
• diode bridge;
• voltage stabilization.

To smooth out voltage ripple, you will need to connect an electrolytic capacitor in parallel to the circuit, the capacitance of which is selected individually, in accordance with the load power.

The stabilizer in this case may well be the publicly available element L-7812. It should be noted that the circuit of 220-volt diode light sources assembled in this way is characterized by stable performance, but before connecting it to the electrical network, it is necessary to carefully insulate the exposed wires and soldering areas.