LED in a 220 volt circuit. Radio communication

One of the important issues when working with LEDs is its connection to AC and high voltage. It is known that the LED cannot be directly powered from the 220 V network. How to properly assemble the circuit and provide power to solve the problem?

Electrical Properties

To answer the above question, it is necessary to study the electrical properties of the LED.

Its current-voltage characteristic is a steep line. This means that with an increase in voltage, even by a very small amount, the current through the radiating semiconductor increases sharply. An increase in current leads to heating of the LED, as a result of which it can simply burn out. This problem is solved by including a limiting resistor in the circuit.

The LED has a low reverse breakdown voltage (about 20 volts), so it cannot be connected to a 220 volt AC network. To prevent the flow of current in the opposite direction, it is necessary to include a diode in the circuit or turn on the second one towards the first LED. The connection must be in parallel.

So, we know that any scheme for connecting an LED to a 220 volt network must contain a resistor and a rectifier, otherwise power will not be possible.

Why is such a scheme needed? First of all, for the design of the network indicator. An LED bulb can be an excellent indicator to help you determine if an electrical appliance is plugged in or not. It is added to the circuit of switches and sockets in order to easily find them in the dark.

Such an indicator begins to glow at a voltage of only a few volts. At the same time, it consumes a minimum amount of electricity due to a small (several miles of amperes) current.

What resistor to use?

To select the optimal resistance of the resistor, you must use Ohm's law.

R \u003d (Unetwork-Ur.) / Ir.nom.

Suppose we took a red LED for the indicator with a nominal current value of 18mA and a forward voltage of 2.0 Volts.

(311-2) / 0.018 \u003d 17167 Ohm \u003d 17 kOhm

Let's explain where the number 311 came from. This is the peak of the sinusoid, along which the voltage in our network changes. Without going into the realm of mathematics with all its calculations, we can simply say that the peak voltage is 220 * √2.

Sometimes there are circuits in which there is no rectifying diode. In this case, the resistance must be increased several times in order to make the current smaller and protect the indicator light from burning out.

Elementary circuit of the current indicator

What is needed to make the simplest indicator, which is powered by a 220 volt network? Here is the list:

• ordinary indicator LED of any color you like;
• resistor from 100 to 200 kOhm (the greater the resistance, the less brightly the bulb will glow);
• diode with a reverse voltage of 100 volts or more;
• a low-power soldering iron so as not to overheat the LED.

Since the number of parts is minimal, the board is not used in the installation. The indicator is connected in parallel with the electrical appliance.

For those who do not have the desire to run around in search of a diode, manufacturers have come up with a ready-made two-color indicator in the form of two LEDs of different colors built into one case. Usually it is red and green. In this case, the number of circuit details is further reduced.

There are other connection schemes in which the resistor is replaced with a capacitor or diode bridges, transistors, etc. are used. But no matter what design features are introduced, the main task is to rectify the current and lower it to a safe value.

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 allowable reverse voltage. Most LEDs have about 20 volts. And when you connect it to the network with reverse polarity (the current is alternating, half a period goes in one direction, and the other half goes in the opposite direction), the full amplitude voltage of the network will be applied to it - 315 volts! Where does such a figure come from? 220 V is the effective voltage, while the amplitude is in (root of 2) \u003d 1.41 times more.

Therefore, in order to save the LED, you need to put a diode in series with it, which will not let the reverse voltage pass to it.

Or put two LEDs back-to-back.

The mains supply option with a quenching resistor is not the most optimal: significant power will be released on the resistor. Indeed, if we apply a 24 kΩ resistor (maximum current 13 mA), then the power dissipated on it will be about 3 watts. You can reduce it by half by turning on the diode in series (then heat will be released only during one half-cycle). The diode must be for a reverse voltage of at least 400 V. When you turn on two counter LEDs (there are even those with two crystals in one case, usually of different colors, one crystal is red, the other is green), you can put two two-watt resistors, each with a resistance of two times less.

I will 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 crystal destruction. Of course, the brightness is very small, but for example, to illuminate the switch in the bedroom in the dark, it will be quite enough.

Due to the fact that the current in the network is alternating, it is possible to avoid unnecessary waste of electricity for heating the air with a limiting resistor. Its role can be played by a capacitor that passes alternating current without heating up. Why this is so is a separate question, we will consider it later. Now we need to know that in order for the capacitor to pass alternating current, both half-cycles of the network must necessarily pass through it. But an LED only conducts current in one direction. So, we put an ordinary diode (or a second LED) in opposite parallel to the LED, and it will skip the second half-cycle.

But now we have disconnected our circuit from the network. Some voltage remained 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 in parallel with the capacitor (so that during normal operation a small current flows through it, which does not cause 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 also put a low-resistance resistor. It will also play the role of a fuse, instantly burning out if the capacitor accidentally breaks down (nothing lasts forever, and this also happens).

The capacitor must be at least 400 volts, or special for alternating current circuits with a voltage of at least 250 volts.

And if we want to make an LED light bulb from several LEDs? We turn them all on in series, the oncoming diode is enough for one at all.

The diode must be designed for a current not less than the current through the LEDs, reverse voltage - not less than the sum of the voltage on the LEDs. Better yet, take an even number of LEDs and turn them on in anti-parallel.

In the figure, three LEDs are drawn 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 about 12 volts). We get the voltage drop across the capacitor Up \u003d 303 V. The capacitance 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 uF. You can put two 0.15uF (150nF) capacitors in parallel.

In conclusion, you should pay attention to issues such as soldering and mounting LEDs. These are also very important issues that affect their viability.

LEDs and microcircuits are afraid of static, improper connection and overheating, the 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 for no more than 3-5 seconds (manufacturer's recommendations). It will not be superfluous 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 legs of the LED should be bent with a small radius (so that they do not break). As a result of the intricate curves, the legs at the base of the case should remain in the factory position and should be parallel and not tense (otherwise it will get tired and the crystal will fall off the legs).

To protect your device from accidental short circuit or overload, fuses should be installed.

Below is a description from the site www.chipdip.ru/video/id000272895


When designing radio equipment, the question of power indication often arises. The age of incandescent lamps for indication has long passed, a modern and reliable radio indication element at the moment is the LED. This article will propose a diagram for connecting an LED to 220 volts, that is, the possibility of powering the LED from a household AC mains - a socket that is in any comfortable apartment.

Niches, shelves, decor items using LED strip, we have to remember that we have 220 V in the network, and not 12 or 24 volts, as is necessary for this backlight. We will talk further about how to connect an LED strip to 220 V.

Depending on the number of LEDs in the tape, they require 12 or 24 V power. But in an ordinary apartment or house there is no such power supply, but there is usually a single-phase network. Connection is possible using two options:

Since tapes with a direct connection to 220 V do not need special means, we will continue to talk about connecting those that need reduced voltage.

Schemes for one tape

The LED strip usually comes in a piece 5 meters long. If this length is enough for you, great. Just take a 220/12 V or 220/24 V converter. Connect a power cord with a plug to the input, and a tape to the output. In this case, the connection diagram looks (figure below) as a serial connection (one by one) of all elements.

Observe polarity when connecting. Plus to plus, minus to minus. These designations (plus and minus, are both on the power supply and on the tape. Do not confuse, otherwise it will not work. To connect one tape, you can take copper wires in a protective sheath (for example, twisted pair), with a cross section of 1.5 mm².

If the length must be more than 5 meters (2, 3 tapes or more)

Often, to illuminate the ceiling or other objects, an LED strip with a length of more than 5 meters is required. It can be 10, 15 or 20 meters, that is, you need to connect two or more tapes. They cannot be connected in series (one after the other). The LEDs closest to the power supply will carry more current, causing them to overheat. They will quickly lose their brightness, and then they will stop burning altogether. In this case, you need to connect the LED strip to 220 V in parallel: stretch the wire from the power supply to one and the other.

If physically one tape should be behind another, we simply pull a long wire from the power supply. Please note: its cross section is 1.5 mm². If you need to connect three or four tapes, we also connect them to the output of the power supply with a separate pair of wires.

With this connection, all tapes will glow the same way. Just be careful: you need to choose an adapter that delivers the desired voltage of 12/24 V with enough current to power all the tapes (how to calculate the required power is a little lower).

This method is good for everyone, except that powerful power supplies are larger, heavier and much more expensive. Weight and dimensions are a problem if you are lighting the ceiling. After all, you need to figure out where to install this equipment, which is far from always easy. And yes, the price is also important. Therefore, it is worth considering the option with two adapters of lower performance.

The diagram shows the connection of two tapes to two adapters. If you need to connect three tapes, it is not necessary to use three adapters. One may be more powerful, it can power two tapes (parallel connection, as in the figure above).

How to power powerful tapes

However, if high power LED strips (from 14 W / m or more) are connected to 220 V according to this scheme, a noticeable voltage drop occurs on each of the LEDs, as a result, the far edge of the tape glows much weaker. If a multi-color RGB tape is connected according to this scheme, it may shine in the wrong colors. To get rid of this phenomenon, each tape is connected to a power source from two sides.

With this method, the wire consumption increases, but the LEDs glow more evenly. It has been observed from experience that this connection method also increases the life of the LEDs - they degrade more slowly. This solution is not mandatory, but it really extends the life and evens out the uneven glow.

Connecting a color RGB tape

The connection principle remains the same. A controller is added to the circuit (it is also called a dimmer), with the help of which the color of the LED glow changes. Another difference is in the number of wires. After the controller, there are not two, but four. Otherwise, there are no differences.

As you can see, both on the controller and on the tape, there are designations 12B / V + - this is a phase wire, R - for connecting red LEDs, G - green, B - blue. In order not to get confused, it is better to use wires of the same colors. Everything will be easier to follow, there will be less chance of getting confused.

If you need to connect several colored ribbons, they are also connected in parallel. Parallels start from the controller outputs (two wires are connected to the output terminals). With this connection, both tapes will change the glow at the same time.

The power of the controller (dimmer) is not always enough to control all the tapes. In this case, an amplifier is used. The diagram becomes more complex, but it indicates the connectors to which the wires must be connected, which greatly simplifies its assembly. Please note that in the figure the connection of the tapes is indicated by four lines, and the power to the inputs of the amplifiers is two, and this power is taken from the outputs of the adapters.

As many tapes are connected to the dimmer (controller) as it can power. In the figure, this is only one tape 5 meters long, therefore, for each subsequent one, its own amplifier is used. In fact, two tapes are “hung” on one controller. The main thing is that he can control them (the characteristics of the controller indicate the length of the tape that can be connected to it).

Also note that the controller and one amplifier are powered from one adapter, the other two amplifiers from the other. This is also not required. If the power of the power supply is sufficient to power all devices (tapes, dimmer, amplifiers), then power will be supplied from only one converter. Another thing is that such a power source costs a lot, and it heats up and makes a lot of noise. Therefore, it is indeed better to implement separate power supply by two less powerful units.

Choice of performance adapters

There are technical data in the description of each tape. It must indicate the voltage that must be applied (12 or 24 V) and the current consumed. That's just the current is usually indicated for 1 meter of tape. If you connect 5 meters, respectively, you will need to multiply this figure by 5. If you connect 10 meters to this power supply, multiply by 10, etc.

If you are still figuring out how much the backlight will cost you and there are no tapes yet or you have not chosen yet, you can use the average data. The current consumption of the most common type of monochrome tapes is shown in the table. They can be taken as an example.

The resulting figure is the minimum value of the current strength that the desired power supply should produce. But constant work at the limit of possibilities greatly reduces the service life of electrical products. Therefore, we add 20-25% of the stock to the figure found (we multiply by 1.2 or 1.25), we round the resulting figure up to a whole number. This will be the current that the adapter should give out.

To make it clearer, let's take an example. Let a meter of tape consume 0.8 A, we will connect 18 meters to the adapter. We are looking for the total current consumption: 0.8 A * 18 = 14.4 A. We add a margin: 14.4 A * 1.2 = 17.28 A. So, we will look for an adapter that will deliver at least 17 Amperes.

In the case of colored RGB LED strips, the current found is added to the found figure, which is necessary for the controller (dimmer) and amplifiers (if they are powered from this source). This data is in the technical description of the devices.

Circuit assembly process

In order to connect the LED strip to 220 V, you will need the LED strips themselves, a power supply, a controller (if needed) wires of the required colors and length. The wires are preferably copper stranded (they are softer, but harder to solder) or from a single wire. Take colored wires, so it will be easier to correctly connect the LED strip to 220 V.

You will also need the following tools:

• scissors;
• heat-shrink tubing;
• soldering iron with rosin and tin ().

Scissors are needed if you need to cut a piece from the LED strip reel. You can only cut in certain places. On the tape, they are indicated by a vertical line, next to which is usually a schematic image of scissors. Another distinguishing feature is the solder pads, which are located on both sides of the cut line.

Next, we take the wires, we clean their ends from insulation (2-3 mm), we play. and the prepared wire we put on a piece of heat shrink tubing of such a size that it is put on the tape in its original state. Next, with cotton dipped in alcohol, we clean the contact pads, tin them (we lower the heated soldering iron into rosin, warm up the pad for a couple of seconds. It should be covered with a thin layer of tin. We solder the wires to the prepared pads. Be careful and do not take a lot of tin when soldering. The pads are located very close, having planted a blot of tin, it is easy to connect them (especially in colored ribbons).

After all the wires are soldered, we lower the heat shrink tube so that it closes all the contacts, we warm it up. Shriveling, it will close all contacts well. In general, it is better to carry out this operation after checking the operability of the circuit. If everything burns, glows, you can isolate.

After soldering the wires to the tape, we connect them to the output of the adapter or controller. Everything is simple here. There is a clamping screw and contact plates. We loosen the screw, fill the bare wire (3-4 mm) between the plates, tighten the screw. We slightly pull the wire a couple of times, checking the contact - if it holds, then everything is fine.

Schemes for the simplest connection of LEDs to 220V

The thing is that this lighting is not only powerful enough, 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 declined. At the moment, there are LEDs of almost any color, which was the reason for their use in various fields of activity. These include lighting of various premises, backlighting of screens and signboards, 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 pre-existing light sources. In specialized stores, you can purchase various items based on LED lighting, ranging from a conventional lamp and LED strip, ending with them all in common that they require a current of 12 or 24 V to be connected.

Unlike other light sources that use a heating element, this one uses a semiconductor crystal that generates optical radiation under the influence of a current.

To understand the schemes for connecting LEDs to a 220V network, you first need to say that it cannot be powered directly from such a network. Therefore, to work with LEDs, you must follow a certain sequence of connecting them to a high voltage network.

Electrical properties of the LED

The current-voltage characteristic of an LED is a steep line. That is, if the voltage increases at least a little, then the current will increase sharply, this will lead to overheating of the LED with its subsequent burnout. To avoid this, it is necessary to include a limiting resistor in the circuit.

But it is important not to forget about the maximum allowable 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 network is 220 volts 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 included in the circuit. It will not pass reverse voltage. In this case, the connection must be parallel.

Another scheme for connecting an LED to a 220 volt network is to install two LEDs in anti-parallel.

As for mains power with a quenching resistor, this is not the best option. Because the resistor will give off strong power. For example, if you use a 24 kΩ resistor, then the power dissipation will be approximately 3 watts. When a diode is connected in series, the power will be halved. The reverse voltage across the diode should be 400 V. When two opposite LEDs turn on, you can put two two-watt resistors. Their resistance should be two times less. This is possible when there are two crystals of different colors in one case. Usually one crystal is red, the other green.

In the case where a 200 kΩ resistor is used, a protection diode is not required, since the return current is small and will not destroy the crystal. This scheme for connecting LEDs to the network has one minus - the small 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 variable, this avoids wasting electricity on heating the air using a limiting resistor. The capacitor does the job. 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 put an ordinary diode (or another additional LED) in opposite parallel to the LED. Then he will skip the second half-cycle.

When the circuit for connecting the LED to the 220 volt network is turned off, voltage will remain on the capacitor. Sometimes even full amplitude at 315 V. This threatens with an electric shock. To avoid this, it is necessary 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, a small current flows through this resistor, which does not heat it.

To protect against impulse charging current and as a fuse, we put a low-resistance resistor. The capacitor must be special, which is designed for an alternating current circuit of at least 250 V, or 400 V.

The LED sequencing scheme involves the installation of 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, then the total voltage drop across the LEDs must be subtracted from the power source.

It is necessary that the installed diode be rated 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 from the amplitude voltage of the network 315 V the sum of the voltage drop of the LEDs. 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 the lack of control over the current.
• The second mistake is connecting LEDs installed in parallel to a common resistor. Due to the fact that there is a scatter 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, due to which it may 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 add the voltages of the LEDs.
• The third mistake is when LEDs that are designed for different currents are switched on in series. This causes one of them to burn weakly, or vice versa - to wear out.
• The fourth mistake is to use a resistor that does not have enough resistance. Because of this, the current flowing through the LED will be too large. Some of the energy, at an overestimated current voltage, is converted into heat, resulting in overheating of the crystal and a significant reduction in its service life. The reason for this is the defects of the crystal lattice. If the voltage is further increased and the p-n junction heats up, this will lead to a decrease in the internal quantum yield. As a result, the brightness of the LED will drop, 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 about 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 a strong heating of the resistor and the process of melting the insulation that touches its wires. Then the paint begins to burn and under the influence of high temperatures destruction occurs. This is due to the fact that the resistor only dissipates the power for which it was designed.

Scheme for switching on a powerful LED

To connect high-power LEDs, you need to use AC / DC converters that have a stabilized current output. This will eliminate the need for a resistor or an LED driver IC. At the same time, we can achieve simple LED connection, comfortable system use and cost reduction.

Before connecting high-power LEDs to the mains, make sure that they are connected to a power source. Do not connect the system to a power supply that is energized, otherwise the LEDs will fail.

LEDs 5050. Characteristics. Switching scheme

Low-power LEDs also include surface LEDs. They are most often used to illuminate buttons in a mobile phone or for a decorative LED strip.

LEDs 5050 (type body 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 peculiarity 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 diffuse lens is transparent and filled with epoxy resin.

In order for the 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 circuit.

Schemes for switching on flashing LEDs

A flashing LED is an LED that has an integrated integrated flash. Its flash frequency is 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 blinking 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 voltage. In addition, it can emit different colors.

About three multi-colored LEDs are built into certain types of flashing LEDs, which have different flash intervals.

Flashing LEDs are also quite economical. The fact is that the electronic circuit for switching on the LED is made on MOS structures, thanks to which a separate functional unit can be replaced with a blinking diode. 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 ordinary ones, the only exception is that the lines of the arrows are not just straight, but dotted. Thus, they symbolize the flashing 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 an oscillator chip.

All components of this device are connected using three golden wire jumpers. To distinguish a blinking LED from a normal one, just look at the transparent housing in the light. There you can see two substrates of the same size.

On one substrate is a crystalline light emitter cube. It is made of rare earth alloy. In order to increase the luminous flux and focus, as well as to form the radiation pattern, a parabolic aluminum reflector is used. This reflector in the blinking LED is smaller in size than in the normal one. This is due to the fact that in the second half of the case there is a substrate with an integrated circuit.

Between themselves, these two substrates communicate with the help of two golden wire jumpers. As for the body of the blinking LED, it can be made either from light-diffusing matte plastic or from transparent plastic.

Due to the fact that the emitter in a flashing LED is not on the axis of symmetry of the body, then for the functioning of uniform illumination it is necessary to use a monolithic colored diffuse light guide.

The presence of a transparent case 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 work is constant, and the frequency is about 100 kHz.

Along with the high-frequency generator, a divider on logic elements also functions. He, in turn, divides the high frequency up to 1.5-3 Hz. The reason for the joint use of a high-frequency generator with a frequency divider is that for the operation of a low-frequency generator, it is necessary to have a capacitor with the largest capacitance for the timing circuit.

Bringing the high frequency up to 1-3 Hz requires the presence of dividers on logic elements. And they can be applied quite easily on a small space of a semiconductor crystal. On the semiconductor substrate, in addition to the divider and master high-frequency oscillator, there is a protective diode and an electronic switch. A limiting resistor is built into the blinking LEDs, which are rated 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 the power supply is reversed, a protective diode is required. It is necessary in order to prevent the failure of the microcircuit.

In order for the operation of high-voltage flashing LEDs to be long-term and uninterrupted, the supply voltage should not exceed 9 volts. If the voltage rises, then the power dissipation of the blinking LED will increase, which will lead to heating of the semiconductor crystal. Subsequently, due to excessive heating, degradation of the flashing LED will begin.

When it is necessary to check the health of a blinking 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 power of the resistor must be at least 0.25 watts.

Mounting LEDs

The installation of LEDs is a very important issue for the reason that it is directly related to their viability.

Since LEDs and microcircuits do not like static and overheating, it is necessary to solder parts as quickly as possible, no more than five seconds. In this case, you need to use a low power soldering iron. The tip temperature should not exceed 260 degrees.

When soldering, you can additionally use medical tweezers. With tweezers, the LED is clamped closer to the case, due to which, during soldering, additional heat is removed from the crystal. So that the legs of the LED do not break, they must not be bent much. They must remain parallel to each other.

In order to avoid overload or short circuit, the device must be equipped with a fuse.

Scheme for smooth turning on LEDs

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 scheme is used to illuminate the interior of the car. But this is not its only application. It is also used in other areas.

A simple LED soft start circuit would consist of a transistor, a capacitor, two resistors, and an LED. It is necessary to choose such current-limiting resistors that can pass a current of 20 mA through each LED string.

The circuit for smoothly turning on and off the LEDs will not be complete without the presence of a capacitor. It is he who allows her to collect. The transistor must be p-n-p-structure. And the current on the collector should not be less than 100 mA. If the LED soft-on circuit is assembled correctly, then, using the example of a car’s interior lighting, the LEDs will turn on smoothly in 1 second, and after the doors are closed, they will turn off smoothly.

Sequential switching of LEDs. Scheme

One of the lighting effects with the use of LEDs is their sequential inclusion. It is called the running fire. Such a scheme works from an autonomous power supply. For its design, a conventional switch is used, which supplies power to each of the LEDs in turn.

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, which is also a decimal counter. Then the voltage is applied to the base of the transistor and opens it. The anode of the LED is connected to the plus of the power source, which leads to a glow.

The second pulse forms a logical unit at the next output of the counter, and a low voltage appears on the previous one and closes the transistor, causing the LED to turn off. Then everything happens in the same sequence.