Diagram of switching the LED into a 220 volt network

LED lighting has become very popular now. The thing is that this lighting is not only powerful enough, but also economically profitable. LEDs are semiconductor diodes in an epoxy shell.

Initially, they were quite weak and expensive. But later in production, very bright white and blue diodes were produced. By that time, their market price had fallen. At the moment, there are LEDs of almost any color, which caused the use of them in various fields of activity. These include the lighting of various rooms, the illumination of screens and signage, the use of traffic signs and traffic lights, in the cabin and headlights of cars, in mobile phones, etc.

Description

LEDs consume very little power, and as a result, such lighting gradually displaces previously existing light sources. In specialized stores you can buy various items, based on LED lighting, from a conventional lamp and LED strip to LED panels. All of them are united by the fact that for their connection it is necessary to have a current of 12 or 24 V.

Unlike other lighting sources that use a heating element, a semiconductor crystal is used here, which generates optical radiation under the influence of current.

In order to understand the scheme of switching on the LEDs into the 220V network, one must first of all say that it can not feed 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 the LED

The current-voltage characteristic of the LED is a steep line. That is, if the voltage increases at least a little, the current will increase dramatically, this will cause the LED to overheat and then burn out. To avoid this, it is necessary to include a limiting resistor in the circuit.

But it's important not to forget about the maximum allowable reverse voltage of 20V LEDs. 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 at 220 volts is variable, 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 the following: a diode is connected to the circuit. He will not miss the reverse voltage. At the same time, the connection must be parallel.

Another scheme for switching the LED into a 220 volt network is to install two LEDs in the opposite direction.

As for the power supply from the network 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 dissipation power is about 3 watts. When the diode is connected in series, the power will be halved. The reverse voltage on the diode should be equal to 400 V. When two opposite LEDs are turned on, two two-watt resistors can be put. Their resistance should be half as much. This is possible, when in one case there are two crystals of different colors. Usually one crystal is red, the other is green.

In the case where a resistor of 200 kΩ is used, the presence of a protective diode is not required, since the current on the return path is small and will not cause the crystal to break. This scheme of including LEDs in the network has one minus - a small brightness of the light bulb. It can be used, for example, to illuminate the indoor switch.

Due to the fact that the current in the network is variable, this avoids unnecessary waste of electricity for heating the air with a limiting resistor. The capacitor manages this task. After all, it passes an alternating current and does not heat up at the same time.

It is important to remember that through the capacitor both half-cycles of the network must pass, so that it can pass an alternating current. And since the LED conducts current only in one direction, it is necessary to put a conventional diode (or even an additional LED) counter-parallel to the LED. Then he will miss the second half-period.

When the scheme of switching on the LED in the 220 volt network is switched off, there will be a voltage on the capacitor. Sometimes even a full amplitude of 315 V. This is threatened with a current shock. To avoid this, it is necessary to provide, in addition to the capacitor, a high-capacity discharge resistor, which in the event of disconnection from the network will immediately discharge the capacitor. Through this resistor, during its normal operation, a slight current flows, not heating it.

To protect against impulse charging current and as a fuse, put 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 scheme of sequential switching of LEDs 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 taken from the power supply.

It is necessary that the installed diode be designed for a current similar to the current passing through the LEDs, and the reverse voltage should 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 and forth.

In one chain there can be more than ten LEDs. To calculate the capacitor, you need to subtract from the peak voltage of the network 315 V the sum of the voltage drop of the LEDs. As a result, we know the number of voltage drop across the capacitor.

LED connection errors

• The first error is when the LED is connected without a limiter, directly to the source. In this case, the LED will very quickly fail, due to the lack of control over the magnitude of the current.
• The second error is the connection to the common resistor of the LEDs installed in parallel. Due to the fact that there is a spread of parameters, the brightness of the burning of the LEDs will be different. In addition, if one of the LEDs fails, an increase in the current of the second LED will occur, which can cause it to burn out. So, when using one resistor, you need to connect the LEDs in series. This allows the current to remain the same when calculating the resistor and to combine the voltage of the LEDs.
• The third mistake is when the LEDs, which are designed for different currents, are connected in series. This causes one of them to burn weakly, or vice versa - to work for wear.
• The fourth mistake is the use of a resistor, which has insufficient resistance. Because of this, the current flowing through the LED will be too large. Some of the energy, with an overestimated voltage, turns into heat, resulting in overheating of the crystal and a significant decrease in its service life. The reason for this is the defects in the crystal lattice. If the voltage increases even more, and the p-n junction becomes hot, 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 the inclusion of the LED in 220V, the circuit of which is very simple, in the absence of reverse voltage limitation. The maximum permissible reverse voltage for most LEDs is approximately 2 V, and the voltage of the reverse half-cycle affects the voltage drop, which is equal to the supply voltage when the LED is locked.
• 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 out and destruction occurs under the influence of high temperatures. All because the resistor dissipates only the power it was designed for.

The scheme of switching on a powerful LED

To connect high-power LEDs, you need to use AC / DC-converters, which have a stabilized current output. This will help to avoid the use of a resistor or integrated circuit driver LEDs. At the same time, we can achieve simple connection of LEDs, comfortable use of the system and reducing costs.

Before switching on the mains power LEDs, make sure that they are connected to the power source. Do not connect the system to a power supply that is under voltage, otherwise it will damage the LEDs.

Light-emitting diodes 5050. Characteristics. Connection diagram

Light-emitting diodes also include SMD LEDs . Most often they are used to illuminate buttons in a mobile phone or for decorative LED strip.

LEDs 5050 (the size of the type: 5 by 5 mm) are semiconductor light sources, the direct voltage of which is 1.8-3.4 V, and the forward current for each 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 several colors. They are called RGB-LEDs. Their body is made of heat-resistant plastic. The diffusion lens is transparent and is filled with epoxy resin.

In order for the LEDs 5050 to work as long as possible, they must be connected to the resistance values in series. For maximum reliability of the circuit, it is better to connect a separate resistor to each circuit.

Schemes for enabling flashing LEDs

The flashing LED is a light-emitting diode in which the integrated pulse generator is integrated . The frequency of flares in it is from 1.5 to 3 Hz.

Despite the fact that the flashing LED is compact enough, it contains a semiconductor chip generator and additional elements.

As for the voltage of the flashing LED, it is universal and can vary. For example, for high-voltage it is Z-14 volts, and for low-voltage 1.8-5 volts.

Accordingly, to the positive qualities of the flashing LEDs, apart from the small size and compactness of the light-signaling device, there is also a wide range of permissible voltage. In addition, it can radiate different colors.

In some types of flashing LEDs, about three different colored LEDs are built in which the flash intervals are different.

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 function node can be replaced with a flashing diode. Due to their small size, flashing LEDs are often used in compact devices that require the presence of small radio elements.

On the diagram, the flashing LEDs are indicated in the same way as the usual ones, except that the arrow lines are not just straight lines, but dotted lines. Thus they symbolize the flashing of the LED.

Through the transparent body of the flashing LED, it can be seen that it consists of two parts. There, on the negative terminal of the cathode base, there is a crystal of the light-emitting diode, and on the anode terminal there is a chip of the generator.

All components of this device are connected by means of three golden wire jumpers. To distinguish the flashing LED from the ordinary one, it is enough to view the transparent case in the light. There you can see two substrates of the same size.

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

Between these two substrates are communicated by means of two golden wire bridges. As for the case of the flashing LED, it can be made either from light-diffusing matte plastic or from transparent plastic.

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

The presence of a transparent case can be found only in flashing large-diameter LEDs, which have a narrow directional pattern.

A high-frequency master oscillator consists of a flashing LED generator. Its operation is constant, and the frequency is about 100 kHz.

Along with the high-frequency generator, a divider on the logic elements also functions. It, in turn, carries out division of high frequency up to 1,5-3 Hz. The reason for the joint application 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 time-setting circuit.

Bringing a high frequency to 1-3 Hz requires the presence of divisors on the logical elements. And they can be easily applied on a small space of a semiconductor crystal. On the semiconductor substrate, in addition to the divider and the master high-frequency generator, there is a protective diode and an electronic key. The limiting resistor is built into the flashing LEDs, which are rated for a voltage of 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 chip from failing.

That the work of high-voltage flashing LEDs was long-term and went smoothly, the supply voltage should not exceed 9 volts. If the voltage increases, the dissipated power of the flashing LED will increase, which will lead to the heating of the semiconductor crystal. Subsequently, due to excessive heating, degradation of the flashing LED will begin.

When it is necessary to check the status of the flashing LED, in order to do it safely, you can use a 4.5 volt battery and a 51 ohm resistor in series with the LED. The power of the resistor should be at least 0.25 W.

Installation of LEDs

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

Since the LEDs and chips do not like statics and overheating, it is necessary to solder the parts as quickly as possible, not more than five seconds. In this case, you need to use a low power soldering iron. The temperature of the sting should not exceed 260 degrees.

When soldering, you can also use a medical tweezer. The tweezers pin the LED closer to the housing, so that when soldering, an additional heat dissipation from the crystal is created. To the legs of the LED did not break, they need to bend not much. They must remain parallel to each other.

In order to avoid overloading or short-circuiting, the device must be provided with a fuse.

Diagram of smooth switching of LEDs

The scheme of smooth switching on and off of light-emitting diodes - popular among others, car owners are interested in it, wishing to tune their cars. This scheme is used to illuminate the car interior. But this is not the only application of it. It is also used in other spheres.

A simple scheme for smoothly switching on the LED should consist of a transistor, a capacitor, two resistors and LEDs. It is necessary to choose such current-limiting resistors, which will be able to pass a current of 20 mA through each chain of LEDs.

The scheme for smooth switching on and off of the LEDs will not be complete without the presence of a capacitor. It is he who allows it to be collected. The transistor must be a pnp-structure. And the current on the collector should not be less than 100 mA. If the scheme of smooth switching on of the LEDs is correctly assembled, then, for example, the car's interior lighting will lightly turn on the LEDs for 1 second, and after closing the doors, it will turn off smoothly.

Alternate activation of LEDs. The scheme

One of the light effects with the use of LEDs is their sequential inclusion. It is called running fire. There is such a circuit from an autonomous power supply. For its design, a conventional switch is used, which supplies the power supply alternately to each of the LEDs.

Consider a device consisting of two microcircuits and ten transistors, which together constitute a master oscillator, control and indexing itself. From the output of the master oscillator, the pulse is transmitted to the control unit, it is also 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 the logical unit at the next counter output, and the low voltage appears on the previous one and closes the transistor, as a result of which the LED will turn off. Then everything happens in the same sequence.