In the diagram, we see a traditional series connection of LEDs connected to a battery.
This connection assumes an equally bright LED glow. But here the resistor "interferes" with us.
Let's consider a little other example. Namely, let's take an LED driver and connect it to three series LEDs.
As a result of the fact that the current strength in the closed circuit is the same, then the same current I 1 \u003d I 2 \u003d I 3 will flow through each diode. The connection without a resistor using a driver also provides the same brightness, and the difference in the voltage drop across the diodes does not play any values. It is reflected only in the value of the potential difference between point 1 and 2.
Calculation of the driver for serial connection of LEDs
The above daisy-chaining LEDs can raise big questions about the choice of the driver itself. Using the calculation algorithm below, you can always independently calculate the driver, depending on the selected connection.
Let's say we need to power three LEDs connected in series with a current of 700 mA.
The voltage drop (fictitious) at this current is from 3.2 to 3.4 V.
Minimum voltage U min \u003d 3 * 3.2 \u003d 9.6 V
Maximum voltage U max \u003d 3.4 * 3 \u003d 10.2 V
The power consumed by the LEDs will be: P \u003d 10.2 * 0.7 \u003d 7.14 W.
Total: our driver must have:
Output current 700 mA
Output voltage 10.2V + - 5%
Output power not less than 7.2 W
It's all! As you can see. no problem. I will not consider the calculation of the resistor in the absence of a driver. These are relics of the past. Any manufacturer already produces LED drivers for every taste and color. Moreover, their cost is negligible. And the efficiency from the "box" is much higher than from a simple resistor.
Pros and cons of daisy chaining LEDs
Plus one and big - cheapness in construction.
There are at least two disadvantages with a serial connection:
- If at least one LED fails, the entire chain will naturally go out. Here, however, you can find another plus ... If the diode is short-circuited, the circuit will not break and the rest of the chips will continue their work.
- If there are many LEDs, then low-voltage power supply is extremely difficult to implement. And this is already a problem. Especially if you need to have safety first.
LED Series Video
For those who are too lazy to read a lot of bukavak, we suggest watching a simple video on the topic: "serial connection of LEDs". From it you will quickly glean information on how to properly connect diodes with such a connection.
In previous articles, various issues of connecting LEDs have been described. But you can't write everything in one article, so you will have to continue this topic. Here we will talk about the different ways to turn on the LEDs.
As mentioned in the articles mentioned, i.e. the current through it must be limited with a resistor. How to calculate this resistor has already been described, we will not repeat ourselves here, but we will give the formula again, just in case.
Picture 1.
Here Upit. - supply voltage, Upp. is the voltage drop across the LED, R is the resistance of the limiting resistor, I is the current through the LED.
However, despite all the theory, the Chinese industry produces all kinds of souvenirs, key rings, lighters in which the LED is turned on without a limiting resistor: just two or three disk batteries and one LED. In this case, the current is limited by the internal resistance of the battery, the power of which is simply not enough to burn the LED.
But here, in addition to burnout, there is another unpleasant property - degradation of LEDs, which is most inherent in white and blue LEDs: after a while, the glow brightness becomes very insignificant, although the current flows through the LED is quite sufficient, at the nominal level.
This is not to say that it does not shine at all, the glow is hardly noticeable, but this is no longer a flashlight. If, at the rated current, degradation occurs no earlier than after a year of continuous glow, then at an overestimated current, this phenomenon can be expected in half an hour. This LED inclusion should be called bad.
Such a scheme can only be explained by the desire to save on one resistor, solder, and labor costs, which is apparently justified with a mass scale of production. In addition, a lighter or keychain is a disposable thing, a penny: the gas runs out or the battery runs out - the souvenir was simply thrown away.
Figure 2. The scheme is bad, but it is used quite often.
Very interesting things are obtained (of course, by accident) if, according to this scheme, you connect an LED to a power supply with an output voltage of 12V and a current of at least 3A: a dazzling flash occurs, a loud enough pop, smoke is heard, and a suffocating smell remains. So this parable comes to mind: “Is it possible to look at the Sun through a telescope? Yes, but only twice. Once with the left eye, the other with the right. " By the way, connecting an LED without a limiting resistor is the most common mistake for beginners, and I would like to warn about it.
To correct this situation, to extend the life of the LED, the circuit should be slightly changed.
Figure 3. Nice diagram, correct.
It is this scheme that should be considered good or correct. To check if the value of the resistor R1 is indicated correctly, you can use the formula shown in Figure 1. Let's assume that the voltage drop across the LED is 2V, the current is 20mA, and the supply voltage is 3V due to the use of two AA batteries.
In general, you do not need to strive to limit the current at the maximum permissible 20mA, you can power the LED with a lower current, well, at least 15 ... 18 milliamperes. In this case, a very slight decrease in brightness will occur, which the human eye, due to the characteristics of the device, will not notice at all, but the service life of the LED will increase significantly.
Another example of poor lighting of LEDs can be found in various flashlights, which are already more powerful than key rings and lighters. In this case, a certain number of LEDs, sometimes quite large, are simply connected in parallel, and also without a limiting resistor, which again is the internal resistance of the battery. Such flashlights are often repaired precisely because the LEDs burn out.
Figure 4. Very bad wiring diagram.
It would seem that the circuit shown in Figure 5 can correct the situation. Just one resistor, and things seemed to be on the mend.
Figure 5. This is a little better.
But even such an inclusion will not help much. The fact is that in nature it is simply not possible to find two identical semiconductor devices. That is why, for example, transistors of the same type have a different gain, even if they are from the same production batch. Thyristors and triacs are also different. Some open easily, while others are so hard that they have to be abandoned. The same can be said about LEDs - two are absolutely identical, especially three or a whole heap, it is simply impossible to find.
Note on the topic. In DataSheet for LED assembly SMD-5050 (three independent LEDs in one package), the inclusion shown in Figure 5 is not recommended. Like, due to the scatter of the parameters of individual LEDs, a difference in their glow can be noticeable. And it would seem, in one building!
Of course, LEDs do not have any gain, but there is such an important parameter as the forward voltage drop. And even if the LEDs are taken from the same technological batch, from the same package, then there will be no two identical ones in it. Therefore, the current for all LEDs will be different. The LED, which has the most current, and sooner or later exceeds the nominal, will burn out before anyone else.
In connection with this unfortunate event, all possible current will go through the two surviving LEDs, naturally exceeding the nominal one. After all, the resistor was calculated "for three", for three LEDs. The increased current will also cause an increased heating of the LED crystals, and the one that turns out to be "weaker" also burns out. The last LED also has no choice but to follow the example of its comrades. Such a chain reaction is obtained.
In this case, the word "burn" means simply an open circuit. But it can happen that in one of the LEDs an elementary short circuit will turn out, shunting the other two LEDs. Naturally, they will definitely go out, although they will remain alive. With such a malfunction, the resistor will heat up intensely and in the end, maybe, it will burn out.
To prevent this from happening, the circuit must be slightly changed: for each LED, install its own resistor, which is shown in Figure 6.
Figure 6. And this is how the LEDs will last a very long time.
Here everything is as required, everything is according to the rules of circuitry: the current of each LED will be limited by its own resistor. In such a scheme, the currents through the LEDs are independent of each other.
But even this inclusion does not cause much delight, since the number of resistors is equal to the number of LEDs. I would like to see more LEDs and fewer resistors. How to be?
The way out of this situation is quite simple. Each LED should be replaced with a string of LEDs connected in series, as shown in Figure 7.
Figure 7. Parallel connection of garlands.
The price to pay for this improvement will be an increase in supply voltage. If only three volts are enough for one LED, then even two LEDs connected in series cannot be ignited from such a voltage. So what voltage is needed to turn on the LED string? Or in other words, how many LEDs can you connect to a power supply with a voltage of, for example, 12V?
Comment. Hereinafter, the name "garland" should be understood not only as a Christmas tree decoration, but also any LED lighting fixture in which LEDs are connected in series or in parallel. The main thing is that there is more than one LED. Garland, it is a garland in Africa!
To get an answer to this question, just divide the supply voltage by the voltage drop across the LED. In most cases, when calculating, this voltage is taken as 2V. Then it turns out 12/2 \u003d 6. But do not forget that some part of the voltage must remain for the damping resistor, at least 2 volts.
It turns out that only 10V is left for the LEDs, and the number of LEDs will become 10/2 \u003d 5. In this state of affairs, in order to obtain a current of 20mA, the limiting resistor must have a nominal value of 2V / 20mA \u003d 100Ω. In this case, the resistor power will be P \u003d U * I \u003d 2V * 20mA \u003d 40mW.
This calculation is quite valid if the forward voltage of the LEDs in the garland, as indicated, is 2V. It is this value that is often taken in calculations as some average. But in fact, this voltage depends on the type of LEDs, on the color of the glow. Therefore, when calculating garlands, you should focus on the type of LEDs. The voltage drops for different types of LEDs are shown in the table shown in Figure 8.
Figure 8. Voltage drop across LEDs of different colors.
Thus, with a 12V power supply, minus the voltage drop across the current limiting resistor, a total of 10 / 3.7 \u003d 2.7027 white LEDs can be connected. But you can't cut off a piece from the LED, so only two LEDs can be connected. This result is obtained if the maximum voltage drop value is taken from the table.
If we substitute 3V into the calculation, then it is quite obvious that three LEDs can be connected. In this case, each time you have to painstakingly recalculate the resistance of the limiting resistor. If real LEDs turn out to have a voltage drop of 3.7V, or maybe higher, three LEDs may not light up. So it's better to stop at two.
It is fundamentally not important what color the LEDs will be, just when calculating, you will have to take into account different voltage drops depending on the color of the LED. The main thing is that they are designed for one current. It is impossible to assemble a series garland of LEDs, some of which with a current of 20mA, and the other part of 10 milliamperes.
It is clear that at a current of 20mA, LEDs with a rated current of 10mA will simply burn out. If you limit the current at 10mA, then the 20mA will not light up brightly enough, like in a switch with an LED: you can see it at night, not during the day.
To make life easier for themselves, radio amateurs are developing various calculator programs that facilitate all kinds of routine calculations. For example, programs for calculating inductances, filters of various types, current stabilizers. There is such a program for calculating LED garlands. A screenshot of such a program is shown in Figure 9.
Figure 9. Screenshot of the program "Calculation_resistor_resistor__Ledz_".
The program works without installation on the system, you just need to download and use it. Everything is so simple and straightforward that no explanations for the screenshot are required at all. Naturally, all LEDs must be of the same color and with the same current.
Limiting resistors are good, of course. But only when it is known that this garland will be powered from a constant voltage of 12V, and the current through the LEDs will not exceed the calculated value. But what if there is simply no source with a voltage of 12V?
Such a situation can arise, for example, in a truck with a 24V on-board network voltage. To get out of such a crisis situation will help a current stabilizer, for example, "SSC0018 - Adjustable current stabilizer 20..600mA". Its appearance is shown in Figure 10. Such a device can be purchased in online stores. The price of the issue is 140 ... 300 rubles: it all depends on the seller's imagination and impudence.
Figure 10. SSC0018 Adjustable Current Regulator
The gimbal specifications are shown in Figure 11.
Figure 11. Technical characteristics of the current stabilizer SSC0018
The SSC0018 current stabilizer was originally designed for use in LED luminaires, but can also be used to charge small batteries. The SSC0018 is easy to use.
The load resistance at the output of the current stabilizer can be zero, you can simply short-circuit the output terminals. After all, stabilizers and current sources are not afraid of short circuits. In this case, the output current will be rated. If you installed 20mA, then this will be so.
From the above, we can conclude that a DC milliammeter can be connected "directly" to the output of the current stabilizer. Such a connection should be started from the largest measurement limit, because no one knows what current is regulated there. Then, by simply rotating the trimmer resistor, set the required current. In this case, of course, do not forget to connect the SSC0018 current stabilizer to the power supply. Figure 12 shows the SSC0018 wiring diagram for powering LEDs connected in parallel.
Figure 12. Connection for supplying LEDs connected in parallel
Everything here is clear from the diagram. For four LEDs with a current consumption of 20mA, a current of 80mA must be set at the output of the stabilizer for each. At the same time, at the input of the SSC0018 stabilizer, a voltage will be required a little more than the voltage drop across one LED, as mentioned above. Of course, a higher voltage is also suitable, but this will only lead to additional heating of the stabilizer microcircuit.
Comment. If, to limit the current using a resistor, the power supply voltage should slightly exceed the total voltage on the LEDs, only two volts, then for normal operation of the SSC0018 current stabilizer this excess should be slightly higher. Not less than 3 ... 4B, otherwise the regulating element of the stabilizer will simply not open.
Figure 13 shows the connection of the SSC0018 stabilizer when using a string of several series-connected LEDs.
Figure 13. Powering the daisy chain through the SSC0018 regulator
The figure is taken from the technical documentation, so let's try to calculate the number of LEDs in the garland and the constant voltage required from the power supply.
The current indicated in the diagram, 350mA, allows us to conclude that the garland is assembled from powerful white LEDs, because as mentioned just above, the main purpose of the SSC0018 stabilizer is lighting sources. The voltage drop across the white LED is 3 ... 3.7V. For the calculation, take the maximum value of 3.7V.
The maximum input voltage of the SSC0018 regulator is 50V. Subtract from this value 5V, required for the operation of the stabilizer itself, 45V remains. This voltage can "light up" 45 / 3.7 \u003d 12.1621621 ... LEDs. Obviously, this should be rounded up to 12.
The number of LEDs can be less. Then the input voltage will have to be reduced (while the output current will not change, so 350mA will remain as it was adjusted), why should 3 LEDs, even powerful ones, be supplied with 50V? Such a mockery can end in tears, because powerful LEDs are by no means cheap. What voltage is required to connect three powerful LEDs, those who wish, and they will always be found, can calculate themselves.
The SSC0018 adjustable current stabilizer device is quite good. But the whole question is, is it always needed? And the price of the device is somewhat confusing. What could be the way out of this situation? Everything is very simple. An excellent current regulator is obtained from integrated voltage regulators, for example, the 78XX or LM317 series.
To create such a current stabilizer based on a voltage stabilizer, only 2 parts are required. The stabilizer itself and one single resistor, the resistance and power of which will help to calculate the StabDesign program, a screenshot of which is shown in Figure 14.
Figure 14. Calculation of the current stabilizer using the StabDesign program.
The program does not require any special explanations. In the Type drop-down menu, the type of stabilizer is selected, the required current is set in the In line and the Calculate button is pressed. The result is the resistance of the resistor R1 and its power. In the figure, the calculation is carried out for a current of 20mA. This is for the case when the LEDs are connected in series. For parallel connection, the current is calculated in the same way as shown in Figure 12.
The LED garland is connected instead of the resistor Rн, which symbolizes the load of the current stabilizer. It is even possible to connect just one LED. In this case, the cathode is connected to the common wire, and the anode to the resistor R1.
The input voltage of the considered current stabilizer is in the range of 15 ... 39V, since the 7812 stabilizer is used with a stabilization voltage of 12V.
It would seem that this is the end of the story about LEDs. But there are also LED strips, which will be discussed in the next article.
When developing electrical circuits in which more than one LED is involved, the question arises which LED connection is better to choose: serial or? Looking ahead, we note that sequential switching is always more efficientbut not always easy to implement. Let's figure out why?
LED volt-ampere characteristic (VAC)
A light-emitting diode is a non-linear element of an electrical circuit, its I – V characteristic is almost identical in shape to a conventional silicon diode. Figure 1 shows the I - V characteristic of a powerful white LED, one of the world's leading manufacturers.
The graph shows that with an increase in voltage by only 0.2 V (for example, a 2.9 ... 3.1 V section), the current strength more than doubles (from 350 mA to 850 mA). The opposite is also true: when the current changes over a fairly wide range, the voltage drop changes very slightly. It is very important.
The second important point is that the voltage drop from sample to sample in one batch can differ by several tenths of a volt (technological spread). For this reason, it must be stabilized in terms of current, not voltage. The luminous flux, by the way, is also standardized depending on the direct current. Now let's see how this information comes in handy when choosing a wiring diagram.
Serial connection (Figure 2).
The diagram shows the series connection of three LEDs HL1 ... HL3 to a constant current source J. For simplicity, let's take an ideal current source, i.e. a source that provides a constant current of the same magnitude, regardless of the load. Since the current in a closed loop is the same, a current of the same magnitude I 1 \u003d I 2 \u003d I 3 \u003d J flows through each element connected in series to this loop. Accordingly, the same brightness is provided. The difference in voltage drops across individual LEDs has no meaning in this case and is reflected only in the magnitude of the potential difference between points 1 and 2.
Let's consider a specific example of calculating such a scheme. Suppose you want to provide power to three series-connected LEDs with a current of 350 mA. The voltage drop at this current, according to the manufacturer, can range from 2.8 V to 3.2 V.
Let's calculate the required range of the output voltage of the current source:
U min \u003d 2.8 x 3 \u003d 8.4 V;
U max \u003d 3.2 × 3 \u003d 9.6 V.
The maximum power consumed by LEDs will be P \u003d 9.6 × 0.35 \u003d 3.4 W.
Thus, the source must have the following parameters:
Output stable current - 350 mA;
Output voltage - 9 V ± 0.6 V (or ± 7%);
Output power - not less than 3.5 W.
Everything is extremely simple.
Commercially available power supplies for LEDs () usually have a wider output voltage range so that the designer of the lighting device is not tied to a specific number of emitting diodes, but has some freedom of action. In this case, you can connect in series to the same source, for example, from 1 to 8 LEDs.
However, the series connection has its drawbacks.
- Firstly, if one of the diodes in the circuit fails, for obvious reasons all the others also go out. An exception is a short circuit of the LED - in this case, the circuit is not broken.
- Secondly, with a large number of LEDs, it is more difficult to implement low-voltage power supply.
For example, if the task is to power 10 LEDs in series (this is a voltage drop of about 30 V) from a car battery, then you cannot do without a boost converter. And this is additional costs, dimensions and a decrease in efficiency.
Parallel connection (Figure 3).
Consider now the parallel connection of the same light emitting diodes.
According to the first Kirchhoff's law:
J \u003d I 1 + I 2 + I 3,
To provide each LED with one-watt mode (I \u003d 350mA), the current source must supply 1050mA at an output voltage of about 3 V.
As mentioned above, LEDs have a certain technological spread of parameters, therefore, in fact, the currents will not be divided equally, but in proportion to their differential resistances.
For example, if the forward voltage drop measured across these LEDs at 350mA was 2.9V, 3V, 3.1V for HL1, HL2 and HL3 respectively. Then, when switched on according to the presented scheme, the currents will be distributed as follows:
I 1 ≈360 mA;
I 2 ≈350 mA;
I 3 ≈340 mA.
This means that the brightness of the glow will be different. To equalize currents in such circuits, resistors are usually connected in series with LEDs (Figure 4).
Equalizing resistors increase the power consumption of the overall circuit and therefore reduce efficiency.
This method of connection is most often used with low-voltage power supplies, for example, in portable devices with electrochemical power sources (accumulators, batteries). In other cases, it is recommended to connect the LEDs in series.
Serial-parallel connection
If it is necessary to connect a large number of LEDs, a series-parallel connection can be used. In this case, several branches with series-connected LEDs are connected in parallel.
LEDs (they are also led) for many years have been actively used both in the production of televisions and as the main lighting of a house or apartment, however, the question of how to properly connect LEDs is relevant to this day.
Today there are a huge number of them, of various powers (super-bright), operating from constant voltage, which can be connected in three ways:
- Parallel.
- Consistently.
- Combined.
There are also specially designed circuits that allow you to connect the LED to a stationary household 220V network. Let's take a closer look at all the options for connecting led, their advantages and disadvantages, as well as how to do it yourself.
Basic principles of connection
As mentioned earlier, the design of the light emitting diode implies their connection exclusively to a direct current source. However, since the working part of the LED is a semiconductor silicon crystal, it is very important to observe the polarity, otherwise the LED will not emit light flux.
Each LED has a technical documentation, which contains instructions and directions for correct connection. If there is no documentation, you can take a look. The marking will help you to find out the manufacturer, and knowing the manufacturer, you can find the required datasheet, which contains information on the connection. This is not a tricky piece of advice.
How to determine the polarity?
There are only 3 ways to resolve the issue:
We figured out the polarity, now we need to decide how to connect the LED to the network. For those who did not understand, read the detailed and interesting article. In it we have collected all possible verification methods, and even with the help of a battery.
Connection methods
Conventionally, the connection takes place in 2 ways:
- To a stationary network of industrial frequency (50Hz) with a voltage of 220V;
- To a network with a safe voltage of 12V.
If you need to connect several led to one power source, then you need to choose serial or parallel connection.
Let's take a look at each of the above examples separately.
Connecting LEDs to 220V
The first thing you need to know when connecting to a 220V network is that for a nominal glow, a current of 20mA must pass through the LED, and the voltage drop across it should not exceed 2.2-3V. Based on this, it is necessary to calculate the value of the current-limiting resistor using the following formula:
in which 0.75 is the led reliability factor, U pit is the voltage of the power source, U pad is the voltage that drops across the light-emitting diode and creates a luminous flux, I is the rated current passing through it, and R is the resistance rating for regulating the current. After corresponding calculations, the resistance rating should correspond to 30 kOhm.
However, do not forget that a large amount of heat will be released on the resistance due to the voltage drop. For this reason, it is additionally necessary to calculate the power of this resistor using the formula:
For our case, U is the difference between the supply voltage and the voltage drop across the LED. After the appropriate calculations, to connect one led, the resistance power must be 2W.
After determining the rating and power of the resistance, you can assemble a circuit to connect one LED to 220V. For its reliable operation, it is necessary to install an additional diode, which will protect the light-emitting diode from breakdown, in the event of an amplitude voltage at the LED terminals of 315V (220 * √2).
The circuit is practically not used, since very large losses occur in it due to the release of heat in the resistance. Consider a more efficient connection to 220 V:
In the diagram, as we can see, a reverse diode VD1 is installed, which passes both half-waves to a 220 nF capacitor C1, on which the voltage drops to the required value.
Resistance R1 with a nominal value of 240 kΩ, discharges the capacitor when the network is off, and does not play any role during the operation of the circuit.
But this is a simplified model for connecting LED, in most LED lamps there is already a built-in driver (circuit) that converts an alternating voltage of 220V to a constant voltage of 5-24V for their reliable operation. You can see the driver circuit in the following photo:
Connecting LEDs to a 12V network
12 volts is a safe voltage that is used in highly hazardous areas. These are the bathrooms, baths, observation pits, underground structures and other rooms.
To connect to a DC voltage source with a nominal value of 12V, similarly, to connect to 220V networks, a damping resistance is required. Otherwise, if you connect it directly to the source, the LED will instantly burn out due to the higher passing current.
The rating of this resistance and its power are calculated using the same formulas:
Unlike 220V circuits, to connect one LED to a 12V network, we need a resistance with the following characteristics:
- R \u003d 1.3 kΩ;
- P \u003d 0.125W.
Another advantage of the 12V voltage is that in most cases it is already rectified (constant), which greatly simplifies the wiring diagram. It is recommended to additionally mount a voltage stabilizer of the KREN type or an analogue.
As we already know, the light-emitting diode can be connected to both 12V and 220V circuits, however, there are several variations of their connection to each other:
- Consistent.
- Parallel.
Serial connection
When connected in series through a current-limiting resistor, several LEDs are collected in one chain, and the cathode of the previous one is soldered to the anode of the next one:
In the circuit, one current (20mA) will flow through all LEDs, and the voltage level will consist of the sums of the voltage drop across each. This means, using this connection diagram, you cannot include any number of LEDs in the circuit, because it is limited by the voltage drop.
Voltage drop is the level of voltage that the light-emitting diode converts into light energy (glow).
For example, in a circuit, the voltage drop across one LED will be 3 Volts. There are 3 LEDs in total. 12V power supply. We believe 3 Volts * 3 led \u003d 9 V- voltage drop.
After simple calculations, we see that we will not be able to include more than 4 LEDs (3 * 4 \u003d 12V) in the parallel circuit, powering them from a conventional car battery (or other source with a voltage of 12V).
If we want to connect more LEd in series, then we need a power supply with a higher rating.
This scheme was quite often found in Christmas tree garlands, however, due to one significant drawback, a mixed connection is used in modern ones. What is the disadvantage, we will analyze below.
Disadvantages of serial connection
- If at least one element fails, the entire circuit becomes unworkable;
- A high voltage source is needed to power large quantities of led.
Parallel connection
In this situation, everything happens the other way around. On each LED, the voltage level is the same, and the current strength consists of the sum of the currents passing through them.
Following from the above, we conclude that if we have a 12V source and 10 LEDs, the power supply must withstand a load of 0.2A (10 * 0.002).
Based on the above calculations - for parallel connection, a current-limiting resistor with a nominal value of 2.4 ohms (12 * 0.2) is required.
This is a deep misconception !!! Why? You will find the answer below
The characteristics of each LED, even of the same series and batch, are always different. In other words: in order for one to light up, it is necessary to pass a current with a nominal value of 20 mA through it, and for another, this nominal value may already be 25 mA.
Thus, if only one resistance is installed in the circuit, the nominal value of which was calculated earlier, a different current will flow through the LEDs, which will cause overheating and failure of the LEDs designed for a nominal value of 18mA, and more powerful ones will shine by only 70% of the nominal value. ...
Based on the foregoing, it should be understood that with parallel connection, it is necessary to set a separate resistance for each.
Disadvantages of parallel connection:
- A large number of items;
- When one diode fails, the load on the others increases.
Mixed connection
This connection method is the most optimal. All LED strips are assembled according to this principle. It involves a combination of parallel and serial connections. How it is performed can be seen in the photo:
The scheme involves the inclusion of parallel not individual LEDs, but sequential chains of them. As a result, even if one or more chains fail, the LED string or tape will still shine the same way.
We have covered the basic ways to connect simple LEDs. Now we will analyze the methods of connecting powerful LEDs, and what problems can be encountered if the connection is incorrect.
How to connect a powerful LED?
For the performance of high-power light-emitting diodes, just like simple ones, we need a power source. However, unlike the previous version, it should be an order of magnitude more powerful.
To light a 1W high power LED, the power supply must be capable of handling at least 350mA of load. If the rating is 5W, then the DC power supply must withstand a load current of at least 1.4A.
For correct operation of a powerful LED, it is imperative to use an integral voltage regulator of the LM type, which protects it from voltage surges.
If you need to connect not one, but several powerful LEDs, we recommend that you familiarize yourself with the rules for serial and parallel connection, which were described above.
Connection errors
Video
Connection errors can lead to unpleasant consequences, from the banal breakdown of LEDs, to self-harm. Therefore, we strongly recommend watching the video, where common errors are analyzed.
Conclusion
After reading the article, we can conclude that all LEDs, regardless of the operating voltage, are always connected in parallel or in series - a school physics course. It is also worth remembering that no LED is connected directly to the 220V network, you always need to use protective elements in the connection diagram. The type of applied protective elements depends on the type of the connected light-emitting diode.
Wiring components are special products that ensure the smooth functioning of electrical systems. Such elements are widely used in industrial enterprises when laying, repairing and pulling cables, as well as when connecting electrical equipment. Well-known manufacturers Hensel, Mennekes, Weidmueller, Wieland manufacture products in accordance with the main requirements of European quality and safety standards.
Varieties of wiring components
The company "Indatek" LLC presents a wide range of products for the installation of electrical systems at the enterprise. Copper is used as a material for the manufacture of conductive products, and ceramic or porcelain mixtures are used for insulating products. In other cases, metal alloys with a protective coating of zinc or nickel are used.
Products for the installation of electrical systems are characterized by resistance to water, corrosion, sudden changes in temperature. Such elements meet safety standards and are harmless to humans. During the manufacturing process, the products are tested for quality using a freely falling weight of 0.25 kg. Plugs, extension sockets, switches are additionally tested for drops from 0.5 m in rotating drums.
Wiring components are divided into groups depending on:
- degrees of strength - products that can withstand the impact of a load falling from a height of 15 cm, 25 cm and 50 cm;
- type of connection - external, which are attached to the surface of the structure, and built-in, which require a special niche.
- temperature resistance - products that can withstand heating up to + 80, + 100, + 130, + 160, + 240 degrees.
Terminals
Wieland terminals are used for connecting wires and cables of various types. Construction - withstand a load of 10-100 A and a voltage of 600 V. More resistant are barrier terminals operating under a voltage of 1 kV and a load of up to 200 A. Products with a spring and screw, such as models WT 2.5 or WKF 1.5 D2 / 2/35 BLAU, fixation provides a stronger clamping of the wire.
Junction boxes and housings
The products are used when installing electrical systems and connecting several devices to one energy source. Such products provide high-quality grounding, transformation, distribution of electricity throughout the system. Polycarbonate is the main material for production. A popular manufacturer is the German company Hensel, whose products are presented in the indatech.ru online store.
Power connectors
Products are devices used to connect electrical equipment to the power grid. It is recommended to use sockets and plugs when working with powerful equipment in a room with high humidity and other unfavorable conditions.
Signal concentrators (SAI)
Signal Hubs (SAI), such as SAISW-3/7 sockets and SAIL-M12GM12W-4-2L3.0T connectors, are essential for the proper operation of automation systems. The products are classified into active and passive buses, as well as power wires and connectors. Such products can be designed to work in extreme conditions: products with IP67 protection withstand exposure to water and harmful substances. Some SAI concentrators are used for explosive work.
