In theory, the diameter of the conductors should correspond to the declared parameters. For example, if it is indicated on the marking that the cable is 3 x 2.5, then the cross section of the conductors must be exactly 2.5 mm 2. In fact, it turns out that the real size can differ by 20-30%, and sometimes more. What does it threaten? Overheating or melting of insulation with all the ensuing consequences. Therefore, before buying, it is advisable to find out the size of the wire in order to determine its cross section. How exactly to calculate the cross section of the wire in diameter and we will find out further.
How and with what to measure the diameter of the wire (wire)
To measure the diameter of the wire, a caliper or micrometer of any type (mechanical or electronic) is suitable. It is easier to work with electronic ones, but not everyone has them. It is necessary to measure the core itself without insulation, therefore first move it away or remove a small piece. This can be done if the seller allows. If not, buy a small piece for testing and take measurements on it. On a conductor stripped of insulation, measure the diameter, after which you can determine the actual cross-section of the wire according to the dimensions found.
Which measuring device is better in this case? If we talk about mechanical models, then a micrometer. It has higher measurement accuracy. If we talk about electronic options, then for our purposes they both give quite reliable results.
If you don't have a caliper or micrometer, take a screwdriver and a ruler with you. You will have to strip a pretty decent piece of the conductor, so this time you are unlikely to do without buying a test sample. So, remove the insulation from a piece of wire 5-10 cm. Wind the wire around the cylindrical part of the screwdriver. The coils are laid close to each other, without a gap. All turns must be complete, that is, the "tails" of the wire must stick out in one direction - up or down, for example.
The number of turns is not important - about 10. It can be more or less, it's just easier to divide by 10. You count the turns, then apply the resulting winding to the ruler, aligning the beginning of the first turn with the zero mark (as in the photo). Measure the length of the section occupied by the wire, then divide it by the number of turns. Get the wire diameter. It's that simple.
For example, let's calculate the size of the wire shown in the photo above. The number of turns in this case is 11, they occupy 7.5 mm. We divide 7.5 by 11, we get 0.68 mm. This will be the diameter of this wire. Next, you can search for the cross section of this conductor.
We are looking for a wire cross-section by diameter: formula
The wires in the cable are circular in cross section. Therefore, in the calculations we use the formula for the area of a circle. It can be found using either the radius (half of the measured diameter) or the diameter (see formula).
Determine the cross section of the wire by diameter: formula
For example, let's calculate the cross-sectional area of the conductor (wire) according to the size calculated earlier: 0.68 mm. Let's use the radius formula first. First we find the radius: we divide the diameter by two. 0.68 mm / 2 = 0.34 mm. Next, we substitute this number into the formula
S \u003d π * R 2 \u003d 3.14 * 0.34 2 \u003d 0.36 mm 2
It is necessary to count as follows: first we square 0.34, then we multiply the resulting value by 3.14. We got the cross section of this wire 0.36 square millimeters. This is a very thin wire that is not used in power networks.
Let's calculate the cable cross-section by diameter using the second part of the formula. It should be exactly the same value. The difference may be in thousandths due to different rounding.
S \u003d π / 4 * D 2 \u003d 3.14 / 4 * 0.68 2 \u003d 0.785 * 0.4624 \u003d 0.36 mm 2
In this case, we divide the number 3.14 by four, then square the diameter, multiply the two resulting numbers. We get a similar value, as it should be. Now you know how to find out the cable cross-section by diameter. Whichever of these formulas is more convenient for you, use that one. No difference.
Correspondence table for wire diameters and their cross-sectional area
It is not always desirable or possible to carry out calculations in a store or in the market. In order not to waste time on calculations or not to make a mistake, you can use the table of wire diameters and cross-sections, which contains the most common (standard) sizes. You can write it down, print it out and take it with you.
| Conductor diameter | Conductor cross section |
|---|---|
| 0.8mm | 0.5 mm2 |
| 0.98 mm | 0.75 mm2 |
| 1.13mm | 1 mm2 |
| 1.38mm | 1.5 mm2 |
| 1.6mm | 2.0 mm2 |
| 1.78mm | 2.5 mm2 |
| 2.26 mm | 4.0 mm2 |
| 2.76mm | 6.0 mm2 |
| 3.57mm | 10.0 mm2 |
| 4.51 mm | 16.0 mm2 |
| 5.64 mm | 25.0 mm2 |
How to work with this table? As a rule, the cables have a marking or a tag on which its parameters are indicated. It indicates the cable marking, the number of cores and their cross section. For example, 2x4. We are interested in the parameters of the core, and these are the numbers that come after the “x” sign. In this case, it is stated that there are two conductors having a cross section of 4 mm 2 . So we will check whether this information is true.
How to work with a table
To check, measure the diameter using any of the methods described, then refer to the table. It states that with such a cross section of four square millimeters, the wire size should be 2.26 mm. If your measurements are the same or very close (there is a measurement error, since the devices are not ideal), everything is fine, you can buy this cable.
But much more often, the actual diameter of the conductors is much less than the declared one. Then you have two ways: look for a wire from another manufacturer or take a larger section. Of course, you will have to overpay for it, but the first option will require a fairly long period of time, and it’s not a fact that you will be able to find a cable that meets GOST.
The second option will require more money, since the price significantly depends on the declared section. Although, not a fact - a good cable, made according to all standards, can cost even more. This is understandable - the cost of copper, and, often, for insulation, subject to technology and standards, is much higher. Therefore, manufacturers are cunning, reducing the diameter of the wires - in order to reduce the price. But such savings can turn into disaster. So be sure to take measurements before buying. Even trusted suppliers.
And one more thing: inspect and feel the insulation. It should be thick, solid, have the same thickness. If, in addition to changing the diameter, there are also problems with insulation, look for a cable from another manufacturer. In general, it is desirable to find products that meet the requirements of GOST, and not made according to TU. In this case, there is hope that the cable or wire will last a long time and without problems. Today this is not easy to do, but if you breed or, quality is very important. That's why it's probably worth looking into.
How to determine the cross section of a stranded wire
Sometimes conductors are used stranded - consisting of many identical thin wires. How to calculate the wire cross-section by diameter in this case? Yes, exactly the same. Take measurements / calculations for one wire, count their number in a bundle, then multiply by this number. So you will find out the cross-sectional area of \u200b\u200ba stranded wire.
Pinout of various Jack (TRS) connectors
Jack connector aka TRS, a common connector for transmitting an audio signal with ring contacts.
There are three standard sizes for this connector.
- Jack 6.35 mm (sometimes called a big jack).
- Mini-jack 3.5 mm
- Micro-jack 2.5 mm.
Also, the connectors differ in the number of contacts (rings):
- Most often it has three pins and is correctly called TRS (stereo signal)
- The variant with two is called TS (mono)
- Four TRRS variant (stereo + microphone\button\etc)
- With five pins TRRRS (stereo + video, etc.)
The standard stereo jack (TRS) has the following pinout:
In professional sound engineering, a balanced connection is often used, then the pin assignment is different:
For headsets of mobile phones today, the TRRS connector (four pins) of size 3.5mm is most often used. For this connector, until 2012, manufacturers usually used a combination of contacts corresponding to the OMTP (Open Mobile Terminal Platform) standard. After 2012, the CTIA (Cellular Telephone Industries Association) sequence became standard practice among electronics manufacturers. Pinout of both standards in the figure below.
When you connect an OMTP headset to a CTIA device in standard mode, the ground is unused. The sound of the headphones at the same time is heard as a characteristic "deaf" mono with a large excess of medium frequencies. When you press the headset button, the microphone closes to the ground contact and the OMTP standard headset headphones work according to the standard scheme in stereo mode.
There are also many possible non-standard pinouts for this connector. Below is the pinout of some plugs from Apple.
In some Motorola phones, a four-pin 2.5mm jack (TRRS) plug with a non-standard pinout was used for the headset:
Hello.
Any modern multimedia device (computer, laptop, player, phone, etc.) has audio outputs: for connecting headphones, speakers, a microphone, and other devices. And it would seem that everything is simple - I connected a device to the audio output and it should work.
But everything is not always so easy ... The fact is that the connectors on different devices are different (although sometimes they are very similar to each other)! The vast majority of devices use connectors: jack, mini-jack and micro-jack (jack in English means "jack"). That's about them and I want to say a few words in this article.
Mini-Jack connector (diameter 3.5 mm)
Rice. 1. mini jack
Why did I start with a mini-jack? It is simply the most popular connector that can only be found in modern technology. Found in:
- - headphones (moreover, both with a built-in microphone and without it);
- - microphones (amateur);
- - various players and phones;
- - speakers for computers and laptops, etc.
Connector Jack (diameter 6.3 mm)
It is much rarer than mini-Jack, but nevertheless quite common in some devices (more, of course, in professional devices than in amateur ones). Eg:
- microphones and headphones (professional);
- bass guitars, electric guitars, etc.;
- sound cards for professionals and other audio devices.
Micro-Jack connector (diameter 2.5mm)
The smallest connector listed. Its diameter is only 2.5 mm and it is used in the most portable technology: phones and players. True, recently, even they began to use a mini-jack in order to increase the compatibility of the same headphones with PCs and laptops.
Mono and stereo
Rice. 4. 2 contacts - Mono; 3 pins - stereo
Please also note that the jack connectors can be either mono or stereo (see Fig. 4). In some cases, this can cause a lot of problems ...
For most users, the following will suffice:
- mono - this means for one sound source (you can only connect a mono speaker);
- stereo - for several sound sources (for example, left and right speakers, or headphones. You can connect both mono and stereo speakers);
- quad - practically the same as stereo, only two more sound sources are added.
Headset jack in laptops for connecting headphones with a microphone
In modern laptops, a headset jack is increasingly common: it is very convenient for connecting headphones with a microphone (there is no extra wire). By the way, on the body of the device, it is usually indicated as follows: a picture of headphones with a microphone (see Fig. 5: on the left - microphone outputs (pink) and headphones (green), on the right - a headset jack).
By the way, the plug for connecting to such a connector should have 4 pins (as in Fig. 6). I talked about this in more detail in my previous article:
Rice. 6. Plug for connecting to the headset jack
How to Connect Speakers, Microphone or Headphones to Computer
If you have the most common sound card on your computer, then everything is quite simple. On the back of the PC, you should have 3 outputs, as in fig. 7 (at least):
- Microphone (microphone) - marked in pink. Needed to connect a microphone.
- Line-in (blue) - used, for example, to record sound from some device;
- Line-out (green) - this is a headphone or speaker output.
Problems most often occur when, for example, you have headset headphones with a microphone and there is no such output on your computer ... In this case, there is dozens of different adapters : there is, including an adapter from the headset jack to the usual ones: Microphone and Line-out (see Fig. 8).
Also, a fairly common problem is the lack of sound (most often after reinstalling Windows). The problem in most cases is due to the lack of drivers (or the installation of the wrong drivers). I recommend using the recommendations from this article:
You may also be interested in the following articles:
- - connecting headphones and speakers to a laptop (PC):
- - extraneous sound in speakers and headphones:
- - quiet sound (how to increase the volume):
Hello people!
Everyone has headphones, and sooner or later, every headphone has problems. 99% of these problems are related to the connector. The thermoplastic connector gradually becomes softer, loosens, peels off from the wire. And it protects the wire at the exit point from the thermoplastic worse and worse. We will repair, or rather just solder a new connector.
When my beloved wife's left ear stopped working on her favorite synheisers, she looked at me with a look when everything was clear without words, and the next day after work I went to Savelovsky Bazaar in Moscow. There are several stalls with slots there. It’s just that it’s convenient for me to go there on the way, but the matter was urgent, the work was standing without headphones. Seeing exactly the same connectors as described here for 300 - 350 rubles a piece, made round eyes, ofigef saying "hop-hop?" I heard - “three hundred, this is a sinheiser !!!”. Well, we know this sinheiser. I took a 20-ruble plastic connector as a temporary hut: 
and on the same evening I got on Ali and found the described lot of four pieces for 2.35 monetary units of a distant overseas country. In rubles, it was carried out in the amount of 152.31, that is, 38 rubles and 8 kopecks per piece. That is, almost 8 times cheaper than the market. It was this glaring difference in price that prompted me to write a review on such a trifle.
We arrived quickly. August 23 evening order - September 3 morning in the mailbox. 
There are 4 connectors in different colors in the package. The seller can also put any specific color that you like, you must ask in the order. Connectors in sealed individual bags. A piece of solder is attached to each, 20 times more than it is necessary to solder it, and five centimeters of black 4 mm heat shrink.
At the request of our beloved wife, we will open and solder the red one. 
The contact part is slightly elongated so that it can be plugged into modern smart phones with a recessed socket, although with a slight thickening. The letters are applied qualitatively, they are not scraped off with a fingernail. 
.A little unusual arrangement inside, no usual petals, but there seems to be no particular problems. All metal parts are covered with something yellow, we have to believe that it is gold. Irradiated with the help of LTI-120 very easily. The applied solder is quite fusible, with flux. 
Soldered also bases of problems. Outside, I put heat shrink on everything and twisted the cap. It turned out nice. 
The cat is on vacation in the country, today without him.
Thank you for your attention!
I plan to buy +59 Add to favorites Liked the review +42 +82When an electric current flows through a cable, some of the energy is lost. It goes to heating the conductors due to their resistance, with a decrease in which the amount of transmitted power and the allowable current for copper wires increase. The most acceptable conductor in practice is copper, which has a low electrical resistance, suits consumers at a cost and is available in a wide range.
The next metal with good conductivity is aluminum. It is cheaper than copper, but more brittle and deforms at the joints. Previously, intra-house domestic networks were laid with aluminum wires. They were hidden under plaster and for a long time they forgot about electrical wiring. Electricity was mainly spent on lighting, and the wires easily withstood the load.
With the development of technology, many electrical appliances appeared, which became indispensable in everyday life and required more electricity. The power consumption increased and the wiring could no longer cope with it. Now it has become unthinkable to supply electricity to an apartment or house without calculating the electrical wiring in terms of power. Wires and cables are selected so that there are no extra costs, and they fully cope with all the loads in the house.
The reason for the heating of the wiring
The passing electric current causes heating of the conductor. At elevated temperatures, the metal quickly oxidizes, and the insulation begins to melt at a temperature of 65 0 C. The more often it heats up, the faster it fails. For this reason, the wires are selected according to the allowable current at which they do not overheat.
Wiring area
The shape of the wire is made in the form of a circle, square, rectangle or triangle. In apartment wiring, the cross section is predominantly round. The copper bus is usually installed in a switch cabinet and is rectangular or square.
The cross-sectional areas of the cores are determined by the main dimensions measured with a caliper:
- circle - S \u003d πd 2 / 4;
- square - S \u003d a 2;
- rectangle - S = a * b;
- triangle - πr 2/3.
The following designations are used in the calculations:
- r - radius;
- d - diameter;
- b, a - width and length of the section;
- pi = 3.14.
Calculation of power in wiring
The power released in the cable cores during its operation is determined by the formula: P \u003d I n 2 Rn,
where I n - load current, A; R - resistance, Ohm; n is the number of conductors.
The formula is suitable when calculating one load. If several of them are connected to the cable, the amount of heat is calculated separately for each energy consumer, and then the results are summarized.
The permissible current for copper stranded conductors is also calculated from the cross section. To do this, fluff the end, measure the diameter of one of the wires, calculate the area and multiply by their number in the wire.
for different operating conditions
It is convenient to measure wire cross-sections in square millimeters. If you roughly estimate the allowable current, mm2 of copper wire passes 10 A through itself, while not overheating.
In a cable, adjacent wires heat each other, so for it you need to choose the thickness of the core according to the tables or as adjusted. In addition, the sizes are taken with a small margin upwards, and then they are selected from the standard range.
The wiring can be open and hidden. In the first version, it is laid outside on surfaces, in pipes or in cable channels. Hidden passes under plaster, in channels or pipes inside structures. Here, the working conditions are more stringent, since in closed spaces without air access, the cable heats up more strongly.
For different operating conditions, correction factors are introduced, by which the rated continuous current should be multiplied, depending on the following factors:
- single-core cable in a pipe with a length of more than 10 m: I \u003d I n x 0.94;
- three in one pipe: I = I n x 0.9;
- laying in water with a protective coating type Kl: I = I n x 1.3;
- four-core cable of equal cross section: I \u003d I n x 0.93.
Example
With a load of 5 kW and a voltage of 220 V, the current through the copper wire will be 5 x 1000/220 = 22.7 A. Its cross section will be 22.7/10 = 2.27 mm 2. This size will provide the allowable current for heating copper wires. Therefore, a small margin of 15% should be taken here. As a result, the cross section will be S \u003d 2.27 + 2.27 x 15 / 100 \u003d 2.61 mm 2. Now, to this size, you should choose a standard wire cross-section, which will be 3 mm.
Heat dissipation during cable operation
A conductor cannot be heated by a passing current indefinitely. At the same time, it gives off heat to the environment, the amount of which depends on the temperature difference between them. At a certain moment, an equilibrium state occurs and the temperature of the conductor is set constant.
Important! With properly selected wiring, heating losses are reduced. It should be remembered that for irrational (when the wires overheat) you also have to pay. On the one hand, a fee is charged for the extra consumption of the meter, and on the other hand, for the replacement of the cable.
Wire section selection
For a typical apartment, electricians do not particularly think about which wiring sections to choose. In most cases, these are used:
- input cable - 4-6 mm 2;
- sockets - 2.5 mm 2;
- main lighting - 1.5 mm 2.
Such a system copes well with loads if there are no powerful electrical appliances, which sometimes need to be supplied separately.
Great for finding the allowable copper wire current, table from the reference book. It also provides calculation data when using aluminum.
The basis for the choice of wiring is the power of consumers. If the total power in the lines from the main input P \u003d 7.4 kW at U \u003d 220 V, the permissible current for copper wires will be 34 A according to the table, and the cross section will be 6 mm 2 (closed gasket).
Short-term operating modes
The maximum allowable short-term current for copper wires for operating modes with cycle durations up to 10 minutes and operating periods between them no more than 4 minutes is reduced to a long-term operating mode if the cross section does not exceed 6 mm 2. With a cross section above 6 mm 2: I add \u003d I n ∙ 0.875 / √T p.v. ,
where T p.v - the ratio of the duration of the working period to the duration of the cycle.
Power off during overloads and short circuits is determined by the technical characteristics of the circuit breakers used. Below is a diagram of a small apartment control panel. Power from the meter is supplied to the 63 A DP MCB introductory circuit breaker, which protects the wiring up to the 10 A, 16 A and 20 A circuit breakers of individual lines.
Important! The thresholds for the operation of the automata must be less than the maximum allowable wiring current and higher than the load current. In this case, each line will be reliably protected.
How to choose the lead wire to the apartment?
The value of the rated current on the input cable to the apartment depends on how many consumers are connected. The table shows the necessary devices and their power.
The current strength from a known power can be found from the expression:
I = P∙K and /(U∙cos φ), where K and = 0.75 is the simultaneity factor.
For most electrical appliances that are active loads, the power factor cos φ \u003d 1. For fluorescent lamps, vacuum cleaner motors, washing machines, etc., it is less than 1 and must be taken into account.
The long-term permissible current for the devices listed in the table will be I \u003d 41 - 81 A. The value is quite impressive. You should always think carefully when you buy a new electrical appliance, whether the apartment network will pull it. According to the table for open wiring, the cross section of the input wire will be 4-10 mm 2. Here it is also necessary to take into account how the apartment load will affect the common house. It is possible that the housing office will not allow connecting so many electrical appliances to the entrance riser, where a busbar (copper or aluminum) passes through the distribution cabinets for each phase and neutral. They simply will not be pulled by an electric meter, which is usually installed in a switchboard on the landing. In addition, the fee for overrunning the electricity norm will grow to an impressive size due to increasing coefficients.
If wiring is done for a private house, then here it is necessary to take into account the power of the outlet wire from the main network. The commonly used SIP-4 with a cross section of 12 mm 2 may not be enough for a large load.
Selection of wiring for individual consumer groups
After the cable for connecting to the network has been selected and an input automat that protects against overloads and short circuits has been selected for it, it is necessary to select the wires for each consumer group.
The load is divided into lighting and power. The most powerful consumer in the house is the kitchen, where an electric stove, washing machine, dishwasher, refrigerator, microwave and other electrical appliances are installed.
For each outlet, 2.5 mm 2 wires are selected. According to the table for hidden wiring, he will miss 21 A. The supply scheme is usually radial - from Therefore, wires of 4 mm 2 should fit the box. If the sockets are connected by a loop, it should be borne in mind that a cross section of 2.5 mm 2 corresponds to a power of 4.6 kW. Therefore, the total load on them should not exceed it. There is one drawback here: if one outlet fails, the rest may also be inoperative.
It is advisable to connect a separate wire with a machine to a boiler, electric stove, air conditioner and other powerful loads. The bathroom also has a separate input with an automatic machine and an RCD.
A 1.5 mm 2 wire is used for lighting. Now many use the main and additional lighting, where a larger cross section may be required.
How to calculate three-phase wiring?
The type of network affects the calculation of the allowable. If the power consumption is the same, the permissible current loads on the cable cores for will be less than for single-phase.
To power a three-core cable at U = 380 V, the formula is applied:
I = P/(√3∙U∙cos φ).
The power factor can be found in the characteristics of electrical appliances or it is equal to 1 if the load is active. The maximum allowable current for copper wires, as well as aluminum wires at three-phase voltage, is indicated in the tables.
Conclusion
To prevent overheating of conductors during continuous load, it is necessary to correctly calculate the cross-section of the conductors, on which the permissible current for copper wires depends. If the power of the conductor is not enough, the cable will fail prematurely.
