The color designation of the resistor. The designation of the power of the resistors in the circuit

In the electrical circuits, current resistors are used. A huge number of different types are produced. To determine the entire variety of details, for each introduced a conventional designation of the resistor. They are marked in various ways, depending on the modification.

Types of resistors

A resistor is a device that has an electrical resistance, its main purpose is to limit the current in the electrical circuit. Industry produces different types of resistors for a variety of technical devices. Their classification is carried out in different ways, one of them is the nature of the change in resistance. According to this classification, there are 3 types of resistors:

1. Constant resistors. They do not have the opportunity to arbitrarily change the resistance value. By appointment, they are divided into two types: general and special applications. The latter are divided according to their intended purpose into high-precision, high-resistance, high-voltage and high-frequency ones.
2. Variable resistors (they are also called adjusting resistors). Possibility to change the resistance with a control knob. According to the design they are very different. There are combined with a switch, dual, built (that is, on one axis there are two or three resistors) and many other varieties.
3. Trimmer resistors. Applied only during the adjustment of the technical device. The tuning organs are accessible only under the screwdriver. A large number of different modifications of these resistors are produced. They are used in all sorts of electrical and electronic devices, from tablet computers to large industrial installations.

Some types of resistors considered are shown in the photo below.

Classification of components by installation method

There are 3 main types of installation of electronic components: hinged, printed and for micromodules. For each type of installation, their elements are designed, they vary greatly in size and design. Resistors, capacitors, and semiconductor devices are used for surface mounting . They are produced with wire leads, so that they can be soldered into the circuit. In connection with the miniaturization of electronic devices, this method is gradually losing relevance.
For printed mounting, more compact parts are used, with terminals for soldering into or without a printed circuit board . For connection to the circuit, these parts have contact pads. Printed installation significantly contributed to reducing the size of electronic products.

For printing and micromodule editing, smd-resistors are often used. They are very small in size, easily built into the circuit board and micromodules. They are available in various nominal resistance, power and dimensions. In the newest electronic devices, smd-resistors are predominantly used.

Rated resistance and dissipated power of resistors

The nominal resistance, expressed in ohms, kilohms or megaohms, is the main characteristic of the resistor. This value is given in the schematic diagrams, directly applied to the resistor in the alphanumeric code. Recently, the color designation of resistors has often been used.

The second most important characteristic of a resistor is dissipated power, it is expressed in watts. Any resistor when it passes current through it is heated, that is, dissipates power. If this power exceeds the permissible value, the resistor breaks down. According to the standard, the designation of the power of the resistors on the circuit is almost always present, this value is often applied to its housing.

The nominal resistance tolerance and its temperature dependence

Of great importance is the error, or deviation from the nominal value, measured in percent. It is impossible to accurately manufacture a resistor with the declared resistance value, there will necessarily be a deviation from the set value. The error is indicated directly on the case, more often in the form of a code from color strips. It is estimated as a percentage of the nominal resistance value.

Where there are large temperature fluctuations, resistance versus temperature, or the temperature coefficient of resistance, the abbreviated designation - TCR, measured in relative units ppm / ° C, is of considerable importance. The TCS shows how much of the resistor's resistance changes if the medium temperature increases (decreases) by 1 ° C.

Conditional graphic designation of a resistor in the circuit

When drawing the schemes, compliance with the state standard GOST 2.728-74 for conventional graphic designations (UGOs) is required. The designation of a resistor of any type is a 10x4 mm rectangle. Based on this, graphic images are created for other types of resistors. In addition to the UGO, it is required to designate the power of the resistors on the circuit, this facilitates its analysis in troubleshooting. In the table below, the UGO of the permanent resistances with the power dissipation is indicated.

Below the photo shows permanent resistors of different power.

Conditional graphic designation of variable resistors

UGO variable resistors are applied to the circuit diagram in the same way as permanent resistors, according to the state standard GOST 2.728-74. The table shows the image of these resistors.

The photo below shows the variables and trimmer resistors.

Standard designation of resistance of resistors

International standards are usually denoted by the resistor nominal resistance on the circuit and on the resistor itself a little differently. The rules for this designation, together with examples of examples, are given in the table.

It can be seen from the table that the designation on resistor circuits of constant resistance is made by an alphanumeric code, first the numerical value of resistance occurs, then the unit of measure is indicated. On the resistor case it is customary to use the letter in place of a comma instead of a comma, if it is ohms, then E or R is put, if k1 is, then the letter K. When designating megaohms, the letter M. is used instead of a comma.

Color marking of resistors

The color designation of the resistors was adopted in order to make it easier to infor- mation about the technical characteristics on their case. For this, several color strips of different colors are applied. In total, the designation of strips is 12 different colors. Each of them has its own specific meaning. The color code of the resist is applied from the edge, at a low accuracy (20%), 3 strips are applied. If the accuracy is higher, you can see already 4 strips on the resistance.

With a high accuracy of the resistor, 5-6 strips are applied. In the marking containing 3-4 strips, the first two indicate the resistance value, the third strip is a multiplier, this quantity is multiplied by it. The next strip determines the accuracy of the resistor. When the marking contains 5-6 strips, the first 3 correspond to the resistance. The next bar is a multiplier, the 5th strip corresponds to the accuracy, and the sixth to the temperature coefficient.

To decode the color codes of resistors, there are reference tables.

Surface Mount Resistors

Surface mounting is when all the parts are placed on the board from the side of the printed tracks. In this case, holes for mounting the elements are not drilled, they are soldered to the tracks. For this installation industry produces a wide range of smd-components: resistors, diodes, capacitors, semiconductor devices. These elements are much smaller in size and technologically adapted for automated installation. Using smd-components allows you to significantly reduce the size of electronic products. Surface mounting in electronics has practically already superseded all other types.

With all the advantages of the installation in question, it has a number of drawbacks.

1. Printed circuit boards manufactured using this technology are afraid of shocks and other mechanical loads, since smd components are damaged.
2. These components are afraid of overheating during soldering, because they can crack from strong temperature changes. This defect is difficult to detect, it usually manifests itself during work.

Standard notation for smd resistors

First of all, smd-resistors differ in size. The smallest frame size is 0402, a little bit larger is 0603. The smd-resistor's most common size is 0805, and more is 1008, the next size is 1206 and the largest is 1812. Resistors of the smallest size have the smallest power.

The designation of smd-resistors is carried out by a special digital code. If the resistor is of size 0402, that is the smallest, then it is not marked in any way. Resistors of other sizes are additionally different in terms of the nominal resistance tolerance: 2, 5, 10%. All these resistors are marked with 3 digits. The first and second of them show the mantissa, the third one - the multiplier. For example, code 473 is read as R = 47 ∙ 10 ³ Ω = 47 kΩ.

All resistors, which have 1% tolerance, and size more than 0805, are marked with four digits. As in the previous case, the first figures show the nominal mantissa, and the last digit indicates the multiplier. For example, code 1501 is deciphered as follows: R = 150 ∙ 10 ¹ = 1500 Ω = 1.5 kΩ. Similarly, the remaining codes are read.

The simplest circuit diagram

Correct designation of resistors and other elements on circuits is the main requirement of state standards when designing electronic and electrical products. The standard establishes rules for the conventions of resistors, capacitors, inductances and other circuit components. The diagram shows not only the designation of a resistor or another element of the circuit, but also its nominal resistance and power, and for capacitors - the operating voltage. Below is an example of a simple schematic diagram with elements denoted by the standard.

Knowing all the conditional graphic symbols and reading the alphanumeric codes to the elements of the diagrams will make it easy to understand the principle of the circuit operation. In this article, only resistors are considered, and there are quite a few elements of the circuits.