We should make sure that types of markings for all the types of resistors, caps, ICs, and everything else are thoroughly explained. This is not terribly important to engineers, who are more concerned with theory and just pull them out of a labeled box. But to the hobbyist this is pretty important, and also difficult to learn, because there are so many nonintuitive ways to label things.
Should we put the color code and SMT numbering explanations at the top, and then tell in each section what they stand for? (ohms, picofarads, microhenries) "The color-digit pairs used in the resistor example below are standard, but the tolerance and higher multiplier values are for resistors only."
- 1 Resistors
- 2 Capacitors
- 3 Inductors
- 4 Transistors
- 5 ICs
Most axial resistors use a pattern of colored stripes to indicate resistance. SMT ones follow a numerical pattern. Cases are usually brown, blue, or green, though other colors are occasionally found like dark red or dark gray.
4-band axial resistors
Four band identification is the most commonly used color coding scheme on all resistors. It consists of four colored bands that are painted around the body of the resistor. The scheme is simple: The first two numbers are the first two significant digits of the resistance value, the third is a multiplier, and the fourth is the tolerance of the value. Each color corresponds to a certain number, shown in the chart below. The tolerance for a 4-band resistor will be 2%, 5%, or 10%
|Color||1st band||2nd band||3rd band||Multiplier||Tolerance||Temp. Coefficient|
|Brown||1||1||1||×101||±1% (F)||100 ppm|
|Red||2||2||2||×102||±2% (G)||50 ppm|
|Gold||×0.1 (10−1)||±5% (J)|
|Silver||×0.01 (10−2)||±10% (K)|
For example, if you are looking for a 12K (12000 ohm) resistor with ±5% tolerance, you would be looking for a Brown (1) Red (2) Orange (×103) Gold (±5%) resistor.
12×103 ohm = 12000 Ω = 12 kΩ
Note that red to violet are the colors of the rainbow where red is low energy and violet is higher energy. Resistors use specific values, which are determined by their tolerance. These values repeat for every exponent, 6.8, 68, 680. This is useful because the digits, and hence the first two or three stripes, will always be similar patterns of colors, which you will learn to recognize without checking a chart. To help you remember them, the standard values for 10% resistors are:
5-band axial resistors
5-band identification is used for higher precision (lower tolerance) resistors (1%, 0.5%, 0.25%, 0.1%), to notate the extra digit. The first three bands represent the significant digits, the fourth is the multiplier, and the fifth is the tolerance.
SMD (surface mounted device) or SMT (surface mount technology; same thing) resistors are found mostly on devices where large scale integration is present. They generally use an alphanumeric numbering system.
For surface mount resistors, a numerical code is used. For 10% tolerance resistors, 3 numbers are used, for 1% resistors, 4 digits are used. The scheme is similar to color codes, in that the first two or three digits are the significant digits, and the last digit is the multiplier (expressed as an exponent of 10). This is easy to remember as "the first digits then as many zeros as the last digit after it" ohms. "683" for instance, represents 68 with three zeros after it: 68 000 = 68 kΩ. Likewise, "4991" represents 499 with 1 zero after it: 499 0 = 4.99 kΩ.
For small resistance values, an alternate notation is often used. For these, an R is used in place of the decimal. For example, 5R6 = 5.6 Ω.
They are the smallest class of discrete resistors available.
For large power resistors and potentiometers, the value is usually written out explicitly as "2Ω", for instance. Some power resistors have their power rating imprinted on the component body. An example of a 10W "2Ω" power resistor follows.
In the top example, the colors are brown (1) - black (0) - orange (×103) - gold (5%). This means 1 0 ×103 Ω ± 5% = 10 ± 0.5 kΩ. This resistor has a value anywhere from 9.5 to 10.5 kΩ
The second example has 5 stripes. They are brown (1) - black (0) - black (0) - red (×102) - brown (1%). This means 1 0 0 ×102 Ω ± 1% = 10 ± 0.1 kΩ. This resistor then has a value anywhere from 9.9 to 10.1 kΩ.
Note that these are both 10 kΩ.
The third example is a larger power resistor, and is labeled green (5) - blue (6) - black (×100) - gold (5%). This means 5 6 ×100 Ω ± 5% = 56 ± 2.8 Ω. This resistor then has a value anywhere from 53.2 to 58.8 Ω. It has a higher power rating than the others, which is not labeled, but is obvious from its larger size.
Axial electrolytic capacitors are electrolytic capacitors that have connections on both ends. These are most frequently used in devices where there is no space for vertically mounted capacitors. See photograph above.
The arrowed stripe indicates the polarity, with the arrows pointing towards the negative pin. Warning: connecting electrolytic capacitors in reverse polarity can easily damage or destroy the capacitor. Most large electrolytic capacitors have the voltage, capacitance, temperature ratings, and company name written on them without having any special color coding schemes. Most electrolytic capacitors in general have light blue, black, dark purple or brown colors, although some specialized ones come in yellow and other colors. If for some reason you are uncertain about the polarity, the can is always the negative connection. Most axial caps have both ends visible. The positive end has a rubber insulation and the negative side is only aluminium.
Radial electrolytic capacitors are like axial electrolytic ones, except both pins come out the same end. Usually that end (the "bottom end") is mounted flat against the PCB and the capacitor rises perpendicular to the PCB it is mounted on. This type of capacitor probably accounts for at least 70% of capacitors in consumer electronics (that don't use SMT components). See photograph above.
Like their axial counterparts, many radial electrolytic capacitors have the voltage, capacitance, temperature ratings, polarity, and company name directly written on them without having any special color coding schemes.
Tantalum capacitors are useful due to their low leakage current, reliability, and their ability to keep stable capacitance over a wide range of temperatures. below is a diagram:
They have special markings. The stripe on the side indicates polarity. Usually with a store bought component, the longer lead is positive. Warning: connecting tantalum capacitors in reverse polarity can easily damage or destroy the capacitor. Generally it will have the capacitance written in µF, and the working voltage below it. In some cases (often when µF is not printed), the value (in pF) is encoded with three numbers; the first two digits being the significant figures, with the third being the multiplier (i.e. number of zeros). Tantalum capacitors are most commonly dipped and have a shiny coating, as well as vary in color, being yellow, red, and sometimes blue. Most axial tantalum capacitors look completely different.
The dark line on the SMT variety is the positive terminal. The dipped axial through-hole variety will be marked with a + or a dark line to indicate the positive terminal.
Ceramic capacitors are generally non-polarized and almost as common as radial electrolytic capacitors.
Generally, they use an alphanumeric marking system. The number part is the same as for SMT resistors, except that the value represented is in pF. They may also be written out directly, for instance, 2n2 = 2.2 nF. For capacitors the tolerance code is:
|A||± 0.05 pF|
|B||± 0.1 pF|
|C||± 0.25 pF|
|D||± 0.5 pF|
letters with * are not used consistently.
how similar is this to resistors?
For example, .047K = .047 µF 10%.
The dielectric material is sometimes designated by another code: (note: the materials in the table below are not ceramic capacitors as implied, but plastic and paper)
|KT||Polyester Film / Foil|
|MKT||Metallized Polyester (PETP)|
|KC||Polycarbonate Film / Foil|
|KS||Polystyrene Film / Foil|
|KP||Polypropylene Film / Foil|
Please note that the table above is valid most of the time but not always because it is not a real standard. To be real sure you may check the data sheet from the manufacturer in mind.
The cap color can also indicate the dielectric:
Axial ceramic capacitors
These often have a yellow body, and use the same color band system as resistors, except that the value indicated is in pF.
Multilayer Ceramic capacitors
These usually use the same alphanumeric system.
These are often not even labeled. If they are labeled, it is the same system as SMT resistors, but representing pF. Polarized capacitors are marked with a stripe on the positive end of the package, though some electrolytic SMT capacitors are marked on the negative end of the package. They are rectangular, and often black or tan colored. The black capacitors are easily mistaken for diodes due to the white stripe on one end...
Sometimes the value of an inductor is printed directly on it. If no units are given, µH can be assumed. If it looks like the system used by SMT resistors, it is probably that system, except that the value represented is in µH. Inductors as a class of components are current and magnetic sensitive devices. Inductors work by creating a magnetic field around the windings. The current of a electron flow causes energy to transfer into the field. Similarly, if there is a no current but a field present, coiled wiring responds by creating a current in the wiring. This is the original source of the name Inductor, it induces a current when exposed to a field, or a field when exposed to a current.
If an inductor uses the color code system, the value represented is in µH. Expect to see a wide silver or gold band before the normal colored bands, and a thin tolerance band at the end. but have some more information that is not given. Identified on PCB assemblies with the letter designation of L, the last letter in the word coil.
Diode:- in electronics a diode is a two terminal electronic component with asymmetric transfer characteristic, with low (ideally zero) resistance to current flow in one direction, and high (ideally infinite) resistance in the other.