5.1 Resistor Color Code
Carin Mita
An electronic color code or electronic colour code (see spelling differences) is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables. Different codes are used for wire leads on devices such as transformers or in building wiring.
In the 1920s,[citation needed] the RMA resistor color code was developed by the Radio Manufacturers Association (RMA) as a fixed resistor coloring code marking. In 1930, the first radios with RMA color-coded resistors were built.[1][2] Over many decades, as the organization name changed (RMA, RTMA, RETMA, EIA)[3] so was the name of the code. Though known most recently as EIA color code, the four name variations are found in books, magazines, catalogs, and other documents over more than 94 years.
Color bands were used because they were easily and cheaply printed on tiny components. However, there were drawbacks, especially for color blind people. Overheating of a component or dirt accumulation may make it impossible to distinguish brown from red or orange. Advances in printing technology have now made printed numbers more practical on small components. The values of components in surface mount packages are marked with printed alphanumeric codes instead of a color code.
Precision resistors may be marked with a five band system, to include three significant digits, a power of 10 multiplier (number of trailing zeroes, and a tolerance band. An extra-wide first band indicates a wire-wound resistor.[6]
Zero ohm resistors, marked with a single black band,[10] are lengths of wire wrapped in a resistor-like body which can be mounted on a printed-circuit board (PCB) by automatic component-insertion equipment. They are typically used on PCBs as insulating "bridges" where two tracks would otherwise cross, or as soldered-in jumper wires for setting configurations.
The "body-end-dot" or "body-tip-spot" system was used for cylindrical composition resistors sometimes still found in very old equipment (built before the Second World War); the first band was given by the body color, the second band by the color of one end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was in the body color, silver, or gold for 20%, 10%, 5% tolerance (tighter tolerances were not routinely used).[11][12][13][14]
Capacitors may be marked with 4 or more colored bands or dots. The colors encode the first and second most significant digits of the value in picofarads, and the third color the decimal multiplier. Additional bands have meanings which may vary from one type to another. Low-tolerance capacitors may begin with the first 3 (rather than 2) digits of the value. It is usually, but not always, possible to work out what scheme is used by the particular colors used. Cylindrical capacitors marked with bands may look like resistors.
Extra bands on ceramic capacitors identify the voltage rating class and temperature coefficient characteristics.[11] A broad black band was applied to some tubular paper capacitors to indicate the end that had the outer electrode; this allowed this end to be connected to chassis ground to provide some shielding against hum and noise pickup.
A similar six-dot code by EIA had the top row as first, second and third significant digits and the bottom row as voltage rating (in hundreds of volts; no color indicated 500 volts), tolerance, and multiplier. A three-dot EIA code was used for 500 volt 20% tolerance capacitors, and the dots signified first and second significant digits and the multiplier. Such capacitors were common in vacuum tube equipment and in surplus for a generation after the war but are unavailable now.[17]
Standards IEC 60062 / EN 60062 do not define a color code for inductors, but manufacturers of small inductors use the resistor color code, typically encoding inductance in microhenries.[18] A white tolerance ring is used by TDK to indicate custom specifications.[18]
Power transformers used in North American vacuum-tube equipment were often color-coded to identify the leads. Black was the primary connection, red secondary for the B+ (plate voltage), red with a yellow tracer was the center tap for the B+ full-wave rectifier winding, green or brown was the heater voltage for all tubes, yellow was the filament voltage for the rectifier tube (often a different voltage than other tube heaters). Two wires of each color were provided for each circuit, and phasing was not identified by the color code.
Audio transformers for vacuum tube equipment were coded blue for the finishing lead of the primary, red for the B+ lead of the primary, brown for a primary center tap, green for the finishing lead of the secondary, black for grid lead of the secondary, and yellow for a tapped secondary. Each lead had a different color since relative polarity or phase was more important for these transformers. Intermediate-frequency tuned transformers were coded blue and red for the primary and green and black for the secondary.[17]
Wires may be color-coded to identify their function, voltage class, polarity, phase or to identify the circuit in which they are used. The insulation of the wire may be solidly colored, or where more combinations are needed, one or two tracer stripes may be added. Some wiring color codes are set by national regulations, but often a color code is specific to a manufacturer or industry.
Building wiring under the US National Electrical Code and the Canadian Electrical Code is identified by colors to show energized, neutral, and grounding conductors, and to identify phases. Other color codes are used in the UK and other areas to identify building wiring or flexible cable wiring.
Mains electrical wiring, both in a building and on equipment, was once usually red for live, black for neutral, and green for earth, but this was changed as it was a hazard for color-blind people, who might confuse red and green; different countries use different conventions. Red and black are frequently used for positive and negative of battery or other single-voltage DC wiring.
Thermocouple wires and extension cables are identified by color code for the type of thermocouple; interchanging thermocouples with unsuitable extension wires destroys the accuracy of the measurement.
Modern personal computer peripheral cables and connectors are color-coded to simplify connection of speakers, microphones, mice, keyboards and other peripherals, usually according to coloring schemes following recommendations such as PC System Design Guide, PoweredUSB, ATX, etc.
Local area network cables may also have non-standardised jacket colors identifying, for example, process control network vs. office automation networks, or to identify redundant network connections, but these codes vary by organization and facility.
The online resistor calculator is a tool by Utmel Electronic used to calculate resistor values for 4 band, 5 band, and 6 band resistors, in the range of ohms, Kilo Ohms, and Mega Ohms typically. And this resistance calculator is developed to calculate the color code using the resistor color codes on their surface.Just select the right color corresponding to each column and you can get the Resistor value on the right of the calculator immediately.
Take a 4-band resistor as the example, 10k ohm resistor color code 4 band is: Brown-Black-Orange-Red. So the 1st band of Color: Brown, 2nd band: Black, Multiplier: Orange and Tolerance: Red. Thus, the output of resistor value is 10K ohms 2%. And the below picture shows you the 100 Ohm Resistor Color Code for 4-band resistors.
Resistors are usually used in electrical components with the aim of restricting the flow of electric current. They are usually tiny components with wire leads protruding from all sides. Resistors are special electronic components in circuits. It is made with the purpose of a precise quantity of electrical resistance.
The range of resistors may be from less than 1 Ohm (Ω) to over 20 mega Ohms (Ω) or 20 million Ohms (Ω). And there are two types of resistors: variable resistors and fixed resistors. A variable resistor can provide different values of resistance, however, the fixed resistor just has a single value. Meanwhile, there are 4 main classes of fixed resistors: carbon-composition resistors, Film resistors, wire wound resistors, and surface-mount resistors.
Generally, the carbon-composition resistors have 3 to 6 resistor color bands. And the below electrical color code resistor chart shows you the resistor strips of the 3 band type, 4 band type, 5 and 6 band type. Compared with a 4-band resistor, a 5-band type is more precise because of its third significant digit. And a 6-band resistor has the 6th band, which is a temperature coefficient band.
From the following Resistor color code chart Calculator, we know that each color for resistor represents a number if it's found on 6-band and 5-band type from 1st to 3rd band or a 4-band resistor from the 1st to 2nd. And it is a multiplier if it is located on the 4th band of 5-band and 6-band type or the 3rd band of a 4-band resistor. You can get the tolerance values of a resistor on the 4th band for the 4-band type according to the 4 band resistor color code chart and the 5th for the 5-band and 6-band type through the below resistor color chart 5 band and 6 band. A 6-band type resistor has the 6th band, which shows you the temperature coefficient. And this value indicates how much the actual resistance value of this 6-band resistor changes when the temperature changes.
The easiest way to identify a resistor Color code is to know which colors represent the most significant digits. The following steps will guide you in reading a resistor color code.
1) Look for the colored bands on the resistor's body.
2) Determine which of these colors have a leading role in representing numbers.
3) Identify the numbers represented by these colors and their position.
4) Read off each of these digits from left to right on the band where it's located.