Electronic color code

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Electronic color codes are used to indicate the values or ratings of electronic components, very commomly for resistors, but also for capacitors, inductors, and others.

The advantage of color coding (over printed text) on physically small components is the inherent increase in marking AREA, which makes the values easier to read without magnification. Color coded markings are also more resistant to abrasion.

A significant drawback, on the other hand, is color degradation due to aging, oxidation and overheating. In the days of classical chassis televisions, for example, overheated resistors would change their color bands, making it virtually impossible to distinguish BROWN from RED from ORANGE, except by circuit analysis and deduction. This could mean the difference between a 330Ω, 3.3KΩ or 33KΩ resistor respectively (a factor of 100). An overheated 33KΩ resistor often looked like 330Ω. Dirt, grime, unusual lighting and color blindness could also be a major problem.

In modern equipment, color coded components are rarely used, because most passive components outside of integrated circuits, if there indeed are any, come in the form of surface-mount chips (typically 0.1" x 0.1", or smaller). These tiny gray chips are too small for any human readable markings, unless you have a microscope.

An alternative method of marking small components is to print 3 digits on them: 2 value digits followed by the power of ten multiplier. Thus the value of a resistor marked 472 is 4,700 ohms; a capacitor marked 104 is 100 nF (100,000 pF). This can be confusing; a resistor marked 472 might seem to be a 472 ohm unit, and we must rely upon experience to interpret markings. Another way is to use the "Kilo" or "Mega" prefixes in place of the decimal point:

   e.g. 1K2 = 1.2K = 1200, 4M7 = 4.7M = 4 700 000.

For 1% resistors, a three-digit alphanumeric code is sometimes used, which is not obviously related to the value at all. For instance, a resistor marked 68C is 499(68) × 100(C) = 49,900 ohms.

It is sometimes not obvious whether a color coded component is a resistor, capacitor, or inductor, and this may be deduced by knowledge of its circuit function, physical shape or by measurement (capacitors have nearly infinite resistance; unfortunately, so do faulty open-circuit resistors and inductors).

Color codes are also used to identify individual wires or twisted pairs in a multi-wire cable, particularly for telephone and digital cables. It is simple to identify both ends of a wire by its color coding. Cable marking is not restricted to single colors. Typically, solid blue, say, may be used for one live conductor, while blue and white stripes may be used for the related earth return which forms a twisted pair with it.

1 Resistors, capacitors and inductors
2 Mnemonics
3 Examples
4 See also
5 External links

[edit] Resistors, capacitors and inductors

Resistor values are always coded in ohms, capacitors in picofarads (pF), inductors in microhenries (µH), and transformers in volts.

band A is first significant figure of component value
band B is the second significant figure
band C is the decimal multiplier
band D if present, indicates tolerance of value in percent (no color means 20%)

For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%.

Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-STD-199 for further details.

Tight tolerance resistors may have three bands for significant figures rather than two, and/or an additional band indicating temperature coefficient, in units of ppm/K.

All coded components will have at least two value bands and a multiplier; other bands are optional (italicised below).

The Standard EIA Color Code Table per EIA-RS-279 is as follows:

Color	Value digit 1	Value digit 2	Value digit 3	Multiplier	Tolerance	Temp. Coefficient
Black	0	0	0	×10⁰
Brown	1	1	1	×10¹	±1% (F)	100 ppm/K
Red	2	2	2	×10²	±2% (G)	50 ppm/K
Orange	3	3	3	×10³		15 ppm/K
Yellow	4	4	4	×10⁴		25 ppm/K
Green	5	5	5	×10⁵	±0.5% (D)
Blue	6	6	6	×10⁶	±0.25% (C)
Violet	7	7	7	×10⁷	±0.1% (B)
Gray	8	8	8	×10⁸	±0.05% (A)
White	9	9	9	×10⁹
Gold				×0.1	±5% (J)
Silver				×0.01	±10% (K)
None					±20% (M)

[edit] Mnemonics

A useful mnemonic for remembering the first ten color codes matches the first letter of the color code, by order of increasing magnitude. There are many variations:

Bright Boys Rave Over Young Girls But Veto Getting Wed
B. B. R O Y of Great Britain has a Very Good Wife
Better Be Right Or Your Great Big Venture Goes West
Bad Beer Rots Our Young Guts, But Vodka Goes Well
Bad Boys Rape Our Young Girls But Violet Gives Willingly, Get Some Now (Originally written by D. A. Gehlke^{[citation needed]})
Bad Boys Rape Our Young Girls Behind Victory Garden Walls
Black Bastards Rape Our Young Girls But Violet Gives Willingly (Offensive, but easier to remember)
Bye Bye Rosie, Off You Go, Birmingham Via Great Western
Bob Brown Runs Over Your Garden, But Violet Grey Won't (Originally written by David Stothard)
Black Bugs Race Over Yellow Grass Beside Violent Grey Water

A more staid memory aide is the fact that the central part of the code follows the color spectrum (Roy G. Biv). 204.138.110.15 15:38, 23 November 2006 (UTC)