The electronic color code discussed here is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables.
The electronic color code was developed in the early 1920s by the Radio Manufacturer's Association.
Colorbands were commonly used (especially on resistors) because they were easily printed on tiny components, decreasing construction costs. 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 from orange. Advances in printing technology have made printed numbers practical for small components, which are often found in modern electronics. Resistor, capacitor and inductor
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).
Resistor values are always coded in ohms, capacitors in picofarads (pF), and inductors in microhenries (µH).
· 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%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.
Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability);
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 color code per EN 60062:2005 is as follows:
Color Significant
figures Multiplier Tolerance Temp. Coefficient (ppm/K)
Black 0 ×100 – 250 U
Brown 1 ×101 ±1% F 100 S
Red 2 ×102 ±2% G 50 R
Orange 3 ×103 – 15 P
Yellow 4 ×104 – 25 Q
Green 5 ×105 ±0.5% D 20 Z
Blue 6 ×106 ±0.25% C 10 Z
Violet 7 ×107 ±0.1% B 5 M
Gray 8 ×108 ±0.05% A 1 K
White 9 ×109 – –
Gold – ×10-1 ±5% J –
Silver – ×10-2 ±10% K –
None – – ±20% M –
1. Any temperature coefficients not assigned its own letter shall be marked "Z", and the coefficient found in other documentation.
As an example, let us take a resistor which (read left to right) displays the colors yellow, violet, yellow, brown. We take the first two bands as the value, giving us 4, 7. Then the third band, another yellow, gives us the multiplier 104. Our total value is then 47 x 104 Ω, totalling 470,000 Ω or 470 kΩ. Our brown is then a tolerance of ±1%.
Resistors use specific values, which are determined by their tolerance. These values repeat for every order of magnitude; 6.8, 68, 680, and so forth. This is useful because the digits, and hence the first two or three stripes, will always be similar patterns of colors, which make them easier to understand.
Zero ohm resistors are manufactured; these are lengths of wire wrapped in a resistor-shaped body which can be substituted for another resistor value in automatic insertion equipment. They are marked with a single black band.
The 'body-end-dot' or 'body-tip-spot' system was used for radial-lead composition resistors sometimes found in vacuum-tube equipment; the first band was given by the body color, the second band by the color of the 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 colored gold or silver to give the tolerance, otherwise it was 20%.
Extra bands on ceramic capacitors will identify the voltage rating class and temperature coefficient characteristics. 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.
Polyester film and "gum drop" tantalum electrolytic capacitors are also color coded to give the value, working voltage and tolerance.
Diode part number
The part number for diodes was sometimes also encoded as colored rings around the diode, using the same numerals as for other parts. The JEDEC "1N" prefix was assumed, and the balance of the part number was given by three or four rings.
Postage stamp capacitors and war standard coding
Capacitors of the rectangular 'postage stamp" form made for military use during World War II used American War Standard (AWS) or Joint Army Navy (JAN) coding in six dots stamped on the capacitor. An arrow on the top row of dots pointed to the right, indicating the reading order. From left to right the top dots were: black, indicating JAN mica or silver indicating AWS paper. first and second significant figures. The bottom three dots indicated temperature characteristic, tolerance, and decimal multiplier. The characteristic was black for +/- 1000 ppm/ degree c, brown for 500, red for 200, orange for 100, yellow for -20 to +1-- ppm/ degree c, and green for 0 to +70 ppm/degree C. 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.
Mnemonics
A useful mnemonic matches the first letter of the color code, by order of increasing magnitude. There are many variations:
· Badly Burnt Resistors On Your Ground Bus Void General Warranties
· Better Build Roof Over Your Garage Before Vehicle Gets Wet
· Boys better remember our young girls become very good wives.. BYU Engineering Department
· Bad boys rape our young girls behind victory garden walls.
· Bad boys rape 'onest young girls but virgins go without.
· Bad boys run our young girls behind victory garden walls.
· Bad boys rape our young girls but Violet gives willingly.
· Big boys race our young girls but Violet generally wins.
The tolerance codes, gold, silver, and none, are not usually included in the mnemonics; one extension that includes them is:
· Bad beer rots our young guts but vodka goes well – get some now.
Since B can stand for both "black" and "brown", variations are formed such as "Black boys rape our young girls...".
A politically-correct mnemonic that has attained some traction in recent years is:
· Big brown rabbits often yield great big vocal groans when gingerly slapped.
Another mnemonic that is not offensive and can be used in the classroom is:
· B. B. ROY of Great Britain has Very Good Wife.
Other mnemonics commonly taught in UK engineering courses include:
· Bye Bye Rosie Off You Go Birmingham Via Great Western
· Bye Bye Rosie Off You Go Bristol Via Great Western
· Bye Bye Rosie Off You Go But Via Great Western
· Bye Bye Rosie Off You Go do Become a Very Good Wife
· Bill Brown Realized Only Yesterday Good Boys Value Good Work
The colors are sorted in the order of the visible light spectrum: red (2), orange (3), yellow (4), green (5), blue (6), violet (7). Black (0) has no energy, brown (1) has a little more, white (9) has everything and grey (8) is like white, but less intense.
Examples
Resistors color code
From top to bottom:
· Green-Blue-Brown-Black-Brown
o 560 Ω ± 1%
· Red-Red-Orange-Gold
o 22,000 Ω ± 5%
· Yellow-Violet-Brown-Gold
o 470 Ω ± 5%
· Blue-Gray-Black-Silver
o 68 Ω ± 10%
Note: The physical size of a resistor is indicative of the power it can dissipate, not of its resistance.
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