engineering

Electronic color code

Electronic color code is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Electronic color code rather than just read about it. In short: An electronic color code 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.

Key takeaways

Electronic color code belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Electronic color code to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Electronic color code from memory before moving on to harder problems.

Reference excerpt

An electronic color code 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.

History

Before industry standards were established, each manufacturer used its own unique system for color coding or marking their components. In the 1920s, 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. Over many decades, as the organization name changed (RMA, RTMA, RETMA, EIA) 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 96 years. In 1952, it was standardized in IEC 62:1952 by the International Electrotechnical Commission (IEC) and since 1963 also published as EIA RS-279. Originally only meant to be used for fixed resistors, the color code was extended to also cover capacitors with IEC 62:1968. The code was adopted by many national standards like DIN 40825 (1973), BS 1852 (1974) and IS 8186 (1976). The current international standard defining marking codes for resistors and capacitors is IEC 60062:2016. In addition to the color code, these standards define a letter and digit code named RKM code for resistors and capacitors. 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.

Resistors

Color band system To distinguish left from right there is a gap between the C and D bands:

In the above example, a resistor with bands of red, violet, green, and gold has first digit 2 (red; see table below), second digit 7 (violet), followed by 5 (green) zeroes: 2700000 ohms. Gold signifies that the tolerance is ±5%. 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.

Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details. Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating temperature coefficient of resistance (TCR), in units of ppm/K. All coded components have at least two value bands and a multiplier; other bands are optional. The standard color code per IEC 60062:2016 is as follows:

Resistors use various E series of preferred numbers for their specific values, which are determined by their tolerance. These values repeat for every decade of magnitude: ... 0.68, 6.8, 68, 680, ... For resistors of 20% tolerance the E6 series, with six values: 10, 15, 22, 33, 47, 68, then 100, 150, ... is used; each value is approximately the previous value multiplied by 6√10. For 10% tolerance resistors the E12 series, with 12√10 as multiplier, is used; similar schemes up to E192, for 0.5% or tighter tolerance are used. The separation between the values is related to the tolerance so that adjacent values at the extremes of tolerance approximately just overlap; for example, in the E6 series 10 + 20% is 12, while 15 − 20% is also 12. Zero ohm resistors, marked with a single black band, 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.

Body-end-dot system 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).

Examples

From top to bottom:

Green, blue, black, black, brown 560 ohms ±1% Red, red, orange, gold 22000 ohms ±5% Yellow, violet, brown, gold 470 ohms ±5% Blue, grey, black, gold 68 ohms ±5% The physical size of a resistor is indicative of the power it can dissipate. There is an important difference between the use of three and of four bands to indicate resistance. The same resistance is encoded by:

Red, red, orange = 22 followed by 3 zeroes = 22000 (excluding default, silver, or gold tolerance) Red, red, black, red = 220 followed by 2 zeroes = 22000 (excluding brown or other band for tolerance)

Mnemonics

Useful mnemonics have been created to make it easier to remember the numeric order of resistor color bands:

Betty Brown Runs Over Your Garden But Violet Gingerly Walks. Bad Bears Raid Our Yummy Grub But Veto Grey Waffles. BB ROY from Great Britain has a Very Good Wife. The following example includes the tolerance codes — gold, silver and none:

Bad Beer Rots Out Your Guts But Vodka Goes Well – Get Some Now. The colors are sorted in ascending order of visible light photon frequency/energy like in a rainbow to make them easy to remember and to reduce the significance of possible read errors due to color shifts and fading over time: 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.

… excerpt ends here. Continue reading the full article.

Illustrations

Electronic color code: A 2.26 kΩ, 1%-precision resistor with 5 color bands (E96 series), from top, 2-2-6-1-1; the last two brown bands indicate the multiplier (×10) and the tolerance (1%). — A 2.26 kΩ, 1%-precision resistor with 5 color bands (E96 series), from top, 2-2-6-1-1; the last two brown bands indicate the multiplier (×10) and the tolerance (1%).

Electronic color code: A 0 Ω resistor (zero ohm), marked with a single black band — A 0 Ω resistor (zero ohm), marked with a single black band

Worked examples

Example 1 — a first encounter with Electronic color code

Start with the simplest possible case. Write down what Electronic color code claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Electronic color code before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Electronic color code ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Electronic color code

In research: Electronic color code appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Electronic color code in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Electronic color code is common in secondary-school and first-year university syllabi. It links to neighbouring topics Color codes, Electrical components, Electronic engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Electronic color code outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Electronic color code in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Electronic color code means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Electronic color code out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Electronic color code in simple terms?

Why does Electronic color code matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Electronic color code?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Electronic color code.