From Resistors to ICs Color Codes

I have been reverse engineering since before the advent of solid state circuits. When I looked up color codes here at Instructables, I was surprised to find just a few one page Instructables on component color codes.

The color codes we all know and love come from EIA standards, (Electronics Industries Association) and they were used on almost every device at one time or another, even vacuum tubes. They are still in use on many devices used in electronics today.

I work on many older electronic devices; capacitors and resistors can go out of tolerance with time. Older devices often have color coded components not seen in newer electronics today, and the exact component quite often is no longer available. I can reverse engineer the circuit and guess at what the appropriate replacement component is and its value or I can look up the color code and select a modern replacement that will work. Looking up the components values and properties from its color code is easier than reverse engineering from scratch.

These are some of the color codes I use when working on electronics.

The EIA standard color code used in electronics is simple; although through the year’s colors and the color bars have remained basically the same, some of their values have changed with technology. Most color codes read from left to right with a gap on the right side and round components may have the gap on the bottom.

The EIA standard color code for significant numbers; start at two significant digits and go up to four significant digits in some components and semiconductors. Starting at black for zero, brown for one, red for two, orange for three, yellow for four, green for five, blue for six, violet for seven, gray for eight, and white for nine.

The multiplier is the same colors as the significant digits only you multiply in the tens depending on the color, I move the decimal place over the number of zeros indicated by the color’s number, nothing for black, one zero for brown, two zeros for red, and so on just like the significant digits. Also depending on the component’s color code adding Gold and Silver to the multiplier, divide by 10 for gold or divide by 100 for silver.

Gold 0.1

Silver 0.01

So a resistor with a brown black and red color band followed by a silver band to the far right is a 1,000 Ω resistor with a 10% tolerance, or a 1 KΩ resistor with a 10% tolerance.

Tolerance is the accuracy of the component to the color code. So if a resistors color code indicates it is a 1,000 Ω resistor with a 10% tolerance, the resistors true resistance is somewhere between 1,100 Ω and 900 Ω. Tolerance has changed with technology and growing precision many older components have tolerances up to twenty percent. These components will have a black or no color band where the tolerance band should be.

The voltage color band is on capacitors, but not all capacitors have a marked voltage rating and not all capacitor types have the same voltage ratings. So the voltage color code of one group of capacitors will have different values from the voltage color code of another group of capacitors. The voltage rating is the maximum voltage you can apply to a capacitor before it starts to break down.

Temperature coefficient, “alpha” (α), is not shown on the basic color code. On some resistors and capacitors you will find a color band for temperature coefficient. The temperature coefficient on capacitors and resistors indicates the rate of value change of the component with changes in temperature of the component. Resistor and capacitor values change for any temperature other than the standard temperature usually specified at 20 degrees Celsius.

For pure metals, this coefficient is a positive number, meaning that resistance increases with increasing temperature. For the elements like carbon, silicon, and germanium, this coefficient is a negative number, meaning that resistance decreases with increasing temperature. This change in resistance and capacitance can affect the performance of some electronics devices.

The amount of change is determined with these formulas:

R = Rref [1+α(T – Tref)]

C = Cref [1 + α(T – Tref)]

Where

R = Resistance of resistor at temperature “T”

Rref = resistance of resistor at Tref usually 20⁰ C (Celsius)

α = Temperature coefficient of the component

T = Temperature of component in degrees Celsius

Tref = Temperature reference of the component usually 20⁰ C (Celsius)

And

C = Capacitance of capacitor at temperature “T”

Cref = Capacitance of capacitor at Tref usually 20⁰ C (Celsius)

α = Temperature coefficient of the component

T = Temperature of component in degrees Celsius

Tref = Temperature reference of the component usually 20⁰ C (Celsius)

All resistance is measured in ohms (Ω), resistors under 1 ohm are called milliohms (mΩ). Resistors 1 ohm and over but under 1,000 ohms are usually called ohm (Ω). Resistors from 1,000 ohm but under 1,000,000 ohm are usually called kilo ohm (KΩ). And resistors from 1,000,000 up are called mega ohm (MΩ).

Most color coded resistors read from left to right with a gap and the tolerance to the far right. The first color band on the left is the first significant digit. The second significant digit is the second color band from the left. The multiplier is the third color band from the left, and the tolerance is the fourth color band on the far right. However not all resistors read that way.

Older resistors may only have three bands to the left with no color band on the right, making its tolerance 20%.

With five band resistors the third color band is the third significant digit, the fourth color band is the multiplier and the fifth color band to the far right is the tolerance.

Six band resistors have the sixth band next to the tolerance or where the tolerance should be with the tolerance beside the multiplier and the sixth band is the temperature coefficient.

All capacitance is measured in farads; picofarads (pF) 0.000,000,000,001 farad, nanofarads (nF) 0.000,000,001 farad and microfarads (uF) 0.000,001 farad. Ceramic capacitors are marked in picofarads (pF).

Three band ceramic capacitors and there color codes read much like color coded resistors, starting from left to right with a gap on the far right or the bottom of disk shaped capacitors. The first color band sometimes larger and more pronounced on the left side of the capacitor is the first significant digit. The second significant digit is the second color band from the left. The multiplier is the third color band from the left. These capacitors may have a tolerance of 20%.

Four band ceramic capacitors read much the same the fourth band is the tolerance on the far right.

Five band ceramic capacitors reading from the left to the right, the first color band on the left often larger and more pronounced is the temperature coefficient, and then comes the first significant digit, the second significant digit, the multiplier, and the far right is the tolerance.

Capacitance on mica and molded paper capacitors are marked in picofarads (pF). Mica and molded paper capacitor color codes have from three to six colored dots and are marked by an arrow of some kind for reading. Although you read the colors much like color coded resistors, they don’t always read in the same order. In addition they have Type, Voltage, and Class in their color codes. So pay attention to the posted color code chart when reading them.

Ceramic capacitors with voltage ratings are marked in picofarads (pF) and read much like other ceramic color coded capacitors, starting from left to right with a gap on the far right of the capacitor. The first color band may be larger and on the left of the capacitor is the first significant digit. The second color band from the left is the same size as the first is the second significant digit. Slightly smaller the third color band from the left is the multiplier, and the tolerance is the fourth color band with voltage on the far right.

Ceramic disk capacitor color codes with voltage, read much the same, but you start reading the color bands from the top and read to the bottom of the capacitor. The first color band on the top is the voltage, the second band from the top is the first significant digit. The second significant digit is the third color band from the top. The multiplier is the fourth color band from the top, and the tolerance is the fifth color band on the bottom.

Metalized Polyester and Pin capacitors come with and without voltage ratings. Starting from the top and reading the color bands to the bottom of the capacitor. The first color band on the top is the first significant digit. The second significant digit is the second color band from the top. The multiplier is the third color band from the top, and the tolerance is the fourth color band, when they have a voltage rating it is the fifth color band on the bottom of the capacitor.

Tantalum capacitors are electrolytic capacitors and their capacitance is marked in microfarads (uF). Tantalum capacitor color codes with voltage, read much like color coded resistors, starting from the top to the bottom of the capacitor.

The first color band on the top is the first significant digit. The second color band from the top is the second significant digit. The multiplier is the dot in the middle of the first and second color bands. The voltage is the bottom color band with the positive lead to the right when you are looking at the multiplier dot. Usually without a tolerance they have an added color pink, for 35 volts to the color code.

Inductance is measured in Henries, there are nanohenries (nH) 0.000,000,001 henries, microhenries (uH) 0.000,001 henries, millihenries (mH) 0.001 henries. Other than SMD (Surface Mounted Device) inductors being read in nanohenries (nH), color coded inductors are read in microhenries (uH).

Like resistors, inductors are read from left to right with a gap and the tolerance to the far right. The first color band on the left is the first significant digit. The second significant digit is the second color band from the left. The multiplier is the third color band from the left, and the tolerance is the fourth color band on the far right. However not all of them are read that way.

Dipped inductors the first color dot on the left is the multiplier, the second dot from the left is the second significant digit and the third dot is the first significant digit with no tolerance.

Some three color band inductors have no multiplier.

And five color band inductors with a silver band as the first color band on the left are military solderable leads.

Semiconductor color codes are less reliable than resistor, capacitor, or inductor color codes. Some color codes are maker specific as in this Philips SMD code book. Single color band diodes may tell you the type of diode and the cathode end of the diode, but without alphanumerical markings like (2.4). You would never know it is a 2.4 volt Zener diode.

Some manufactures that make two color band diodes use the same color bands for different series of diodes.

Most germanium diode color bands just tell you the cathode end of the diode.

And some manufactures that make three color band diodes use the same color bands for different series of diodes.

Four band diode color codes are much more reliable using color bands for alphanumerical representations for the part numbers you can look up on websites and data books. The first two color bands are prefixes the last two are numerals like the significant digits in a standard EIA color code.

These sites are good for looking up the datasheets once you have the part numbers.

http://www.maxim4u.com/

http://www.alldatasheet.com/

The JEDEC series diode color code assumes the first two digits are 1N, the next two to four digits in the part numbers are the color bands. Each color band represents numbers like the standard significant digits in the EIA color code. The last color band in four and five color band diodes is the suffix letter if the diode has a suffix.

This can make the diodes part number hard to read if you are not familiar with the diode are you looking at. Is it a 1N400G or a 1N4007?

In short diode color codes work best if you already know what diode you are working with.

Unless you repair or reverse engineer older electronics like I do, you won’t have much use for transistor color codes. They were common at one time but they are not of much use today. The color code assumes standard transistor prefixes like 2N for JEDEC transistors. The significant digits are standard EIA color codes from two to four significant digits read from top to bottom. When the color bars are on the top of the transistor they are read from left to right.

So if the transistors color bands are red, red, red, red, meaning 2222. A quick look at the datasheet will tell you if it is a 600 mW NPN general purpose transistor like MPS2222 or 2N2222 or if it is a 2SD2222 power transistor.

Common Transistor Prefixes

MJ: Motorolla power, metal case

MJE: Motorolla power, plastic case

MPS: Motorolla low power, plastic case

MRF: Motorolla HF, VHF transistor

RCA: RCA

RCS: RCS

TIP: TI power transistor (platic case)

TIPL: TI planar power transistor

TIS: TI small transistor (plastic case)

ZT: Ferranti

ZTX: Ferranti

Pro-Electron prefixes.

BC

BD

BF

BL

BS

BU

And the last group of prefixes.

2SA

2SB

2SC

2SD

2SJ

2SK

Like transistors integrated circuits used color codes for a short time the prefix was the first color bar the first set of significant numbers were the second color bar and the last two color bars are the last two significant numbers.

This is a list of company letter prefixes for Integrated Circuits manufacturers, normally these prefixes are used as the first part of the part number for a device. For example, a RCA logic device may have a part number CD4049, CD indicates it is a RCA device the remainder is the part number.

If the part number is MC14049 the device is made by Motorola, denoted by the MC.

CA; RCA (analog)

CD; RCA (digital)

DM; National Semiconductor (digital)

GD Goldstar (digital)

HA; Hitachi (analog)

HD; Hitachi (digital)

MC; Motorola

TA; Toshiba

TC; Toshiba