Sunday, November 11, 2012

Resistor Color Codes

Most people dealing with electronics these days know how to read a Resistor Color Code Value Chart, but beginners probably dont. This tutorial should walk you through how to read a chart to determine resistors in your projects. So lets get started.

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element [1]. They come in many compositions, but there are three primary ones that people use: carbon film, metal film and wire-wound resistors. For more information about all other kids of resistors, as well as a detailed explanation of the three types mentioned here, refer to the Wikipedia page on resistors.

Classification of resistors consists of three main properties. Resistance, which is measured in ohms, is the actual value of the resistor. Without this, you cant tell one resistor from another. The second is the tolerance value, which is shown as a percentage, and is represented by a color band of its own. The last property is the power rating of the resistor, which is measured in Watts [2].

The value of the resistor, as well as the tolerance percentage can both be found by using the following chart.

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For four banded resistors, the first band is the first number in the value of the resistor. The second is the second number in the value. The third is the number of zeroes behind the first two numbers, also referred as the multiplier. For example, Red-Red-Black, would be 220 Ohms. Similarly, 1K Ohms would be Brown-Black-Red.

For five banded resistors, the third band represents a third value, the fourth band is the multiplier, and the fifth band is the tolerance. These types of resistors are usually blue, green or brown, depending on the manufacturer.

The tolerance value represents what error the value known might be off from the actual value of the resistor. Most electronics use the standard 5% or 10% resistors, which is represented by a gold or silver band. Sensors and precision electronics require higher tolerances. Those come as actual color bands. Most precision resistors come with a 1% tolerance (Brown), though, other tighter tolerances can be found. So a 237 Ohm resistor with a 0.5% tolerance would take the 5-banded color code, Red-Orange-Violet-Black-Green.

The wattage rating of a resistor is determined separately by the size of the resistor. The larger the diameter and length of a resistor, the higher wattage it can handle.

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