A colour code is a system for displaying the information by using different colours. The earliest examples of colour codes were in the use of long-distance communication. It was with the help of flags. On the forms and signage, the use of colour can distract through the black and white text there. Resistor Colour coding scheme is a similar kind of scheme. I use the coloured bands to easily identify the resistors resistive value as well its percentage tolerance. In electronics, there are many different types of Resistors available. These are useful in both electrical and electronic circuits to control the flow of current or to produce the voltage drop. Let us understand the Resistor Colour Codes in detail in this article.
Introduction to Resistor Colour Codes
It consists of the set of individual coloured rings or bands in the spectral order, where each one is representing each digit of the value of the resistor. The resistor colour code markings are always read one band at a time conventionally in left to right manner.
The larger width tolerance band oriented to the right side indicates its tolerance value. Earlier, without the industry standards, each manufacturer was using its own unique system for colour coding or marking schemes. During the year 1920s, Radio Manufacturers Association developed the RMA resistor colour code. It was the fixed resistor colouring code marking.
The resistance value for a resistor is normally expressed through the use of a 4-band colour code. For this typical four-band code, the first two bands will tell about the first two digits of the resistance. Whereas the third band will tell about the addition of zeros. Also, the fourth band will tell about its tolerance.
Sometimes, schemes with 5 or 6 bands are needed. For the five-band colour code, the first three bands will tell about the first three digits of the resistance. The fourth band will tell that how many zeros to be added. The fifth band tells about its tolerance.
Always we have to read the resistors from left to right. Resistors never begin with a metallic band on the left. If we have a resistor with the gold or silver band on one end, then it will be a 5% or 10% tolerance resistor. We have to position the resistor with this band on the right side and again read it from left to right.
The colour code values for denoting the tolerance rating of resistors are given as:
Brown = 1%, Red = 2%, Gold = 5%, and Silver = 10 %.
If the resistor has no fourth tolerance band then its default tolerance will be 20%.
Different Types of Registers
Resistors are the common component in the electronic circuits and devices. The main purpose of the resistor is to maintain the specified values of voltage and current in such circuit. A Resistor is mainly working on the principle of Ohm’s law. This law states that the voltage across the resistor is directly proportional to the current flowing through it. Some different kinds of resistors available in the market with the diverse rating and sizes are as follows:
- Wire wound resistors
- Metal film resistors
- Thick film and Thin film resistors
- Network and Surface Mount Resistors
- Variable Resistors
- Special resistors
- Carbon Composition Resistor.
- Carbon Film Resistor.
- Light Dependent Resistor.
Different Resistor Colour Code Schemes
- Four Band Resistor Colour Code:
These Colour Codes are useful on the resistors in carbon, carbon film and similar metal film types. These are mainly useful for electronics engineers to learn. In this four-band resistor colour code, the first three bands which are closest with each other will indicate the value in ohms. Out of these, the first two indicate two numbers. The third one is called the multiplier band and indicates the number of zeros. For example, red, red, red will indicate 2200 ohm. It is normally called as 2.2 Kilo ohm. This last version is popular in many circuit diagrams. To avoid the 2.2K being read as 22K instead of 2K2, where the decimal point will not be obvious.
The multiplier band will have some colour between black (means no zeros) and indicating a value between10 ohm. Also a value less than 100 ohms. The blue (means 6 zeros), indicates the value in the tens of millions, such as 10,000,000 ohms will be brown, black, blue.
- Five Band Resistor Colour Code:
Resistors are also available in many different versions of the Preferred Values. Some of these versions are containing a wider range of values and hence requiring the more accurate numerical values. These are closer intolerance ratings and can be achieved in the four band colour code. Thus the five band code was created to accommodate this with greater accuracy. Most type of resistors in this series is having a tolerance rating of \pm 1% or \pm 2%.3.
3. Six Band Colour Code:
In the six band code, another column is there to accommodate the temperature coefficient. It defines the probable change in the resistor value per degree Celsius, between its values over the specified temperature range. In general, carbon resistors are having the negative temperature coefficient and therefore, it will reduce their resistance as they heat up.
On the other hand metal film resistors, however, can be available for having either a positive or a negative temperature coefficient. It is depending on the manufacturer‘s choice of metals. Its main aim is to produce the resistor whose temperature coefficient is within any variation of values is close to the zero as possible.
These changes are in the resistance, but normally in very small value. It is measured in parts per million, for example, 50 ppm per degree Celsius. Thus, it may be calculated as 1 M \Omega resistor having a \pm 2% tolerance value for red band 5. Might be expected to change its value by the 1000 \Omega when its temperature changes by 20 degree Celsius.
Q.1. What are the different bands in the Register colour coding?
Solution: The four band colour codes are the most common in variation. These resistors are having two bands for the resistance value with one multiplier and one tolerance band. For example, on the left, these bands are green, blue, red and gold. Thus, by using these colour codes, we may find that green stands for 5 and blue for 6.
Q.2. What is the meaning of R in the resistors?
Solution: R represents the resistance of the resistor. In the ohm’s law V = IR
I is the current through the resistor in amperes (A),
R is the resistance value of the resistor measured in ohms
V is the voltage across the endpoints of the resistor in volts (V)
Q.3: How to read and determine the Resistor Value through Resistor Colour Codes?
Solution: Hold the resistor with the gold or silver band to the right and read the colour codes from the left to the right. Then select the colour codes from the bands on the resistor. Further, read the colours from left to right. The resistance value based on the colour code provided is now displayed.
Q.4: What type of resistor should I use in the circuit?
Solution: A rule of thumb for using the appropriate Resistor is to find the resistor having twice the power rating. Usually, we may just use the cheapest resistor which we may find with the correct power rating.