What is a Carbon Composition Resistor & Its Working

The basic type of resistor is a carbon composition resistor because it was designed in the early days of the 1960s. These resistors were established through wire-wound type resistors but these kinds of resistors are not frequently used because other kinds of resistors have better specifications like voltage dependence, tolerance, stress, etc. Early 20th century, these resistors are available with uninsulated bodies where the two lead wires of these were covered in the region of the resistance element rod ends & soldered. This is the history of the carbon composition resistor.

What is a Carbon Composition Resistor?

Definition: Carbon composition resistor is also known as carbon composite otherwise carbon comp. This is an old type of resistor but used as a main resistor in many tube or valve based devices such as radios, TVs, electronic devices, etc. The Carbon composition resistor function is, it is one kind of fixed resistor, used to restrict or reduce the flow of current to a certain stage.

As compared with present resistors, carbon composition resistors’ performance is poor, expensive, and less stable. The heat of soldering of this resistor can make a non-reversible transform in the value of resistance of internal moisture content. These resistors do not contain the close tolerances of any metal film otherwise carbon types. The Carbon composition resistor diagram is shown below.

The resistance of this resistor mainly depends on three main factors like the quantity of carbon included, solid cylindrical rod’s length & cylindrical rods cross-sectional region.

Carbon Composition Resistor Construction

The CCR (Carbon composition resistors) includes a resistive element with leads of embedded wire otherwise metal end caps to which the lead wires are connected. The body of this resistor can be covered with paint or plastic materials to protect them. The lead wires were covered around the ends of the resistance element rod & soldered. The color-coding of this resistor can be done based on the paint and the resistive element is designed with a blend of carbon powder & an insulating material like ceramic.

The resistance of this resistor can be is determined through the ratio of the material filled to the carbon. When the concentration of carbon is high then it is called a good conductor and result in less resistance. The value of these resistors will change once they are affected through high voltages. Also, internal moisture content must exposure to a humid environment for some duration of time because the soldering heat of the resistor can create a non-reversible transform within the value of resistance.

These resistors are still accessible but fairly expensive. The values of these resistors range from 1ohm to 22 megohms. In most of the applications, these resistors are not used because of the high cost but are used in welding controls & power supplies.

Noise

The carbon composition resistor generates two types of noise like Johnson/Thermal & current noise

Johnson Noise

This kind of noise is also called thermal noise. This noise can be generated through the charge carriers because of the thermal agitation.

Current Noise

This noise is mainly caused when current flows through internal transforms within the resistor.

Specifications

The typical carbon composition resistor specifications include the following. The different parameters of this resistor along with their performance are listed below.

• Availability of tolerance is ±5%, ±10%, ±20%
• Resistance value ranges from 1Ω to 10MΩ
• Load life is +4 (% change over 1000h)
• Maximum noise is 6 µV/V
• The temperature coefficient is >±1000 ppm/°C
• The voltage coefficient is 0.05%/V
• The maximum temperature of the resistor is 120°C

Why Carbon is Used?

Carbon composition resistors are designed with different materials, in that carbon material is used for the past many years. One of the major reasons is that resistors that are designed out of carbon are considered extremely consistent and they don’t fail frequently. These types of resistors are also extremely efficient at high energy stages.

Carbon resistors are available in two types like carbon composition as well as a carbon film. They include both clay additive and graphite (solid carbon) to assist with durability. At present, these are used very less because of expensive, less reliable within high moisture applications.

Carbon film resistors became very popular and used in consumer devices over the past many years. These are designed with a carbon film layer on an insulating material such as ceramic. As compared with carbon composition, carbon film resistors are used in several applications with the exclusion of high voltage applications such as power supplies. These resistors are less costly as compared with carbon composition type resistors.

Color Coding

The color-coding of carbon resistors can be calculated using two methods like general color coding and precision color coding.

General Type

In general color coding of carbon resistor, the resistor is available with 4 color bands with ± 5% of tolerance. In that, the primary two color bands on the resistor signify the numeric part of the resistance value whereas the third band is called the multiplier. The fourth band is used for tolerance.

For instance, in the four-color band resistor, the first color is red (2), the second color is yellow (4), the third color is orange (103) and the fourth band is gold (tolerance = ± 5%). So, the final color code value of this resistor is 24 x 103 ± 5%

Precision Type

In precision color coding of the resistor, the resistor is available with 5 color bands which specified the color code value of the resistor. The main difference between both the general type and precision type is that the primary 3 color bands on the resistor specify the numeric value, the 4th color band specifies the multiplier & finally, the last color band specifies the tolerance. This kind of color-coding is employed wherever the tolerance is below ± 2%

For instance, in the five-color band resistor, the first color on the resistor is green (5), the second color is blue (6), the third color is red (2), the fourth color is brown (multiplier = 101) & the final color is silver (tolerance = ± 10%). So, the final color code value of this resistor is 562 X 101 ± 10%

Advantages

The advantages of a carbon composition resistor include the following.

• It can endure high energy pulses.
• Less cost
• These are available in small size

Disadvantages

The disadvantages of a carbon composition resistor include the following.

• The stability of the carbon composition resistor is poor
• Generates huge noise
• Accuracy is less
• It absorbs the water so it can lead to an increase/decrease in the resistance.
• These resistors are not ideal for current electronic devices which are highly sensitive
• They do not work well for long-term in humid, moisture, beneath high-temperature environment applications.
• They are extremely responsive to changes in temperature.
• The capacity of power dissipation is small.

Applications of Carbon Composition Resistor

The applications of the carbon composition resistor include the following.

• Used in high-frequency applications
• It is used to limit the current in the circuits
• Welding control & surge protection circuits
• Used to protect the circuits
• Used in the DC power supplies with high voltage
• Used in the devices like X-ray, laser, radar & welding technology also.
• Used in electronic, test equipment, and computers.

Thus, this is all about an overview of the carbon composition resistor. The resistors like carbon film and carbon composition are an outstanding choice when utilized in suitable applications like electronic circuits because of their benefits which are listed in the above. Because electronic circuits use extremely fewer currents, so these resistors are appropriate and secure. But, due to some drawbacks, these resistors cannot be utilized in all kinds of circuits but they are very famous because of their small size as well as less cost. Here is a question for you, what are the main factors that carbon composition resistor depends on?