Resistors can be seen in almost every electronic circuit. Basically, it is used to reduce the flow of electric current and regulate the flow of electrons. In electronics, there are many kinds of resistors used for various applications. Mainly they are classified on the basis of their applications, temperature coefficient, tolerance, size, power, reliability, etc.
resistors can be divided into two groups called linear resistors and non-linear resistors. The linear resistors are also subcategories namely fixed resistors and variable resistors(Adjustable). Today, I am going to unlock the details about different kinds of resistors. In this tutorial, you will learn -
Types of resistor
A. Linear resistors -
a. Fixed resistors -
1. Carbon composition resistors.
2. Wire wound resistors.
3. Thin-film resistors.
• Carbon film resistors.
• Metal film resistors.
4. Thick film resistors.
• Metal oxide resistors.
• Cermet oxide resistors (Network resistors).
• Fusible resistors.
b. Variable resistors -
1. Potentiometer.
2. Rheostats.
3. Trimmers.
B. Non-linear resistors -
1. Thermisters.
2. Varistors.
3. Photoresistors or Light dependent resistors (LDR).
A. Linear resistors
(a). Fixed resistors
In these types of resistors, the resistance value can not be changed that means they offer a fixed amount of resistance in the circuit. There are different kinds of fixed resistors like -
1. Carbon composition resistors
This type of resistor is a fixed resistor made from the mixture of granulated or carbon powder or graphite, an insulation filter, or a resin binder. The ratio of the insulation material determines the actual resistance of the resistor.
The insulating powder made in the shape of rods and there are two metal caps on both ends of the rod. They are available in 1 ohm to 25 megaohms and in power rating from 1/4 watt to up to 5 watts.
2. Wire wound resistors
These types of resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or fiberglass core. They operate safely up to 350℃.
The power rating of this type of resistor is 2 watts up to 200 watts or more and the resistance value is 1 ohm up to 200k ohms or more. This resistor is designed for use in high power, high sensitivity, and accurate measurement applications.
3. Thin-film resistors
The thin-film resistors are made of high grid ceramic rode and resistive material. There are two types of thin-film resistors called carbon film resistors and metal film resistors.
• Carbon film resistors
The core of the carbon film resistors is made of a high-grade ceramic material called the substrate. It contains an insulating material rod that is overlaid with a thin resistive carbon layer.
The power rating range of this type of resistor is 0.125 watt to 5 watts at 70℃ and it has 200 to 600 volts maximum working voltage range. Special carbon film resistors are used in applications requiring high pulse stability.
• Metal film resistor
Metal film resistors are made in the same construction, as carbon film resistors, but the main difference is that there is metals like nickel-chromium (NiCr) are used instead of carbon. The temperature coefficient of this type of resistor is generally between 50 and 100 ppm/K.
4. Thick film resistor
Thick film resistors are also made like a thin film resistor, but the difference is that there is a thick film instead of a thin film. There are some kinds of thick film resistors like Metal oxide resistors, cermet oxide resistors, and fusible resistors.
• Metal oxide resistors
Metal oxide film resistors are made by oxidizing a thin film of tin chloride on a heated glass rod (Substrate) which results in it operates at a higher temperature and makes it greater stability than metal film. They are used in applications with high endurance demands.
• Cermet oxide resistors
The internal area of this type of resistor is made of ceramic insulation materials. And then a layer of carbon or metal alloy film wrapped around the resistor and then fix it in a ceramic material called cermet. The shapes of this type of resistor are in square and rectangular types.
• Fusible resistors
This type of resistor same as a wire wound resistor. If the power rating of the circuits is increased above the specified value, then the resistor is fused. that's why it is called a fusible resistor. They widely used in TV sets, amplifiers, and expansive electronic circuits.
(b). Variable resistors
In this type of resistor, the value of the resistance can be changeable. The value of the resistance can be changed by adjusting a rotating shaft or wiper or a linear slider.
They are used in the radio receiver for volume control and tone control resistance. There are some kinds of variable resistors like potentiometers, Rheostats, and trimmers.
1. Potentiometers
A potentiometer is a variable resistor that has three terminals with a continuously adjustable tapping point.
This tapping point controlled by a rotating shaft or wiper or by a linear slider. When the shaft rotates the value of resistance changes and the voltage is controlled.
The potentiometer is used as a voltage divider in electronic circuits. They are used in radio, variable power supply, and musical instruments, etc.
2. Rheostats
Rheostats are a two or three-terminal device that is used for the current controlling purpose or manual operation.
They are also known as variable wire wound resistors because to make a rheostat, the nichrome wire is wound around a ceramic core and then assembled in a protective shell.
The available power rating of these resistors is 3 to 200 watts and the resistance range is 1 ohm up to 150 ohms.
3. Trimmers
Trimmer is a variable resistor that comes with an additional screw. The value of the resistance can be changed by changing the position of the screw to rotate by a small screwdriver.
They are made by using carbon composition, carbon film, cermet, and wire materials. They are available in the range of 50 ohms up to 5 megaohms. The power rating of this type of resistor is 1/3 watts to 3/4 watts.
B. Non-linear resistors
1. Thermisters
Thermister is a type of variable resistor which is very sensitive to temperature.
The resistance of this resistor is inversely proportional to the temperatures i.e when the temperature increases the value of resistance decrease and when the temperature decreases the value of resistance decreased.
These types of resistors are made of cobalt, nickel, strontium, and metal oxide of manganese.
2. Varistors
To protect the electronic circuits from voltage destructive spikes a special type of variable resistor is used and the resistor is called varistors.
When voltages increases (due to lighting or line faults ) then it reduces the level of voltage to a secure level i.e it changes the level of voltage.
3. Photoresistors
A photoresistor is a light-sensitive resistor. When light falls upon it then the resistance changes. The value of the resistance of a photoresistor is directly proportional to the intensity of light i.e when the intensity of light increases the value of resistance increased and vice versa.
Photoresistors are made from semiconductor materials to enable them to have their light-sensitive properties. They are used in light sensing applications like light meters, light-activated relay control circuits, automatic street light controlling circuits, and photographic devices and equipment.
Surface-mount resistors
Surface mount device(SMD) resistors are just one form of component that uses surface mount technology(SMT).
SMT was developed to meet the ongoing desire for printed circuit board manufacture to use smaller components and be faster, more efficient, and cheaper.
The SMD resistors are made by a ceramic substrate and then depositing a thin film of resistive material.
They are square, rectangular, or oval in shape, with very low profiles. They have small leads or pins that are soldered to pads on the surface of the board.
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