PCB resistors – what they are and when to use them
Whenever it involves electronic circuits, resistors play a significant role. PCB resistors are the basic components of all analog or digital circuitry, without which things won’t work. They are everywhere in our day-to-day lives, in our computers and smartphones,etc. Since resistor values affect electronics in so many ways, beginners must understand the importance of each type and where to use them. Here is a complete guide for PCB resistors.
Table of Contents
What is a PCB Resistor?
A PCB resistor is a passive electronic component with resistance between 50Ω and 1GΩ. Etching or resistor shows the resistance value.
A PCB resistor limits current flow and reduces the voltage drop across a circuit board. It also helps to create an electronic filter to remove unwanted signals from a signal source.
The most common resistors are carbon film, metal film, wire wound, ceramic, and surface mount.
What are the different types of PCB resistors and their applications?
The most common types of PCB resistor are:
Carbon film resistors: they are made of a thin layer of carbon deposited on an insulating substrate. They have lower noise than carbon composition resistors, but their stability is not as good. Carbon film resistors are used in general purpose circuits where the current is low, and the voltage is relatively high.
Metal-oxide film resistors: they are made by depositing a thin layer of metal oxide on an insulating substrate. Due to capacitance effects between the leads attached to the resistor body and lead frame, this resistor is noisy at higher frequencies. Circuits with moderate frequencies and low or medium currents use metal-oxide film resistors.
Metal film resistors: they are made by depositing a very thin layer of metal on an insulating substrate. They have better temperature stability than metal oxide film resistors. Still, they may have some noise issues due to parasitic inductance between leads attached to the resistor’s body and lead frame at high frequencies (above 1 MHz).
Wire wound resistors: Used for high-power applications such as heating elements in toasters and hair dryers. These resistors use thin wire wrapped around a core made from solid material such as ceramic or plastic with an insulating coating on the outside. Wire wound resistors are available in many sizes, including surface mount packaging.
Surface mount resistors: Surface mount resistors typically have a low profile design that allows them to fit easily into tight spaces on PCBs (printed circuit board). This type of resistor requires special installation tools because it doesn’t have leads like other types of resistor designs. Surface mount resistors are available in both through-hole and surface mount configurations, so they can be used in both thru-hole and surface mount projects.
What is the function of resistors in the PCB board?One of the most popular and likely easiest to comprehend components on PCBs are resistors. Their purpose is to control the flow of the current or sometimes be a heater converting electrical energy into heat.
What is the effect of the resistor on PCB board function and quality?Resistors are passive components in PCB to limit current flow, resist voltage, or change the direction of electric current. They add resistance to a circuit to adjust the flow of electrons and control the amount of power consumed by the device. Most electronic circuits use resistors as passive components. The main function of a PCB resistor is to reduce voltage or current, but many different types of resistors can be used for other purposes.
How do you identify a resistor in a PCB board?The most common method of identifying a PCB resistor is using a multimeter. A multimeter will test the value of the resistor by measuring its resistance (in ohms). Designers can do this by placing one probe on each lead and reading the resistance shown on display. If designers have an analog meter, they’ll need a chart to convert this value by using ohm’s law (R=V/I).
How do you test a PCB resistor?
The easiest way to test a resistor is to use a multimeter. This will tell the resistance value and if it’s working correctly or not.
If designers prefer a low-cost alternative, they can use a breadboard instead. Here’s how:
- Place the resistor on the breadboard so the leads stick out on either side of the board.
- Connect one lead of the multimeter to one side of the resistor (ground) and connect the other lead to the other side of the resistor (power).
- If the multimeter has an auto-ranging feature, then use it; otherwise, set it manually at 20k ohms. The meter should read 20k ohms or less if it’s working properly.
How to choose the right PCB resistor?Choosing the right PCB resistor depends on its:
- Power rating: determine how much current can safely flow through the resistor without overheating or burning out.
- Accuracy: determines how closely the actual resistance value matches the specified value.
- Tolerance: the differences between nominal values that are allowed for each size of resistor.
How to solder a resistor on a PCB?
Follow these steps to solder a PCB resistor on a circuit board:
1. Clean the surface of the PCB and remove any dirt, oil, or grease.
2. Apply flux to the pads of the components and the leads of the components. The flux helps to make soldering easier and improves reliability.
3. Start soldering.
What is the PCB resistor code?
The PCB resistor code is a method of marking resistors to identify their resistance and tolerance. Three- and four-digit codes, as well as the EIA-96 scheme, are the most commonly used.
In the end, even though PCB manufacturers can use many different PCB resistors, the basic functions remain the same. They give the circuits all essential components of resistance to enable them to work efficiently while maintaining voltage control – they can act as either a resistor or a bridge.
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