Arquivo de What They Are and How They Work - Electronic Circuits https://www.elcircuits.com/category/what-they-are-and-how-they-work/ Circuits, tips, projects, and electronics tutorials for beginners and enthusiasts. Fri, 12 Dec 2025 15:03:32 +0000 en-US hourly 1 https://wordpress.org/?v=6.9.4 https://www.elcircuits.com/wp-content/uploads/2025/11/cropped-LOGO-ELC-500x500px-elcircuits.com_-1-32x32.png Arquivo de What They Are and How They Work - Electronic Circuits https://www.elcircuits.com/category/what-they-are-and-how-they-work/ 32 32 Ohm’s Law: The Definitive Guide | Theory, Formulas (V=I.R), and 5 Real-World Applications https://www.elcircuits.com/ohms-law-complete-guide/ https://www.elcircuits.com/ohms-law-complete-guide/#respond Sat, 29 Nov 2025 18:20:21 +0000 https://elcircuits.com/?p=2526 Ohm’s Law: Relationship between voltage, current and resistance in electrical circuits. 🌐 You can read this article in: Português | Español Master the fundamental principles of electricity and become an expert in circuit projects! 🔌 Did you know? Ohm’s Law is one of the most important concepts in electricity and is present in virtually all electronic devices we use daily, from your smartphone to complex electrical systems. 📜 The History Behind the Law: Who was Georg Ohm? Born in Erlangen, Germany, in 1789 (and not in 1879 as sometimes cited), Georg Simon Ohm was a brilliant physicist and mathematician whose curiosity led him to decipher one of the greatest mysteries of his time: the relationship between electrical quantities. At a time when electricity was almost magic, Ohm brought clarity and mathematics to the field. His contribution was so monumental that the unit of electrical resistance, the Ohm (Ω), was named in his honor. Thanks to him, today we can predict, control and design circuits with incredible precision. Shall we discover his legacy together? 🧐 What is Ohm’s First Law? The Simplified Concept In essence, Ohm’s First Law is the golden rule of electricity. It describes in a simple and elegant way how the three main quantities of an electrical circuit are related: Voltage, Current and Resistance. Imagine that the law establishes an agreement between these three elements. The magical formula that expresses this relationship is: V = R × I Where each letter represents: V: Voltage or Potential Difference. It is the “force” that drives electrons, measured in Volts (V). Think of it as the water pressure in a faucet. R: Resistance. It is the opposition that the material offers to the flow of current. It is measured in Ohms (Ω). It would be like the “narrowness” of the pipe. I: Electric Current. It is the flow of electrons that passes through the circuit. It is measured in Amperes (A). It is equivalent to the amount of water flowing through the pipe. The law states that, for a resistor with constant resistance, the current (I) is directly proportional to the voltage (V) applied. Doubling the voltage, you double the current. It’s that simple! If you know two of these values, you can easily calculate the third. 🔑 The Best Analogy: Understanding Ohm’s Law with Water To fix this concept, nothing better than a practical analogy. Think of a simple water system: Fig. 2 – Hydraulic Analogy to visualize Voltage, Current and Resistance. Voltage (V) is the pressure that the water exerts in the tank. More height in the tank means more pressure. Current (I) is the flow of water that passes through the system per second. Resistance (R) is the water wheel that consumes part of the energy of the flow. A wheel with more blades or larger diameter offers more resistance to the water flow. If you increase the water pressure (increase the Voltage), more water will flow through the system (increase the Current), making the wheel spin faster. If you maintain the pressure but increase the resistance of the wheel (more blades or larger diameter), the water flow will decrease (the Current will decrease). It’s exactly how Ohm’s Law works! 🧪 The Three Essential Formulas of Ohm’s Law Knowing the main formula V = R × I is great, but in practice, you’ll need to calculate each of the quantities. To facilitate this, we can rearrange the equation. And to memorize, nothing better than the famous Ohm’s Law Triangle. Fig. 3 – Ohm’s Law Triangle: Practical calculation guide The magic happens here: cover the letter representing the Voltage (V), Resistance (R), or Current (I) you want to find in the triangle, and the position of the other two will show you the formula to use. 1️⃣ To calculate Voltage (V) Cover the ‘V’ in the triangle. The ‘R’ and ‘I’ remain side by side, indicating a multiplication. V = R × I 2️⃣ To calculate Current (I) Cover the ‘I’. The ‘V’ remains over the ‘R’, indicating a division. I = V ÷ R 3️⃣ To calculate Resistance (R) Cover the ‘R’. The ‘V’ remains over the ‘I’, also indicating a division. R = V ÷ I With these three formulas at the tip of your tongue (or at your fingertips), you’re ready to solve most basic electrical circuit problems! 🪛 Practical Examples: Applications of Ohm’s Law in Circuits Theory is fundamental, but practice is what solidifies knowledge. Ohm’s Law is applied in countless everyday situations of an engineer, from sizing simple components to analyzing complex systems. Below, we present five practical examples that demonstrate the direct and precise application of this law in real scenarios. 🔌 Example 1 (Circuit): In a simple circuit, we have a 10 Volt source connected to a 500 Ω resistor. What is the electric current that flows through the circuit? Fig. 4 – Simple circuit to apply Ohm’s Law calculation. 1️⃣ Step: Identify what you need to find. The problem asks for the electric current (I). 2️⃣ Step: Identify the data you already have. Voltage (V) = 10 V Resistance (R) = 500 Ω 3️⃣ Step: Choose the correct formula. To find the current (I), we use the formula: I = V ÷ R 4️⃣ Step: Substitute the values and calculate. I = 10 V ÷ 500 Ω I = 0.02 A To make it easier to read, we can convert Amperes (A) to milliamperes (mA), knowing that 1 A = 1000 mA. I = 0.02 × 1000 = 20 mA Done! A current of 20 milliamperes flows through the circuit. See how simple it is? 🔴 Example 2 (LED): You want to connect an LED to a 5V source. The LED datasheet specifies a forward voltage (Vf) of 2.1V and an ideal operating current (If) of 20mA. What should be the value of the series resistor to ensure safe and efficient operation of the component? 1️⃣ Step: Identify what you need to find. The problem asks for the value of the resistor (R). 2️⃣ Step: Identify the data you already have. Source voltage (Vsource)

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Ohm's Law: Formula V=RI illustrating the relationship between voltage, current and resistance in an electrical circuit.
Ohm's Law: Relationship between voltage, current and resistance in electrical circuits.

🌐 You can read this article in: Português | Español

Master the fundamental principles of electricity and become an expert in circuit projects!

🔌 Did you know? Ohm's Law is one of the most important concepts in electricity and is present in virtually all electronic devices we use daily, from your smartphone to complex electrical systems.

📜 The History Behind the Law: Who was Georg Ohm?

Born in Erlangen, Germany, in 1789 (and not in 1879 as sometimes cited), Georg Simon Ohm was a brilliant physicist and mathematician whose curiosity led him to decipher one of the greatest mysteries of his time: the relationship between electrical quantities. At a time when electricity was almost magic, Ohm brought clarity and mathematics to the field.

His contribution was so monumental that the unit of electrical resistance, the Ohm (Ω), was named in his honor. Thanks to him, today we can predict, control and design circuits with incredible precision. Shall we discover his legacy together?

🧐 What is Ohm's First Law? The Simplified Concept

In essence, Ohm's First Law is the golden rule of electricity. It describes in a simple and elegant way how the three main quantities of an electrical circuit are related: Voltage, Current and Resistance.

Imagine that the law establishes an agreement between these three elements. The magical formula that expresses this relationship is:

V = R × I

Where each letter represents:

  • V: Voltage or Potential Difference. It is the "force" that drives electrons, measured in Volts (V). Think of it as the water pressure in a faucet.
  • R: Resistance. It is the opposition that the material offers to the flow of current. It is measured in Ohms (Ω). It would be like the "narrowness" of the pipe.
  • I: Electric Current. It is the flow of electrons that passes through the circuit. It is measured in Amperes (A). It is equivalent to the amount of water flowing through the pipe.

The law states that, for a resistor with constant resistance, the current (I) is directly proportional to the voltage (V) applied. Doubling the voltage, you double the current. It's that simple! If you know two of these values, you can easily calculate the third.

🔑 The Best Analogy: Understanding Ohm's Law with Water

To fix this concept, nothing better than a practical analogy. Think of a simple water system:

Hydraulic Analogy of Ohm's Law: a water tank (voltage), water flow (current) and a water wheel (resistance).
Fig. 2 - Hydraulic Analogy to visualize Voltage, Current and Resistance.

  • Voltage (V) is the pressure that the water exerts in the tank. More height in the tank means more pressure.
  • Current (I) is the flow of water that passes through the system per second.
  • Resistance (R) is the water wheel that consumes part of the energy of the flow. A wheel with more blades or larger diameter offers more resistance to the water flow.

If you increase the water pressure (increase the Voltage), more water will flow through the system (increase the Current), making the wheel spin faster. If you maintain the pressure but increase the resistance of the wheel (more blades or larger diameter), the water flow will decrease (the Current will decrease). It's exactly how Ohm's Law works!

🧪 The Three Essential Formulas of Ohm's Law

Knowing the main formula V = R × I is great, but in practice, you'll need to calculate each of the quantities. To facilitate this, we can rearrange the equation. And to memorize, nothing better than the famous Ohm's Law Triangle.

Ohm's Law Triangle, a visual tool to remember the formulas for V, R and I.
Fig. 3 - Ohm's Law Triangle: Practical calculation guide

The magic happens here: cover the letter representing the Voltage (V), Resistance (R), or Current (I) you want to find in the triangle, and the position of the other two will show you the formula to use.

1️⃣ To calculate Voltage (V)

Cover the 'V' in the triangle. The 'R' and 'I' remain side by side, indicating a multiplication.

V = R × I

2️⃣ To calculate Current (I)

Cover the 'I'. The 'V' remains over the 'R', indicating a division.

I = V ÷ R

3️⃣ To calculate Resistance (R)

Cover the 'R'. The 'V' remains over the 'I', also indicating a division.

R = V ÷ I

With these three formulas at the tip of your tongue (or at your fingertips), you're ready to solve most basic electrical circuit problems!

🪛 Practical Examples: Applications of Ohm's Law in Circuits

Theory is fundamental, but practice is what solidifies knowledge. Ohm's Law is applied in countless everyday situations of an engineer, from sizing simple components to analyzing complex systems. Below, we present five practical examples that demonstrate the direct and precise application of this law in real scenarios.

🔌 Example 1 (Circuit): In a simple circuit, we have a 10 Volt source connected to a 500 Ω resistor. What is the electric current that flows through the circuit?

Diagram of a simple circuit with a 10V source and a 500Ω resistor for Ohm's Law calculation.
Fig. 4 - Simple circuit to apply Ohm's Law calculation.

1️⃣ Step: Identify what you need to find.

The problem asks for the electric current (I).

2️⃣ Step: Identify the data you already have.

  • Voltage (V) = 10 V
  • Resistance (R) = 500 Ω

3️⃣ Step: Choose the correct formula.

To find the current (I), we use the formula: I = V ÷ R

4️⃣ Step: Substitute the values and calculate.

I = 10 V ÷ 500 Ω
I = 0.02 A

To make it easier to read, we can convert Amperes (A) to milliamperes (mA), knowing that 1 A = 1000 mA.

I = 0.02 × 1000 = 20 mA

Done! A current of 20 milliamperes flows through the circuit. See how simple it is?

🔴 Example 2 (LED): You want to connect an LED to a 5V source. The LED datasheet specifies a forward voltage (Vf) of 2.1V and an ideal operating current (If) of 20mA. What should be the value of the series resistor to ensure safe and efficient operation of the component?

1️⃣ Step: Identify what you need to find.

The problem asks for the value of the resistor (R).

2️⃣ Step: Identify the data you already have.

  • Source voltage (Vsource) = 5 V
  • LED voltage (Vf) = 2.1 V
  • LED current (If) = 20 mA = 0.02 A

3️⃣ Step: Choose the correct formula.

First, we need to calculate the voltage that the resistor needs to "absorb": VR = Vsource - Vf. Then, we apply Ohm's Law to find R: R = VR ÷ If

4️⃣ Step: Substitute the values and calculate.

VR = 5V - 2.1V = 2.9V
R = VR ÷ If = 2.9V ÷ 0.02A = 145 Ω → 150Ω (commercial value)

💡 Practical tip: Always choose the closest commercial value above the calculated one to ensure the LED lasts longer!

🏭 Example 3 (Automation): You are installing a sensor in a 24V DC industrial automation system, located 50 meters away from the source and consumes 100mA. The wiring used is a 1.5 mm² copper cable, with a resistance of approximately (0.0124 Ω/m). What is the voltage that actually reaches the sensor, considering the voltage drop in the round-trip cable?

1️⃣ Step: Identify what you need to find.

The problem asks for the voltage that reaches the sensor (Vsensor).

2️⃣ Step: Identify the data you already have.

  • Source voltage (Vsource) = 24 V
  • Sensor current (I) = 100 mA = 0.1 A
  • Cable resistance per meter = 0.0124 Ω/m
  • Cable length = 50 m (go) + 50 m (return) = 100 m

3️⃣ Step: Choose the correct formula.

First, we calculate the total resistance of the cable (Rtotal). Then, we use Ohm's Law to find the voltage drop (Vdrop) in this cable: Vdrop = I × Rtotal. Finally, we subtract this drop from the source voltage: Vsensor = Vsource - Vdrop

4️⃣ Step: Substitute the values and calculate.

Rtotal = 100m × 0.0124 Ω/m = 1.24 Ω
Vdrop = I × Rtotal = 0.1A × 1.24Ω = 0.124V
Vsensor = Vsource - Vdrop = 24V - 0.12V = 23.876V

The voltage drop is minimal, but this calculation is crucial for higher power systems or low voltage signals, where this loss can be critical.

💡 Important alert: In real systems, drops above 5% (1.2V in 24V) can cause failures. Always calculate the voltage drop over long distances!

🤖 Example 4 (Logic Level Compatibility): You need to connect the digital output of an Arduino or PLC that operates with 5V logic to an input pin of an ESP32, which accepts a maximum of 3.3V. To protect the ESP32, you decide to use a voltage divider to reduce the signal. The divider is formed by R1 (connected to the 5V signal) and R2 (connected to GND). If you set R2 to 10 kΩ, what should be the value of R1?

1️⃣ Step: Identify what you need to find.

The problem asks for the value of the resistor R1.

2️⃣ Step: Identify the data you already have.

  • Input voltage (Vin) = 5 V
  • Output voltage (Vout) = 3.3 V
  • Resistor R2 = 10 kΩ

3️⃣ Step: Choose the correct formula.

The voltage divider formula is: Vout = Vin × (R2 / (R1 + R2)). We need to isolate R1 in this equation.

4️⃣ Step 4: Substitute the values and calculate.

3.3V = 5V × (10kΩ / (R1 + 10kΩ))
3.3 / 5 = 10kΩ / (R1 + 10kΩ)
0.66 × (R1 + 10kΩ) = 10kΩ
0.66 × R1 + 6.6kΩ = 10kΩ
0.66 × R1 = 3.4kΩ
R1 = 3.4kΩ / 0.66 ≈ 5.15 kΩ → 5.1kΩ (commercial value)

💡 Teacher's Note: This voltage divider method is a simple and effective solution for unidirectional and low speed signals (e.g., activating an input pin). For bidirectional communication (like I2C) or high-speed (SPI, UART), the professionally correct approach is to use a logic level converter module. It's safer, more robust, and guarantees data integrity.

🔋 Example 5 (Battery): You tested a battery: without load, the voltage at its terminals is 12.6V, but when connecting a load of 2A, the voltage at the terminals drops to 12.1V. What is the internal resistance (Rint) of the battery?

1️⃣ Step: Identify what you need to find.

The problem asks for the internal resistance of the battery (Rint).

2️⃣ Step: Identify the data you already have.

  • No-load voltage (Vno load) = 12.6 V
  • Load voltage (Vwith load) = 12.1 V
  • Load current (I) = 2 A

3️⃣ Step: Choose the correct formula.

The voltage drop in the battery is caused by its own internal resistance. This drop (ΔV) is proportional to the current that passes through it, according to Ohm's Law: ΔV = I × Rint, where ΔV = Vno load - Vwith load.

4️⃣ Step: Substitute the values and calculate.

ΔV = Vno load - Vwith load = 12.6V - 12.1V = 0.5V
Rint = ΔV / I = 0.5V / 2A = 0.25 Ω

💡 Teacher's tip: Batteries with internal resistance above 0.5Ω are worn out and don't deliver enough power for starting or heavy loads.

🤔 Frequently Asked Questions (FAQ)

To ensure your project is a success, we've compiled some of the most common questions about Ohm's Law. Check them out!

Does Ohm's Law apply to all electronic components? 🔽

No. Ohm's Law applies perfectly to "ohmic" components, such as most metal resistors. However, components like diodes, transistors, and incandescent lamps have a resistance that varies with voltage or temperature, and therefore do not follow a linear relationship.

What is the difference between Ohm's First and Second Law? 🔽

The First Law (V=R×I) describes the relationship between voltage, current, and resistance at a point in the circuit. The Second Law (R = ρ × L / A) calculates the resistance of a material based on its physical properties: the resistivity of the material (ρ), the length (L), and the cross-sectional area (A).

Why is Ohm's Law so important? 🔽

It's the foundation for the analysis, design, and diagnosis of virtually all electrical and electronic circuits. Without it, it would be impossible to calculate the current in a circuit, size a resistor to protect an LED, or understand the voltage drop in a wire.

🧾 Conclusion: The Key to the World of Electricity

Ohm's First Law is much more than a simple formula; it's the fundamental language that describes how electricity behaves. Understanding V = R × I gives you the power to predict, control, and innovate in the world of electronics.

Whether you're a student starting your journey, a professional looking to refresh your memory, or a hobbyist working on your next project, mastering Ohm's Law is the first and most crucial step to success.

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

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Best regards,

The ElCircuits Team ⚡

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]]> https://www.elcircuits.com/ohms-law-complete-guide/feed/ 0 Varistor Explained: How It Works and Where to Use It https://www.elcircuits.com/varistor-how-it-works-usage/ https://www.elcircuits.com/varistor-how-it-works-usage/#respond Thu, 27 Nov 2025 21:03:16 +0000 https://elcircuits.com/?p=2514 Varistors: Essential components for electronic circuit protection 🌐 You can read this article in: Português | Español Hello, electronics enthusiasts! If you’ve ever wondered how your electronic devices survive voltage spikes, the answer may lie in a small component called a Varistor. In this complete guide, we’ll explore everything about these silent protectors that save our devices daily. A Varistor is a variable resistor whose resistance depends on the applied voltage. The name is a linguistic amalgam of two words: “Variable” and “Resistor”. These components are true guardians of electronic circuits, acting as shields against overvoltages that could permanently damage sensitive equipment. They are also known by the names: VDR (Voltage Dependent Resistor) – Voltage Dependent Resistor MOV (Metal Oxide Varistor) – Metal Oxide Varistor Unlike conventional resistors, varistors have non-ohmic characteristics and are classified as non-linear resistors. This unique characteristic makes them indispensable in protection applications. 🧐 How Varistors Work: The Protection Mechanism To understand how a varistor works, imagine an intelligent traffic guard that only allows cars (electric current) to pass when the speed (voltage) exceeds a safe limit. Similarly, a varistor remains with high resistance (practically insulating) under normal operating conditions, but its resistance drops drastically when the voltage reaches a specific threshold value. Unlike potentiometers and rheostats, where the resistance changes gradually from a minimum to a maximum value, the operation of a Varistor is more abrupt: when subjected to a certain voltage (threshold voltage), the differential resistance suddenly drops to a very low value. Varistors are composed of semiconductor elements that provide overvoltage protection in a circuit. Their functionality is similar to a Zener diode, allowing voltages below the limit to pass unchanged, but diverting excess energy when the voltage exceeds the safe value. In practice, the main function of the Varistor is to protect against excessive transient voltages in the circuit. These transient voltages are usually caused by electrostatic discharges, lightning surges, or switching of inductive loads, phenomena that we will detail later. 🔧 Types of Varistors: Know the Variations There are several types of varistors, each with specific characteristics for different applications. Let’s explore the main types: 1️⃣ Zinc Oxide Varistor (MOV) The zinc oxide varistor is the most common type of varistor. It is composed of a zinc oxide ceramic material that has high resistance under normal conditions, but its resistance decreases significantly when a surge voltage is applied. Zinc oxide varistors are widely used for surge protection in electronic equipment and power systems. Their popularity is due to the excellent cost-benefit ratio and efficiency in protecting against a wide range of overvoltages. 2️⃣ Zinc Oxide Varistor with Bismuth This is a variation of the traditional zinc oxide varistor that contains a small amount of bismuth in its composition. This addition aims to improve the electrical and performance characteristics of the varistor. Bismuth is added to zinc oxide to promote the formation of a more stable and uniform semiconductor grain boundary layer, resulting in a varistor with improved electrical characteristics. 🔽 The main advantages of the zinc oxide varistor with bismuth addition include: Lower breakdown voltage: Bismuth reduces the breakdown voltage of the varistor, allowing it to start conducting at a lower voltage compared to the conventional zinc oxide varistor. More stable temperature coefficient: The addition of bismuth helps to stabilize the temperature coefficient of the varistor, making it less sensitive to temperature variations. Better performance at high temperatures: The zinc oxide varistor with bismuth addition has better thermal resistance, allowing it to maintain its performance even in high temperature conditions. 3️⃣ Metal Oxide Varistor (MO) The metal oxide varistor uses a metal oxide instead of zinc oxide. It offers surge response characteristics similar to zinc oxide varistors, but with faster response properties and greater energy absorption capacity. These varistors are often found in high-power applications and industrial voltage surge protection systems, where fast response is crucial. 4️⃣ Silicon Carbide Varistor (SiC) The silicon carbide varistor is used for high voltage and high power applications. It has a fast response to voltage surges and is capable of handling high energy levels. Silicon carbide varistors are often found in power systems, power transmission, and other high-power applications, where energy dissipation capability is a critical factor. 💡How Voltage Change Affects the Varistor’s Resistance? This characteristic is determined by the semiconductor composition of the varistor. When manufactured with semiconductor material, its intrinsic characteristics cause the Varistor to change its resistance with high operating voltages. When the voltage applied to a Varistor is greater than its nominal value (threshold voltage), the effective resistance of the Varistor drops drastically and continues to decrease as the applied voltage increases. The curve representing the static resistance of the Varistor in relation to its applied voltage is shown in Figure 2 below: Fig. 2 – Characteristic resistance curve Varistor – Threshold voltage 🔌 Varistor Symbol In circuit diagrams, varistors are represented by specific symbols that differentiate them from other components. Knowing these symbols is essential to correctly identify varistors in electrical schematics. Fig. 3 – Varistor: Symbols and Standards 👉 How Does a Varistor Help Suppress Voltage Transients? To understand this, let’s first identify the sources of transient voltage. The origin of these transients in electrical circuits is independent of whether they operate from an AC or DC source, and can come from the circuit itself or from external sources. These transients result in an increase in voltage to several thousand volts, which can be catastrophic for the circuit. Imagine a small river that suddenly turns into a devastating flood – that’s how voltage transients can affect a delicate electronic circuit. The varistor acts as an intelligent containment system, detecting the abnormal voltage increase and providing a low resistance path to divert the excess energy, thus protecting the most sensitive components of the circuit. 📊 Voltage-Current (V-I) Characteristics  According to Ohm’s law, the current-voltage characteristic curve of a resistor is a straight line, assuming the resistor value is kept constant. In this case, the current flowing through a resistor is directly proportional

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Varistores: Electronic components for overvoltage protection
Varistors: Essential components for electronic circuit protection

🌐 You can read this article in: Português | Español

Hello, electronics enthusiasts!

If you've ever wondered how your electronic devices survive voltage spikes, the answer may lie in a small component called a Varistor. In this complete guide, we'll explore everything about these silent protectors that save our devices daily.

A Varistor is a variable resistor whose resistance depends on the applied voltage. The name is a linguistic amalgam of two words: "Variable" and "Resistor". These components are true guardians of electronic circuits, acting as shields against overvoltages that could permanently damage sensitive equipment.

They are also known by the names:
  • VDR (Voltage Dependent Resistor) - Voltage Dependent Resistor
  • MOV (Metal Oxide Varistor) - Metal Oxide Varistor

Unlike conventional resistors, varistors have non-ohmic characteristics and are classified as non-linear resistors. This unique characteristic makes them indispensable in protection applications.

🧐 How Varistors Work: The Protection Mechanism

To understand how a varistor works, imagine an intelligent traffic guard that only allows cars (electric current) to pass when the speed (voltage) exceeds a safe limit. Similarly, a varistor remains with high resistance (practically insulating) under normal operating conditions, but its resistance drops drastically when the voltage reaches a specific threshold value.

Unlike potentiometers and rheostats, where the resistance changes gradually from a minimum to a maximum value, the operation of a Varistor is more abrupt: when subjected to a certain voltage (threshold voltage), the differential resistance suddenly drops to a very low value.

Varistors are composed of semiconductor elements that provide overvoltage protection in a circuit. Their functionality is similar to a Zener diode, allowing voltages below the limit to pass unchanged, but diverting excess energy when the voltage exceeds the safe value.

In practice, the main function of the Varistor is to protect against excessive transient voltages in the circuit. These transient voltages are usually caused by electrostatic discharges, lightning surges, or switching of inductive loads, phenomena that we will detail later.

🔧 Types of Varistors: Know the Variations

There are several types of varistors, each with specific characteristics for different applications. Let's explore the main types:

1️⃣ Zinc Oxide Varistor (MOV)

The zinc oxide varistor is the most common type of varistor. It is composed of a zinc oxide ceramic material that has high resistance under normal conditions, but its resistance decreases significantly when a surge voltage is applied.

Zinc oxide varistors are widely used for surge protection in electronic equipment and power systems. Their popularity is due to the excellent cost-benefit ratio and efficiency in protecting against a wide range of overvoltages.

2️⃣ Zinc Oxide Varistor with Bismuth

This is a variation of the traditional zinc oxide varistor that contains a small amount of bismuth in its composition. This addition aims to improve the electrical and performance characteristics of the varistor.

Bismuth is added to zinc oxide to promote the formation of a more stable and uniform semiconductor grain boundary layer, resulting in a varistor with improved electrical characteristics.

🔽 The main advantages of the zinc oxide varistor with bismuth addition include:

  • Lower breakdown voltage: Bismuth reduces the breakdown voltage of the varistor, allowing it to start conducting at a lower voltage compared to the conventional zinc oxide varistor.
  • More stable temperature coefficient: The addition of bismuth helps to stabilize the temperature coefficient of the varistor, making it less sensitive to temperature variations.
  • Better performance at high temperatures: The zinc oxide varistor with bismuth addition has better thermal resistance, allowing it to maintain its performance even in high temperature conditions.

3️⃣ Metal Oxide Varistor (MO)

The metal oxide varistor uses a metal oxide instead of zinc oxide. It offers surge response characteristics similar to zinc oxide varistors, but with faster response properties and greater energy absorption capacity.

These varistors are often found in high-power applications and industrial voltage surge protection systems, where fast response is crucial.

4️⃣ Silicon Carbide Varistor (SiC)

The silicon carbide varistor is used for high voltage and high power applications. It has a fast response to voltage surges and is capable of handling high energy levels.

Silicon carbide varistors are often found in power systems, power transmission, and other high-power applications, where energy dissipation capability is a critical factor.

💡How Voltage Change Affects the Varistor's Resistance?

This characteristic is determined by the semiconductor composition of the varistor. When manufactured with semiconductor material, its intrinsic characteristics cause the Varistor to change its resistance with high operating voltages.

When the voltage applied to a Varistor is greater than its nominal value (threshold voltage), the effective resistance of the Varistor drops drastically and continues to decrease as the applied voltage increases.

The curve representing the static resistance of the Varistor in relation to its applied voltage is shown in Figure 2 below:

Characteristic resistance curve Varistor - Threshold voltage
Fig. 2 - Characteristic resistance curve Varistor - Threshold voltage

🔌 Varistor Symbol

In circuit diagrams, varistors are represented by specific symbols that differentiate them from other components. Knowing these symbols is essential to correctly identify varistors in electrical schematics.

Varistor Symbols and Standards
Fig. 3 - Varistor: Symbols and Standards

👉 How Does a Varistor Help Suppress Voltage Transients?

To understand this, let's first identify the sources of transient voltage. The origin of these transients in electrical circuits is independent of whether they operate from an AC or DC source, and can come from the circuit itself or from external sources.

These transients result in an increase in voltage to several thousand volts, which can be catastrophic for the circuit. Imagine a small river that suddenly turns into a devastating flood - that's how voltage transients can affect a delicate electronic circuit.

The varistor acts as an intelligent containment system, detecting the abnormal voltage increase and providing a low resistance path to divert the excess energy, thus protecting the most sensitive components of the circuit.

📊 Voltage-Current (V-I) Characteristics 

According to Ohm's law, the current-voltage characteristic curve of a resistor is a straight line, assuming the resistor value is kept constant. In this case, the current flowing through a resistor is directly proportional to the applied voltage.

However, in the case of a Varistor, the current-voltage characteristic curve is not a straight line. This is due to the unusual resistance behavior of the Varistor, where a small change in the applied voltage can cause a significant change in the current flowing through it.

The voltage-current characteristic curve of a Varistor is shown in Figure 4 below:

Current/Voltage Characteristic Curve of a Varistor
Fig. 4 - Current/Voltage Characteristic Curve of a Varistor

The characteristic current-voltage curve of a Varistor shows a linear relationship between current and voltage when the Varistor is not conducting. This occurs because the current flowing through the Varistor will remain constant and the value is very low - this is called the leakage current, generally on the order of a few milliamperes.

This small current will remain constant until the voltage applied across the Varistor reaches its nominal voltage, also called the clamping voltage. The nominal voltage of a Varistor is the voltage across it, measured with a specified DC current of 1mA.

When the applied voltage of the Varistor reaches its nominal voltage, the behavior of the Varistor changes from the insulation state to the conduction state. The resistance of the Varistor becomes very small when the applied transient voltage is greater than or equal to the nominal voltage of the Varistor.

This occurs due to a phenomenon called avalanche breakdown in semiconductor materials, a form of current multiplication that allows large currents in materials that previously acted as insulators. Due to this situation, the small leakage current increases rapidly.

Even though the current flowing through the Varistor increases, the voltage across it is limited to a value close to the nominal voltage. This means that the Varistor acts as a self-regulator for the transient voltages applied across it, allowing more current to flow through the Varistor.

Thus, after crossing the nominal voltage of the Varistor, the current-voltage curve becomes a steep non-linear curve. Due to this characteristic, a Varistor can pass currents varying extensively over a very narrow range of voltages, cutting off any voltage spikes.

🛡️ Practical Applications of Varistors

Now that we understand how varistors work, let's explore where they are used in the real world:

  • Power supplies: Protect against voltage spikes in the power grid
  • Surge protectors: In power strips and voltage stabilizers
  • Telecommunications equipment: Protect telephone and data lines
  • Industrial systems: In control panels and automation
  • Home appliances: In TVs, computers, and other sensitive devices
  • Power systems: In transformers and substations

⚠️ How to Select the Appropriate Varistor

To select the correct varistor for your application, consider the following factors:

  1. Nominal voltage: Must be higher than the maximum normal operating voltage of the circuit
  2. Energy absorption capacity: Determines how much energy the varistor can dissipate during a surge
  3. Maximum surge current: The maximum current that the varistor can withstand without damage
  4. Response time: How quickly the varistor responds to a voltage spike
  5. Physical size: Must be compatible with the available space in the project

🧾Conclusion: The Invisible Guardian of Electronic Circuits

Varistors are essential electronic components for protecting equipment against voltage surges. They function as a kind of "relief valve" for excessive electrical current, dissipating it safely and protecting the connected devices.

Furthermore, varistors are widely used in various applications, from telecommunications equipment to renewable energy systems. Understanding the functioning and importance of varistors is fundamental to ensure the safety and efficiency of electronic equipment in our daily lives.

When designing or repairing electronic circuits, never underestimate the importance of including appropriate varistors for overvoltage protection. They may seem like simple components, but they are true anonymous heroes that save valuable equipment from irreparable damage.

🤔 Frequently Asked Questions (FAQ)

To ensure your project is a success, we've compiled some of the most common questions about varistors. Check it out!

What is the difference between a varistor and a Zener diode? 🔽

Both protect against overvoltage, but work in different ways. A Zener diode is polarized and protects only in one direction, while a varistor is bipolar and protects against voltage spikes in both directions. Additionally, varistors can dissipate much more energy than Zener diodes.

Can a varistor be used multiple times or does it need to be replaced after a surge? 🔽

It depends on the magnitude and duration of the surge. For small surges, a varistor can operate repeatedly without significant degradation. However, after a significant surge that exceeds its energy absorption capacity, the varistor may be damaged and need replacement.

How to correctly install a varistor in a circuit? 🔽

A varistor should be installed in parallel with the circuit or component to be protected, as close as possible to the power entry point. In AC circuits, it is connected between phase and neutral (or ground), while in DC circuits, it is connected between positive and negative.

What is the lifespan of a varistor? 🔽

The lifespan of a varistor depends on several factors, including the frequency and magnitude of voltage surges it faces. Under normal conditions, a varistor can last many years, but each voltage surge it absorbs slightly reduces its lifespan. Varistors in areas with many electrical storms or grid instability may need more frequent replacement.

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,

The ElCircuits Team ⚡

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]]> https://www.elcircuits.com/varistor-how-it-works-usage/feed/ 0 Understanding Electromagnetic Relays – Characteristics & Applications https://www.elcircuits.com/electromagnetic-relay-working-characteristics-applications/ https://www.elcircuits.com/electromagnetic-relay-working-characteristics-applications/#respond Sun, 03 Oct 2021 13:04:00 +0000 https://elcircuits.com/how-electromagnetic-relays-work-their-characteristics-and-applications/ Electromagnetic Relays: Types, Operation, Characteristics and Applications! Electromagnetic Relays: Understanding Operation and Practical Applications 🌐 You can read this article in: Português | Español Hello Everyone! Have you ever imagined how a simple component the size of a coin can control industrial motors or entire electrical systems? That’s exactly what electromagnetic relays do. They are the “bridge” between weak signals and high-power circuits, essential in home automation, industrial machines, and even household appliances..  In today’s post, we’ll explore in detail the operation, characteristics, and practical applications of electromagnetic relays. 🔍 Why are Relays so Important? Electromagnetic relays are fundamental components in electronics and automation, functioning as electrically controlled switches. They allow a low-power circuit to control a high-power circuit safely and in isolation, being essential in numerous applications, from simple hobby projects to complex industrial systems. 🤔 What is an Electromagnetic Relay? An electromagnetic relay is an electromechanical device that uses voltage, converts it into electromagnetic force, forming a magnetic field to control the switching of electrical contacts. It is composed of a small coil, a movable armature with spring, and switching contacts.  When a current flows through the coil, the electromagnet is activated, attracting the movable armature and switching the contacts. This allows a low-power signal to control a high-power circuit. 💡 Analogy for Better Understanding Think of a relay as a light switch controlled by a magnet. When you turn on the switch (energize the coil), the magnet attracts a lever (armature) that closes or opens another electrical circuit. This allows you to control a high-power lamp using only a small low-power switch! ℹ️ Main Types of Relays There are several types of relays, each designed to meet specific needs. The main types include: Relay Type Characteristics Typical Applications Electromagnetic Uses coil and contact system Motor control, home automation Solid State (SSR) No moving parts, uses semiconductors Temperature control, LED lighting Thermal Monitors temperature, uses bimetallic strip Overload protection, climate control Time Controls operation time Soft motor starting, irrigation 1. Electromagnetic Relay  Characteristics: The most common, use a coil and a contact system to control current flow. Operation: Uses a coil to generate magnetic field and move contacts. Applications: Switching in electronic circuits, power supplies, switches. Control of electric motors Home automation systems (e.g., smart lighting) Industrial safety circuits Fig. 2 – Example of Industrial Electromagnetic Relay 2. Solid State Relay (SSR) Characteristics: No moving parts, use semiconductor components to control current flow. Advantages: No moving parts, longer lifespan and silent operation. Applications: Load driving circuits Temperature control in industrial furnaces High-frequency LED lighting Fig. 3 – Example of Solid State Relay 🌟 Advantages of Solid State Relays Silent operation (no mechanical clicks) High switching speed Less wear (no moving parts) Galvanic isolation between input and output Resistant to vibrations and mechanical shocks 3. Thermal Relay Characteristics: Monitor temperature and disconnect the circuit when overheating occurs. How it works: Uses a bimetallic strip that deforms with heat. Applications: Overload protection in electric motors Climate control systems Fig. 4 – Example of a Thermal Relay 4. Time Relay Characteristics: Allow control of the operation time of electrical circuits. Functionality: Adds programmable delays to switching. Applications: Soft motor starting Automatic irrigation systems Fig. 5 – Example of a Time Relay ⏱️ Types of Time Relays Time relays can be classified as: On energization: start counting when they receive power On de-energization: start counting when power is cut off Cyclic: automatically alternate between on/off states Star-delta: specific for starting three-phase motors 👨‍🔧 Operation of the Electromagnetic Relay (Our Focus) The operation of an electromagnetic relay can be understood by analyzing its internal structure, as illustrated in Figure 6 below. The electromagnetic coil is the heart of the relay, responsible for generating the magnetic field that switches the contacts. Fig. 6 – Schematic diagram of an electromagnetic relay 1️⃣ Coil Energization: When a current flows through the coil, a magnetic field is generated. 2️⃣ Contact Switching: The magnetic field attracts the movable armature, switching the contacts from NC (Normally Closed) to NO  (Normally Open). 3️⃣ De-energization: When the current in the coil ceases, the movable armature returns to its original position due to the spring force, switching the contacts back to NC. Fig. 7 – Operation of the Electromagnetic Relay in Practice 🛠️ Characteristics and Architecture of an Electromagnetic Relay – Standard 5-Pin Model In Figure 8 below, we present a 5-pin electromagnetic relay, which will serve as a reference to exemplify its internal architecture. This type of relay is widely used, being considered a standard model for its simplicity, availability in the market and ease of understanding. Fig. 8 – Characteristics and Architecture of an Electromagnetic Relay – Standard 5-Pin Relay In general, most electromagnetic relays available today are composed of five fundamental elements, which work in conjunction to perform electrical switching. They are: 1. Electromagnetic Coil Responsible for generating the magnetic field when energized. 2. Movable Armature Moving part that switches the contacts when attracted by the magnetic field. 3. Switching Contacts NC (Normally Closed), NO (Normally Open) and COM (Common). 4. Magnetic Core Improves the efficiency of the magnetic field. 5. Return Mechanism Usually a spring that returns the armature to the original position. These components form the functional core of the relay, enabling the actuation of electrical circuits safely and in isolation, as illustrated in Figure 9 below. Fig. 9 – Internal architecture of an Electromagnetic Relay – Standard 5-Pin Relay 🧲 Configuration of the Electromagnetic Relay Electromagnetic relays can have different configurations, and named with designations such as: ➡️ SPST (Single Pole Single Throw) The SPST relay has a total of four terminals. Of these two terminals can be connected or disconnected. The other two terminals are necessary for the coil to be connected. ➡️ SPDT (Single Pole Double Throw) The SPDT relay has a total of five terminals. Of these two are the coil terminals. A common terminal is also included, which connects to any of the other two. ➡️ DPST (Double Pole Single Throw) The DPST relay has a total of six terminals. These terminals are divided into two pairs. Thus,

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Electromagnetic Relays: Types, Operation, Characteristics and Applications!

Electromagnetic Relays: Types, Operation, Characteristics and Applications!

Electromagnetic Relays: Understanding Operation and Practical Applications

🌐 You can read this article in: Português | Español

Hello Everyone!

Have you ever imagined how a simple component the size of a coin can control industrial motors or entire electrical systems? That’s exactly what electromagnetic relays do. They are the “bridge” between weak signals and high-power circuits, essential in home automation, industrial machines, and even household appliances.. 

In today’s post, we’ll explore in detail the operation, characteristics, and practical applications of electromagnetic relays.

🔍 Why are Relays so Important?

Electromagnetic relays are fundamental components in electronics and automation, functioning as electrically controlled switches. They allow a low-power circuit to control a high-power circuit safely and in isolation, being essential in numerous applications, from simple hobby projects to complex industrial systems.

🤔 What is an Electromagnetic Relay?

An electromagnetic relay is an electromechanical device that uses voltage, converts it into electromagnetic force, forming a magnetic field to control the switching of electrical contacts. It is composed of a small coil, a movable armature with spring, and switching contacts. 

When a current flows through the coil, the electromagnet is activated, attracting the movable armature and switching the contacts. This allows a low-power signal to control a high-power circuit.

💡 Analogy for Better Understanding

Think of a relay as a light switch controlled by a magnet. When you turn on the switch (energize the coil), the magnet attracts a lever (armature) that closes or opens another electrical circuit. This allows you to control a high-power lamp using only a small low-power switch!

ℹ️ Main Types of Relays

There are several types of relays, each designed to meet specific needs. The main types include:

Relay Type Characteristics Typical Applications
Electromagnetic Uses coil and contact system Motor control, home automation
Solid State (SSR) No moving parts, uses semiconductors Temperature control, LED lighting
Thermal Monitors temperature, uses bimetallic strip Overload protection, climate control
Time Controls operation time Soft motor starting, irrigation

1. Electromagnetic Relay 

  • Characteristics: The most common, use a coil and a contact system to control current flow.
  • Operation: Uses a coil to generate magnetic field and move contacts.
  • Applications:
    • Switching in electronic circuits, power supplies, switches.
    • Control of electric motors
    • Home automation systems (e.g., smart lighting)
    • Industrial safety circuits
Example of Industrial Electromagnetic Relay

Fig. 2 – Example of Industrial Electromagnetic Relay

2. Solid State Relay (SSR)

  • Characteristics: No moving parts, use semiconductor components to control current flow.
  • Advantages: No moving parts, longer lifespan and silent operation.
  • Applications:
    • Load driving circuits
    • Temperature control in industrial furnaces
    • High-frequency LED lighting
Example of Solid State Relay

Fig. 3 – Example of Solid State Relay

🌟 Advantages of Solid State Relays

  • Silent operation (no mechanical clicks)
  • High switching speed
  • Less wear (no moving parts)
  • Galvanic isolation between input and output
  • Resistant to vibrations and mechanical shocks

3. Thermal Relay

  • Characteristics: Monitor temperature and disconnect the circuit when overheating occurs.
  • How it works: Uses a bimetallic strip that deforms with heat.
  • Applications:
    • Overload protection in electric motors
    • Climate control systems
Example of a Thermal Relay

Fig. 4 – Example of a Thermal Relay

4. Time Relay

  • Characteristics: Allow control of the operation time of electrical circuits.
  • Functionality: Adds programmable delays to switching.
  • Applications:
    • Soft motor starting
    • Automatic irrigation systems
Example of a Time Relay

Fig. 5 – Example of a Time Relay

⏱️ Types of Time Relays

Time relays can be classified as:

  • On energization: start counting when they receive power
  • On de-energization: start counting when power is cut off
  • Cyclic: automatically alternate between on/off states
  • Star-delta: specific for starting three-phase motors

👨‍🔧 Operation of the Electromagnetic Relay (Our Focus)

The operation of an electromagnetic relay can be understood by analyzing its internal structure, as illustrated in Figure 6 below. The electromagnetic coil is the heart of the relay, responsible for generating the magnetic field that switches the contacts.

Schematic diagram of an electromagnetic relay showing the coil and switching contacts

Fig. 6 – Schematic diagram of an electromagnetic relay

  • 1️⃣ Coil Energization: When a current flows through the coil, a magnetic field is generated.
  • 2️⃣ Contact Switching: The magnetic field attracts the movable armature, switching the contacts from NC (Normally Closed) to NO  (Normally Open).
  • 3️⃣ De-energization: When the current in the coil ceases, the movable armature returns to its original position due to the spring force, switching the contacts back to NC.
Operation of the Electromagnetic Relay in Practice

Fig. 7 – Operation of the Electromagnetic Relay in Practice

🛠️ Characteristics and Architecture of an Electromagnetic Relay – Standard 5-Pin Model

In Figure 8 below, we present a 5-pin electromagnetic relay, which will serve as a reference to exemplify its internal architecture. This type of relay is widely used, being considered a standard model for its simplicity, availability in the market and ease of understanding.

Characteristics and Architecture of an Electromagnetic Relay - Standard 5-Pin Relay

Fig. 8 – Characteristics and Architecture of an Electromagnetic Relay – Standard 5-Pin Relay

In general, most electromagnetic relays available today are composed of five fundamental elements, which work in conjunction to perform electrical switching. They are:

1. Electromagnetic Coil

  • Responsible for generating the magnetic field when energized.

2. Movable Armature

  • Moving part that switches the contacts when attracted by the magnetic field.

3. Switching Contacts

  • NC (Normally Closed), NO (Normally Open) and COM (Common).

4. Magnetic Core

  • Improves the efficiency of the magnetic field.

5. Return Mechanism

  • Usually a spring that returns the armature to the original position.

These components form the functional core of the relay, enabling the actuation of electrical circuits safely and in isolation, as illustrated in Figure 9 below.

Internal architecture of an Electromagnetic Relay - Standard 5-Pin Relay

Fig. 9 – Internal architecture of an Electromagnetic Relay – Standard 5-Pin Relay

🧲 Configuration of the Electromagnetic Relay

Electromagnetic relays can have different configurations, and named with designations such as:

➡️ SPST (Single Pole Single Throw)

The SPST relay has a total of four terminals. Of these two terminals can be connected or disconnected. The other two terminals are necessary for the coil to be connected.

SPST Relay

➡️ SPDT (Single Pole Double Throw)

The SPDT relay has a total of five terminals. Of these two are the coil terminals. A common terminal is also included, which connects to any of the other two.

SPDT Relay

➡️ DPST (Double Pole Single Throw)

The DPST relay has a total of six terminals. These terminals are divided into two pairs. Thus, they can act as two SPST, actuated by a single coil. Of the six terminals, two of them are coil terminals.

DPST Relay

➡️ DPDT (Double Pole Double Throw)

The DPDT relay is the largest of all. It mainly has eight relay terminals. Of these two rows are designed to be switched by terminals. They are designed to act as two SPDT relays that are actuated by a single coil.

DPDT Relay

Each configuration offers different switching possibilities.

Configuration Number of Terminals Controlled Circuits Typical Application
SPST 4 1 simple circuit Simple on/off switching
SPDT 5 1 circuit with 2 options Selection between two sources
DPST 6 2 independent circuits Simultaneous control of 2 circuits
DPDT 8 2 circuits with 2 options each Polarity reversal, complex selection

🔗 Related Content

If you liked this project, you might also be interested in these other articles:

🧱 Applications of Relays

Relays are widely used in various applications:

⚙️ Motor Control

To turn on and off electric motors in industrial and residential systems.

🛡️ Circuit Protection

Overload relays protect motors and circuits against overloads.

🏭 Industrial Automation

In industrial control systems for process automation.

🚨 Alarm and Security Systems

For control of alarms and residential and industrial security systems.

🔧 Practical Examples in Daily Life

  • Automotive: Relays control headlights, horns and fuel pumps
  • Residential: Thermostats and automated lighting systems
  • Appliances: Microwaves, washing machines and refrigerators
  • Telecommunications: Switching in telephone and network systems

💡 How to Choose the Ideal Relay: Essential Tips for Safe and Efficient Selection

The correct choice of a electrical relay is fundamental to ensure safety, durability and performance in your automation or control system. See the main factors to consider when selecting a relay:

1. Contact and Coil Protection

Contact protection

Minimizes wear caused by electrical arcs, especially in circuits with inductive loads.

Coil protection

Avoids voltage surges during switching, extending the life of the relay and protecting the circuit components.

2. Certifications and Technical Compliance

Opt for relays that have recognized regulatory approvals (such as UL, CE and IEC), ensuring compliance with electrical safety standards and reliability.

3. Switching Time

For applications that require speed, such as protection systems, choose high-speed relays, which offer optimized response times.

4. Electrical Ratings

Current

Relays range from low current models to industrial relays up to 3,000 A.

Voltage

Options range from 300 V AC to 600 V AC, and can reach 15,000 V in specific high-voltage models.

Application Recommended Relay Type Key Specifications
Home automation Electromagnetic or SSR 5-10A, 12-24V DC or 110-220V AC
Industrial motor control Industrial electromagnetic 20-100A, 24-380V AC
Thermal protection Thermal relay Adjustable for motor current
High-frequency circuits Solid State (SSR) Low noise, high speed

✅ Checklist for Selecting the Ideal Relay

  • Check the coil voltage
  • Confirm the current capacity of the contacts
  • Evaluate the load type (resistive/inductive)
  • Consider the operating environment
  • Check safety certifications
  • Evaluate mechanical and electrical life
  • Consider the necessary switching time
  • Check galvanic isolation

🧾 Conclusion

Electromagnetic relays are versatile and essential devices in many applications. Understanding their operation and characteristics is crucial to use them efficiently. If you are designing a circuit or automation system, relays offer a reliable and effective solution for controlling electrical circuits.

📝 Key Points to Remember

  • Electromagnetic relays function as switches controlled by magnetism
  • They allow low-power circuits to control high-power circuits
  • There are different types of relays for specific applications
  • Proper relay selection is fundamental for system safety and efficiency
  • Relays continue to be essential components even with the advancement of electronics

❓ Frequently Asked Questions

Find answers to common questions about this amplifier circuit below.

Can I use this amplifier with 4Ω speakers? 🔽

We don’t recommend it. This Bridge configuration was designed to work with a minimum impedance of 8Ω. Using 4Ω speakers can overload the ICs, causing overheating and possible permanent damage.

Is it necessary to use heat sinks on the TDA7294 ICs? 🔽

Yes, absolutely! The TDA7294 ICs dissipate significant heat during operation, especially at high powers. We recommend using adequate heat sinks for each IC, with sufficient area to keep the temperature below 80°C.

Can I convert this amplifier into a stereo system? 🔽

To create a stereo system, you would need to build two circuits identical to this one, one for each channel. Alternatively, you could configure each TDA7294 individually (instead of in bridge) to create two lower power channels.

What is the expected sound quality of this amplifier? 🔽

The TDA7294 is known for its excellent sound quality, with low harmonic distortion (typically less than 0.1%) and low noise. You can expect a clean and detailed sound, suitable for high-fidelity audio applications.

Is this amplifier suitable for guitars or musical instruments? 🔽

Yes, this amplifier works very well for guitars and other musical instruments. Its high power and low distortion provide a clean and dynamic sound. For guitar applications, you may want to add a preamplifier circuit or effects before this power stage.

🚀 Did you like this article? Leave your comment!

Share your experiences with relays or ask your questions in the comments section below. Your participation helps enrich our content!

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,
The ElCircuits Team ⚡

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]]> https://www.elcircuits.com/electromagnetic-relay-working-characteristics-applications/feed/ 0 How to Read Polyester & Ceramic Capacitor Codes – Complete EIA Guide https://www.elcircuits.com/read-polyester-ceramic-capacitor-codes-eia-guide/ https://www.elcircuits.com/read-polyester-ceramic-capacitor-codes-eia-guide/#respond Fri, 09 Jul 2021 10:30:00 +0000 https://elcircuits.com/how-to-read-polyester-and-ceramic-capacitors-complete-guide-to-codes-and-eia-table/ Complete guide for identifying polyester and ceramic capacitors 🌐 You can read this article in: Português | Español Hello, electronics enthusiasts! Ever felt lost when faced with those tiny electronic components with mysterious codes? You’re not alone! With the vast number of manufacturers and standards on the market, deciphering the information on polyester and ceramic capacitors can seem like a puzzle. But don’t worry! Today we’re going to unravel these secrets together. In this complete guide, you’ll learn to interpret capacitor codes, identify capacitance values in microfarads (μF) and picofarads (pF), understand tolerance and working voltage, and much more! Fig. 2 – Examples of codifications found on polyester and ceramic capacitors Get ready to transform these electronic enigmas into practical knowledge that will boost your projects! Quick Tip: Before we dive into the details, know that capacitors with values above 1μF usually have their value written directly on the body, while smaller ones use numerical codes that we’ll decipher together! 🧐 The Challenge of Reading Capacitors: Why Is It So Complicated? Imagine you’re assembling a circuit and come across a tiny capacitor marked only with “104”. What does this mean? And why isn’t it clearly written as “0.1μF”? The answer lies in space economy and industrial standardization. For values greater than 1μF (1 microfarad), as in aluminum electrolytic or tantalum capacitors, manufacturers generally write the value directly on the body. However, for values below 1μF, the story is different! Most polyester and ceramic capacitors use a three-digit code followed by a letter. But don’t worry, we’ll transform this “secret alphabet” into something you’ll understand with your eyes closed! Fun Fact: The correct symbol for microfarad is μ (Greek letter mu), but since not all keyboards have this character, it’s common to replace it with the letter “u” in technical texts. Now you know why you see “uF” instead of “μF” out there! 📚 Understanding Farad Submultiples Before deciphering the codes, let’s review (or learn) about the submultiples of the Farad, the unit of measurement for capacitance. Think of it like measuring distances: we use kilometers for long distances and meters or centimeters for shorter ones. With capacitors, something similar happens! A pF (picofarad) is the smallest practical submultiple used in electronics. To give you an idea, 1 picofarad is 1,000,000 times smaller than 1 microfarad (μF). That’s right, a million times smaller! Between the picofarad and the microfarad, we have the nanofarad (nF), which is exactly 1000 times larger than the picofarad and 1000 times smaller than the microfarad. Relationship between units: 1 μF = 1,000,000 pF 1 μF = 1,000 nF 1 nF = 1,000 pF And to give you an idea of the scale, 1 Farad (F) is equal to 1,000,000 μF – an extremely high capacitance for common applications! Multiple (10n) Name Symbol Submultiple (10n) Name Symbol 100 farad F       101 decafarad daF 10-1 decifarad dF 102 hectofarad hF 10-2 centifarad cF 103 kilofarad kF 10-3 millifarad mF 106 megafarad MF 10-6 microfarad µF 109 gigafarad GF 10-9 nanofarad nF 1012 terafarad TF 10-12 picofarad pF 1015 petafarad PF 10-15 femtofarad fF 1018 exafarad EF 10-18 attofarad aF 1021 zettafarad ZF 10-21 zeptofarad zF 1024 yottafarad YF 10-24 yoctofarad yF Need to convert between these units? Use our online capacitance conversion calculator! Capacitance Conversion Calculator: Picofarad pF, Nanofarad nF, Microfarad μF and Farad F! ✅ Decoding Capacitors: The Three-Digit System Now that we understand the units, let’s get to what matters: decoding capacitors! For most capacitors with values between 1pF and 1μF (practically all, except electrolytics), the values are indicated with a three-digit code. The rule is simple: the first two digits represent the significant numbers, and the third digit indicates how many zeros should be added to these numbers. The result is always expressed in picofarads (pF). Practical Example: A capacitor marked as “473” means 47 + 3 zeros = 47,000 pF, which is the same as 47 nF or 0.047 μF. Easy, isn’t it? ⛏️ Practical Examples of Codifications! Let’s analyze 4 different categories of markings found on capacitors, as shown in Figure 4 below: Fig. 3 – Examples of codifications on polyester capacitors 1. Capacitor with code “104”: 104 — Indicates the capacitance: 10 + 4 zeros = 100,000 pF = 100 nF = 0.1 μF This is one of the most common values in electronic circuits! 2. Capacitor with code “104” and voltage “400V”: 400V — Maximum working voltage 104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF 3. Capacitor with code “104J” and voltage “250V”: 104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF J — Tolerance of ±5% 250V — Maximum working voltage 4. Capacitor with code “2A104J”: 2A — Code for voltage of 100V (we’ll see this in detail) 104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF J — Tolerance of ±5% Golden Tip: When you find a capacitor with a three-digit code, always calculate the value in picofarads first and then convert to the most appropriate unit (nF or μF). This will avoid confusion and interpretation errors! 🪛 In Practice: Converting Capacitor Values Now let’s put into practice what we’ve learned with some real examples: Example 1: Capacitor marked as “472” 47 + 2 zeros = 4,700 pF Converting: 4,700 pF ÷ 1,000 = 4.7 nF Converting again: 4.7 nF ÷ 1,000 = 0.0047 μF Example 2: Capacitor marked as “103” 10 + 3 zeros = 10,000 pF Converting: 10,000 pF ÷ 1,000 = 10 nF Converting again: 10 nF ÷ 1,000 = 0.01 μF Example 3: Capacitor marked as “220” 22 + 0 zeros = 22 pF In this case, no conversion is necessary, as the value is already in picofarads! 📖 EIA Table: Decoding Voltages and Tolerances Besides capacitance, we need to understand two other crucial parameters: working voltage and tolerance. For this, the EIA (Electronic Industries Alliance) established standardized codes that we’ll explore now. 📊 EIA Table of Voltage Codes The maximum working voltage is

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Complete guide for identifying polyester and ceramic capacitors

Complete guide for identifying polyester and ceramic capacitors

🌐 You can read this article in: Português | Español

Hello, electronics enthusiasts!

Ever felt lost when faced with those tiny electronic components with mysterious codes? You’re not alone! With the vast number of manufacturers and standards on the market, deciphering the information on polyester and ceramic capacitors can seem like a puzzle.

But don’t worry! Today we’re going to unravel these secrets together. In this complete guide, you’ll learn to interpret capacitor codes, identify capacitance values in microfarads (μF) and picofarads (pF), understand tolerance and working voltage, and much more!

Examples of codifications found on polyester and ceramic capacitors

Fig. 2 – Examples of codifications found on polyester and ceramic capacitors

Get ready to transform these electronic enigmas into practical knowledge that will boost your projects!

Quick Tip: Before we dive into the details, know that capacitors with values above 1μF usually have their value written directly on the body, while smaller ones use numerical codes that we’ll decipher together!

🧐 The Challenge of Reading Capacitors: Why Is It So Complicated?

Imagine you’re assembling a circuit and come across a tiny capacitor marked only with “104”. What does this mean? And why isn’t it clearly written as “0.1μF”?

The answer lies in space economy and industrial standardization. For values greater than 1μF (1 microfarad), as in aluminum electrolytic or tantalum capacitors, manufacturers generally write the value directly on the body. However, for values below 1μF, the story is different!

Most polyester and ceramic capacitors use a three-digit code followed by a letter. But don’t worry, we’ll transform this “secret alphabet” into something you’ll understand with your eyes closed!

Fun Fact: The correct symbol for microfarad is μ (Greek letter mu), but since not all keyboards have this character, it’s common to replace it with the letter “u” in technical texts. Now you know why you see “uF” instead of “μF” out there!

📚 Understanding Farad Submultiples

Before deciphering the codes, let’s review (or learn) about the submultiples of the Farad, the unit of measurement for capacitance. Think of it like measuring distances: we use kilometers for long distances and meters or centimeters for shorter ones. With capacitors, something similar happens!

A pF (picofarad) is the smallest practical submultiple used in electronics. To give you an idea, 1 picofarad is 1,000,000 times smaller than 1 microfarad (μF). That’s right, a million times smaller!

Between the picofarad and the microfarad, we have the nanofarad (nF), which is exactly 1000 times larger than the picofarad and 1000 times smaller than the microfarad.

Relationship between units:

  • 1 μF = 1,000,000 pF
  • 1 μF = 1,000 nF
  • 1 nF = 1,000 pF

And to give you an idea of the scale, 1 Farad (F) is equal to 1,000,000 μF – an extremely high capacitance for common applications!

Multiple (10n) Name Symbol Submultiple (10n) Name Symbol
100 farad F      
101 decafarad daF 10-1 decifarad dF
102 hectofarad hF 10-2 centifarad cF
103 kilofarad kF 10-3 millifarad mF
106 megafarad MF 10-6 microfarad µF
109 gigafarad GF 10-9 nanofarad nF
1012 terafarad TF 10-12 picofarad pF
1015 petafarad PF 10-15 femtofarad fF
1018 exafarad EF 10-18 attofarad aF
1021 zettafarad ZF 10-21 zeptofarad zF
1024 yottafarad YF 10-24 yoctofarad yF

Need to convert between these units? Use our online capacitance conversion calculator!

✅ Decoding Capacitors: The Three-Digit System

Now that we understand the units, let’s get to what matters: decoding capacitors! For most capacitors with values between 1pF and 1μF (practically all, except electrolytics), the values are indicated with a three-digit code.

The rule is simple: the first two digits represent the significant numbers, and the third digit indicates how many zeros should be added to these numbers. The result is always expressed in picofarads (pF).

Practical Example: A capacitor marked as “473” means 47 + 3 zeros = 47,000 pF, which is the same as 47 nF or 0.047 μF. Easy, isn’t it?

⛏️ Practical Examples of Codifications!

Let’s analyze 4 different categories of markings found on capacitors, as shown in Figure 4 below:

Examples of codifications on polyester capacitors

Fig. 3 – Examples of codifications on polyester capacitors

1. Capacitor with code “104”:

  • 104 — Indicates the capacitance: 10 + 4 zeros = 100,000 pF = 100 nF = 0.1 μF
  • This is one of the most common values in electronic circuits!

2. Capacitor with code “104” and voltage “400V”:

  • 400V — Maximum working voltage
  • 104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF

3. Capacitor with code “104J” and voltage “250V”:

  • 104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF
  • J — Tolerance of ±5%
  • 250V — Maximum working voltage

4. Capacitor with code “2A104J”:

  • 2A — Code for voltage of 100V (we’ll see this in detail)
  • 104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF
  • J — Tolerance of ±5%

Golden Tip: When you find a capacitor with a three-digit code, always calculate the value in picofarads first and then convert to the most appropriate unit (nF or μF). This will avoid confusion and interpretation errors!

🪛 In Practice: Converting Capacitor Values

Now let’s put into practice what we’ve learned with some real examples:

Example 1: Capacitor marked as “472”

  • 47 + 2 zeros = 4,700 pF
  • Converting: 4,700 pF ÷ 1,000 = 4.7 nF
  • Converting again: 4.7 nF ÷ 1,000 = 0.0047 μF

Example 2: Capacitor marked as “103”

  • 10 + 3 zeros = 10,000 pF
  • Converting: 10,000 pF ÷ 1,000 = 10 nF
  • Converting again: 10 nF ÷ 1,000 = 0.01 μF

Example 3: Capacitor marked as “220”

  • 22 + 0 zeros = 22 pF
  • In this case, no conversion is necessary, as the value is already in picofarads!

📖 EIA Table: Decoding Voltages and Tolerances

Besides capacitance, we need to understand two other crucial parameters: working voltage and tolerance. For this, the EIA (Electronic Industries Alliance) established standardized codes that we’ll explore now.

📊 EIA Table of Voltage Codes

The maximum working voltage is crucial to ensure the capacitor is not damaged. The EIA established two-letter codes to represent these voltages:

Code Voltage (VDC) Code Voltage (VDC) Code Voltage (VDC)
0G 4V 0L 5.5V 0J 6.3V
1A 10V 1C 16V 1E 25V
1H 50V 1J 63V 1K 80V
2A 100V 2Q 110V 2B 125V
2C 160V 2Z 180V 2D 200V
2P 220V 2E 250V 2F 315V
2V 350V 2G 400V 2W 450V
2H 500V 2J 630V
3A
1000V

📊 EIA Table of Tolerance Codes

Tolerance indicates the maximum allowed variation in the capacitor’s value. For example, a 100nF capacitor with a tolerance of 5% (J) can have an actual value between 95nF and 105nF.

Code Tolerance Code Tolerance
B ± 0.10pF H ± 3%
C ± 0.25pF J ± 5%
D ± 0.5pF K ± 10%
E ± 0.5% M ± 20%
F ± 1% N ± 30%
G ± 2% P +100%, -0%
Z +80%, -20%

Attention: Asymmetrical tolerances (like P and Z) are used in filter capacitors, where a value higher than the nominal doesn’t affect the circuit’s operation, but a lower value may compromise its functioning.

👉 Practical Reading: Polyester Capacitor 2A104J

Let’s analyze a real capacitor of 100nF, with tolerance of +/- 5% and maximum working voltage of 100V, according to Figure 6 below:

Polyester Capacitor 100nF +/- 5% 100V

Fig. 4 – Polyester Capacitor 100nF +/- 5% 100V

In this capacitor, we have the code 2A104J. Let’s decode each part:

  • 2A — Code for voltage of 100V (according to the EIA table)
  • 104 — Capacitance: 10 + 4 zeros = 100,000 pF = 100 nF = 0.1 μF
  • J — Tolerance of ±5%

Therefore, this is a 100nF (or 0.1μF) capacitor with tolerance of ±5% and maximum working voltage of 100V.

📝 Practical Tips for Capacitor Identification

In many cases, the maximum working voltage can be clearly written on the capacitor body, especially in models designed for high voltages. However, in low-voltage capacitors, this information may not be explicit.

Here are some practical tips to identify the working voltage when it’s not clearly marked:

  • Physical size: In general, capacitors with higher working voltage are physically larger for the same capacitance. As they say, “size matters”!
  • Application: Capacitors used in low-voltage circuits (5V, 12V, 24V) generally support between 50V and 100V.
  • Material type: Tantalum capacitors are smaller than polyester ones for the same capacitance, but generally have lower voltages.

Golden Rule: When in doubt about a capacitor’s voltage, always opt for one with a higher voltage than needed for your application. Using a capacitor with a lower voltage than required can result in damage to the component and the circuit!

🔧 Practical Applications of Different Types of Capacitors

Knowing how to read capacitor codes is essential, but understanding where to apply them is equally important. Let’s explore the most common applications for polyester and ceramic capacitors:

Ceramic Capacitors

  • Decoupling: Used to filter noise in power supply lines of integrated circuits
  • Signal coupling: To block DC components and allow AC signals to pass
  • Timing circuits: Together with resistors to create delays
  • Filters: In audio and RF circuits

Polyester Capacitors

  • Line filters: In power supplies to reduce interference
  • Audio circuits: In equalizers and crossovers
  • Motor starting: In single-phase motors
  • High-frequency applications: Where value stability is important

Electrolytic Capacitors

  • Power supply filters: used to smooth DC voltage after rectification, reducing ripple.
  • Audio coupling and decoupling: in amplifiers, they allow AC signal passage and block DC.
  • Timer circuits: together with resistors (RC), to define charge and discharge times.
  • Energy storage: in power supplies and inverters, they store energy to provide quick current during demand peaks.
  • Motor starting circuits: in single-phase motors, they provide initial torque.
  • Switching power supplies: act in filtering and stabilizing output voltage.
  • Linear supplies and regulators: help with voltage stability and elimination of residual noise.

🤔 Dúvidas Frequentes (FAQ)

❓ Frequently Asked Questions about Capacitors

1. Can I replace a polyester capacitor with a ceramic one of the same value?🔽

It depends on the application. In decoupling and high-frequency circuits, ceramic ones are generally better. In audio and filter applications, polyester ones may offer more linear characteristics. Always check your project’s specifications.

2. What happens if I use a capacitor with a lower voltage than needed?🔽

The capacitor may suffer dielectric breakdown, resulting in a short circuit. This can damage not only the capacitor but also other circuit components. Always use capacitors with voltage equal to or higher than required.

3. How to identify polarity in polyester and ceramic capacitors?🔽

Polyester and ceramic capacitors are generally non-polarized, meaning they can be connected in any direction. Only electrolytic and tantalum capacitors have defined polarity.

4. Why do some capacitors have asymmetrical tolerances?🔽

Asymmetrical tolerances (like +100%, -0%) are used in filter capacitors, where a value higher than the nominal doesn’t affect the circuit’s operation, but a lower value may compromise its functioning.

5. How to store capacitors correctly?🔽

Store in a dry place with controlled temperature. Polyester and ceramic capacitors are quite stable, but avoid places with excessive humidity or extreme temperatures.

🎯 Conclusion: Mastering the Art of Reading Capacitors

Congratulations! Now you’re equipped with the necessary knowledge to decipher the mysterious codes of polyester and ceramic capacitors. Remember the main points:

  • The three-digit code represents the capacitance in picofarads
  • The EIA tables help identify voltages and tolerances
  • Always check the working voltage before using a capacitor
  • Each type of capacitor has its ideal applications

With this skill, you’re ready to tackle electronic projects with more confidence and precision. Keep practicing and exploring the fascinating world of electronics!

🔗 Related Content

Original article published on FVML (Portuguese) – February 19, 2019

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,
The ElCircuits Team ⚡

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]]> https://www.elcircuits.com/read-polyester-ceramic-capacitor-codes-eia-guide/feed/ 0 How ATX Power Supplies Work – Diagnose Problems in 10 Easy Steps https://www.elcircuits.com/how-atx-power-supplies-work-diagnose-problems/ https://www.elcircuits.com/how-atx-power-supplies-work-diagnose-problems/#respond Mon, 14 Sep 2020 23:33:00 +0000 https://elcircuits.com/how-atx-power-supplies-work-learn-to-diagnose-problems-in-10-simple-steps/ How ATX Power Supplies Work: Learn to Diagnose Problems in 10 Simple Steps Hello, electronics enthusiasts! 🌐 You can read this article in: Português | Español ATX Switched-Mode Power Supplies have some interesting features when compared to standard Switched Mode Power Supply (SMPS). In the ATX power supply, there are different output voltages: + 12V, + 5V, + 3.3V, -12V, -5V and 5VSB. There are some variations on these types of Power Supply, but in the general context, the pattern is this. The way SMPS work is pretty much the same. They control the output voltage by opening and closing the switching circuit so as to maintain the opening and closing time of this circuit, that is, the width of pulses and their frequencies, to obtain the desired voltage. There are separate processes for everything to work smoothly. So let’s see the modular diagram to unravel the steps of these processes so that we can step by step understanding. This is the block in modules divided by steps, to improve our understanding. This is the block in modules divided by steps, to improve our understanding. There are distinct processes that need to work together for everything to function properly. Let’s take a look at the modular diagram to break down each step and better understand how these processes unfold. There are 10 basic steps involved in operating an ATX power supply, although there are additional underlying modules that are intrinsically connected to these steps. We won’t go into too much depth here, but for those who want a more detailed explanation, we’ve included a video in Portuguese at the end of this article, created by our partner site. So let’s understand these steps: Step 1 – Transient Filter Is through that stage that the voltage coming from your network, whether 110 or 220V AC should enter. Fig. 2 – How SMPS Works – Transient Filter This voltage goes through basic protection, fuse, that if some step ahead short, the fuse opens, avoiding to burst everything ahead, and in the same line, we have NTC (Negative Temperature Coefficient), It’s a surge current limiter, in series with the electric circuit. In its value of ohmic resistance decreases as its temperature rises, its initial resistance is approximately 15 Ohms, which we can understand by the Ohms’ law, advantages one has in using it in series after the power supply switches it on lowers its resistance to approximately 0.5 Ohms. EMI filters also exist, these are used to avoid high-frequency noise and a huge amount of harmonics generated by the switches that can propagate through the electrical network and cause interference in nearby electronic equipment. Step 2 – Primary Rectification Fig. 3 – How SMPS Works – Primary Rectification In this stage we find the rectifier bridge or an arrangement formed by four common diodes, which has the function of rectifying a full-wave voltage, that is, rectifying an alternating electric current (AC), transforming it into a continuous electric current (DC). Step 3 – Filtration Fig. 4 – How SMPS Works – Filtration After rectification, the DC signal, Ripples (which are small variations, capacitors are responsible for filtering and stabilization IE, a decrease of these Ripples, in the rectified voltage, this voltage rises to something around 300V, which are used in power switches, this part is fundamental to the correct stabilization of source especially if its source is of high power. Step 4 – Power Switches Fig. 5 – How SMPS Works – Power Switches These switches can be Bipolar Power Transistors such as MOSFETs, or any other type, but they differ from ordinary transistors, by the type of operation in which these transistors work. These switching transistors dissipate less power than a common working transistor in a linear source because they work as a switch on/off at high speeds, depending on the design of the source, they suffer variations that are usually between 20Khz to 100kHz. They are directly responsible for the output voltage, and stability of that voltage, through of the commands received by the Control Circuit. Step 5 – Output Transformer Fig. 6 – How SMPS Works – Output Transformer The transformer is a high-frequency CHOPPER TRANSFORMER, and they also work with alternating voltage, when passing through the switches voltage will be a square wave AC type PWM, but with high frequency, not with the same frequency of 60Hz of the input voltage. The switches work on two different levels, High and Low, when it is HIGH, voltage goes through it normally, causing a constant voltage level in the input of coil of the transformer, action of these transistors, goes from HIGH to LOW very quickly. This will induce the winding to have the necessary voltages according to the winding and frequency placed on these switches. Step 6 – Fast Rectifier Fig. 7 – How SMPS Works – Fast Rectifier With the voltage generated by high-frequency switches, a diode is needed to meet this demand, so we have the high-speed diodes called SCHOTTKY DIODES or fast recovery diodes since ordinary diodes would not be able to work with high-frequency voltages. Step 7 – Output Filters Fig. 8 – How SMPS Works – Output Filters The inductor – This has the function of eliminating high-frequency harmonics so that they do not travel to the equipment that will be fed, imagine if these harmonics pass to a micro-controller for example, could cause undue loads and errors of reading in the control processes. And the Capacitors – They are the ones that filter and stabilize the voltage at the output, avoiding ripples and instabilities at the output. 🔗 Related Content If you liked this project, you might also be interested in these other articles: Symmetrical SMPS Switched Power Supply using IR2153 and IRF840 – 2x50V 350W + PCB Adjustable Switching Power Supply 5.1 to 40V, 2.5 Amp using L4960 + PCB Switched Power Supply SMPS 13.8V 10A using IR2153 IC and IRF840, with PCB How to Modify an ATX Power Supply to 13.6V, 22 Amperes Mini Switching Power

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How ATX Power Supplies Work: Learn to Diagnose Problems in 10 Simple Steps

How ATX Power Supplies Work: Learn to Diagnose Problems in 10 Simple Steps

Hello, electronics enthusiasts!

🌐 You can read this article in: Português | Español

ATX Switched-Mode Power Supplies have some interesting features when compared to standard Switched Mode Power Supply (SMPS).

In the ATX power supply, there are different output voltages: + 12V, + 5V, + 3.3V, -12V, -5V and 5VSB. There are some variations on these types of Power Supply, but in the general context, the pattern is this.

The way SMPS work is pretty much the same.

They control the output voltage by opening and closing the switching circuit so as to maintain the opening and closing time of this circuit, that is, the width of pulses and their frequencies, to obtain the desired voltage.

There are separate processes for everything to work smoothly. So let’s see the modular diagram to unravel the steps of these processes so that we can step by step understanding.

This is the block in modules divided by steps, to improve our understanding.

This is the block in modules divided by steps, to improve our understanding.

This is the block in modules divided by steps, to improve our understanding.

There are distinct processes that need to work together for everything to function properly. Let’s take a look at the modular diagram to break down each step and better understand how these processes unfold.

There are 10 basic steps involved in operating an ATX power supply, although there are additional underlying modules that are intrinsically connected to these steps.

We won’t go into too much depth here, but for those who want a more detailed explanation, we’ve included a video in Portuguese at the end of this article, created by our partner site.

So let’s understand these steps:

Step 1 – Transient Filter

Is through that stage that the voltage coming from your network, whether 110 or 220V AC should enter.

How SMPS Works - Transient Filter

Fig. 2 – How SMPS Works – Transient Filter

This voltage goes through basic protection, fuse, that if some step ahead short, the fuse opens, avoiding to burst everything ahead, and in the same line, we have NTC (Negative Temperature Coefficient), It’s a surge current limiter, in series with the electric circuit.

In its value of ohmic resistance decreases as its temperature rises, its initial resistance is approximately 15 Ohms, which we can understand by the Ohms’ law, advantages one has in using it in series after the power supply switches it on lowers its resistance to approximately 0.5 Ohms.

EMI filters also exist, these are used to avoid high-frequency noise and a huge amount of harmonics generated by the switches that can propagate through the electrical network and cause interference in nearby electronic equipment.

Step 2 – Primary Rectification

How SMPS Works - Primary Rectification

Fig. 3 – How SMPS Works – Primary Rectification

In this stage we find the rectifier bridge or an arrangement formed by four common diodes, which has the function of rectifying a full-wave voltage, that is, rectifying an alternating electric current (AC), transforming it into a continuous electric current (DC).

Step 3 – Filtration

How SMPS Works - Filtration

Fig. 4 – How SMPS Works – Filtration

After rectification, the DC signal, Ripples (which are small variations, capacitors are responsible for filtering and stabilization IE, a decrease of these Ripples, in the rectified voltage, this voltage rises to something around 300V, which are used in power switches, this part is fundamental to the correct stabilization of source especially if its source is of high power.

Step 4 – Power Switches

How SMPS Works - Power Switches

Fig. 5 – How SMPS Works – Power Switches

These switches can be Bipolar Power Transistors such as MOSFETs, or any other type, but they differ from ordinary transistors, by the type of operation in which these transistors work.

These switching transistors dissipate less power than a common working transistor in a linear source because they work as a switch on/off at high speeds, depending on the design of the source, they suffer variations that are usually between 20Khz to 100kHz.

They are directly responsible for the output voltage, and stability of that voltage, through of the commands received by the Control Circuit.

Step 5 – Output Transformer

How SMPS Works - Output Transformer

Fig. 6 – How SMPS Works – Output Transformer

The transformer is a high-frequency CHOPPER TRANSFORMER, and they also work with alternating voltage, when passing through the switches voltage will be a square wave AC type PWM, but with high frequency, not with the same frequency of 60Hz of the input voltage.

The switches work on two different levels, High and Low, when it is HIGH, voltage goes through it normally, causing a constant voltage level in the input of coil of the transformer, action of these transistors, goes from HIGH to LOW very quickly.

This will induce the winding to have the necessary voltages according to the winding and frequency placed on these switches.

Step 6 – Fast Rectifier

How SMPS Works - Fast Rectifier

Fig. 7 – How SMPS Works – Fast Rectifier

With the voltage generated by high-frequency switches, a diode is needed to meet this demand, so we have the high-speed diodes called SCHOTTKY DIODES or fast recovery diodes since ordinary diodes would not be able to work with high-frequency voltages.

Step 7 – Output Filters

How SMPS Works - Output Filters

Fig. 8 – How SMPS Works – Output Filters

The inductor – This has the function of eliminating high-frequency harmonics so that they do not travel to the equipment that will be fed, imagine if these harmonics pass to a micro-controller for example, could cause undue loads and errors of reading in the control processes.

And the Capacitors – They are the ones that filter and stabilize the voltage at the output, avoiding ripples and instabilities at the output.

🔗 Related Content

If you liked this project, you might also be interested in these other articles:

Step 8 – Driver Transformer

How SMPS Works - Driver Transformer

Fig. 9 – How SMPS Works – Driver Transformer

The driver transformer in this case is nothing less than one responsible for traffic of information coming from the Integrated Circuit Controller, and pass these commands to the switches, so as to bring insulation or electrical decoupling between primary and secondary.

In this topology there is a pair of transistors that also switch the Transformer Drive to receive these PWM pulses from the driver IC, passing this information to the power step we already saw in Step 4.

Step 9 – PWM control

How SMPS Works - PWM control

Fig. 10 – How SMPS Works – PWM control

The brain of a switched source is its PWM controller, they are dedicated integrated circuits, to perform that work, but they do not work alone, there are also current sensors, which also vary from source to source, but it is very likely that you will find in its source TL341 IC, it has the aspect of a transistor, but, it is not a transistor, it is very popular for its cost-benefit.

This circuit is connected to the output of the power supply, receives Feedback, and directs the voltage information to the IC that controls the oscillator that generates a rectangular signal whose pulse width is controlled and sent to the Transformer Drive that sends these commands to the step of power.

If the power at the output to raise the voltage tends to drop, the circuit activates the instantaneous correction in the pulse width of the switching transistors and the voltage keeps stabilized.

Step 10 – Primary Power Supply VSB

How SMPS Works - Primary Power Supply VSB

Fig. 11 – How SMPS Works – Primary Power Supply VSB

VSB stands for Voltage Standby, which is technically a power supply that keeps its output active, whenever the source power cord is connected to the mains, its capacity is approximately 2 Amps, and this depends on the total power of the source.

This active voltage line is to keep the circuit active and is necessary for when the power on button is activated through PSON, which is the start of the power supply, then the oscillator will activate the power line also powers the motherboard hardware to activate peripherals via software, keyboard, network, and so on.

For those who want a more in-depth, step-by-step explanation, we recommend watching the detailed video (in Portuguese) available on our partner’s YouTube channel. It complements this article with visual support and additional insights.

[Watch the original video in Portuguese in video below or – Click Here

✨ Our Gratitude and Next Steps

We sincerely hope this guide has been useful and enriching for your projects! Thank you for dedicating your time to this content.

Your Feedback is Invaluable:

Have any questions, suggestions, or corrections? Feel free to share them in the comments below! Your contribution helps us refine this content for the entire ElCircuits community.

If you found this guide helpful, spread the knowledge!

🔗 Share This Guide

Best regards,
The ElCircuits Team ⚡

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