How to Use Inductors: Examples, Pinouts, and Specs

Inductors are passive electrical components that store energy in a magnetic field when electric current flows through them. They are widely used in electronic circuits for their ability to resist changes in current and to filter or smooth signals. Inductors are commonly found in power supplies, radio frequency (RF) circuits, and signal processing applications. Their versatility makes them essential in applications such as energy storage, noise suppression, and tuning circuits.

• Power Supplies: Used for filtering and energy storage in DC-DC converters.
• RF Circuits: Employed in tuning and impedance matching.
• Signal Filtering: Used in low-pass, high-pass, and band-pass filters.
• Transformers: Inductors are a key component in transformer design.
• Energy Storage: Found in applications like inductive charging and flyback converters.

Inductors come in various shapes, sizes, and specifications depending on their intended use. Below are the key technical parameters to consider:

• Inductance (L): Measured in henries (H), typically in microhenries (µH) or millihenries (mH).
• Current Rating: Maximum current the inductor can handle without overheating.
• Saturation Current: The current at which the inductor's core saturates, reducing its inductance.
• DC Resistance (DCR): The resistance of the inductor's winding, measured in ohms (Ω).
• Self-Resonant Frequency (SRF): The frequency at which the inductor's impedance becomes purely resistive.
• Core Material: Determines the inductor's performance (e.g., ferrite, iron powder, air core).

Inductors typically have two terminals, but their configuration may vary depending on the type (e.g., axial, radial, or surface-mount). Below is a general description:

For specialized inductors like transformers or coupled inductors, additional pins may be present for secondary windings.

1. Determine the Required Inductance: Calculate the inductance value needed for your application using circuit design equations (e.g., LC filter or resonance formulas).
2. Select the Right Inductor: Choose an inductor with appropriate inductance, current rating, and core material.
3. Connect the Inductor: Place the inductor in series or parallel as required by the circuit design. Ensure proper orientation if using polarized inductors (though most are non-polarized).
4. Verify Circuit Parameters: Check the circuit's operating frequency and ensure it is within the inductor's self-resonant frequency range.

• Avoid Core Saturation: Ensure the current through the inductor does not exceed its saturation current rating.
• Minimize Parasitics: Use shielded inductors or proper PCB layout techniques to reduce electromagnetic interference (EMI).
• Thermal Management: Monitor the inductor's temperature to prevent overheating, especially in high-current applications.
• Use Decoupling Capacitors: Pair inductors with capacitors to create effective filters or resonant circuits.

Below is an example of using an inductor in a simple LC filter circuit to smooth a PWM signal from an Arduino UNO:

/*
  Example: Using an LC filter with Arduino UNO
  This code generates a PWM signal on pin 9, which is smoothed using an LC filter.
  The inductor (e.g., 100 µH) and capacitor (e.g., 10 µF) form the filter.
*/

const int pwmPin = 9; // PWM output pin

void setup() {
  pinMode(pwmPin, OUTPUT); // Set pin 9 as output
}

void loop() {
  analogWrite(pwmPin, 128); // Generate a 50% duty cycle PWM signal
  delay(1000);              // Wait for 1 second
  analogWrite(pwmPin, 255); // Generate a 100% duty cycle PWM signal
  delay(1000);              // Wait for 1 second
}

• Connect the Arduino's PWM pin (e.g., pin 9) to one terminal of the inductor.
• Connect the other terminal of the inductor to the positive terminal of the capacitor.
• Connect the negative terminal of the capacitor to ground.
• The smoothed output can be measured across the capacitor.

1. Inductor Overheating:

   • Cause: Exceeding the current rating or poor thermal management.
   • Solution: Use an inductor with a higher current rating or improve cooling.

2. Unexpected Noise or EMI:

   • Cause: Parasitic effects or poor PCB layout.
   • Solution: Use shielded inductors and optimize PCB design to minimize interference.

3. Circuit Not Functioning as Expected:

   • Cause: Incorrect inductance value or improper connections.
   • Solution: Verify the inductor's specifications and ensure proper placement in the circuit.

4. Core Saturation:

   • Cause: Current exceeds the saturation current rating.
   • Solution: Select an inductor with a higher saturation current rating.

• Q: Can I use any inductor for high-frequency applications?
  A: No, ensure the inductor's self-resonant frequency is higher than the operating frequency.

• Q: How do I measure an inductor's value?
  A: Use an LCR meter to measure the inductance accurately.

• Q: What happens if I use an air-core inductor instead of a ferrite-core inductor?
  A: Air-core inductors have lower inductance and are less efficient but avoid core saturation.

• Q: Can inductors be used in AC circuits?
  A: Yes, inductors are commonly used in AC circuits for filtering, tuning, and impedance matching.

By following this documentation, you can effectively select, use, and troubleshoot inductors in your electronic projects.