How to Use Inductors: Examples, Pinouts, and Specs

Inductors are passive electrical components that store energy in a magnetic field when electrical current flows through them. They are typically made of a coil of wire wound around a core, which can be air, ferrite, or another magnetic material. Inductors are widely used in electronic circuits for their ability to resist changes in current and to filter or store energy.

• Filtering: Used in power supplies and audio circuits to filter out unwanted noise or ripple.
• Energy Storage: Found in DC-DC converters and other power management circuits.
• Tuning Circuits: Used in radio frequency (RF) circuits to select specific frequencies.
• Transformers: Inductors are a key component in transformer design for voltage conversion.
• Chokes: Used to block high-frequency AC signals while allowing DC or low-frequency signals to pass.

• Inductance Range: Typically measured in henries (H), ranging from nanohenries (nH) to millihenries (mH).
• Current Rating: Maximum current the inductor can handle without overheating or saturating.
• DC Resistance (DCR): The resistance of the wire used in the coil, measured in ohms (Ω).
• Saturation Current: The current at which the core material saturates, reducing inductance.
• Self-Resonant Frequency (SRF): The frequency at which the inductor's parasitic capacitance resonates with its inductance.

Inductors are typically two-terminal components. Below is a general description of the terminals:

For surface-mount inductors, the pins are often labeled as A and B or may not have explicit markings. Always refer to the manufacturer's datasheet for specific pin configurations.

1. Determine the Required Inductance: Calculate the inductance value needed for your application using circuit design formulas (e.g., for LC filters or resonant circuits).
2. Select an Appropriate Inductor: Choose an inductor with the correct inductance, current rating, and SRF for your application.
3. Connect the Inductor: Place the inductor in series or parallel in the circuit, depending on the desired function (e.g., series for filtering or parallel for resonance).
4. Avoid Saturation: Ensure the current through the inductor does not exceed its saturation current rating.
5. Minimize Parasitics: Place the inductor close to other components in high-frequency circuits to reduce parasitic effects.

• Core Material: Choose the core material based on the operating frequency. Ferrite cores are ideal for high-frequency applications, while iron cores are better for low-frequency circuits.
• Shielding: Use shielded inductors in sensitive circuits to minimize electromagnetic interference (EMI).
• Temperature: Ensure the inductor operates within its specified temperature range to avoid performance degradation.
• Orientation: For inductors with polarity markings (rare), ensure correct orientation.

Below is an example of using an inductor in a simple low-pass filter circuit to smooth a PWM signal from an Arduino UNO.

• The Arduino generates a PWM signal on pin 9.
• The inductor (10 mH) and a capacitor (100 µF) form a low-pass filter to smooth the PWM signal into a DC voltage.

// Arduino code to generate a PWM signal on pin 9
// This signal can be smoothed using an inductor-capacitor filter

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

void loop() {
  analogWrite(9, 128); // Output a 50% duty cycle PWM signal
  delay(1000);         // Wait for 1 second
  analogWrite(9, 255); // Output a 100% duty cycle PWM signal
  delay(1000);         // Wait for 1 second
}

1. Inductor Overheating:

   • Cause: Exceeding the current rating or operating at high frequencies.
   • Solution: Use an inductor with a higher current rating or better thermal properties.

2. Low Inductance Performance:

   • Cause: Saturation of the core material.
   • Solution: Select an inductor with a higher saturation current rating.

3. Noise in the Circuit:

   • Cause: Electromagnetic interference (EMI) from the inductor.
   • Solution: Use shielded inductors or place the inductor away from sensitive components.

4. Incorrect Inductance Value:

   • Cause: Using an inductor with the wrong specifications.
   • Solution: Double-check the inductance value and other parameters before installation.

• Q: Can I use any inductor for high-frequency applications?
  A: No, you need to select an inductor with a high self-resonant frequency (SRF) and low core losses for high-frequency circuits.

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

• Q: What happens if I exceed the saturation current of an inductor?
  A: The inductance will drop significantly, and the inductor may overheat or fail.

• Q: Can inductors be connected in series or parallel?
  A: Yes, inductors can be connected in series to increase total inductance or in parallel to decrease total inductance.

This documentation provides a comprehensive guide to understanding and using inductors effectively in electronic circuits. Always refer to the manufacturer's datasheet for specific details about the inductor you are using.