</p><br/><p>When working with relays in electronic circuits, one important detail often overlooked is the need to protect other components from voltage spikes generated when the relay coil is turned off. This phenomenon occurs because a relay coil is essentially an inductor, and inductors resist changes in current. When current flowing through the coil is suddenly interrupted—such as when the switching transistor or driver circuit stops supplying power—the magnetic field around the coil collapses rapidly. This collapse induces a high voltage spike in the opposite direction, which can reach hundreds of volts. Without protection, this spike can damage sensitive components like transistors, microcontrollers, or integrated circuits connected to the relay control circuit.<br/></p><br/><p>To prevent this damage, engineers use a technique called relay coil suppression.<br/></p><br/><p>The most common and effective method involves placing a diode across the relay coil terminals.<br/></p><br/><p>Oriented with its cathode toward the positive rail and anode toward the negative.<br/></p><br/><p>This diode is called a flyback diode, freewheeling diode, or clamp diode.<br/></p><br/><p>While the coil is active, the diode remains off and does not interfere with normal operation.<br/></p><br/><p>But when the power is removed and the coil’s magnetic field collapses, the induced voltage forward biases the diode.<br/></p><br/><p>Creating a controlled feedback path where energy dissipates gradually without damaging components.<br/></p><br/><p>By circulating current in a loop, peak voltages are clamped to safe, predictable values.<br/></p><br/><p>Selecting the right diode is critical for reliable operation.<br/></p><br/><p>The diode’s forward current rating should equal or exceed the coil’s nominal current.<br/></p><br/><p>And have a peak inverse voltage rating higher than the supply voltage.<br/></p><br/><p>A common choice is the 1N4007 diode for low to medium current relays.<br/></p><br/><p>When rapid coil deactivation is required, faster recovery diodes improve response time.<br/></p><br/><p>To accelerate current decay, engineers sometimes add a resistor  <a href="https://www.guerzhoy.a2hosted.com/index.php/The_Future_Of_Relays_In_Digital_And_Quantum_Computing">انواع رله</a> in series with the flyback diode.<br/></p><br/><p>Though this increases the voltage spike slightly and must be balanced with component ratings.<br/></p><br/><p>Alternative suppression techniques include MOVs or RC snubber circuits.<br/></p><br/><p>They are preferred in applications where rapid relay release is critical.<br/></p><br/><p>When millisecond-level response times are required.<br/></p><br/><p>Most engineers favor the flyback diode for its simplicity, low cost, and long-term durability.<br/></p><br/><p>In summary, adding a flyback diode across a relay coil is a simple but essential practice.<br/></p><br/><p>It prevents semiconductor failure, reduces maintenance, and enhances circuit durability.<br/></p><br/><p>Any semiconductor switch controlling a relay coil must have flyback protection.<br/></p><br/><p>This one-component solution dramatically increases system reliability.<br/></p>

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