</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>The standard approach to mitigating relay-induced voltage spikes is known as coil suppression.<br/></p><br/><p>A widely adopted solution is to install a diode directly in parallel with the relay coil.<br/></p><br/><p>Positioned so that the cathode attaches to the supply voltage terminal and  <a href="https://medhost.com.mx/forums/users/eldencotter2/">رله</a> the anode to ground.<br/></p><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Mir_Gul_Khan_Nasir_tomb.jpg/960px-Mir_Gul_Khan_Nasir_tomb.jpg"><br/><p>It is also known as a snubber diode, suppression diode, or free-wheeling diode.<br/></p><br/><p>When the relay is energized, the diode is reverse biased and has no effect on the circuit.<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>Enabling the coil’s residual energy to bleed off through a closed, low-resistance path.<br/></p><br/><p>This slow dissipation of energy prevents the voltage spike from reaching harmful levels.<br/></p><br/><p>The flyback diode must be chosen carefully.<br/></p><br/><p>It must be rated for at least the continuous current drawn by the relay coil.<br/></p><br/><p>And have a peak inverse voltage rating higher than the supply voltage.<br/></p><br/><p>The 1N4007 is frequently selected for general-purpose relay applications.<br/></p><br/><p>In fast-switching circuits, a Schottky or signal diode like the 1N4148 minimizes turn-off delay.<br/></p><br/><p>A damping resistor in series with the diode can shorten the energy dissipation time.<br/></p><br/><p>Though this increases the voltage spike slightly and must be balanced with component ratings.<br/></p><br/><p>Another method of suppression involves using a metal oxide varistor or an RC snubber network.<br/></p><br/><p>These are alternatives to the flyback diode and are sometimes used when the diode’s slow discharge is not acceptable.<br/></p><br/><p>When millisecond-level response times are required.<br/></p><br/><p>However, for most general purpose applications, the simple and inexpensive flyback diode remains the preferred solution due to its reliability and effectiveness.<br/></p><br/><p>Including a flyback diode is a fundamental design requirement for relay-driven circuits.<br/></p><br/><p>This protection safeguards sensitive electronics, prolongs longevity, and ensures stable operation.<br/></p><br/><p>Never operate a relay coil without this diode when using MOSFETs, BJTs, or IC drivers

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