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What Is a Solenoid Latch?

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  • Written By: Paul Scott
  • Edited By: A. Joseph
  • Last Modified Date: 15 November 2016
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    Conjecture Corporation
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A solenoid latch is a remote locking mechanism that employs the actuation motion supplied by a solenoid to achieve its locking action. This actuation motion is generated by a moving plunger connected to the latching mechanism. A static wire wound coil is situated close to the plunger and connected to an external power source via a control circuit. When the control circuit is activated, the coil is energized, creating a strong magnetic field that pulls the plunger toward it, supplying the latching action in the process. Solenoid latches are used in a wide variety of lock types, including security doors, safes and vehicle doors.

Remote latching or locking action is used in many security and vehicle door applications and generally is facilitated using a solenoid latch. Similar in most respects to manually operated latches, these devices differ only in the inclusion of an electromagnetic solenoid element. This allows the latch to be released remotely or even automatically by energizing the solenoid coil via a control circuit. An operator in a remote location or an automated system such as a security card reader or timer then needs only to complete the circuit, and the door will open. Most solenoid latch mechanisms are of the night latch type, meaning that they re-lock automatically when the door is closed again.

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The activation of the solenoid latch occurs because of the electromagnetic power of the solenoid. The latch tab is connected to a moving plunger that is located near a wire coil. An external electric power source is connected to the solenoid via a control circuit that, when activated, energizes the coil. This creates a powerful magnetic field around the solenoid latch coil, which pulls the moving plunger toward it. This movement is then transferred to the latch, which pulls out of its locked position.

The latch might be kept in the unlocked position for as long as the control circuit is active or for a pre-determined period of time that is controlled by a timer circuit. When the power is cut to the solenoid, a spring pushes the latch back into the locking position. If the door is then closed, the latch re-engages, and the door is once again locked. In some cases, a latching solenoid is used to keep the lock deactivated until a second, reverse-polarity electric pulse is sent to the solenoid coil. This functionality makes the solenoid latch ideal for remote access security doors, safes and automobile doors where push-button, key-card or keypad-code access is required.

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