Degauss Circuit for Electromagnetic Door Locks
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Solution Overview
Problem
Existing electromagnetic door locks face challenges in rapidly neutralizing the magnetic field to meet building code requirements, ensuring the strike can be separated from the electromagnet within the required time using minimal force, due to residual magnetism after current removal.
Innovation Solution
A degauss circuit that utilizes a pulse width modulation (PWM) controller to maintain a constant current through the coil, incorporating a series RLC circuit to cause ringing and reverse the coil current, effectively neutralizing the magnetic field through uncontrolled or controlled degauss operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If current is removed from the coil to unlock the door, then the magnetic holding force is reduced, but residual magnetism remains causing delayed separation of the strike plate
Solution Approach 1:
The patent applies reverse polarity degaussing by activating a second coil with opposite polarity to the first coil. When the first coil is de-energized, the second coil generates a magnetic field in the opposite direction, actively neutralizing the residual magnetism in the armature plate. This inversion approach directly counteracts the harmful residual magnetism rather than simply waiting for it to decay naturally, thereby achieving rapid strike plate separation and meeting building code requirements.
2Reliability
If a degauss circuit is added to neutralize residual magnetism, then building code requirements are met, but device complexity increases
Solution Approach 1:
The patent combines the locking and degaussing functions into a single electromagnetic lock assembly by integrating two coils (first and second coils) within the same magnetic circuit. The first coil provides the primary magnetic field for locking, while the second coil provides the reverse polarity field for degaussing. This merging approach eliminates the need for separate external degaussing circuits, reducing overall system complexity while ensuring compliance with building codes that require rapid neutralization of residual magnetism.
Solution Approach 2:
The electromagnetic lock assembly serves multiple functions: the first coil provides the main magnetic field for door locking, the second coil provides the reverse polarity field for degaussing, and together they enable both secure locking and rapid unlocking compliant with building codes. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while achieving code compliance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures rapid and efficient neutralization of the magnetic field, allowing the strike to be separated from the electromagnet within the mandated time and force, thus complying with building codes.
Implementation Method 1
A pulse width modulation (PWM) controller varies the frequency and/or duty cycle to a switch in series with the coil. Coil current feedback is used to adjust the PWM frequency and/or duty cycle so as to maintain the current through the coil at a certain level to maintain a desired holding force on the door lock.
Implementation Method 2
A degauss circuit in-line with the current flowing through the coil is provided. When triggered either in an uncontrolled or controlled manner, a series RLC circuit that includes the coil inductance and resistance causes ringing to occur whereby the coil current reverses direction with sufficient amplitude and duration to degauss the coil.
Implementation Method 3
The process of degaussing removes or neutralizes the magnetic field of an electromagnetic lock such that building code requirements are met whereby the strike can be separated from the electromagnet within the required time using the mandated amount of force.
Data Source
AI summary
A novel and useful degauss circuit for use with electromagnetic door locks. The door lock circuit is configured to provide a constant current to the electromagnetic coil load. A pulse width modulation (PWM) controller varies the frequency and/or duty cycle to a switch in series with the coil. Coil current feedback is used to adjust the PWM frequency and/or duty cycle so as to maintain the current through the coil at a certain level to maintain a desired holding force on the door lock. A degauss circuit inline with the current flowing through the coil is provided. When triggered either in an uncontrolled or controlled manner, a series RLC circuit that includes the coil inductance and resistance causes ringing to occur whereby the coil current reverses direction with sufficient amplitude and duration to degauss the coil.