Degauss circuit for use in an electronically actuated door lock

Patent metadata

Field	Value
Publication number	US-2018075961-A1
Application number	US-201715698853-A
Country	US
Kind code	A1
Filing date	Sep 8, 2017
Priority date	Sep 9, 2016
Publication date	Mar 15, 2018
Grant date	—

Abstract

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.

First claim

What is claimed is:

1 . A method of degaussing an electromagnet coil, the method comprising:
providing a pulse width modulated (PWM) controller configured to maintain a constant current flow through said coil; providing a capacitor in-line with said current flow through said coil; during a degauss operation, switching said capacitor in series with said coil to form a series LC causing ringing with sufficient amplitude and duration to effectively degauss said coil; and bypassing said capacitor other than during said degauss operation.

2 . The method of degaussing an electromagnet coil in accordance with claim 1 wherein said switching step is provided by a transistor.

3 . The method of degaussing an electromagnet coil in accordance with claim 2 wherein said transistor is an n-channel Field-Effect Transistor (FET).

4 . The method of degaussing an electromagnet coil in accordance with claim 1 comprising the further steps of:
providing an electromagnetic lock wherein said coil is wrapped around a ferromagnetic core and is configured to operate said electromagnetic lock and wherein an uncontrolled degaussing operation occurs.

5 . The method of degaussing an electromagnet coil in accordance with claim 1 comprising the further steps of:
providing an electronically activated door lock wherein said coil is wrapped around a ferromagnetic core and is configured to operate said electronically activated door lock and wherein a controlled degaussing operation occurs.

6 . The method of degaussing an electromagnet coil in accordance with claim 5 wherein said electronically activated door lock is a maglock.

7 . A system for degaussing an electromagnetic coil comprising:
a pulse width modulated (PWM) controller configured to provide a constant current flow; an electromagnet having a coil for receiving said constant current flow from said PWM controller; a capacitor operatively disposed in-line with said current flow; and a switching device disposed in series with said coil configured to cause ringing with sufficient amplitude and duration to effectively degauss said coil, wherein said capacitor may be selectively bypassed when said coil is not degaussed.

8 . The system for degaussing an electromagnetic coil in accordance with claim 7 wherein said switching device is an n-channel Field-Effect Transistor (FET).

9 . The system for degaussing an electromagnetic coil in accordance with claim 7 wherein a signal generated by said PWM controller is approximately 23 kHz.

10 . The system for degaussing an electromagnetic coil in accordance with claim 7 wherein said coil is configured to operate an electronically activated door lock, wherein said electronically activated door lock includes an armature and an electromagnet comprised of said coil and a ferrous material core, and wherein when said coil is energized, current passing through said electromagnet creates a magnetic flux that causes the armature to attract to said electromagnet.

11 . The system for degaussing an electromagnetic coil in accordance with claim 10 wherein said electronically activated door lock is a maglock and said armature is an armature plate.

Assignees

• Hanchett Entry Systems Inc

Inventors

• Davis Brett L
• Shaffer Randall
• Anderson Eric

Classifications

• E05C19/166

  electromagnetic · CPC title

• E05B2047/0048

  Circuits, feeding, monitoring · CPC title

• H01F13/006 Primary

  Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material (for erasing of information on magnetic record carriers G11B5/00) · CPC title

• E05B47/0002

  with electromagnets · CPC title

• E05B2047/0068

  Door closed · CPC title