Self-powered Wireless Intrusion Alarm System

Abstract

The invention pertains to an alarm system including a magnetic pulse generator for producing an output pulse in response to a change in magnetic flux in response to an intrusion of a designated area, a radio transmitter circuit responding to the pulse from the magnetic pulse generator by transmitting a signal to a remote receiver circuit which in turn generates a pulse for actuating an intrusion alarm circuit.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following cofiled copending patent applications:

Filing Ser. No. Title WE Case Date 7/14/72 271,877 An Improved Magnetic 43,127 Pulse Generator 7/14/72 271,880 Transmitter Circuit 43,128 7/14/72 271,878 Receiver Discriminator 43,849 Circuit

BACKGROUND OF THE INVENTION

Security systems for protecting homes and businesses are becoming increasingly popular due to the increase in vandalism and theft. The commonly used protective system involves a wiring of doors and windows in such a manner that an unauthorized opening of the door or window activates an electric circuit which in turn produces an alarm. The conventional systems require battery power sources, extensive wiring and specially designed switching devices making a conventional security system susceptible to tampering and failure as well as rendering the cost prohibitive.

SUMMARY OF THE INVENTION

The self-powered wireless intrusion alarm system described below in connection with the attached drawing includes a magnetic pulse generator including a magnet and a pickup coil assembly including a soft iron core or pole piece and a coil such that rapid movemement of the pole piece relative to the magnet causes rapid change in the flux linkage therebetween and this in turn results in the generation of an output pulse signal in the coil. The pulse generated by the magnetic pulse generator is applied to an electrically connected RF transmitter circuit which in turn transmits an RF signal to a remote radio receiver circuit. A receiver circuit in turn produces an output signal which is supplied to an intrusion alarm indication circuit.

Magnetic pulse generators of the type described in Design News, May 10, 1967, page 204 are commercially available from the Suprel Division of Globe Industries, Inc., Dayton, Ohio.

The system disclosed herein provides significant advantages over the other prior art in that it requires no separate power source to energize the transmitter and no interconnecting wire between the transmitter and receiver circuits.

The invention will become more readily apparent from the following exemplary description in connection with the accompanying drawing.

DESCRIPTION OF THE DRAWING

The drawing is a schematic illustration of a typical embodiment of a self-powered wireless intrusion alarm system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawing there is illustrated a self-powered wireless intrusion alarm system 10 comprised of a magnetic pulse generator 20 for responding to the movement of a monitored object, i.e., window W, by supplying a signal pulse to RF transmitter circuit 40 which responds by transmitting a signal via antenna 42 to the antenna 52 of the receiver circuit 50. An output signal corresponding to the received signal is supplied by receiver circuit 50 to the alarm circuit 60 which may be typically an audible or a visual alarm indicating device. The occurrence of an intrusion in the form of movement of the window W is manifested by an alarm indication in the alarm circuit 60.

The magnetic pulse generator 20 is comprised of magnet 22 having a north pole N and a south pole S. The magnet 22 is slidably positioned for movement within stationary housing 24. A spring element 25 acts in compression between the stationary housing 24 and the magnet 22 such that with the window in the closed position as illustrated, the linkage mechanism 30 forces the magnet 22 into the stationary housing 24 thus increasing the compression force developed by the spring element 25. With the window in the closed position illustrated, the magnet can be considered to be in a latched condition.

The linkage assembly 30 consists of pivot arm 32 which is pivoted about pivot point 33 against the tension force developed by tension spring element 34 by the actuator arm 36 extending from the window W when the window W is positioned in the closed position. This counterclockwise motion of the pivot arm 32 about the pivot point 33 causes the pivot arm to raise the mwgnet 22 within the stationary housing 24. Movement of the widow from the closed position to an open position will remove the force of the actuator arm 36 on the pivot member 32 thus permitting the spring member 34 to produce clockwise motion of the pivot arm 32 thereby releasing the magnet 22 from the raised or latched position. The compressed spring member 25 will then rapidly accelerate the magnet 22 toward the pickup coil assembly 26. The pickup coil assembly 26 consists of a soft iron pole piece 27 and a coil 28 wound thereabout. The rapid movement of the magnet 22 towards the pickup coil assembly 26 will produce a rapid increase in flux linkage therebetween. This rapid buildup in flux linkage will produce an electrical pulse in the coil 28 which pulse is subsequently applied to the RF transmitter circuit 40. The implementation and operation of the transmitter circuit 40 can be satisfied by any radio transmitter circuit operating at a suitable frequency such as AM, FM, CB, SW, etc. which is powered by the pulse developed by the magnetic pulse generator in response to the rapid movement of the magnet 22 relative to the pickup coil assembly 26.

While the magnetic pulse generator 20 is illustrated in schematic form in the drawing, a more detailed representation and description of a suitable magnetic pulse generator is presented in the above-identified copending patent application entitled "Improved Magnetic Pulse Generator." Furthermore, while the pulse is described as being produced by the rapid movement of the magnet toward the pickup coil assembly it is equally apparent that movement of the pickup coil assembly relative to the magnet would likewise produce the same results. Furthermore, since all that is necessary is the rapid relative movement of magnet 22 and pole piece 27 to provide a rapid change in magnetic flux to produce the necessary output pulse, an embodiment equally suitable would be one in which the relative movement represents a rapid separation of the magnet and pole piece thus producing a rapid collapse of a magnetic field in contrast to the rapid buildup of magnetic flux as would be the case in the above described embodiment.

The power required to transmit a signal over a distance of between 50 to 100 feet, which represents typical positioning of the transmitter circuit 40 and the receiver circuits 54 in a security installation, is quite small as indicated by the fact that citizen band radios are capable of transmitting up to distances of 2 miles with less than 100 millowatts of input power.

While the RF transmitter circuit 40 can be implemented through many known techniques a detailed representation and description of a suitable transmitter circuit is presented in the copending above-identified patent application entitled "Transmitter Circuit."

The output signal produced by the RF transmitter circuit 40 in response to the output of magnetic pulse generator 20 is transmitted by an antenna 42 and picked up by the antenna 52 of the remote receiver circuit 50. As in the case of the RF transmitter circuit 40 the receiver circuit 50 can be implemented through the use of any one of numerous available radio receiver circuits compatible with the frequency of the signal transmitted by RF transmitter circuit 40 in response to the output pulse from the magnetic pulse generators 20. The receiver circuit 50 in turn develops an output signal for actuating the alarm circuit 60 which provides audio and/or visual manifestation of the intrusion represented by movement of the window from the closed to the opened position.

A detailed description and representation of a receiver circuit suitable for application in this configuration is presented in the above identified copending patent application and entitled "Receiver-Discriminator Circuit. "

Claims

We claim as our invention:

1. In a self-powered wireless intrusion alarm system for responding to disturbance of an object such as a window or a door, the combination of, a magnetic pulse generator means including a magnet having a north and south pole, a pole piece and an electrical coil operatively associated therewith, said pole piece aligned with said north and south poles to establish a path of magnetic flux, actuator means operatively connected between said object and said magnetic pulse generator means for maintaining said pole piece and said magnet in a preset relationship in the absense of a disturbance of said object, said actuator means disrupting said preset relationship of said magnet and said pole piece in response to a disturbance of said object to cause relatively rapid movement of said magnet and said pole piece either toward or away from one another to produce a rapid change in the magnetic flux and a corresponding electrical output pulse in said coil, RF transmitter circuit means operatively connected to said magnetic pulse generator means and responding to said output pulse from said magnetic pulse generating means by transmitting a corresponding RF signal, and radio receiver circuit means responding to said RF output signal by generating an output signal suitable for actuating an intrusion alarm circuit.

2. In a self-powered wireless intrusion alarm system as claimed in claim 1 wherein said actuator means includes means for maintaining said magnet and said pole piece in a latched spaced apart relationship during said preset condition, and bias means for causing rapid relative movement of said pole piece and said object toward one another to produce an electrical output signal in response to a disturbance of said object.