Moisture alarm system

• US 4,502,044 A
• Filed: 05/19/1982
• Issued: 02/26/1985
• Est. Priority Date: 05/19/1982
• Status: Expired due to Fees

• Current Assignee: James R. Farris, James R. Farris Jr
• Original Assignee: James R. Farris, James R. Farris Jr
• Inventors: Farris, James R., Farris, James R. Jr.
• Primary Examiner(s): Gill, James J.
• Application Number:
  US06/379,619
• Time in Patent Office: 1,014 Days
• Field of Search: 340/604, 340/605, 73/171, 331/65
• US Class Current: 340/604
• CPC Class Codes: E04D 13/006 Provisions for detecting water leakage
• CPC Class Codes: G01M 3/045 with electrical detection means
• CPC Class Codes: G08B 21/20 responsive to moisture

Abstract

This invention is directed to a system for detecting the presence of moisture in a given location such as the attic of a building or house before the moisture has had an opportunity to penetrate plaster walls or cause other damage. The disclosed invention includes a detector for detecting the presence of minute quantities of moisture contemporaneous with their initial appearance, which responds to the presence of moisture by exhibiting a decrease in its internal impedance. An audible signal-generating circuit is coupled to the detector and responds to the resultant decrease in the impedance of the detector by commencing to oscillate at a pre-determined audio frequency. Since it is possible that prior to the discovery of the alarm signal the moisture may have evaporated, which ordinarily might cause the impedance through the detector to return to its normal value and thus terminate the audible signal, there is additionally provided a circuit to sustain the signal for an indefinite period of time even after the evaporation of the moisture which thus permits the discovery of the existence of moisture at a later time.

Claims

1. A moisture alarm system comprising:

(a) a grid having at least two conductors, said conductors being provided with a plurality of interjacently spaced extensions conncted to said conductors, said grid further providing an impedance between said conductors which decreases in the presence of moisture;

(b) an absorbent flexible sheet to which said grid is secured;

(c) a regenerative oscillator circuit coupled to said conductors of said grid, said oscillator circuit being responsive to said decrease in said impedance between said conductors such that said oscillator circuit commences to oscillate at a predetermined audio frequency when said impedance decreases to a predetermined value, said oscillator including an LC tank circuit, said LC tank circuit including a first capacitor and a coil connected across said first capacitor, said coil also being a primary winding of an audio frequency transformer, said primary winding having a center tap connected to one of said conductors of said grid, said oscillator circuit further having emitter, base and collector electrodes, said emitter electrode being connected to a ground potential within said oscillator circuit, said base electrode being serially connected through resistance means to said other conductor of said grid;

(d) a transducer for converting oscillations of said oscillating circuit to an audible sound, said transducer being coupled to a secondary winding of said transformer;

(e) a second capacitor connected in circuit with said collector electrode, said LC tank circuit, and said base electrode for feeding back a portion of said oscillators of said circuit to said base electrode;

(f) a direct current power source connected in circuit with said emitter electrode and said center tap of said LC tank circuit; and

(g) switching means serially connected in circuit with said power source for interrupting a flow of current from said power source.

2. The moisture alarm system of claim 1 wherein said transistor is a PNP type.