An improved Taguchi Gas Sensor type detection and alarm system for smoke, gases or the like, which is particularly adapted for use in environments where the only available source of electrical operating power is an ordinary storage battery, is provided and employs an electrical oscillator coupled with the storage battery for providing both the low voltage high current electrical power required for activating the Taguchi Gas Sensor and an audio frequency output signal for operating an audible warning component of the system when the sensor has detected the presence of smoke, gases or the like. The electrical circuit coupling the audio warning component with the output of the oscillator includes an electrically controlled switching device responsive to detection of existence of a hazardous condition by the sensor; and such circuit also includes in the coupling between the sensor and the switching device, means for providing a suitable delay prior to operation of the switching device to prevent the generation of false warning signals during warm-up or "purging" of the sensor upon start-up of the system. The preferred embodiment of the invention further provides an auxiliary oscillator of substantially lower frequency than the first mentioned oscillator which is coupled with the latter to provide a distinctive dual tone warning signal alternating between different audio frequencies. The improved apparatus is adapted for implementation by means of integrated circuit modules for the primary active electronic components.
A gas detector (11) provides a comparator (22) having a plurality of inputs to provide a simplistic but yet reliable sensing sequence for detecting a contaminated gas such as carbon monoxide. A first input (55) is supplied from an enable circuit (41) which disables the comparator (22) for a predetermined period of time to prevent operation of an associated alarm (33) to permit a heater (14) of a gas sensor (12) to be initially energized to properly condition the associated gas sensing electrodes (13). A second input (16) is supplied from the gas sensor (12) to continually monitor the carbon monoxide concentration to provide an alarm (33) when sensing a high level of gas contamination. A third input (34) provides a latching circuit to continually activate the alarm (33) until the power input (15) is de-energized. A fourth input (27) provides a predetermined reference voltage to the comparator (22). A second comparator (35) senses a low or intermediate level of gas concentration to energize a second signal (39) and is likewise disabled by the enable circuit (41) for a predetermined time while the sensor (12) is being initially conditioned for operation.
A smoke alarm with high and low pitched tones including a conventional smoke detector adapted to activate upon the detection of smoke associated with fire. A first high tone buzzer is included for emitting a high pitched tone upon activation of the smoke detector. A second low tone buzzer is included for emitting a low pitched tone upon the activation of the smoke detector. The first buzzer and second buzzers are adapted to allow the emitted tone thereof to be adjusted thus affording persons with hearing disabilities warning of the presence of fire.
A high input impedance circuit is employed to sense the condition of a bridge such as a Wheatstone bridge containing ionization chambers for smoke detection. The circuit comprises two CMOS inverters connected to operate as a differential signal detector, one inverter connected at its gate electrodes to one output terminal of the bridge and the other similarly connected to the other output terminal of the bridge. The system includes a simple null and sensitivity adjustment.
A combined smoke and gas detector utilizes a conventional smoke detector IC (44) which is operable to drive a piezo element (46) and an LED (94) to provide indication of a smoke or gas detection. An ionization chamber (58) is operable to detect smoke and a gas detector (98) is operable to detect gas. A comparator (104) detects the output of the gas detector (98) for input to the logic circuitry of the IC (44). The LED (94) is modulated to provide a distinction between gas detection and smoke detection in addition to the tone output from the piezo element (46).
4327361 - Gas sensor - Owned by The United States of America as represented by the Secretary of the Army (Washington, DC)
A variable resistance gas sensor controls the output frequency of a varia frequency tone generator. A tone decoder monitors the output frequency of the tone generator. When the gas concentration attains a predetermined threshold value, the tone decoder produces an output signal which activates a latch circuit to energize an alarm device. The latch circuit continues to energize the alarm device even after the gas concentration is reduced below the threshold value until manually reset.
