GB2378558A

GB2378558A - Flammable gas detector providing two levels of warning

Info

Publication number: GB2378558A
Application number: GB0120597A
Authority: GB
Inventors: Munawar Waheed; Laszlo Vukitsevits
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-07-21
Filing date: 2001-08-24
Publication date: 2003-02-12
Anticipated expiration: 2021-08-24
Also published as: GB0120597D0; GB2378558B; GB0117833D0

Abstract

Domestic warning device for indicating the presence of flammable gases and providing two levels of visual/audible warning dependent upon the concentration of the gas sensed. The device is mains powered and has an internal power supply for operation during mains failure. The device may optionally provide remote sensing, remote visual indication and remote status monitoring via a Personal Computer.

Description

Domestic Gas detection Description Background Currently there are no devices on the domestic market that provide members of the general public protection from the build-up of combustible gasses. I. e. (Butane/Propane/town gas) The primary function of this invention is to provide an early warning in the domestic environment to the above problem.

The invention is intended for domestic use i. e. homes, caravans, boats or any other confined area that uses gas.

Essential Features of the device 1 Power is derived from the Mains supply via a 12v Plug-in adapter.

2 An internal battery provides the unit with up to 1 Hr of operation in the case of mains failure.

3 Warning is provided in two ways: Two LED indicators provide three levels of warning.

A. Safe condition B. Gas Detected C. Danger of Explosion.

Audible warning is provided using a two-stage peizio sounder A. Gas detected B. Danger of Explosion.

4. The unit will be encased in an ABS plastic enclosure. The available colours being Day glow Orange, Green, Smoked glass, black and white.

Non Essential features of the device Refer to Drawing Figure 1.

1. The visual indication may be mounted remotely by the entrance to a room or building.

2. Battery or Mains supply is indicated by pulsing the Power on LED.

3. Provision has been made for control of external devices i. e.

Monitoring via a PC data link Control of external hardware (shutoff valves etc.) 4 The sensor may be remotely mounted should no suitable power supply be close to the sensing area/Control unit.

5 A second sensor may be incorporated either locally or remotely to detect Carbon Monoxide build up.

Drawing Introduction Figure 1 Overall system.

Figure 2 Circuit Schematic Operational description The circuit utilises a lA 5v regulator allowing an input supply voltage from +7 to +24v DC to be employed.

Regulation is provided for the Gas Sensor heater, the gas sensor element, the voltage comparator and the Control Microprocessor.

INITIAL STATE Refer to Drawing Figure 2.

Initially in its quiescent state the resistance of the gas sensing element is greater than 30k. The resistor R18 although indicated, as a variable type should be fixed according to the gas being detected, Nominally 4k7 for Methane Rl, R2 and R3 are chosen so that 2. 0v is present on Pin 5 of Ul and 3v is present on Pin 3 of U 1. These voltages represent equivalent gas concentrations of 600 PPM and 1500 PPM of Methane respectively.

With less than 2v at Pins 2 & 6 the controller will illuminate the Green SAFE Led only indicating a safe environment.

A parallel output from the safe and unsafe led is available as a remote indicator/ control signal.

The input supply is monitored for Mains or Battery operation and the power on indicator pulsed accordingly.

U2 is included for future Carbon Monoxide detection.

TRIGGERED STATE Concentrations of methane gas greater than 600ppm will cause the Gas Sensing element to drop in resistance to below 20k, after which a voltage greater than 2. 0v will be present on pin 5 ofUl. This will cause the output ofUlB (pin 7) to switch to Ov signalling the microprocessor to toggle the SAFE and UNSAFE LED's and pulse the piezio oscillator at 2 Hz indicating a Gas Detected Condition. At the same time the microprocessor will transmit a serial command to the remote PC indicating the current status.

R8 will also be pulled to ground so as to provide hysteresis (stability) in the triggered state.

Further increases in Gas concentrations will cause the sensor resistance to fall until Gas concentrations reach greater than 1500 PPM Methane, at this level over 3v will

be present at pin 2 of U I. This will cause the output of U 1 A (pin l) to switch to Ov signalling the microprocessor to drive the Red UNSAFE Led only and drive the piezio oscillator at a constant tone. This will indicate a"Danger of Explosion" condition. Again the microprocessor will transmit a serial command to the remote PC indicating the current status.

REMOTE PC LINK Using the RS232 protocol the following characters will be transmitted continually at 9600 Baud N, 8, 1 to indicate the Detector status: 'A'= Over 1500 PPM Methane Detected. (Alarm)

'W = Over 600 PPM Methane Detected. (Warning) 'S'= Under 600 PPM Methane Detected. (Safe) SETUP 1. Apply +9v (nominal) @ 100mua to the gas detect unit and wait for 2 minutes for the heaters to stabilise at normal working temperature.

2. Test by injecting a known concentration of gas.

Claims

Claims 1. A domestic warning device to indicate the presence of flammable gasses
2. A warning device as claimed in claim 1 that provides two levels of warning.
3. A warning device as claimed in claim I that provides remote visual indication if required.

4. A warning device as clamed in claim 2 that provides power supply backup with monitoring.

5. A warning device as claimed in claim 1 that provides optional status monitoring from a Personal Computer.

6. A warning device as claimed in any proceeding claim will consist of an Electronic Circuit Board encased in an ABS plastic housing.

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Amendments to the claims have been filed as follows CLAIMS 1. A domestic warning device arranged to indicate the presence of a flammable gas, said device comprising a sensor arranged to detect the presence of a flammable gas, a warning means arranged to generate a warning and being provided remotely from said sensor, and processing circuitry connected to both said sensor and said warning means, said processing circuitry being arranged to cause said warning means to generate a first warning upon detection of a first concentration of said flammable gas by said sensor and a second warning upon detection of a second concentration of said flammable gas by said sensor.

2. A warning device according to claim 1 which comprises a second sensor arranged to indicate the presence of carbon monoxide 3. A warning device according toclaim 1 or 2 which further comprises an internal battery.
4. A warning device according to any preceding claim in which the warning means includes a visual indication.
5. A warning device according to any of claims 4 in which the visual indication is mounted remotely from the device.
6. A warning device according to any of claims 1 to 4 in which the sensor is mounted remotely from the device.
7. A warning device according to any preceding claim which arranged to detect one or more of the following: butane; propane; town gas.

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8. A warning device according to any preceding claim in which provision has been made for monitoring via a PC data link.
9. A warning device according to any preceding claim in which provision has been made for control of external hardware.
10. A warning device according to claim 9 in which the external hardware comprises shut off valves, etc.