INFRA-RED DETECTOR

Abstract: An infra-red detector, intended particularly for use in a smoke detector, adapted to be triggered by any conventinal pulsed infra-red remote control. Allows a ceiling mounted smoke detector to be readily switched off for a period of time when triggered by a non-serious incident. Instead of being switched off, it may instead provide a different audible or visual signal. The detector may be fitted to new alarms or retrofitted to existing devices. The infra-read detector is only powered up and triggerable when the smoke detector's alarm is active, thereby reducing battery consumption and ensuring the alarm is not inadvertently switched off when there is a fire.

Description: INFRA-RED DETECTOR The present application relates to the field of infra-red detectors and their use as controllers of electronic devices, sensors and actuators. In particular, the present application relates to the use of an infra-red detector for controlling hard to reach devices such as ceiling mounted smoke alarms. Smoke alarms are in common use in domestic and industrial environments where they provide a loud alarm whenever they sense smoke. Typically, smoke alarms are fixed to ceilings as this is the optimal place for them to detect smoke which naturally rises upwards. As a result of their location on ceilings, smoke alarms are hard to reach. When smoke detectors are accidentally triggered by eg a non-serious incident in a kitchen such as burning toast, the occupant then finds it difficult to switch the smoke alarm off. Often the occupant will have to find something to stand on to enable them to reach the ceiling-mounted alarm and may then have to open the smoke alarm casing and remove the battery in order to stop it ringing. It is not uncommon for people to find that their alarm is set off by non-serious events on a regular basis and this is a considerable source of irritation. Therefore, it is desirable to provide smoke alarms which can be readily switched off for a short period of time when a non- serious smoke-creating incidents occur. Furthermore, in most contemporary smoke alarms it is necessary to remove the battery in order to stop the alarm once it has been triggered. The owner of the smoke alarm may then forget to replace the battery after a non- serious event and therefore inadvertently leave the detector off when a serious fire outbreak occurs. This could be very dangerous and so it is also desirable to find a way of making smoke alarms which can be easily switched off for a temporary period of time. One solution to this problem is provided in US Patent 4,788,530 to Maurice Bernier. This document discloses a smoke alarm which has nearby a switch mounted at a convenient location within easy reach on a wall near the detector. When the smoke alarm is set off by a false alarm the user presses the switch, temporarily disconnecting the smoke alarm. A timing mechanism switches the smoke alarm on again after a period of time. Furthermore, this device is adapted to be connected to a dry cell battery within a smoke alarm and so may be retrofitted into any alarm using standard batteries. US Patent 4,600,314 to George Theriault discloses a smoke alarm and mountable remote cut-off timer with an LED for indicating improper connection to the battery and a hook and loop fastening means for attaching the timer to a wall remote from the alarm itself. All these three disclosures have the problem that they would be reasonably expensive to produce when compared with the low cost of a standard smoke alarm and would require time and effort to fit and produce unsightly wiring around the sides of rooms and buildings. The present invention aims to solve the problem by providing a smoke alarm which is cheap, easy to use and install, does not require external wiring and which can be readily switched off for a short period of time by a user when there is a false alarm. The present invention also aims to provide a sensor module which can be retrofitted to existing smoke alarms. Furthermore, the invention finds broad applicability to all manner of sensors and actuators which are hard to reach. According to a first aspect of the present invention there is provided a sensor or actuator having an infra- red detector for detecting infra-red light, characterised in that the function of the sensor or actuator is changed in response to the detection of any pulsed infra-red light. Preferably, the sensor or actuator is an alarm that responds to an event. Most preferably, the sensor or actuator is a smoke detector having an alarm which responds to the detection of smoke. Preferably, the change is a reduction in the volume and/or pattern of sound emitted by the alarm. The infra-red detector may be adapted to screen out electrical and/or optical interference. Preferably, the infra-red detector has an omnidirectional lens. The function of the sensor or actuator is changed only in response to the detection of repeated pulsed sequences of infra-red light. The function of the sensor or actuator is changed in response to detection that a sequence of infra-red light pulses was repeated after a pause. The sensor or actuator may consider pulses which differ only in terms of a signal indicating they are repeat pulses to be the same as those without the repeat pulses. Preferably, the infra-red detector is only operational when the alarm is activated. More preferably, infra-red detector is only operational when the alarm is activated and which is further configured so that the alarm cannot be suppressed before the event. The alarm may have a cover and be adapted only to function when the cover is closed, wherein the cover is provided only with a screw closure. According to a second aspect of the present invention there is provided an infra-red detector for retrofitting to a sensor or actuator, the infra-red detector being adapted to change the function of the sensor or actuator in response to the detection by the infra-red detector of any pulsed infra-red light. Preferably, the sensor or actuator is a smoke alarm. Preferably, the infra-red detector is adapted to screen out electrical and/or optical interference. More preferably, the infra-red detector has an omnidirectional lens. The infra-red detector may adapted to change the function of a sensor or actuator only in response to the detection of repeated pulsed sequences of infra-red light. The sensor or actuator may consider pulses which differ only in terms of a signal indicating they are repeat pulses to be the same as those without the repeat pulses. The function of the sensor or actuator may be changed in response to detection that a sequence of infra-red light pulses was repeated after a pause. The infra-red sensor may be operational only when the alarm is activated. According to a third aspect of the present ' invention there is provided a smoke alarm comprising a smoke sensor, an alarm responsive to the smoke sensor and an infra-red detector for detecting infra-red light, wherein triggering of the alarm is inhibited by the detection of any pulsed infra-red light by the infra-red detector. An example embodiment of the present invention will now be illustrated with reference to the following Figures in which: Figure 1 is a cross-section of a smoke alarm according to the present invention; Figure 2 is a face view of a smoke alarm according to a preferred embodiment of the present invention; Figure 3 is a schematic diagram of the shape of an infra-red remote control pulse; Figure 4 is a block diagram of electronic circuitry for use in the sensor of the present invention; Figure 5 is a flow chart of smoke alarm operation; and Figure 6 is a flow chart of the operation of an alternative smoke alarm embodiment. Figure 1 show a cross-section of a smoke alarm 1 for mounting to a ceiling 2. Smoke alarms are generally mounted onto ceilings as smoke rises and so this is the best location for smoke alarms to be fitted. Smoke alarms use a smoke detector 5 such as an ionisation sensor, optical sensor, or other relevant technology to detect smoke and/or fire. Figure 2 shows a face view of a preferred embodiment, showing ventilation gaps 9 allowing ingress of smoke and emission of sound from an internal siren 6. The smoke alarm 1 also has an infra-red detector 3 with an omnidirectional lens 4 thereon. The key to this invention is that the infra-red detector is adapted to be readily triggered by any household infra-red remote control and thereby suppress the alarm. Infra-red remote controls are well known in the field of hi-fi, television and other household appliances. These remote controls determine which of several buttons for different functions have been pressed and, in turn, emit coded signals which can be used to operate these electrical items. Most households have several such devices and so occupants of building fitted with smoke alarms will usually be able to find an infra-red remote control somewhere close to hand. Appropriate infra-red signals will also be provided by infra-red communication enabled devices such as laptop, palmtop and desktop computers and infra-red enabled telephones. It would be prohibitively expensive to provide a remote control intended specifically for a ceiling mounted smoke alarm as smoke alarms are low-cost items and users would not want the clutter of owning a remote control just for their smoke alarm. However, by devising a sensor and control circuitry which is adapted to be triggered by any household infra-red remote control, the owner of the alarm can simply use any of the remote controls lying around their house and point this at the sensor, overriding it for a pre-determined length of time. Standard remote controls use an infra-red diode to provide a coded pulse pattern in the format shown in Figure 3. The preferred patterns comply with the RC5/RC6 coding protocols developed by Phillips®. Depending on the button pressed on the remote control, a different command code pattern is produced. These correspond to functions such as increasing volume, reducing volume, playing a video tape, stop etc. Furthermore, the pulse pattern also contains a system code for the type of device, such as a television, video or stereo. These are preceded with a start bit as illustrated. If a button is held down, the same code is emitted repetitively, although one bit is changed after the first consecutive emission to indicate that a repeat signal is being emitted. These signals are detected on all equipment with an appropriate infra-red sensor on which the infra-red light falls with sufficient strength. However, this signal is then analysed by conventional infra-red remote controlled devices to see if it has a system code corresponding to that device. The command code is then used to select the particular function to be implemented. Importantly, the smoke alarm described herein merely detects that a pulsed infra-red pattern is received. It does not discriminate depending on the particular address and data code, although it may check the pattern is meaningful in a particular format such as RC5 or RC6. Once triggered by smoke, the alarm is suppressed by detection of any such infra-red pattern. In order to allow the infra-red sensor 3 to be activated as easily as possible, the omnidirectional lens 4 is provided, meaning that infra-red light can be shone on the sensor from a wide range of directions. Furthermore, it is important that the infra-red detector should not be triggered by background noise and the infra-red light emitted ambiently from household lighting. A band pass filter circuit centered on 38kHz reduces low and high frequency interference. Alternatively, additional known filter means may be used to reduce other electromagentic and optical interference. The infra-red detector may be triggered by any infra-red signal of sufficient intensity or, for additional reliability, but preferably it is triggered only when pulses of infra-red are detected. For yet further reliability the alarm might only be suppressed by a repeating pattern of pulsed infra-red light such as is emitted by standard infra-red remote controls. The sensor circuitry will store received pulsed signals and compare them with those receive during the next 0.5 - 2.0 seconds to establish whether there is a repeated signal. The sensor circuitry may readily be adapted using to establish whether the same signal is being repeated with a small modification to show that it is a repeat signal. In an alternative embodiment, the sensor circuitry is triggered by receiving a pulse pattern which stops and then starts again after a set period of time, such as half a second. In this embodiment, a user switches the alarm off by pressing a button on a remote control, taking their finger off and then pressing it again. A first pulse pattern can be stored and the detector can compare that the same pattern is received again, but only after a pause. Again, the circuitry may ignore pulses indicating whether or not a pulse pattern is being repeated in deciding whether or not the same pattern is being received. The detector may also be adapted to be triggered only by pulse patterns which match particular protocols, such as the RC5 or RC6 protocols mentioned above and developed by Phillips®. Instead of switching the alarm off for a period of time in response to an infra-red signal, the alarm may be suppressed by merely reducing the volume for a period of time. Alternatively, or as well, it may produce a different and less unpleasant signal than an activated alarm, for example two short beeps every ten seconds. Conventional smoke alarms give out a periodic audible signal to indicate low battery power and a different audible signal is emitted in response to an infra-red signal to that emitted to indicate low battery power. A light emitting diode 20 pulses to show that the alarm is in its suppressed state. A further inventive element of the infra-red detector controlled suppression function is that it . is only powered up and operated when the alarm has been triggered. When the alarm has been triggered the control circuitry allows the alarm to be silenced or alternative signals produced for a period of time. However, because the circuitry is not operative whilst the alarm is not triggered, there will not be a problem with the alarm being accidentally and perhaps without the knowledge of the occupier, being in the silent mode when smoke is present. This approach also has the benefit of conserving battery power. The control circuitry comprises a standard smoke sensor 5 which would typically trigger a siren 6 whenever smoke is present; however, control circuitry 7 overrides the triggering of the siren under certain circumstances. The infra-red detector 3 has circuitry 8 which determines when the infra-red light is incident upon the sensor and if so overrides the siren for a period of time. Importantly, this override function is only available when the smoke sensor 5 has actually been triggered. This prevents it from being already in override mode when the siren is first triggered. Furthermore, the infra-red detector and associated circuitry may actually be kept switched off when the smoke sensor is not triggered, conserving battery power. Figure 5 shows an example flow chart for operation of a smoke alarm according to the present invention. Once the smoke alarm has been started and initialised it checks whether smoke is present at 11 using a smoke sensor as is well known in the art. If no smoke is present, a timer is deactivated and reset to zero; the battery is then checked at 12. If the battery is in acceptable condition then control returns to 11 and it is again determined whether or not there is smoke present. If instead it is found that the battery is low, then a quarter second beep is made with the siren or a separate sounding means every minute to warn the user that the battery is low. If, however, it is found at 11 that smoke is present then the infra-red detection circuitry is powered up and the timer is tested at 13 to check that it is active. If it is not active and no infra-red signal is detected at 14 then the siren is activated. If the timer is not active and an infra-red signal is detected then the timer is activated and the siren is overridden. Once the timer has been started, it will be found at 13 that the timer is active and it will then be tested at 15 whether the timer has run for 30 seconds (for example) . If it has been active for less than 30 seconds the siren will remain deactivated; otherwise, the timer will be deactivated and reset meaning that the siren will be activated again if smoke is still detected and no infra- red signal is detected. Figure 6 illustrates a flow diagram of a preferred embodiment. As before, the alarm detects whether smoke is present 21 and, if not, keeps the siren and LED off. If the battery is found to be low 22 a 0.25second beep is emitted every minute. When the alarm detects smoke the infra red sensor and sensor circuitry are powered up and this circuitry then checks whether a valid infra-red signal has been received 23. If not, the LED is switched on and the siren is activated. Otherwise, the alarm enters suppressed mode and emits two short beeps every ten seconds, while flashing the LED 20 on and off at around 3 Hz. The individual timing values are a matter of designer preference and may readily be varied. The particular electronic circuit configuration shown is only one example and an electronic engineer will recognise how other circuits, or microprocessor/microcontroller controlled implementations may be developed to provide the same or equivalent functionality. As an additional feature, the alarm only functions when a cover is closed. In contrast with most contemporary smoke alarms it can only be closed with a screw instead of a clip locating mechanism. This dissuades the user from removing the battery from the device meaning that the user is unlikely to remove the battery and forget to replace it thereby finding that the alarm is off when an emergency occurs. As a result of this invention a smoke alarm has been provided which can be conveniently suppressed using any household infra-red remote control by a user even though they cannot themselves reach the smoke sensor. As a result of this, the occupant of the dwelling protected by a smoke alarm is less likely to switch the alarm off for a long period of time due to a non-serious smoke producing event. Because any infra-red remote control can be used to suppress the sensor, and because the cost of the components in this sensor is merely pennies, an economically viable device can be produced. Furthermore, it will be clear to one skilled within the art that this infra-red detector can be retrofitted to other devices. For example, an infra-red detector according to the present invention might be fitted to the smoke alarm and wired into its siren. Alternatively, it might be wired into the power supply to the fire alarm. Some fire alarms have a nuisance button on them already in which case the infra-red detector can be retrofitted to trigger the nuisance button and thereby override the siren when the alarm is triggered and when an infra-red signal is sent to the sensor. Furthermore, it will be clear to one skilled in the art that this technology can also be applied to any type of actuator which is fitted to a device which is hard to reach, for example, water sprinklers, light fittings, fire alarms, air conditioning units, electric curtain closers etc, a panic button, carbon monoxide detectors etc. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the purposes of the present invention. Those skilled in the art will also appreciated that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. Further modifications and improvements may be made within the scope of an invention as herein described.

Claims: CLAIMS 1. A sensor or actuator having an infra-red detector for detecting infra-red light, characterised in that the function of the sensor or actuator is changed in response to the detection of any pulsed infra-red light. 2. A sensor or actuator as claimed in Claim 1 which is an alarm that responds to an event. 3. A sensor or actuator as claimed in Claim 2 which is a smoke detector having an alarm which responds to the detection of smoke. 4. A sensor or actuator as claim in Claim 1 wherein the change is a reduction in the volume and/or pattern of sound emitted by the alarm. 5. A sensor or actuator as claimed in any preceding Claim wherein the infra-red detector is adapted to screen out electrical and/or optical interference. 6. A sensor or actuator as claimed in any preceding Claim wherein the infra-red detector has an omnidirectional lens. 7. A sensor or actuator as claimed in any preceding claim wherein the function of the sensor or actuator is changed only in response to the detection of repeated pulsed sequences of infra-red light. 8. A sensor or actuator as claimed in any Claim 7 wherein the function of the sensor or ' actuator is changed in response to detection that a sequence of infra-red light pulses was repeated after a pause. 9. A sensor or actuator as claimed in any of Claims 2 to 7 wherein the infra-red detector is only operational when the alarm is activated. 10. A sensor or actuator as claimed in any of Claims 2 to 8 wherein the infra-red detector is only operational when the alarm is activated and which is further configured so that the alarm cannot be suppressed before the event. 11. A sensor or actuator as claimed in any of Claims 2 to 10 wherein the alarm has a cover and is adapted only to function when the cover is closed, wherein the cover is provided only with a screw closure. 12. An infra-red detector for retrofitting to a sensor or actuator, the infra-red detector being adapted to change the function of the sensor or actuator in response to the detection by the infra-red detector of any pulsed infra-red light. 13. An infra-red detector as claimed Claim 12 wherein the sensor or actuator is a smoke alarm. 14. An infra-red detector as claimed in Claim 12 or Claim 13 wherein the infra-red detector is adapted to screen out electrical and/or optical interference. 15. An infra-red detector as claimed in any of Claims 12 to 14 having an omnidirectional lens. 16. An infra-red detector as claimed in any of Claim sl2 to 15 adapted to change the function of a sensor or actuator only in response to the detection of repeated pulsed sequences of infra-red light. 17. An infra-red sensor as claimed in Claim 16 wherein the function of the sensor or actuator is changed in response to detection that a sequence of infra-red light pulses was repeated after a pause. 18. An infra-red sensor as claimed in any of claims 13 to 17 which is only operational when the alarm is activated. 19. A smoke alarm comprising a smoke sensor, an alarm responsive to the smoke sensor and an infra-red detector for detecting infra-red light, wherein triggering of the alarm is inhibited by the detection of any pulsed infra-red light by the infra-red detector.

Inventors: OAG JAMIE, OAG, JAMIE
Applicants: OAG JAMIE, OPTIMA SOLUTIONS UK LTD, OAG, JAMIE, OPTIMA SOLUTIONS UK LTD.
Application year: 2001
Main classification: G01N
IPC codes: G08B17