An alarm generates repeated pairs of primary and secondary light flash events when triggered. One light source produces primary flash events of visible light with a wide bandwidth of e.g. 200 nm. Another light source produces secondary flash events of visible light with a narrow bandwidth e.g. less than a third of the primary flash event. The primary and secondary flash events overlap wholly or partially or are consecutive.
The present invention relates to an alarm for generating flash events, such alarms may be used, for example, in a network of alarms which flash when triggered.
Alarms frequently have a light that repeatedly flashes as a part of the response to the alarm being triggered. The use of the light is to attract attention. In order to fulfil this purpose the flash of light must be bright. The brightness level required for such a flash is high.
There is a market demand that a flashing light on a triggered alarm be coloured and therefore be of a narrow bandwidth. Most frequently the demand is for the colour to be red with a central bandwidth frequency in the range of 430THz to 480THz.
Alarms are often devices operating within a system, network or loop of alarms. Due to the requirements of such systems, an alarm can only draw a small amount of current for operation.
Narrow bandwidth light, such as a bandwidth of approximately a quarter or less of the visible spectrum, is not as effective at attracting attention as wide bandwidth light, such as a bandwidth of approximately two thirds or more of the visible spectrum or white light, especially if reflected light is being relied upon or if the light is reflected from a surface. If there is more than one flash bandwidth used as the primary flash, by using different light sources, lens design can become difficult and complex.
The use of a narrow bandwidth flash, such as that described above, of the needed brightness level draws a larger current from an alarm loop. A large draw of current in an alarm loop is difficult and impractical as such loops are not set up to function with large current draws. The greater bandwidth of a wide bandwidth flash, such as that described above, causes a lower brightness level to be required to attract attention than a narrow bandwidth due to the increased power output of each flash given by the extra bandwidth, and to the fact that the eye is generally less sensitive to narrow band light than it is to wider band light. Thus, a lower current is drawn from the loop.
However, if a wide bandwidth flash is used for the improved ability to attract attention and lower draw of current, the market demand for a coloured flash is not met.
At its most general, the present invention proposes a wide bandwidth flash event coloured by a narrow bandwidth flash event.
According to the invention, there may be provided an alarm for generating repeated pairs of primary and secondary light flash events when triggered, comprising: a first light source arranged to produce the primary flash events of visible light with a bandwidth of at least 200nm (nanometres); a second light source arranged to produce the secondary flash events of visible light with a bandwidth of less than a third of the primary flash events, wherein the primary and the secondary flash event within each pair wholly overlap in duration, or the primary and the secondary flash event within each pair partially overlap in duration, or the primary and the secondary flash event within each pair are consecutive in duration. In use, the wide bandwidth primary flash events attract attention due to the brightness and effectiveness of the wider bandwidth. The use of the secondary flash event is to give the observable flash a coloured appearance. The secondary flash may precede or be preceded by the primary flash whilst maintaining the relationship between the durations.
In this case, consecutive is taken to mean one after the other with a limited intermediary gap such that there are not two discernable events. Therefore for this invention two flash events are consecutive if one flash event of a pair is followed by the other flash event with the gap between the end of the preceding flash event and the beginning of the following flash event being not more than 200ms; preferably not more than 100ms
The duration of the primary flash events may be 500ms (milliseconds) or less, and separately the duration of the secondary flash events may be 500ms or less.
The bandwidth of the secondary flash event may be less than 30nm.
There may be a timer element programmed to send out pulse events to cause the primary and the secondary flash events. Note that each pulse event may single pulse, with one pulse event for each flash event, or may be a plurality of trigger pulses in short succession, which results in the corresponding light source appearing to illuminate continuously during the pulse event. Use of pulse events involving a plurality of trigger pulse is known per se to drive light sources such as LEDs.
When there is a partial overlap between the two flash events of each pair of flash events, the overlap in the durations may be 50% or less, preferably 20% or less.
The primary flash events and the secondary flash events may each have a plurality of sources.
According to the invention, there may also be provided a method for an alarm generating a repeated pair of primary and secondary light flash events; wherein when triggered the alarm executes the steps comprising: primary flash events of visible light with a bandwidth of at least 200nm; secondary flash events of visible light with a bandwidth of less than a third of the primary flash events, wherein the primary and the secondary flash event within each pair wholly overlap in duration, or the primary and the secondary flash event within each pair partially overlap in duration, or the primary and the secondary flash event within each pair are consecutive in duration.
An embodiment of the invention is discussed in detail below, by way of example with reference to the accompanying drawings, in which:
An embodiment of the invention comprises an alarm that generates repeated pairs of flash events when it is triggered. One flash event of the pair has a wide bandwidth of extending through 200nm of the visible spectrum, which gives approximately white light. The other flash event of the pair has a narrow bandwidth limiting it to a third of the bandwidth of the wide bandwidth flash event, which limits the narrow bandwidth flash event to approximately one colour region of the visible spectrum.
The wide bandwidth flash event is emitted by one source and the narrow bandwidth flash event is emitted by a second source. When the flashes are emitted by the respective sources, they are controlled by a timing element that is programmed to activate the flash event sources at the correct timings.
In this embodiment of the invention, within a pair of flash events the two flash events have an overlapping timing relationship. The wide bandwidth primary light flash event is followed by the narrow bandwidth secondary light flash event that starts before the primary flash event has ended.
In another embodiment of the invention in each pair of flash events (10) a primary light flash event (11) starts, and at the same time as the primary light flash event (11) finishes a secondary light flash event starts, or as a variation, a secondary light flash event starts and at the same time as the secondary light flash event finishes a primary light flash event (11) starts.
In another variation of this embodiment there is a gap between the end of a preceding flash event and the beginning of a following flash event in a pair of flash events of a maximum gap of 200ms,
In one of the variations of an embodiment of the invention the primary light flash events have a bandwidth of 200nm and the secondary light flash events have a bandwidth of a third of the bandwidth of the primary light flash events such that the flash events produce visible light.
Returning to
In a variation of this embodiment of the invention there is a plurality of first and/or second light sources.
Moreover, it is possible that the light sources are formed by two LEDs integrated together into a single integrated circuit device. Whilst appearing as a single component, the LEDs of such a component may be driven to generate the different light flash events used in the present invention.
When there are a plurality of first light sources and/or second light sources, the timing element (30) is connected to all the light sources to enable their activation.