GB2460721A

GB2460721A - Electrical apparatus having operation status indicator which cn transmit parameter values

Info

Publication number: GB2460721A
Application number: GB0810845A
Authority: GB
Inventors: Robert John Eric Moreton
Original assignee: RED DOT TECHNOLOGIES Ltd
Current assignee: RED DOT TECHNOLOGIES Ltd
Priority date: 2008-06-13
Filing date: 2008-06-13
Publication date: 2009-12-16
Also published as: GB0810845D0

Abstract

An electronic apparatus such as a fire alarm transducer 10 comprises a light emitting device 11 arranged to illuminate to provide an indication of the status of the apparatus. The light emitting device 11 is also pulsed to transmit optically readable data concerning a parameter of the apparatus such as its address code or serial number. The data pulses are of a sufficiently short duration that they are not discernible to the human eye. A remote device 12 is provided for reading the data. The use of a single light emitting device 11 to provide an indication of status and to transmit data saves component costs, saves space and helps to improve the aesthetic appearance of the apparatus.

Description

ELECTRONIC APPARATUS

This invention relates to an electronic apparatus and more particularly but not solely to an addressable fire alarm transducer.

Fire alarm systems are well known which comprise one or more transducers, such as smoke and/or heat detectors, connected across one or more respective pairs of wires extending from a control panel. Each transducer has a unique address code which is transmitted to the control panel along with other signals which, for example, indicate that heat or smoke has been detected or that the transducer is faulty. The control panel is able to determine which transducer sent the signal by analysing the address code. Also, the control panel is able to send control signals back to a particular transducer by transmitting its address code together with the control signal.

A problem with the above-mentioned fire alarm systems is that it is difficult for an engineer to determine the address code of the transducer after it has been installed: this is needed so that the fire alarm system can be tested and so that faulty transducers can be located.

We have now devised an electronic apparatus which alleviates the above-mentioned problems.

In accordance with the present invention, there is provided an electronic apparatus comprising a light emitting device arranged to illuminate to provide an indication of the status of the apparatus, wherein said light emitting device is also pulsed to transmit optically readable data concerning a parameter of the device.

Most electronic apparatus comprise a light emitting device, such as an LED, which illuminates to indicate the functioning of the apparatus. We have realised that this light emitting device can also be used to transmit optically readable data to an external device, so that a parameter of the apparatus, such as its address code or serial number, can easily be determined. The use of a single light emitting device to provide an indication of status and to transmit data saves component costs, saves space and helps to improve the aesthetic appearance of the apparatus.

Preferably the data is transmitted when the light emitting device appears illuminated, the data pulses being of a sufficiently short duration that they are not discernible to the human eye. In this manner, the status indication is unaffected and persons will be unaware that data is being transmitted when the light emitting device appears illuminated.

The light emitting device may be pulsed to indicate the status of the apparatus. In a fire alarm detector, it is known to provide a status indicator which is pulsed on and off, the period and frequency of the pulse is being varied to provide a visible indication of different statuses of the detector, such as operational/ok, fault or activated modes. The data is preferably transmitted when the status indicator is pulsed on, although it can be transmitted when the indicator is off but this is less preferable since the date pulses may be visible.

Preferably the date pulses comprise a synch pulse, which is preferably provided by the leading or trailing edge of a status indicator pulse.

The data pulses may have an optical output level which is different from the optical output level at which the light emitting device indicates the status, such that the average optical output level of the data pulses is preferably substantially the same as the optical output level of the status indication. This helps to make the data pulses less visible to the eye.

Preferably the light emitting device comprises an LED. Whilst LED5 are known to emit light, they can also be used as an optical detector. Thus the apparatus may be arranged to monitor the output of the LED to detect a control signal transmitted from a remote device to the apparatus. This control signal may be used change an operating parameter of the apparatus or to change the type of data output by the LED of the apparatus.

Preferably the apparatus is arranged to monitor for the control signal when the LED is off (ie after a status pulse).

In order to alleviate any risk of the data pulses being visible, the data is preferably transmitted as a self-clocking or other code arranged to minimise the number of successive similar data pulses. An example of such a code is the so-called Manchester Code.

Alternatively, the data level representing binary 0 may be above 0 volts, so that the light emitting device is never fully off when data is being transmitted.

Preferably the apparatus comprises a fire alarm transducer, such as heat and/or smoke detector.

Also in accordance with the present invention, there is provided an electronic apparatus as hereinbefore defined and a remote device for receiving the transmitted data pulses.

Preferably the remote device is arranged to transmit a control signal to the electronic apparatus via said light emitting device.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a side view of a fire alarm detector and a remote interrogation device in accordance with the present invention; Figures 2A and B are waveform diagrams of the output of a status indicator of the detectorofFigurel; and Figures 3A and B are waveform diagrams of one bit of data of the waveform of Figure 2B.

Referring to Figure 1 of the drawings, there is shown a smoke/heat detector 10 of a fire alarm system. The detector 10 is connected across a pair of wires (not shown) extending from a control panel (not shown) in parallel with other detectors, sounders, manual call points and input/output devices etc. The detector 10 comprises external housing which contains an electronic circuit and a smoke/heat sensor. A light emitting diode or so-called LED 11 is mounted on a printed circuit board disposed inside the housing, the LED 11 projecting through an aperture in the housing such that it is visible externally of the detector 10.

Referring to Figure 2A of the drawings, the LED 11 is arranged to flash periodically to indicate the status of the detector 10. Under normal operating conditions, the LED is flashed on for 5 milliseconds every 20 seconds. When there is fault, the LED 11 is flashed on for 5 milliseconds every 1.2 seconds. When the detector 11 has been activated by heat or smoke, the LED 11 is arranged to flash on for 160 milliseconds every 0.5 seconds. This pattern of flashes can be recognised by an engineer to determine the status of the detector 11. It will be appreciated that the frequency and period of the flashes is purely given by way of example and may differ.

The detector 10 as hereinbefore defined is conventional. Referring to Figure 2B of the drawings, a detector in accordance with the present invention is improved in that a series of data pulses 20 are transmitted for a short period (e.g. 1 millisecond) at the start of every light output pulse from the LED 11. The data pulses 20 may carry 8 bits of data, for example indicating the address code or serial number of that particular detector 10. The data pulses 20 are so short in duration that they are not discernable by the human eye and thus the appearance is given that the status pulse is always on throughout the entire pulse period.

The voltage level representing binary 0 may be above 0 volts in order to make the data pulses 20 less visible. In order to avoid the possibility of a succession of binary 0 pulses being seen, the data pulses may be provided as a self-clocking code.

Referring to Figures 3A and B, there is shown one bit of data respectively representing binary 0 and binary 1. The first 25% of the data bit is always binary 1, the following 50% of the data bit is either binary 0 or binary 1 according to the data value to be represented, the final 25% of the data bit is always binary 0. In this manner, a succession of binary 0 bits will always have a voltage transmission from 0 to 1 at the start of the bit and thus long off periods are avoided.

The leading edge of the status pulse acts as a synch so that an external data interrogation device can determine the start of the data. A typical data interrogation device 12 is shown in Figure 1 and comprises an upwardly-facing cup-shaped body which fits over the detector 10 and obscures ambient light and also hides the pulse from view. A photo detector 13 is disposed inside the body and registers in close proximity to the LED 11, such that the light output pulses there from can be detected and read by an appropriate electronic circuit of the interrogation device 12. The interrogation device 12 comprises an elongate handle 14 which allows the user to reach detectors mounted on the ceiling without the need to use a ladder. The electronic circuit for reading and displaying the address code may be provided at the bottom of the handle 14. The interrogation device 12 may also serve as a tool for removing the head of the detector 10 from its base.

The interrogation device 12 may also be arranged to optically transmit the data back to the detector 10, with the functions of the LED 11 and photo detector 13 being reversed. The LED 11 is preferably arranged to read control pulses transmitted by the interrogation device 12 during the period when the LED 11 is off. These control pulses may be arranged to configure an operating parameter of the detector or to vary the kind of data output by the LED 11.

Once the interrogation device 12 has established communication with the detector 10, control data may be exchanged at a rate which may differ from the status pulse rate. Indeed, the status pulses may be disabled during the exchange of control data.

A smoke/heat detector in accordance with the present invention is thus able to output data, such as its address code or serial number, without the need for an additional LED or complicated electronics.

Claims

CLAIMS1. An electronic apparatus comprising a light emitting device arranged to illuminate to provide an indication of the status of the apparatus, wherein said light emitting device is also pulsed to transmit optically readable data concerning a parameter of the device.
2. An electronic apparatus as claimed in claim 1, wherein said light emitting device is pulsed to transmit an address code or serial number of the apparatus.
3. An electronic apparatus as claimed in claim I or claim 2, wherein the data is transmitted when the light emitting device appears illuminated, the data pulses being of a sufficiently short duration that they are not discernible to the human eye.
4. An electronic apparatus as claimed in any preceding claim, wherein the light emitting device is pulsed to indicate the status of the apparatus.
5. An electronic apparatus as claimed in claim 4, wherein the period or frequency of the pulse is varied to provide a visible indication of different statuses of the apparatus.
6. An electronic apparatus as claimed in claims 4 or 5, wherein the data is transmitted when the light emitting device is pulsed on to indicate the status of the apparatus.
7. An electronic apparatus as claimed in any of claims 4 to 6, wherein the data pulses comprise a sync pulse, which is provided by the leading or trailing edge of a status indicator pulse.
8. An electronic apparatus as claimed in any preceding claim, wherein said data pulses have a peak voltage level which is different than the voltage at which the light emitting is operated to indicate the status.
9. An electronic apparatus as claimed in any preceding claim, wherein the light emitting device comprises an LED.
10.An electronic apparatus as claimed in claim 9, wherein the apparatus is arranged to monitor the output of the LED to detect a control signal transmitted from a remote device to the apparatus.
11.An electronic apparatus as claimed in claim 10, wherein the apparatus is arranged to monitor for the control signal when the LED is off.
12. An electronic apparatus as claimed in any preceding claim, wherein the data is preferably transmitted as a self-clocking or other code arranged to minimise the number of successive similar data pulses.
13. An electronic apparatus as claimed in claim 12, wherein said code is a so-called Manchester Code.
14. An electronic apparatus as claimed in any preceding claim, wherein the data level representing binary 0 may be above 0 volts, so that the light emitting device is never fully off.
15.An electronic apparatus as claimed in any preceding claim, wherein the apparatus comprises a fire alarm transducer, such as heat and/or smoke detector.
16. An electronic apparatus substantially as herein described with reference to the accompanying drawings.
17. A kit of parts comprising an electronic apparatus as claimed in any preceding claim in combination with a remote device for receiving the transmitted data pulses.
18. A kit of parts as claimed in claim 17, in which said remote device is arranged to transmit a control signal to the electronic apparatus via the light emitting device.