GB2355549A - A programmable alarm clock - Google Patents

Abstract

An electrically driven alarm clock is described which can be programmed to annunciate an audible message at selectable times during the 24 daily cycle e.g. to "call to prayer". The clock can be realised in 24 or 12 hour versions and the time indicated can be in analogue or digital forms and equipped with energy saving circuitry to make battery operation viable. The alarm times are set by removing pins 8 from one or more series of apertures 6,7 to allow light from e.g. an infrared source to shine on a detector 9 or 10. Preferably the ring of holes 6 is used to denote am times and the ring of holes 7 for pm times.

Description

2355549 Page The invention - the "Call-to-Prayer" clock Clocks can be

fitted with means for setting an alarm at preset times to alert the user to take appropriate action. Most alarm clocks are set once per day to wake the user. Others can set several on and off times during 24 hours, to activate different events during the day. Such clocks are known as "timers". Other timers are more eleborate and offer more complex operations, such as changing the alarm sequence on a daily or weekly basis etc.

According to the present invention, a domestic clock is set to alarm several times a day and when activated calls the faithful to prayer with a spoken message.. The message is recorded, generally in Arabic, in electronic analogue or digital non-volatile memory and may be stored indefinitely. At the chosen time it is played back through a loudspeaker, and may be repeated if required. Otherr languages may be used.

The clock may be realised in several alternative forms: as an analogue or digital clock in a 12 hour or 24 hour mode. The clock movement may be mechanical or more usually electrical, but the storage and read-out of the message will be electrical or electronic.

A specific embodiment of the invention will now be described by way of example which describes a 12 hour analogue clock using a standard Quartz crystal movement to move the hands and an opto-electronic mechanism to determine the times at which the electronically stored message is triggered.

The description is best understood by refering to the the diagram.

The clock mechanism typically has two concentric spindles (1) and (2), (Figure 1), which rotate at 1 revolution per hour (1) and I revolution per 12 hours (2). These normally carry the minute and hour hands respectively.

In the present instance ( Figure 1), spindle (1) is fitted with a minute hand ( not shown), but spindle (2) is fitted with a circular disc (3) on which an hour hand is painted, and shown rotated to approximately the 4 o'clock position. The disc is opaque to infra-red and fitted with a skirt projecting behind it (4), which has a diameter slightly smaller than the disc and prevents infra-red light, transmitted from a IR diode (5) in an outward radial direction from emerging beyond the skirt. The skirt is drilled with 48 (say) small holes to form a continuous ring around the skirt, near where it projects from the disc (6). A second identical ring of holes is drilled parallel to the first but further out from the disc (7). The holes are covered eg by small pegs (8) inserted in them which block the infrared. At chosen points the pegs are removed to allow the infra red beam to pass through. The IR source is mounted to shine its beam vertically upwards in the 12 o'clock position.

As the disc rotates, when one of the unblanked holes passes the 12 o'clock reference position, infra-red will pass through the hole and shine on one of two infra-red detectors (9) and (10) (transistors or diodes) and a signal is produced and amplified to a suitable level. This signal will last as long as it takes the hole to traverse the sensitive area of the Page 2__ detector, which depends, inter alia, on the size of the hole and the size of the detector The holes (blanked and unblanked) will pass the sensor at 15 minute intervals, or less if more holes are drilled at closer spacing. By judicious placing of the unblanked holes a trigger signal may be produced at any time desired during the day every time one such hole passes the 12 o'clock reference position, with the time recorded as AM if the hole is in the ring (6) and as PM if in ring (7). The trigger signal from ring (6) is logically ANDed with -a "I" during the 12 AM hours, signal from ring (7) being ANDed with a logical "0", and the vice-versa during the 12 PM hours. The output from the two AND gates are logically ORed to give the trigger signal. Thus with 48 holes in a ring the device may be "programmed" to give out its message at any time to the nearest 15 minutes. If closer spaced holes are used the resolution can be greater.

The "I" and "0" signals for the AND gates mentioned above are derived from a bistable circuit which changes state at 12 o'clock. This is triggered for example by a third sensor in line with the other two by infra-red picked up through a single hole drilled further out again from the ring (7), in the position which passes the vertical reference at 12 o'clock.

To save power the infra red transmission is made only once every minute and lasts only a short time (eg I mS). This is enough to ensure catching the trigger signal within the time window during which the detector is in the line of sight of the trigger, which lasts for at least two minutes. The duty cycle is therefore extremely low (about I in 60000 with the figures quoted) giving extremely low power. When triggered, the power to the message and audio circuits is turned on for only the duration of the message, (about 10 to 15 seconds), again saving power. With a message being played typically 5 times per day, this gives a duty cycle for audio power usage of less than I in 1100. This makes the additional power to run the timing and annunciating electronics, over and above the power to- run the conventional clock, extremely small, making it perfectly feasible to use battery power for the entire clock.

The trigger signal could last long enough to trigger the message again. It is prevented from doing so by inhibiting the power to the message circuits for several minutes after it has first triggered, thus inhibiting more than one announcement.

The message, which lasts up to 15 seconds, is held in Analogue EEPROM, and read out directly or through an amplifier via a loudspeaker. Standard circuits exist for this.

An alternative digital clock version can be envisaged in which the digital code driving the time display is logically compared with coded times at which an alarm is required, and the message triggered when a match is found. The codes for the required alarm times would be held in an Erasible Programmable Read Only Memory (EPROM), which could be an Electrically Erasible Programmable type (EEPROM), allowing the times to be programmed into the clock at will, and retained indefinitely until reprogrammed.

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Claims (1)

1. Claim

   A clock is described which produces an alarm which provides a unique audible message in the form of a "Call to Prayer" in Arabic to members of the Moslem religion.

   The alarm can be programmed to occur at a number of preset times during the day.

   Clocks can be made analogue or digital, and work in 12 hour or 24 hour mode.

   Power saving circuitry is employed to make battery operation viable