The present invention relates to a projection clock.
BACKGROUND OF THE INVENTION
Projection clocks are known to include an LCD projector
for projecting the time upon a surface such as a bedroom ceiling. It can be difficult
to set such clocks upon the bedside table for example in such manner that its front
panel time display and controls are easily viewed and accessed on the one hand,
and that the projected time displayed on the ceiling is optimised in size, low distortion
and orientation for viewing on the other hand.
OBJECTS OF THE INVENTION
It is an object of the present invention to overcome or
substantially ameliorate the above disadvantage.
SUMMARY OF THE INVENTION
According to the invention, there is provided a projection
clock comprising a base unit that includes power supply means, a clock circuit powered
by way of the power supply means, and a wireless transmitter for wirelessly transmitting
time information provided by the clock circuit. Also comprised is a projection unit
separate from the base unit, which includes a projection circuit and a wireless
receiver for wirelessly receiving said time information, based on which the projection
circuit operatively projects the time.
Preferably, the base unit has a portion for locating the
projection unit sufficiently close to the base unit for receiving said time information
More preferably, the portion of the base unit comprises
More preferably, the base unit includes detecting means
for detecting locating of the projection unit by the base unit and then activating
In a preferred embodiment, the transmitter comprises radio
frequency transmitter and the receiver comprises radio frequency receiver.
In a preferred embodiment, the projection unit includes
a rechargeable power storage device for powering the projection circuit, and the
base unit includes a charging device powered by way of the power supply means for
charging the power storage device.
More preferably, the projection unit includes a low battery
detection circuit for detecting a low battery status of the power storage device
and providing a signal indicative of the low battery status.
Further more preferably, the signal comprises an icon associated
with the time projected by the projection circuit.
It is preferred that the charging device includes a first
contact at the base unit and a second contact at the projection unit connected to
the power storage device, the first and second contacts being arranged for connection
upon placing of the projection unit with the base unit.
It is preferred that the charging device comprises a first
part at the base unit connected to the power supply means and a second part at the
projection unit connected to the power storage device, the first and second parts
operatively interacting with each other inductively.
It is further preferred that the base unit has a portion
for locating the projection unit at such a position that it can receive said time
information from the base unit and be charged by the charging device thereof.
It is yet further preferred that the base unit includes
detecting means for detecting locating of the projection unit by the base unit and
then activating the transmitter, the detecting means comprising the first part of
the charging device.
Advantageously, the projection unit has no operating key
or button accessible on the outside.
It is preferred that the projection unit is generally spherical
having a lower portion including a plurality of small flat regions inclined at different
angles, on which the projection unit can rest to project time at different angles.
It is further preferred that the base is generally rectangular
including a generally part-spherical recess in its upper surface for locating the
BRIEF DESCRIPTION OF DRAWINGS
The invention will now be more particularly described,
by way of example only, with reference to the accompanying drawings, in which:
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
- Figure 1 is a front view of an embodiment of a projection clock in accordance
with the invention, said clock having a base unit and a projection unit resting
- Figure 2 is a rear view of the projection clock of Figure 1;
- Figure 3 is a front view similar to Figure 1, showing the projection unit lifted
from the base unit;
- Figure 4 is a schematic circuit diagram of various components of the projection
- Figure 5 is a schematic circuit diagram of various components of the base unit.
Referring to the drawings, there is shown a projection
clock 10 embodying the invention, which has a generally spherical projection unit
11 that can be seated upon a generally rectangular base unit 12. The base unit 12
has a central part-spherical recess 12A in its top surface that acts as a cradle
for locating the projection unit 11. However, the projection unit 11 can be removed
from the base unit 12 and set down on a horizontal surface such as a desktop, at
a location remote from the base unit 12.
The projection unit 11 projects a time image generally
upwards. Its spherical body has a series of three small flat regions 11A, 11B and
11C from the bottom, which extend, or are inclined, horizontally and at 30°
and 60° upwards respectively such that the projection unit 11 can rest on the
desktop to project a time image selectively at an angle of 90°, 60° or
30° from the desktop.
The projection unit 11 incorporates a MCU (microprocessor
control unit) 15 for general operations and control including clock functions, and
is powered by a built-in regulator 13 controlled by the MCU 15. The regulator 13
is located generally at the bottom of the spherical body for inductive energization
(without electrical contact) by the base unit 12 when the projection unit 11 is
resting thereon. The regulator 13 includes an induction coil 13A for receiving power
by induction, a diode circuit 13B for current rectification, a rechargeable battery
13C for power storage and a regulating circuit 13D for the output.
The projection unit 11 includes a transparent LCD panel
17 extending across the top part of the spherical body, and a projection LED (with
driver circuit) 17A located behind the LCD panel 17, both being controlled by the
MCU 15. In operation, the LCD panel 17 receives a time signal from the MCU 15 and
then turn on the appropriate LCD segments (or matrix dots) for time indication,
with the projection LED 17A emitting a bright red light beam therethrough to project
a time image onto the ceiling or a wall. An adjustable lens covers the LCD panel
17 for focusing the light beam to produce a sharp image.
There is a low battery detection circuit 16 controlled
by the MCU 15 for detecting and indicating a low battery status of the battery 13C,
for example by flashing a flat-battery icon in the projected time image. An internal
power key 18 allows the power to be switched off (and on), which can only be accessed
by opening the spherical body.
Apart from the power key 18 which is hidden anyway, the
projection unit 11 has no operating keys or buttons accessible on the outside such
that its operation cannot be interfered or altered by a user when used in isolation.
The situation is different when the projection unit 11 sits on the base unit 12,
where it is able to accept data and/or control by means of an internal RF receiver
(with an antenna) 14 connected to the MCU 15.
The base unit 12 incorporates an MCU 21 for general operations
and control including clock functions, and an LCD display 25 illuminated by an LED
backlight circuit 19 for displaying time, etc. The panel of the LCD display 25 also
provides five contactless (touch-screen) keys 27 to enable control and data input
from a user. The MCU 21 controls a music IC 22 to generate melody and polyphonic
alarm sounds via a built-in speaker 23 for the clock. A built-in temperature sensor
24 gathers and provides temperature information to the MCU 21 for displaying indoor
temperature on the LCD display 25, whereas outdoor temperature may be measured using
a remote (wireless) sensor.
The base unit 12 further includes an RF (radio frequency)
clock 26 which receives and synchronizes with the radio time/calendar signals broadcast
by the local authority of the country or time zone concerned, such as a remote atomic
time transmitter, for indicating time/date on the LCD display 25 under the control
of the MCU 21. European version of the subject clock is tuned to receive DCS/MSF
signals, whereas US version receives wwvb signals.
There is a DC jack 30 for receiving DC power from an external
power source to supply power, via three regulating circuits 31 of different voltages
as required, to the various parts and components of the system including the projection
unit 11 via induction.
To supply electrical power to the projection unit 11, the
base unit 12 employs a DC-AC converter 20 which includes an induction coil 20A located
adjacent the recess 12A for electro-magnetic interaction with the induction coil
13A of the projection unit 11. The converter 20 operates based on oscillation provided
by an oscillation circuit 29 which is also controlled by the MCU 21. Immediately
upon the projection unit 11 being placed (in the cradle 12A) on the base unit 12,
power is delivered inductively across the coils 20A and 13A for charging the battery
13C in the regulator 13.
While being placed together, apart from charging the projection
unit 11, the base unit 12 will also automatically establish wireless communication
with the projection unit 11 primarily for synchronization of time. This is achieved
by an internal RF transmitter (with an antenna) 28 of the base unit 12, which is
coupled with the RF receiver 14 of the projection unit 11 for transmitting wireless
RF control and/or data signals thereto.
A sudden rise in the load current drawn by the converter
20 is an indication that the projection unit 11 is placed on the base unit 12, as
detected by the MCU 21 which will then activate the RF transmitter 28 and/or send
time sync information thereto for transmission. Based on the official time maintained
by the radio controlled clock 26, the base unit 12 adjusts the time of the projection
unit 11 each time the projection unit 11 is placed on it. The keys 27 on the display
25 of the base unit 12 may be used to switch the projection unit 11 on and off,
while the latter is at home.
Placing of the projection unit 11 on the base unit 12 is
detected via the converter 20. Alternatively, a microswitch fitted adjacent the
cradle 12A may be used to detect the projection unit 11 upon being pressed thereby,
or a reed switch under the cradle 12A for closing by a magnet fixed inside the projection
unit 11. The cradle 12A locates or positions the projection unit 11 sufficiently
close to the base unit 12 such that the power rating of the transmitter 28 and receiver
14 can be minimal.
In operation, the projection unit 11 will turn on for continuous
time image projection when it is removed from the base unit 12. The speaker 23 will
beep once when the projection unit 11 is placed correctly on the base unit 12 i.e.
in the cradle 12A. The projection unit 11 can be set upon the top of a cupboard
or at some location remote from the base unit 12 so that it can be arranged to project
an easily-read image on the ceiling independently of the bed position or orientation
of the base unit 12.
In a slightly different embodiment, electrical power from
the base unit 12 to the projection unit 11 (for charging the latter's battery 13C)
may be supplied via physical contact connection, instead of by way of electro-magnetic
induction as described above. In this case, the bottom of the projection unit 11
and the cradle 12A of the base unit 12 are provided with respective pairs of aligned
metal contacts 11E and 12E (see Figure 3) for electrical connection upon the projection
unit 11 being placed on the base unit 12 (i.e. resting in the cradle 12A). The base
unit contacts 12E may extend as circles co-axially about the cradle 12A such that
the other pair of contacts 11E may make contact with them irrespective of the orientation
of the projection unit 11, or certain positioning means may be utilized to fix the
position of the projection unit 11 in the cradle 12A, such as a pair of complementary
bump and dimple.
To implement contact charging, the aforesaid converter
20 and oscillation circuit 29 in the base unit 12 should be replaced by a charging
circuit of a typical battery charger, whose output is connected to the base unit
contacts 12E. With regard to the projection unit contact 11E, they may be connected
directly to the battery 13C.
The invention has been given by way of example only, and
various other modifications of and/or alterations to the described embodiment may
be made by persons skilled in the art without departing from the scope of the invention
as specified in the appended claims.
For example, the base unit may include a humidity sensor
and the projection unit may project the temperature and humidity readings alongside