GB2305264A - Programmable lamp controller which tracks sunrise and sunset times - Google Patents

Abstract

A lamp control unit 1 tracks daylight to control lamp switches without need for an ambient light sensor. A mode key 5 allows a user to successively move a display 4 through modes in a cyclic pattern. In each mode, the user changes mode parameter values in cyclic patterns by successively pressing a set key 6. A backup battery and controller low-power operation allow factory preprogramming and mains failure tolerance. A high-frequency clock circuit is used when mains is present, a low frequency circuit when backup power is being used. Lamp switching is by a relay-assisted triac circuit, preferably incorporating an optical isolator.

Description

"A Lamp Control Unit" The invention relates to a lamp control unit and particularly to such a unit which tracks sunrise and sunset times without need of an ambient light sensor.

Lamp control units which sense light have been in use for a long time. Because light is sensed, very little user input is required and they have generally performed satisfactorily with little or no user input to their operation. However, as described in US 5,160,853 (Honeywell) and US 4,922,407 (Pittway) control units have been developed which do not need ambient light sensors.

Instead, they use a daylight tracking program to follow daylight. They thus provide the advantages of not needing a light sensor and providing programmable additional options. The former advantage is particularly important if light sensors are awkward to mount because of the location.

However, the aspect, namely programmed operation, which provides these advantages, also causes the major disadvantage of the unit not being 'Xuser-friendly". This we believe contributes to such units not achieving widespread usage, and where used, the full range of options not being availed of.

The invention is therefore directed towards providing a lamp control unit of this type which may be easily operated by a user.

Another object is that the unit be tolerant of mains failures.

According to the invention there is provided a lamp control unit comprising: a power supply; a programmable controller; a display device operatively connected to the controller; a user interface comprising mode and set keys; a lamp switch connected to the controller; wherein the controller is programmed to: track sunrise and sunset times for a fixed latitude and to control the switch responsive to tracked sunrise and sunset times; provide the user with a plurality of modes, at each of which the controller directs display of current parameter values for that mode and allows the user to set fresh values; successively change the current mode in a cyclic pattern with successive depressions of the mode key for simple user mode selection; and successively change a displayed parameter value for a mode in a cyclic pattern with successive depressions of the set key for simple user setting of values.

In one embodiment, time units including years and months are each associated with a particular mode, and numerical values displayed represent the time unit of the current mode.

Preferably, there are year, month, day, and hour/minute time units.

In one embodiment, the controller recognises a null value for a parameter as a setting to ignore that parameter.

In a further embodiment, the power supply comprises a charge storage device and the controller is programmed for low power operation without activation of the display device and with storage of parameter values.

Preferably, the power supply comprises both a mains supply circuit and a charge storage device, the charge storage device being used as a backup supply.

In another embodiment, the controller comprises a highfrequency clock circuit and a low-frequency clock circuit and means for utilising the low-frequency clock circuit when drawing power from the backup supply.

In the latter embodiment, preferably the high-frequency clock circuit operates at a frequency in excess of 2 MHz, and the low-frequency clock circuit at a frequency of less than 100 kHz.

In a further embodiment, the unit further comprises a radio receiver tuned to receive real-time signals to provide a real time reference.

Preferably, the user interface further comprises an override key and the controller is programmed to temporarily change the switch status to an override status in response to user depression of the override key.

In another embodiment, the controller is programmed to operate the switch in response to auxiliary times in addition to the sunrise and sunset times, each such time having an associated mode and parameter value.

Ideally, the unit comprises a plurality of lamp switches and a parameter value indicates operation of all or a subset of the switches at each switching time.

In a further embodiment, a lamp switch comprises a relayassisted-triac circuit.

In another embodiment, the relay-assisted-triac circuit comprises an optical isolator electrically isolating the load from the unit.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a front view of the control unit of the invention; Figs. 2 and 3 are together a circuit diagram of the controller of the unit; Fig. 4 is a detailed front view of an LCD of the control unit; and Fig. 5 is a circuit diagram of part of an alternative construction of controller.

Referring to the drawings, and initially to Fig. 1, there is shown a lamp timer control unit 1. The control unit 1 comprises a casing 2 connected to DIN rail mounting arrangements for mounting on either a symmetric 35 mm DIN rail or an asymmetric 32 mm DIN rail. It may therefore be installed in a wide variety of switchgear cabinets. The control unit 2 comprises an interface 3 having an LCD display 4 and various input switches or buttons. These include a MODE button 5, a SET button 6 and an O'RIDE (override) button 7.

The control unit 1 comprises a controller 10 which is illustrated in Figs. 2 and 3. The controller 10 comprises a 12 V power supply 12 which supplies power for the circuit derived from mains power at terminals 13. It also comprises a varistor 14, a step-down transformer 15, a rectifier bridge 16, and a 12V transient suppressor 17.

The controller 10 also comprises a 4.8 V, 60 mAh NiCd backup battery 20 which is fed by the power supply 12 via a 6K2 resistor 21. A diode 22 is provided to minimise discharge of the battery pack when the mains power supply is removed from the terminals 13. A 6.2 V zener diode 23 prevents the voltage between the battery terminals rising excessively.

The controller 10 also comprises a voltage regulator 30 which provides a 4.2 V supply to a microcontroller 40 (shown in Fig. 3). It also supplies via an "error" pin, a signal to reset the microcontroller 40 in the event of the power supply voltage to the regulator dropping too low.

A selection switch 35 directs power to the regulator 30 from either the 12 V DC supply or the 4.8V back-up supply, whichever has the higher voltage level. This is achieved by receiving an input from each power supply and providing as an output the greater of the two inputs. It provides a smooth transition to avoid noise by providing a switching overlap.

Referring to Fig. 3, pins PBO, PB1, PB2 and PB5 on the microcontroller 40 are set to input with internal pull-up.

The keys MODE, SET and O'RIDE on the interface 3 are connected to pull the pins PB0, PB1 and PB2 low when pressed.

The controller 10 comprises two output lamp switches 50.

Each of the switches 50 is of the relay-assisted triac (RAT) type, the principle of operation of which is described in our British Patent Specification No. GB 2,166,003B. Each switch 50 comprises a relay 52 controlled by a transistor 53 connected to the microcontroller 40, and a triac 54 controlled by a transistor 55 connected to the microcontroller 40. The RAT technique provides excellent reliability. The triac 54 of each switch is each controlled via an opto-coupled triac driver 56 which ensures electrical isolation of the load from the unit.

The controller 10 comprises two clock circuits, namely a low-frequency 32.768 kHz "tuning fork" type quartz crystal clock circuit 60 and a 2.4576 MHz quartz crystal clock circuit 70. Each clock circuit comprises a crystal operating in conjunction with an on-chip oscillator on the microcontroller 40. The clock circuits 60 and 70 provide a stable and accurate timebase over prolonged periods of time. Heretofore, such timebases have been achieved by use of very expensive and complex clock circuits such as circuits within an "oven" to maintain the crystal at a constant temperature, or alternatively a temperature controller oscillator. Use of such complex and expensive circuits are avoided in the invention by sue of the clock circuits 60 and 70 and the switch 35.The switch 35 operates to inform the microcontroller 40 when it switches power supplies by setting a flag to a high or low value as appropriate. The microcontroller 40 then operates according to the relevant clock circuit 60 or 70. The high-frequency circuit 60 operates under normal circumstances, when mains power is available and when the mains supply is available at the terminals 13. In general, the higher the frequency a microcontroller operates at, the more supply current it requires. This is not a problem when mains is available. Further, when a high-frequency clock circuit is being used, there is very little change with temperature and indeed an error of only 10 ppm is achieved over the temperature range of -20 C to +700C. This results in time accuracy of better than 1 second per day.An important aspect of the control unit is the fact that the low-frequency clock circuit 60 is used if the mains supply is not available. The frequency v.temperature response of the 32.768 kHz circuit 60 is parabolic in nature and there will be an error of approximately 77 ppm (6.5 seconds per day) if this is used as the time base. However, the low-frequency circuit 70 is used only when the mains supply is not available and the microcontroller 40 is in a low-power mode. In this mode, at 0.5 s intervals, an interrupt is generated by an internal controller controlled by the clock circuit 60 to "wake up" the microcontroller 40, which updates its internal clock calendar and switch settings and then goes back to "stop" mode.Because the microcontroller 40 spends the most of its time in stop mode, and in this mode the power supply current is much lower than in the normal "awake" mode, the average power supply current is dramatically reduced. Any inaccuracy which results in use of the low-frequency clock circuit 60 will generally be very low as the number and duration of mains supply failures is generally very small. The unit may also comprises a radio receiver tuned to receive LW time signals from an atomic clock. This is a simple way of monitoring real time in a very accurate manner.

Also, to prevent inaccuracies arising, the microcontroller 40 is programmed to repeatedly check registers to determine if they have been corrupted by noise.

Another important aspect of the control unit 1 is that the battery 20 is capable of maintaining the controller 10 in a functioning programmed state for several weeks. This is important commercially as it allows the end user to simply "fit and forget" and not have the task of programming themselves, this being done at manufacture. However, as explained below, programming is very simple.

The microcontroller 40 operates under program control to set variables using only the three user input keys, namely the MODE, SET and O'RIDE buttons 5, 6 and 7 respectively.

This provides a very simple user interface as the user must simply select the mode by depressing the button 5 until the correct mode indicator appears on the display 4 and then depress the key 6 until the correct parameter value appears for that mode. For most modes, the unit both displays the parameter values (settings) and allows programming upon depression of the SET key 6. The override key 7 may be used to provide a temporary override on the programmed inputs. It will be appreciated that this provides for setting the parameters of the control unit 1 in an extremely simple manner.

The microcontroller 40 includes programs stored in nonvolatile on-board memory for tracking of daylight hours over the calendar period. The program is set according to the latitude. The rate of change of daylight from one day to the next is updated every two weeks. This allows excellent accuracy.

The following describes the manner in which the controller operates and interfaces with the user. The three programmable activation times are SOLAR TIME ON, NORMAL TIME OFF, NORMAL TIME ON and SOLAR TIME OFF. The first and fourth of these activation times are generated by the program according to the determined daylight hours at any particular time. NORMAL TIME OFF and NORMAL TIME ON are auxiliary activation times which generally fall within the SOLAR TIME ON and OFF times. This allows versatility in controlling of the two output switches.

As an example, at a particular place in the UK on 14/09/'96 sunset is 18:18 and sunrise is at 05:34. If one wishes to switch on one hour before sunset, switch off at 23:30, switch on again at 03:00 and switch off one hour after sunrise then SOLAR TIME ON should be set to 17:18, NORMAL TIME OFF to 23:30, NORMAL TIME ON to 03:00 and SOLAR TIME OFF to 06:34. The unit would (on 14/09/'96) therefore switch on at 17:18, off at 23:30, on at 03:00 and off at 06.34.

Now let us consider the sunset and sunrise times in the same place on 02/05/'97. Sunset is now 19:26 and sunrise is now 04:31. SOLAR TIME ON has now changed to 18:26, NORMAL TIME OFF remains at 23:30, NORMAL TIME ON remains at 03.00 and SOLAR TIME OFF has now changed to 05:31. So the control has changed its SOLAR TIME ON and SOLAR TIME OFF settings to ensure that the lighting is switched on 1 hour before sunset and switched off 1 hour after sunrise.

As a second example, in the same UK location let us say that on 14/09/'96 one wishes to turn on lighting at 05:00, off at sunrise, on at sunset and off at 19:00 then SOLAR TIME ON should be set to 18:18, NORMAL TIME OFF to 19:00, NORMAL TIME ON to 05:00 and SOLAR TIME OFF to 05:34.

On the 14/09/'96 therefore the unit would switch. on at 05:00, off at 05:34, on at 18:18 and off at 19:00.

On the 02/05/'97 sunrise is at 04:31 and sunset at 19:26.

SOLAR TIME ON has now changed to 19:26, NORMAL TIME OFF remains at 19:00, NORMAL TIME ON remains at 05:00 and SOLAR TIME OFF has changed to 04:31.

The control (if on) would switch off at 04:31 and would not switch on again at 05.00.

If the control were on then it would switch off at 19:00 and would not switch on again at 19:26.

This illustrates two important features of the control.

1. Before midday, if the NORMAL TIME ON setting is later or equal to the SOLAR TIME OFF setting then the NORMAL TIME ON setting has no effect on switching.

2. After midday, if the SOLAR TIME ON setting is later than or equal to the NORMAL TIME OFF setting the SOLAR TIME ON has no effect on switching.

The control unit is preprogrammed at manufactured for a particular latitude (in 1 degree steps) and should only be used at this latitude to ensure the control accurately compensates for the rate of change of sunrise and sunset times throughout the year.

Regarding the three input keys, "MODE" allows the unit to be cycled through the display/programming modes available on the control, "SET" allows the setting of a particular variable value within a mode by cyclic incrementing of the value through its allowed range, and "O'RIDE" provides a means of testing the load connected to the output and can be used to turn on the controlled lighting to provide light for programming the control. The "O'RIDE" mode is temporary and is itself over-ridden when the time coincides with the next switch on or switch off.

The modes of operation of the control (in sequence order) are as follows: 1. NORMAL MODE 2. SET/DISPLAY SOLAR TIME ON (HOURS, MINUTES) 3. SET/DISPLAY NORMAL TIME OFF (HOURS, MINUTES) 4. SET/DISPLAY NORMAL TIME ON (HOURS, MINUTES) 5. SET/DISPLAY SOLAR TIME OFF (HOURS, MINUTES) 6. SET/DISPLAY YEAR (10's, l's) 7. SET/DISPLAY MONTH 8. SET/DISPLAY DAY 9. SET/DISPLAY TIME (HOURS, MINUTES) 10. SET/DISPLAY GMT/BST AUTOMATIC ADJUST 11. DISPLAY LATITUDE SETTING OF CONTROL.

Referring to Fig. 4, the LCD display 4 is illustrated with all possible legends shown. For any single mode, only a subset will be illuminated. The following describes the eleven modes.

1. In NORMAL MODE the LCD displays the current time (HOURS:MINUTES in 24-hour format) and the status of the control. It is therefore a default mode in which useful information is displayed. The second increments are indicated by the colon flashing once per second. The legends that display are "TIME" and either the "ON" or "OFF" output status legends. The "O-RIDE" legend indicates that the control is in O'RIDE mode, a special case of NORMAL MODE. If the control is in NORMAL MODE with its output off then pressing "O'RIDE" once switches on the output; pressing it again switches off the output c The status of the output is indicated by the LCD legend.

2. SET/DISPLAY SOLAR TIME ON (HOURS, MINUTES) mode is entered by pressing the "MODE" key once whilst in NORMAL MODE. Entering this mode results in the display of the legends "SOLAR", "SET" , "TIME" and "ON". "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The time of switching (HOURS:MINUTES in 24-hour format) is displayed with the hours initially flashing. Each press of the "SET" key increments the hour value until "23" is reached at which point the next key press results in "- -", the next "00", the next "01" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the hours value as previously described. Pressing the "MODE" key changes the display such the minutes now flash.Again, setting of the minutes is accomplished using the set key in a similar fashion to setting the hours. Of course, the maximum value is now "59".

Pressing the "MODE" key again enters the SET/DISPLAY NORMAL TIME OFF (HOURS, MINUTES) mode.

3. SET/DISPLAY NORMAL TIME OFF (HOURS, MINUTES) mode is entered as described at the end of Section 2.

Entering this mode results in the display of the legends "NORMAL", "SET", "TIME" and "OFF". "O'RIDE", if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The time of switching (HOURS:MINUTES in 24-hour format) is displayed with the hours initially flashing. Each press of the "SET" key increments the hour value until "23" is reached at which point the next key press results in "- -", the next "00", the next "01" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the hours value as previously described. Pressing the "MODE" key changes the display such that the minutes now flash.

Again, setting of the minutes is accomplished using the set key in a similar fashion to setting the hours. Of course, the maximum value is now "59".

Pressing the "MODE" key again enters the SET/DISPLAY NORMAL TIME ON (HOURS, MINUTES) mode.

4. SET/DISPLAY NORMAL TIME ON (HOURS,MINUTES) mode is entered as described at the end of section 3.

Entering this mode results in the display of the legends "NORMAL", "SET", "TIME" AND ON. "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The time of switching (HOURS:MINUTES in 24-hour format) is displayed with the hours initially flashing. Each press of the "SET" key increments the hour value until "23" is reached at which point the next key press results in "- -", the next "00", the next "01" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the hours value as previously described. Pressing the "MODE" key changes the display such that the minutes now flash.

Again, setting of the minutes is accomplished using the set key in a similar fashion to setting the hours. Of course the maximum value is now "59".

Pressing the "MODE" key again enters the SET/DISPLAY SOLAR TIME OFF (HOURS, MINUTES) mode.

5. SET/DISPLAY SOLAR TIME OFF (HOURS:MINUTES) mode is entered as described at the end of section 4.

Entering this mode results in the display of the legends "SOLAR", "SET", "TIME" AND "OFF". "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The time of switching (HOURS:MINUTES in 24-hour format) is displayed with the hours initially flashing. Each press of the "SET" key increments the hour value until "23" is reached at which point the next key press results in "- -", the next "00", the next "01" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the hours value as previously described. Pressing the "MODE" key changes the display such the minutes now flash.

Again, setting of the minutes is accomplished using the set key in a similar fashion to setting the hours. Of course, the maximum value is now "59".

Pressing the "MODE" key again enters the SET/DISPLAY YEAR (10's, l's) mode.

6. SET/DISPLAY YEAR (10's, l's) mode is entered as described at the end of section 5. Entering this mode results in the display of the legends "SET" and "YEAR". "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The YEAR is displayed as a 2 digit value with the 10's of years initially flashing. Each press of the "SET" key increments the 10's of years value until "9" is reached at which point the next key press results in "0", the next "1" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the 10's of years value as previously described. Pressing the "MODE" key changes the display such that the units of years now flash.

Again, setting of the units of years is accomplished using the set key in a similar fashion to setting the 10's of years. Pressing the "MODE" key again.enters the SET/DISPLAY MONTH mode.

7. SET/DISPLAY MONTH mode is entered as described at the end of section 6. Entering this mode results in the display of the legends "SET" and "MONTH". "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The MONTH is displayed as a flashing 2 digit value. Each press of the "SET" key increments the value until "12 is reached at which point the next key press results in "01", the next "02" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the month's value as previously described. Pressing the "MODE" key again enters the SET/DISPLAY DAY mode.

8. SET/DISPLAY DAY mode is entered as described at the end of section 7. Entering this results in the display of the legends "SET" and "DAY". "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The DAY of month is displayed as a flashing 2 digit value. Each press of the "SET" key increments the value until the maximum number of days for the month is reached at which point the next key press results in "01", the next "02" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the month's value as previously described. Note that if the year is a leap year the maximum value for February will be 29 days. Pressing the "MODE" key again enters the SET/DISPLAY TIME (HOURS, MINUTES) mode.

9. SET/DISPLAY TIME (HOURS, MINUTES) mode is entered as described at the end of section 8. Entering this mode results in the display of the legends "SET" and "TIME". "O'RIDE" if activated before entering this mode remains in effect whilst in this mode to allow programming of the switching setting with the lamps on. The time of switching (HOURS, MINUTES) is displayed with the hours initially flashing. Each press of the "SET" key increments the hour value until "23" is reached at which point the next key press results in "00", the next "01" etc.. Holding the "SET" key pressed results in continuous cyclic incrementing of the hours value as previously described. Pressing the "MODE" key changes the display such that the minutes now flash. Again, setting of the minutes is accomplished using the set key in a similar fashion to setting the hours.Of course the maximum value is now "59". Pressing the "MODE" key again enters the SET/DISPLAY GMT/BST AUTOMATIC ADJUST mode.

10. SET/DISPLAY GMT/BST AUTOMATIC ADJUST mode is entered as described at the end of section 9. Entering this mode results in the display of a special symbol and a "1" or a "0". If a "0" is set then the BST/GMT adjust is deactivated and if a "1" is set then BST/GMT adjust is activated. Pressing the SET key toggles the display between 2 and "0". Note that when activated the time clock goes back one hour at 02:00 on 30th October and forward by one hour at 02:00 on 30th March. The SOLAR TIME ON and SOLAR TIME OFF settings adjust in the same manner as the time clock whereas the NORMAL TIME OFF and NORMAL TIME ON settings do not adjust. Pressing the "MODE" key again enters the DISPLAY LATITUDE SETTING OF CONTROL mode.

11. DISPLAY LATITUDE SETTING OF CONTROL mode is entered as described at the end of section 10. Entering this mode results in the display of the preprogrammed latitude (in degrees) that the control is set to operate at with either the legend "NORTH" or "SOUTH" as appropriate. The operating latitude is preprogrammed in the factory and cannot be altered by the operator. "O'RIDE" if activated before entering this mode remains in effect whilst in this mode.

Pressing the "MODE" key again returns the control to NORMAL MODE.

If the unit is in NORMAL MODE and the mains supply to the unit is turned off, the unit enters low power operation.

In this mode the unit operates from the internal NiCd battery pack 20 which is continuously trickle charged whilst the mains is supplied to the unit. This backup battery pack enables the unit to maintain and update it's onboard clock, calendar, SOLAR TIME ON, NORMAL TIME OFF, NORMAL TIME ON and SOLAR TIME OFF settings in the event of power failure. To maximise the length of time the unit can keep "running" off the battery the unit self adjusts to ensure minimum internal power consumption. This is achieved by switching off the LCD and allowing the relay to deenergise.

If the unit is in LOW POWER mode and the "SET" key is pressed then the control enters "NORMAL" mode. Releasing the "SET" key returns the control to LOW POWER mode. If the "MODE" key is pressed then the control enters SET/DISPLAY SOLAR TIME ON (HOURS:MINUTES). This allows programming of the control on battery power i.e. with no mains supply. After cycling through the programming modes described the unit reverts to low power operation if there is still no mains supply. If the mains supply to the control is withdrawn, the internal relay deenergises and because it is normally closed the output changes to the "load on" State.

Pressing the "MODE" and "SET" keys together results in the unit entering a known preprogrammed state where the date is set to 01/01/'95, the time to 00:00 and the switch on and switch off times to --:-- (null switch settings which the timer control ignores). In general, null settings are used to indicate to the microcontroller 40 those parameters which should be ignored.

Note that if the control is powered up for the first time and the Internal NiCd battery is not charged the display will flash to indicate that the time should be programmed.

It will be appreciated that the invention provides a control unit of simple construction for tracking sunrise/sunset times throughout the year for a given latitude. Because there are only three input keys, only two of which are required for programming, user programming is very simple. The mode key 5 allows easy selection of a general mode, and then easy selection of a subset mode such as hour setting or time setting. The backup battery 20 ensures continuity of operation and prevents the inconvenience of the user re-programming after power failures. This backup period is maximised because of the twin clock circuit arrangement, the LOW POWER MODE operation, and the LW radio receiver (if present).

The invention is not limited to the embodiments hereinbefore described. For example, it is envisaged that the frequencies of operation of the clock circuits may be different, and this depends for example on those components which are commercially available. It is also envisaged that the control unit may comprise a temperature sensor which provides information to the microcontroller 40 to allow it to compensate for the effect of temperature on the low-frequency clock circuit 60. It is also envisaged that the control unit includes a radio receiver for capture of time signal information, for example from long wave signals such as the 60 kHz MSF transmitter in England.This design, would, for example, allow the backup battery to be much smaller, and if the time switch settings were to be stored in non-volatile flash or EEPROM memories, one could eliminate the battery altogether in some applications. The time period for operation of the control unit described is 24 hours, however, this could be one week, one month or any other time duration, depending on the intended use.

Programming may be further simplified by removing the SOLAR TIME ON/OFF setting modes, in which case these times are exactly the sunset and sunrise times where present.

Further, auxiliary times between these two times may be fixed, say midnight and 05:30. In this example, the NORMAL TIME OFF time 05:30 would be inapplicable if later than SOLAR TIME OFF. The NORMAL TIME ON/OFF times may be used to control only one of the switches. For example, only one switch may open at NORMAL TIME OFF and close again at NORMAL TIME ON. This provides added versatility.

It is of course possible that there be only one switch, or more than two or switches of different types. For example, referring to Fig. 5, an alternative switching arrangement is shown, in which parts similar to those described with reference to the previous drawings are indicated by the same reference numerals. In this embodiment, there is a relay-assisted-triac type switch 50 and also a simple relay switch 80 connected to one of the transistors 53. The second transistor 53 is redundant.

The switch 80 is suitable for low frequency and/or low load applications and simplifies construction of the unit.

It is also envisaged that the input keys may be on a handheld "remote control" device instead of directly on the unit casing. Further, the unit may provide a single auxiliary time, which may be referred to as NORMAL TIME OFF. At this time, one of the switches may be opened, the remaining one opening at a time determined according to sunrise (SOLAR TIME OFF). Further, there may be no auxiliary times provided for.

The invention is not limited to the embodiments hereinbefore described, but may be varied in construction and detail within the scope of the claims.

Claims (15)

CLAINS

1. A lamp control unit comprising: a power supply; a programmable controller; a display device operatively connected to the controller; a user interface comprising mode and set keys; a lamp switch connected to the controller; wherein the controller is programmed to: track sunrise and sunset times for a fixed latitude and to control the switch responsive to tracked sunrise and sunset times; provide the user with a plurality of modes, at each of which the controller directs display of current parameter values for that mode and allows the user to set fresh values; successively change the current mode in a cyclic pattern with successive depressions of the mode key for simple user mode selection; and successively change a displayed parameter value for a mode in a cyclic pattern with successive depressions of the set key for simple user setting of values.

2. A lamp control unit as claimed in claim 1, wherein time units including years and months are each associated with a particular mode, and numerical values displayed represent the time unit of the current mode.

3. A lamp control unit as claimed in claim 2, wherein there are year, month, day, and hour/minute time units.

4. A lamp control unit as claimed in any preceding claim, wherein the controller recognises a null value for a parameter as a setting to ignore that parameter.

5. A lamp control unit as claimed in any preceding claim, wherein the power supply comprises a charge storage device and the controller is programmed for low power operation without activation of the display device and with storage of parameter values.

6. A lamp control unit as claimed in claim 5, wherein the power supply comprises both a mains supply circuit and a charge storage device, the charge storage device being used as a backup supply.

7. A lamp control unit as claimed in claim 6, wherein the controller comprises a high-frequency clock circuit and a low-frequency clock circuit and means for utilising the low-frequency clock circuit when drawing power from the backup supply.

8. A lamp control unit as claimed in claim 7, wherein the high-frequency clock circuit operates at a frequency in excess of 2 MHz, and the low-frequency clock circuit at a frequency of less than 100 kHz.

9. A lamp control unit as claimed in any preceding claim, wherein the unit further comprises a radio receiver tuned to receive real-time signals to provide a real time reference.

10. A lamp control unit as claimed in any preceding claim, wherein the user interface further comprises an override key and the controller is programmed to temporarily change the switch status to an override status in response to user depression of the override key.

11. A lamp control unit as claimed in any preceding claim, wherein the controller is programmed to operate the switch in response to auxiliary times in addition to the sunrise and sunset times, each such time having an associated mode and parameter value.

12. A lamp control unit as claimed in any preceding claim, wherein the unit comprises a plurality of lamp switches and a parameter value indicates operation of all or a subset of the switches at each switching time.

13. A lamp control unit as claimed in any preceding claim, wherein a lamp switch comprises a relay assisted-triac circuit.

14. A lamp control unit as claimed in claim 13, wherein the relay-assisted-triac circuit comprises an optical isolator electrically isolating the load from the unit.

15. A control unit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.