AU675589B2 - Automatic on/off light switch apparatus - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Kagatsu Kabushiki Kaisha ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Automatic on/off light switch apparatus The following statement is a full description of this invention, including the best method of performing it known to me/us:- 0*e flo e *o I l l

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6 BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an automatic on/off light switch apparatus capable of automatically lighting a lamp load in response to the decrease in luminance of outdoor light and turning off the lamp load at a predetermined lights-out time.

Description of the Related Art Most lamps (referred to merely as lamp loads hereinafter), such as streetlamps, illuminated signboards including neon signs, and lighting devices for lighting up buildings and the like, are so controlled by an automatic on/off light *es switch apparatus having a so-called automatic switch-off function as to be turned on in response to the detection of a decrease in the illuminance of outdoor light and turned off after a lapse of a predetermined lighting time.

Another well-known type of automatic on/off light switch apparatus detects the ambient illuminance, automatically turns on a streetlamp when the illuminance is lowered, turns off when raised thereby continues lighting the streetlamp till dawn.

However, even if the streetlamp is continuously lighted till dawn, good results in proportion to the power consumed in lighting cannot be obtained. Therefore, an automatic on/off light switch apparatus having an automatic switch-off function is frequently used.

Such automatic on/off light switch apparatus consists of a combination of a switch circuit having a photoelectric sensor for detecting the illuminance, and a timer for setting the lighting time. When it gets dark after sunset, the switch circuit can be actuated to automatically turn on a lamp load. When a preset lighting time passes after the lamp load is turned on, the timer is actuated to forcibly break the switch circuit and automatically turn off the lamp load. Therefore, it is possible to avoid wasteful lighting from midnight till dawn.

Since the lighting time is fixed in the timer of the above conventional automatic on/off light switch apparatus, if the sunset time shifts from season to season, the time at which the lamp load is turned off (referred to as lights-out time hereinafter) also shifts widely. For example, if the lighting time is set in summer so that the lamp load will be turned off about 12 when the sunset time is advanced by a few hours in winter, the lights-out time is also advanced. To the contrary, if the lighting time is set to obtain the desired lights-out time in winter, the lights-out time is too late in summer.

SUMMARY OF THE INVENTION It is a main object of the present invention to provide an automatic on/off light switch apparatus with which the lights-out time can be kept almost the same by mounting a time counter for counting the time after sunset at double the speed of the time during the day even if the sunset time changes according to seasonal variation.

In order to achieve the above object, there is provided an automatic on/off light switch apparatus comprising a counter for counting the time during the day from dawn, subsequently counting the time after sunset at double the speed of the daytime, and outputting a signal when the total value of counted time reaches a preset value, and a switch means connected between the counter and a lamp load to start to supply electric power to the lamp load at sunset and break off the power supplied to the lamp load when the signal is outputted from the counter.

Two oscillators of different frequencies are connected to an input terminal of the counter, and pulse signals outputted from the oscillators are respectively assigned to count the time during the day and to count the time after sunset. It is thereby possible to count the time after sunset at double the speed of the daytime.

The above two oscillators may be replaced with one oscillator. In this case, the oscillator is required to be able to switch frequencies. Furthermore, two kinds of pulse signals outputted selectively from the oscillator can be respectively assigned to count the time during the day and to count the time after sunset.

In the above structure of the present invention, the counter counts a time Ta during the day and a time Tb after sunset, and counts Tb at double the speed of Ta. Therefore, a time T counted by the counter equals Ta+2Tb. It is assumed that the time Tb after sunset means a time between sunset and the lights-out time. Since the switch means turns on a lamp load as soon as the sun sets and turns off the lamp load at the conclusion of the preset time, the lighting time of the lamp load at this time agrees with the time Tb after sunset counted by the counter.

For example, the dawn time and the sunset time in various parts of Japan change as indicated by curves A and B of Fig.2.

Fig. 2 reveals that the time T Ta+2Tb) to be counted by the counter is approximately equal to 20 hours (within a range of 19.9 hours to 20.9 hours) without distinction of season when the lights-out time is set at 22 o'clock. In other words, when T is S set at 20 hours, the counter counts up the time about 22 o'clock in all seasons, thereby allowing the lamp load to be turned off °o at almost the same lights-out time around 22 o'clock. Although the change characteristics of the dawn time and the sunset time owing to seasonal variation vary from place to place, such variation of the change characteristics can be practically ignored.

This is because it is sufficient to keep the lights-out time of a streetlamp and the like almost the same and it is unnecessary to a precisely maintain a fixed lights-out time. The lights-out time may be moved up or back from 22 o'clock by only changing a set value of the time T and changing the time to be counted up by the counter.

The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the structure of an automatic on/off light switch apparatus according to an embodiment of the present invention; Fig. 2 is a table showing a relationship T Ta+2Tb in the embodiment; and Fig. 3 is a block diagram showing the principal part of another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, an automatic on/off light switch apparatus 10 is comprised of two oscillators 11 and 12, a counter eq..

14 and an output relay RL functioning as a switch means.

Output terminals of photoelectric switches PSa and PSb are respectively connected to input terminals of the oscillators 11 and 12. Output terminals of the oscillators 11 and 12 are connected to an input terminal of the counter 14 through an OR gate 13, and an output terminal of a setting device 14a Is connected to another input terminal of the counter 14. An output terminal of the counter 14 and an output terminal of the photoelectric switch PSb are connected to input terminals of an AND gate 15. An output terminal of the AND gate 15 is connected to an input terminal of the output relay RL.

A normally open contact RLa of the output relay RL is connected t power supply AC in series with a lamp load L.

The photoelectric switches PSa and PSb each operate according to the detection of the ambient illuminance of outdoor light. The photoelectric switch (the first photoelectric switch) PSa finds that the ambient illuminance exceeds a predetermined level because of sunrise, and actuates the oscillator 11. On the other hand, the photoelectric switch (the second photoelectric switch) PSb finds that the ambient illuminance falls below the predetermined level because of sunset, and actuates the oscillator 12. Either of the photoelectric switches PSa and PSb and either of the oscillators 11 and 12 always operate near sunset.

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Both or none of them must not operate simultaneously. The oscillators 11 and 12 can respectively output pulse signals Sl and S2 of oscillation frequencies fl and f2, and the frequency f2 is double the frequency fl. The predetermined level can be, specifically, selected from an illuminance range of 10 lux to 100 lux.

0* The counter 14 counts the pulse signals Sl and S2 outputted from the oscillators 11 and 12 through the OR gate 13. In other words, the counter 14 can count the time Ta during the day by counting the pulse signals S1 from the oscillator 11 which is actuated at dawn, and count the time Tb after sunset at double the speed of the daytime Ta after counting the time Ta during the day by counting the pulse signals S2 from the oscillator 12 which is actuated at sunset. The pulse signals Sl and S2 are pulse strings in accordance with the oscillation frequencies fl and f2 of the oscillators 11 and 12, and f2 is double fl. The counter 14 can thereby count the time T Ta+2Tb.

The counter 14 compares T with a preset time To set in the setting device 14a every time it counts T, and outputs a time-up signal S3 at the time when T equals To or above.

On the other hand, the AND gate 15 generates a control signal when the photoelectric switch PSb operates and the time-up signal S3 from the counter 14 is not present, thereby actuating the output relay RL. In other words, it is necessary to output the time-up signal S3 when T equals To or above and to turn on a lamp load L when T is less than To. The output relay RL can connect the lamp load L to the power supply AC to turn on the lamp load L in response to actuation of the photoelectric switch PSb at sunset, and can disconnect the lamp load L from the power supply AC to turn off when the counter 14 counts up the time To.

a a It is known, as shown in Fig. 2, that the time T Ta+2Tb) counted by the counter 14 is almost constant without distinction of season when a lights-out time t of the lamp load L is set at ta. In this case, Fig. 2 shows that T is approximately equal to 20 (hours) when ta equals 22 (o'clock). In other words, the counter 14 can realize an almost constant lights-out time ta 22 (o'clock) when the preset time To is 20 (hours). The lights-out time ta is moved back by an hour by increasing the preset time To by two hours, and advanced by an hour by decreasing To by two hours. However, since the preset time To must be, in general, equal to Ta or above, the minimum value of the preset time To is about 15 hours in the case of Fig. 2.

[Another Embodiment] The two oscillators 11 and 12 may be replaced with one oscillator 16 as shown in Fig. 3. It is assumed that the oscillator 16 has an oscillation frequency fl when the photoelectric switch PSa operates, and an oscillation frequency f2 2fl) when the photoelectric switch PSb operates. In other words, the oscillator 16 outputs pulse signals S4 while switching between the oscillation frequencies fl and f2 depending on which of the photoelectric switches PSa and PSb operates. Therefore, the counter 14 can count the time T Ta+2Tb by counting the pulse seeo signals S4.

Although the switch means is the output relay RL in the above embodiment of the present invention, it may be an arbitrary semiconductor switching device, such as a transistor, a TRIAC, a SCR and the like. Furthermore, since the photoelectric switches PSa and PSb complementarily operate each other, they may be Scombined into one photoelectric switch. For example, when PSb is a omitted in Fig. 3, the oscillator 16 operates at the frequency fl in operation of PSa and at the frequency f2 in non-operation of PSa.

As described above, according to the present invention, since a counter for counting the time after sunset at double the speed of the daytime and a switch means for controlling a lamp load in response to the count-up of the counter are used in combination, the counter can ingeniously utilize the change characteristics of dawn and sunset times peculiar to each place.

Therefore, it is possible to keep the lights-out time of a lamp load almost the same without distinction of season by comparing the time counted by the counter with a preset time.

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Claims (8)

1. An automatic on/off light switch apparatus, compris- ing: a counter for counting the time during the day from dawn, subsequently counting the time after sunset at double the speed of the daytime, and outputting a signal when the total of counted time reaches a preset time; and switch means connected between said counter and a lamp load to start to supply electric power to said lamp load at sunset and break the power supplied to said lamp load vhen the signal is outputted from said counter.

2. An automatic on/off light switch apparatus according to claim 1, wherein two oscillators of different oscillation frequencies are respectively connected to input terminals of said counter, and said counter counts the time by counting pulse signals outputted from said oscillators.

3. An automatic on/off light switch apparatus according to claim 2, wherein a first photoelectric switch for detecting a C rise of the ambient illuminance above a predetermined level is connected to one of said oscillators, and a second photoelectric S switch for detecting a fall of the ambient illuminance below the predetermined level is connected to the other oscillator.

4. An automatic on/off light switch apparatus according to claim 1, wherein one oscillator capable of switching oscilla- tion frequencies is connected to an input terminal of said coun- c ter, and said counter counts the time by counting two kinds of pulse signals selectively outputted from said oscillator.

An automatic on/off light switch apparatus according to claim 4, wherein a first photoelectric switch for detecting a rise of the ambient illuminance above a predetermined level and a second photoelectric switch for detecting a fall of the ambient illuminance below the predetermined level are connected to said uscillator.

6. An automatic on/off light switch apparatus according to claim 1, wherein a setting device for setting said preset time is connected to said counter.

7. An automatic on/off light switch apparatus according to claim 3 or 5, wherein said first and second photoelectric switches are combined into one. •eee e*oe 9 oo *e ;~3s 12

8. An automatic on-off switch apparatus substantially as hereinbefore described with reference to the drawings. disclosed herein or referred to or indi ein the specification and/or claim is application, individuall ectively, and any and all combinations o-9;9 .y two or more of said stope or features- DATED this THIRTY FIRST day of OCTOBER 1994 oby DAVIES COLLISON CAVE Patent Attorneys for the applicant(s) *SS DATED this THIRTY FIRST day of OCTOBER 1994 Kagatsu Kabushiki Kaisha by DAVIES COLLISON CAVE Patent Attorneys for the applicant(s) S I I ABSTRACT OF THE DISCLOSURE An automatic on/off light switch apparatus has a counter for counting the time during the day from dawn, hubsequently counting the time after sunset at double the speed of the day- time, and outputting a signal when the total value of counted time reaches a preset value, and a switching device connected between the counter and a lamp load to start to supply electric power to the lamp load at sunset and break the power supplied to the lamp load when the signal is outputted from the counter. A photoelectric 3witch is connected to an input terminal of the counter. Counting of the time during the day is started when it gets light, and the supply of electric power to the lamp load is started when it gets dark. 0 *OO•