GB2143966A

GB2143966A - Electronic apparatus for switching at predetermined times

Info

Publication number: GB2143966A
Application number: GB08320167A
Authority: GB
Inventors: Stephen Day
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-07-26
Filing date: 1983-07-26
Publication date: 1985-02-20
Also published as: GB8320167D0

Abstract

Electronic apparatus controls the switching time of street lamps or other electrical equipment in a predetermined manner throughout the year according to a table of switching times stored in electronic memory. The time reference for the switch controller is an accurate quartz crystal (1) controlled electronic date time and day circuit 2 and overall control of the system is effected by a stored-program controlled microprocessor 5. <IMAGE>

Description

SPECIFICATION Electronic apparatus for switching street lamps at predetermined times This invention relates to the control of switching times of street lamps.

A street lamp is required to be illuminated during the hours of darkness. However, in order to save the cost of consumption of electricity it is common practice amongst lighting authorities to switch street lamps off during hours of the night when they are not required. Typically street lamps are switched off between the hours of midnight and 5.30 am. Consequently in a typical situation a street lamp is required to be switched on from dusk till midnight and from 5.30 am till dawn.

Various methods have been employed to control the switching of street illumination. A number of schemes employ signalling via the mains or an auxiliary data connection to switch many street lights on or off under remote control. It has become common however, for street lamps to be switched on and off by apparatus individual to each lamp. This invention relates primarily to an apparatus which is designed to control an individual light, though in a modified form it could be extended to control the switching of power to a number of nearby lights powered by the same mains supply.

A common arrangement where lights are individually controlled, is to have a device sensitive to ambient illumination, such as a photocell, which controls the contact of a relay, often of the thermal type, and consequently switching the light on when ambient light falls at dusk and off again when ambient light increases at dawn. This arrangement is simple and effective. The inertia of a thermal relay, which is commonly employed, ensures that lights do not switch on and off haphazardly as light levels slowly change.

There are two common arrangements employing photocells. One is to have the photocell mounted in the top of the lamp, and the power relay within the base accessible from ground level.

Another arrangement is to have a combined photocell and relay switch arrangement mounted as an integral apparatus fitted in the top of the lamp body and adjacent to the bulb. Electricaily the circuit is the same in both cases.

This simple arrangement is effective in switching the lamp off during the day, but does not have the means to effect switching off during the early morning hours, typically between midnight and 5.30 am.

Various methods have been amployed to effect early morning switch-off. One means of effecting this is to have an electro-mechanical clock timer arranged to open a contact for the appropriate times of the night. Such a timer is powered by the mains, and can be arranged to continue functioning for a certain time during a power failure. However this apparatus suffers from the disadvantage that when there is a long power failure the clock can stop and it is then necessary for all street lamp timers to be manually reset-an irksome task.

Another approach that has been employed is to utilise the electricity supply frequency as a timing reference. Electronic circuitry is arranged to count the number of mains cycles between switch on at dusk, and switch off at dawn.as indicated by the ambient light sensing element. Division of the number of mains cycles occuring between these times by 2 dictates the switch off time for the next (approximately) mid-night time and the electronic circuitry then determines switch on time by means of counting the appropriate number of mains cycles amounting to typically 51/2 hours before switching the light on again. In this approach dusk switch-on is controlled by the photocell. Midnight switch off and switch on at 5.30 am is controlled by electronic circuitry referring to the previous day's light conditions. Dawn switch-off is directly controlled by the light sensor.

The consistency of midnight switch off time achieved by the means described is accurate to within i 1 5 minutes typically throughout the year. The main drawback of this system is that if there is a power failure on the previous day, time reference is lost, and then the light must be left on during the whole of the following night.

In order to overcome the disadvantages of the previously described arrangements the present invention dispenses with all external timing and light sensing arrangements such as photocells, electromechanical clocks and mains cycle counting arrangements. The means of achieving this objective is to incorporate within one integral piece of electronic apparatus an accurate time standard and an electronic reference table of switching times for the street lamp power applicable to the whole year. The power switching relay may be arranged to be an integral part of the apparatus or to be driven by the controlling apparatus.

Typically the time reference of the invention is a quartz crystal oscillator providing a reference frequency to an electronic day date and year timer. At time of manufacture or installation the timer is set to the current day and date. Typically such a device will remain accurate to within 10 minutes over a 20 year period, provided standby battery power is provided for the event of mains failure.

Switching times of the street lamp are dictated by the local authority. A table of these switching times is programmed into electronic memory of the programmable read only mem ory type or of mask programmable type.

These switching times can be arranged to be as desired by the lighting authority. Typically each band of latitude would have a particular table of switch on and switch off times related to daylight hours during the year. The table of times can be for each day of the year though sufficient accuracy is achieved by having a table of times fixed for each week, fortnight or other acceptable period, thereby reducing the requisite amount of electronic memory storage.

The midnight switch off times and early morning switch on times can be arranged to be part of the electronic memory table, or since they are constant with respect to diurnal time, switches or links can be set according to the local conditions. In this way the late night switch off can be set at installation to say midnight, 00.30, 01.00 etc. and early morning switch on can be similarly adjusted typically from 4.00 am to 7.00 am.

In order to implement my invention a further controlling element is required which examines the date day and time reference, comparing it with the table of switching times and setting the street lamp to be either on or off as required for the particular time of day.

This task is performed by a microelectronic processor or microcontroller operating according to a stored program either integral with or external to the microelectronic controlling device.

The whole apparatus as described in principle in the foregoing description can be conveniently installed within the mains supply to the street lamp. Once installed operation remains automatic and unattended for a period of 20 years or more.

Features and advantages of the present invention will become apparent from the following description of an embodiment thereof, given by way of example with reference to the accompanying drawings in which: Figure 1 is a circuit diagram of a particular complete embodiment of the invention.

Figure 2 is a plan of the operations to be performed by the software instructions controlling the invention.

Referring to Figure 1, a circuit diagram is illustrated which shows one particular embodiment of my invention in sufficient detail to allow anyone skilled in the art of electronics to construct it.

The time reference in this embodiment is the 32.768 KHz crystal, 1, which sets the oscillation frequency of the integral oscillator within the clock circuit, 2, an MSM5832.

This is a low power CMOS circuit which is kept permanently supplied with power via the standby pcwer circuit, 3.

The current required by the MSM5832 is of the order of 20 microamps. This means that only a small rechargeable battery within the standby power circuit can maintain the clock running during long times of power failure, even up to several months if required.

At the time of installation the MSM5832 is set to the correct time and date by the use of the set-up control switches, 4. Typically this device will maintain an accuracy of 30 seconds per year.

This means that after 20 years the clock will still be accurate to within ten minutes which is sufficiently accurate for control of lamp switching times.

If desired the correct time and date can be set at time of manufacture, and as long as installation time is typically within three months it will not be necessary to perform any adjustments at the time of installation since the clock will have maintained correct time on its battery standby power since manufacture.

The processor, 5, used in this embodiment is an INTEL 8748 single chip controller which contains 1000 bytes of ultra violet eraseable program memory. The program requires approximately 250 bytes of memory and the reference table of times based on changes every week requires only 208 bytes of storage. This latter allows switching times set within 6 minute increments of the time of day and two switch-on and two switch-off times per day. Consequently each week requires only 4 bytes of storage making 208 bytes for the whole year's table. The 8748 thus has plenty of memory to meet the requirements of our invention.

The 8748 addresses the MSM5832 via one of the 2 ports available and data indicative of the day, time and date is returned to the processor via the 8748 data bus.

The set up controls,4 , connected to processor port inputs, consist of an arrangement of switch contacts designed to allow, in conjunction with the 8748, the correct date and time to be set into the clock circuit at time of manufacture or installation. The offset switching-time links, 6, are soldered links connected to further port input lines of the processor which can be used to offset switching times from the memory reference table according to particular local needs.

The only output of the processor is to switch the power to the lamp on or off. This is amplified, as shown, by the transistor, 7, driving a relay coil within the output relay 8.

Various other arrangements are possible for the output circuit; for example the transistor can be arranged to drive a thermal relay or the output relay shown can be connected to another relay which actually applies power to the lamp.

We have described embodiment based on an 8748 processor. The mask-programmed 8048 is a suitable processor, and pin compatible with the 8748. Other arrangements are possible where a processor is employed without integral memory such as an 8035 addressing external program and data memory in a 2716 EPROM or other mask programmed 2 Kbyte memory. Yet another alternative is an 8048 mask programmed with the operating instructions and referring to a data table of switching times within external memory.

Many implementations of our invention are possible using INTEL microprocessor components or those of any other microelectronic component manufacture. The detailed embodiment of Figure 1 illustrates the principles of our invention and shows how a very small number of components can be used to implement our invention.

The processor in Figure 1 must operate according to a series of program instructions.

Figure 2 illustrates our particular embodiment of a software flow chart, and incorporates the essential features of my invention.

Every second the date and time is examined in the clock. The reference table of switching times is then accessed according to the current date. According to the current time of day the lights are switched either on or off as dictated by the switching time table (taking into account any time offset indicated by the offset switching links in Figure 1).

The set up controls are then examined to see if it is required to set or change the setting of the time and date within the clock.

If so the program instructions allow setting of the date and time via response to the set up controls. If not, or after completion of set up the processor program waits for the beginning of the next second.

The software program repeats frequently, typically once per second, so that after a mains failure the lights will be switched on if required almost immediately. The set up routine will typically be used only at manufacture, or installation, and then only at rare intervals as long as perhaps 10 or 20 years, or according to the dictates of accuracy of switching time needed by the user.

Although my description has been given with particular reference to street lighting the invention can equally well be applied to switching of any form of illumination, such as forecourt lighting, or shop premises lighting, advertising lighting, traffic sign lighting or any other application where switching on times require to be varied according to the time of year in sympathy with varying hours of darkness, or according to any other pattern of switching times required by the user. Furthermore the invention can be used for the control of any electrical apparatus other than illuminating lamps by means of connection to power switching means of appropriate type.

Claims

1. Electronic apparatus comprising an accurate date and time reference, a table of data indicative of switching times throughout a calendar year or other extended time period, controlling means arranged to compare said time reference with said table, and output means arranged to provide an output signal connectable to power switching means, said switching means being operable to cause an electrical device to be switched on and off according to the times set by the said table.

2. Apparatus according to claim one where said electrical device to be switched on and off is an illuminating lamp.

3. Apparatus according to claim one where a table of data is structured so as to take into account the varying periods of darkness occurring within a calendar year.

4. Apparatus according to claims 1 and 2 where power and switching means are an integral part of the apparatus.

5. Apparatus according to claims 1 and 2 where power switching means are external to the apparatus.

6. Apparatus according to claims 1 to 5 where the table of times and a controlling programme are stored within the controlling means.

7. Apparatus according to claims 1 to 5 where the table of times and a controlling programme are stored in a device separate from the controlling means.

8. Apparatus according to claims 1 to 7 where a component or the whole of the apparatus continues to function in times when mains power supply to the apparatus is interrupted.

9. Apparatus according to claims 1 to 8 where a table of dates and times refers to individual days throughout a year or other extended time period.

10. Apparatus according to claims 1 to 8 where a table of dates and times refers to individual groups of consecutive days throughout a year or extended time period.

11. Apparatus according to claims 1 to 8 where a table of dates and times refers to a combination of individual days of the week groups of days of the week or any other arrangement of information indicative of switching times.

1 2. Apparatus according to claims 1 to 11 where offset of switching times indicated by the table can be introduced by inputs to the controlling means such offsets being settable to a plurality of different times applicable to particular groups of switching times.

1 3. An apparatus for controlling the switching on and off of an electrical apparatus at predetermined times throughout an extended time period as herein before particularly described with reference to Figures 1 and 2 of the drawings.