CA1112295A - Programmable lighting control system - Google Patents
Programmable lighting control systemInfo
- Publication number
- CA1112295A CA1112295A CA322,439A CA322439A CA1112295A CA 1112295 A CA1112295 A CA 1112295A CA 322439 A CA322439 A CA 322439A CA 1112295 A CA1112295 A CA 1112295A
- Authority
- CA
- Canada
- Prior art keywords
- control system
- lamp control
- lamp
- microprocessor
- processor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000001360 synchronised effect Effects 0.000 claims abstract description 4
- 230000003111 delayed effect Effects 0.000 claims description 8
- 238000005286 illumination Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- OWNRRUFOJXFKCU-UHFFFAOYSA-N Bromadiolone Chemical compound C=1C=C(C=2C=CC(Br)=CC=2)C=CC=1C(O)CC(C=1C(OC2=CC=CC=C2C=1O)=O)C1=CC=CC=C1 OWNRRUFOJXFKCU-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000000386 athletic effect Effects 0.000 description 1
- 235000021167 banquet Nutrition 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M5/25—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M5/257—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M5/2573—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with control circuit
- H02M5/2576—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only with control circuit with digital control
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/36—Controlling
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/36—Controlling
- H05B41/38—Controlling the intensity of light
- H05B41/39—Controlling the intensity of light continuously
- H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
- H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
- H05B41/3924—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by phase control, e.g. using a triac
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/36—Controlling
- H05B41/38—Controlling the intensity of light
- H05B41/40—Controlling the intensity of light discontinuously
- H05B41/42—Controlling the intensity of light discontinuously in two steps only
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
- Circuit Arrangement For Electric Light Sources In General (AREA)
Abstract
PROGRAMMABLE LIGHTING CONTROL SYSTEM
ABSTRACT OF THE DISCLOSURE
A high intensity discharge lamp control system includes a dimming circuit in which each lamp is placed in series with a pair of reactive elements, one of which may be elec-trically bypassed. A programmable digital microprocessor, synchronized with the phase of the AC power, adjusts the bypass time, thereby providing individual control of the brightness of each lamp. The microprocessor will accept multiple control inputs. Using such inputs, the system may be programmed to optimize lighting conditions at each point in an area to be illuminated while minimizing the electrical energy consumed by the lighting system. The microprocessor may be easily reprogrammed to compensate for changing light-ing requirements.
ABSTRACT OF THE DISCLOSURE
A high intensity discharge lamp control system includes a dimming circuit in which each lamp is placed in series with a pair of reactive elements, one of which may be elec-trically bypassed. A programmable digital microprocessor, synchronized with the phase of the AC power, adjusts the bypass time, thereby providing individual control of the brightness of each lamp. The microprocessor will accept multiple control inputs. Using such inputs, the system may be programmed to optimize lighting conditions at each point in an area to be illuminated while minimizing the electrical energy consumed by the lighting system. The microprocessor may be easily reprogrammed to compensate for changing light-ing requirements.
Description
B~CKGRO~ND 0~ T~IE INVENTION
Eield of the Invention .. . _ This invention relates to lamp control circuits fo~
high intensity discharge lamps, such as mercury vapor lamps, having two electrode termlnals and no heater. More specifi-cally, the invention is directed toward programmable digital lamp control systems.
DescriJption of the Prior Ar.t Probably the simplest control circuit for a lighting system consists of a switch placed in the power line to the entire light system. A user turns on the switch to receive full illumination and turns off the switch to extinguish all lighting. It is o~ten desirable, however, to provide for adjustable control of a lighting system to account Eor differ~
ent uses requirin~ di~ferent lighting levels. A school gymna-sium, for exarnple, does not require as much lighting when `; used for a banquet as during an athletic event. Furthermore, in recent years, concern has developed over the energy con-sumption of systems using electrical power. Therefore, it has become increasingly desirable to satisfy lighting require-ments while achi~ving a minimum amount of energy consumption.
One way in which to improve a lighting system is to switch the power to each lamp in the system independently, thereby providing a greater degree of control over the illumi-nation levels which may be selected. Such a control system may work quite well in applications involvlng a limited amount of space, such as in a relatively small area which requires ~3-L
.
only a small number of lamps. Individual switchiny, however, is not practical when applied to larger commercial or indus-trial installations. The extra wiring required can become unduly expensive and, in addition, it woul~ be unrealistic to expect the users of a large lighted area to take full advantage of the potential of an individually s~itched lamp system, since the time consuming manual switchiny which would be required would soon become unduly burdensome.
Low voltage lighting control systems have been developed which reduce the expense of installing a multiplicity of indi-vidually switched lamp units and make such an alternative more practical Eor larger applications. Low voltage control, however, adds only a limlted amount of ~lexibility to a lighting system. Each lighting unit must be either supplied with full power or turned off. Thus a level of brightness fallin~ between these extremes cannot be selected with such systems.
In res~onse to the need for a ~reater range of control over a lighting system, dimmer circuits have been developed.
Dimming circuits adapted for use with incandescent and fluo-rescent liqhting systems are well known in the art. In addition, a practical dimming circuit which may be used for dim~ing high intensity gas discharge lamps has been invented.
Such a dimming system is disclosed in U.S. Patent No.
3,~16,7~4, entitled "~ligh Intensity Gas Discharge Lamp Dimmer System", and, in improved form, in [).S. Patent No. 3,B94,265, entitled "~igh Int~nsity Lamp Dimming Circuit", both assigned to the same assignee as the present application. This system allo~s for the selective reduction of current through a high h~
intensity discharge lamp to provide dlmminy without damaye to the lamp, by bypassing current around an accompanying bal-last element and thereby achieving a reduction o~ the lamp current for part of a half-cycle of the power cycle.
The use of dimming systems allows a lighting system to be made much more adaptable to the particular lighting re-~uirements to be fulfilledO Consequently, energy savings can be realized through precisely adjusting the light power to the minimum level required for acceptable illumination.
In addition, with a number of dimming units a lighting system may be arranged to provide the optimum light intensity and directional lighting pattern for each point within the lighted area. Additional flexibility may be achieved with multiple dimming controls at remote locations. Such a system, for exampl~, which i5 designed for use with a high intensity gas discharge lighting system, is disclosed in U. S. patent No.
4,144,478 granted March 13, 1979, entitled "Lamp System Take Control Dimming Circuit", assigned to the same assignee as the present application.
Even when using dimming controls, however, the extent to which a lighting system can be adjusting to varying needs is limited. As the size of the system increases, for example, a practical limit is imposed on the number of dimming circuits which can be utilized. As with individually switched lighting units, it becomes impractical to effectively utilize individ-ually dimmed lamps on a large scale. Furthermore, the re-quirement for manually adjusting a lighting system may become inconvenient in a large scale operation.
.~
In addition, other control parameters may be desirable in a lighting system. ~ ~ore efficient system may be real-ized, if dayligt~t i~ available to illuminate an area during certain times of the day. A device which is responsive to light, such as a photocell, could be incorporated into the system to automatically extinguish some or all of the arti-ficial light at times when the natural li~ht provides suffi-cient illumination. Many other useful automatic inputs can be envisioned. ~ 24 hour timer, for example, could auto-matically and reliably reduce lighting levels at times whenregular lighting is normally not required.
The possibilities for more efficient and versatile con-trol of electrical systems have expanded in recent years with the availability of relatively inexpensive digital elec-tronics. tlodern technology enables the production of micro-processors which contain a large number of logic devices, yet occupy a small amount of space. Such devices are also becoming increasingly in~xpensive. A microprocessor can be equipped witll a memory unit to perform a larye number of con-trol tasks. Furthermore, such digital device~ may be readilyand conveniently reprogrammed, maki~ them highly adaptable to chanying conditions~ One example of the application of such a microprocessor to a liyhting control system may be found in an article by McGowan and Feiker, entitled "A New Approach To Lighting System Control", in the Journal of the Illuminating Engin~ering Svciety, October, 1976, at page 3~.
It is therefore a eature o this invention to provide a programmable dimmer control system for high intensity dis-charge lamps.
z~
It is also a feature of this invention to provide a pro-grammable dimmer control system which may be readily and eco-nomically adapted to automatically contr~l any desired number of lamps individually.
It is another feature of this invention to provide a dimmer control system or a high intensity discharge light ing system which may be easily reprogrammed to suit changing needs in the lighted area.
It is another feature of this invention to provide a programmabl~e dimmer control system which will accept inputs from a variety of control sources.
It is yet another feature of this invention to provide a programmable dimmer control system for high intensity dis-charge lamps in which the gate source voltage for the dimmer circuit is controlled by a digital logic component.
.
SIJI'IIIARY OF T~IE INVENTION
~ lamp control system for a high intensity gas discharge lighting system includes a ballast means, with a reactor por-tion, connected to a lamp. A gated~b~pass means is provided for bypassing the reactor portion of the ballast. A detector senses each zero voltage crossing point of the AC power and synchronizes a digital processor, which provides a phase delayed lamp control si~nal to the gated bypass meansO
In a preferred embodiment, the digital processor is a microprocessor operating in conjunction with a read only memory. The memory operates in conjunction with control inputs to the microprocessor to enable the microproce.ssor to z~s compute appropriate phase delayed lamp control signals for each lamp.
single digital processor may be utilized to control a plurality o~ individual lamps through a gated bypass circuit for each lamp.
BRIEF DESCRIPTION OF THE DRAWINGS
.. . . . . . . . . .. .... ..
In order to further describe the features, advantages, and objects of the lnvention~ particular embodimen~s are illustrated in the appended drawings, which form a part of this- specification. It should be noted, however, that these drawings illustrate only ty~ical embodiments of the invention and thereEore should not be considered to iimit its scope, as the inventive concept may be expressed in other equally effec-tive embodiments.
.. .
In the drawings:
Figure 1 is a block diagram of a preferred embodiment of a high intensity gas discharge lamp control system in accord-ance with the present invention. ~
Figure 2 is a schematic diagram showing one embodiment o~ a dimmer circuit for a high lntensity discharge lamp which may be used with the present inven~ion.
Figure 3 is a wave form diagram illustrating the ampli-tude and phase relationships be~ween certain voltages and currents in the dimmer circuit shown in Figure 2.
. , .
DESCRIPTION C)F T~IE PREFERRED EME3ODI~1ENT
Referrillg to the drawings, and first to Figure 1, hi911 intensity discharge lamps 10 are connected to an AC power line 12 through individual dimmer circuits 14. The dimmer circuits 14 receive control signals from a microprocessor 16 through a digital driver 20. Microprocessor 16, which is is sychronized to the pha~e of the AC power line by a zero crossing detector 18, sends a synchronized control signal to each dimmer circuit 14. The appropriate dimming signal for each individual dimmer circuit is selected according to a program provided by a preprogrammed read only memory unit 22 in conjunction with any number of inputs, such as inputs 24, 26, and 28.
The read only memory unit 22 provides the microprocessor with a preselected program, enabling the microprocessor to provide the apyroyriate light level for each lamp when a given set of conditions, as indicated by one or more input signals~ is received. The manual override input 24 typically is a keyboard input allowing manual selection of individual light levels for each lamp, or selec~lon of a preprogrammed lighting pattern such as, for example, a work day lighting pattern for an office, or a night time pattern at reduced levels for a cleanup crew. Other inputs, such as inputs 26 and 28, may be used to provide automatic control. ~he signals from such inputs may be utilized to adjust the lic3hting level according to a particular time of the day or week, or ~o acl~
just the lighting level according to natural light ~vailable, or may be inputs ~rom any number o~ other control sources.
$~
Now refe~ring to Figure 2, a schematic o~ a xero crossing detection circuit 18 which may be u~ilized with the present invention is illustrated, connected through microprocessor 16 to a dimming circuit 14 used with the present invention.
Those skilled in the art will recognize that a single dimming circuit for one hi~h intensi~y discharge lamp is shown, while one such dimming circuit i~ provided for each lamp in a lighting system, as illustrated in Figure 1. TransEormer io steps down the power line voltage, which is connected across the-primary winding of transformer 30. ~he stepped down voltage from the secondary of t-ransformer 30 is full wave rectified by bridge rectiEier 32. This rectified voltage is then applied to monostable multivibra~or 34, which employs a Schmitt trig~er input.
One such multivibrator which may be utilized in this invention is the Texas Instruments No. 74121. The value~ -of the timing resistor 36 and the timing capacitor 38 are appropriately selected to adjust the output of the multi-vibrator 14 to the appropriate pulse width. The output from monostable multivibrator 34 is applied as an input, throuyh line 40, to the microprocessor. rrhe snicroprocessor, by using this reerence timing pulse from the power line, provides a phase delayed control signal which adjusts the lamp current for the desired level o~ brightness.
Now referring to the dimming circuit 14 in Firgure 2, a high intensity discharge lamp 10 is connected ~n series with two inductive ballast elements 42 and 4~, the entire series being connected across power lines 46 and 4~. ~ gated bypass means is provided eor balla~ element 44 in the form of triac 50. The gate source voltage for triac 50 is 5Up-plied to the gate terminal 52 of the triac by the secondary of transformer 54 whith shunt resistor 56 being connected across the secondary leads of transformer 54. A capacitor 58 and a resistor 60 are connected in series between the first and second main terminals of the triac 50 and act as a snub~er device, to prevent the triac 50 from exhibiting false turn on due to commutatin~ dv/dt. The gate source voltage turn on si~nal is received at the primary of trans- ;
former 54 from the microprocessor 16, throu~h resistor S2.
The operation of this dimming circuitry may be more fully understood by reference to Figure 3, which illustrates the phase relationships of the dimming circuitry. When triac 50 is conducting, a complete bypass around element 42 is achieved with a maximum amount o~ current, desiqnated "Full Lamp Currentn, ~lowing through lamp 10. Conversely, when triac 50 is not conducting, a minimum amount of current flows through lamp 10, as indicated ~y the "Dim Lamp Current"
curve shown in Figure 3~ By allowing triac 50 to conduct or part of the power cycler the currellt through lamp 10, and hence the illumination ~herefro~ may be varied between the dim lamp current and full lamp current values. Such an intermediate current value i5 also indicated in Figure 3.
It is apparent, therefore, that merely controlling the period of conduction of the triac 50 will also control the illumi-nation level provided by lamp 10.
Triac 50 should not be rendered conductive until the current throu~h and ~he voltage across element 42 are both of the same polarity. If triac 50 were rendered conductive when the voltage across element 42 ~nd the current there-through were not of the same polariky, a phenomenon known as "hal~ cycle conduction" would occur. In such a situation, the lamp would appear to flash from dim to full bright each half cycle, and would produce an irritating strobe effect to the eye that would also be harmful to the lamp.
Considering the polarity cycles indicated in Figure 3, the current through element 42 does not go positive until point 6~. At this time, the reactor voltage is already positive. At point 66, the reactor voltage goes negative, although the current through the inductive element 42 is still positive. The gate range 68 of time over which ~he gate voltage may be applied is hence determined to be that time lying between points 64 and 66.
The operation of the dimming circuitry described and illustrated herein is similar to that disclosed in U. S.
Patent No. 3 r 894,265, entitled "High Intensity Lamp Dimming Circuit", assigned to the same assignee as the present appli-cation. For a more complete description of the operation of such dimming circuitry, the above patent should be consulted.
Referring now to the operation of the microprocessor 16, each time the microprocessor receives a reference timing pulse from the zero crossing detector circuitry, an interrupt routine is accomplished. In conjunction with data obtained from the various inputs to the microprocessor, the read only memory supplies a program se~uence which enables khe microprocessor to compute an appropriate di~lming signal.
.~
The microprocessor then transmits a gate source voltage slgnal to triac 50, which is thereby sufficientl~ delayed in phase to provide the appropriate current level to the high intensity discharge lamp 10. In this manner, the microproces50r con-trols the brightness level at which the lamp is operating.
The microprocessor used in thi~ invention may be any suitable s~andard model available. For example, one embodi-ment of this invention has been constructed using the Motorola MEK6800D2 evaluation k~t, including the MC6800 microproce~so~
unit. ~ sample program which has been used in this embodiment of the inven~ion is listed în Table ~. This program set~
the data lines to func~ion as outpu~ lines, readies the microprocessor to wait for an interrupt, and initializes the microprocessor registers.
LDA A ., I~
FF
STA A EXT Causes the data line on the B
side to function a~ outputs ~0 LDA A IMM Enables the interrupt by a low to high transition on the interrupt control line STA A EXT
LDS IMM Sets the stack pointer 30. FF
LDX IMM Clears the index register QO
CLI Clears the interrupt m~rk NOP
NOP Wait~ for the interrupt BRA
FC
The program in Table I is used in conjunction with an interrupt service routine, which is set out in Table II.
The interrupt routine delays the gate signal by a predeter~
mined incremellt of time with respect to the zero crossing of the line voltage, controls the gate signal pulse width, and readies the microprocessor to await another interrupt, TABLE I I
CLR A
STA A DIR Clears index register FC
STA A DI~
FD
LDA B EXT Clears the interrupt flag oE the PIA control register LDA B IMM
EF
AND B DI~
STA B EXT Clears the interrupt mask of the CCR
STA A DIR
FE
LDA A IMM
STA ~ DIR
FF
~TI
CPX DIR Compares the index register to memory location bo bo BNE REL
Fb : LDA A IMM
FF
STA A ~x~r Set~ the output lin~s Otl the B side INC ~XT
~$~
LU~ A IMM
Q5 Determines the gate signal pulse wid~h Sus A DIR
b2 ~NE
CLR A
STA A DIR
STA A ~XT Clears the output lines on the B side NOP
NOP Wai ts for an interrupt BRA
FC
A microprocessor is an e~specially advantageous addition to a lighting control system~ A single microprocessor is capable of controlling a large number of lamps individually, and thus a single microprocessor system, ~s here disclosed, may be used to control the entire lighting system for a large area,.t?r even to control an entire building's lighting systems. Furthermore, once such a system is installed, any alterations necessitated by changing lighting requirements can be incorporated very simply. To modify the control se-quence, a read only memory is programmed to meet the new requirements, and the newly proyramln`è~ read only memory simply replaces the memory unit previously installed in the system~ In this fashion, any changes, however extensive, can be readily incorporated into the lighting system. Thus, for example, if a building is remodeled, such a lighting sys-tem would not thereby be outdated. Once installed, the system remains easily adaptable to meét changint3 lit3hting needs, while conserving a ma~imum amount of energy anc3 thereby effectint3 savings in operatiny costs.
While particular embodiments of this invention have been shown and discussed, it will be understood that the inverltion is not limited thereto, since many modifications may be made and will become apparent to tho~e skilled in the art~
For example, although one zero cros5ing detecting cir-cuit has been illustrated, any number of other circuits which are capable of establishing a reference timing pulse from the AC power line can ~e used as well. For example, a phase-locked-loop can be locked to the line frequency and used to provide timing pulses.
It should also be noted that many other inputs may be provided to the microprocessor or obtaining the desired con-trol of lighting in a given situation. In some areas, for example, electric utility users are subject to a demand pen-alty, which imposes a hiyher rate for electricity when the user's consumption of electricity exceeds a certain rate.
In such a situation, the microproces50r could be programmec]
to monitor electrical consumption and automatically reduce lighting levels should tha~ consumption approach the penalty rate.
Eield of the Invention .. . _ This invention relates to lamp control circuits fo~
high intensity discharge lamps, such as mercury vapor lamps, having two electrode termlnals and no heater. More specifi-cally, the invention is directed toward programmable digital lamp control systems.
DescriJption of the Prior Ar.t Probably the simplest control circuit for a lighting system consists of a switch placed in the power line to the entire light system. A user turns on the switch to receive full illumination and turns off the switch to extinguish all lighting. It is o~ten desirable, however, to provide for adjustable control of a lighting system to account Eor differ~
ent uses requirin~ di~ferent lighting levels. A school gymna-sium, for exarnple, does not require as much lighting when `; used for a banquet as during an athletic event. Furthermore, in recent years, concern has developed over the energy con-sumption of systems using electrical power. Therefore, it has become increasingly desirable to satisfy lighting require-ments while achi~ving a minimum amount of energy consumption.
One way in which to improve a lighting system is to switch the power to each lamp in the system independently, thereby providing a greater degree of control over the illumi-nation levels which may be selected. Such a control system may work quite well in applications involvlng a limited amount of space, such as in a relatively small area which requires ~3-L
.
only a small number of lamps. Individual switchiny, however, is not practical when applied to larger commercial or indus-trial installations. The extra wiring required can become unduly expensive and, in addition, it woul~ be unrealistic to expect the users of a large lighted area to take full advantage of the potential of an individually s~itched lamp system, since the time consuming manual switchiny which would be required would soon become unduly burdensome.
Low voltage lighting control systems have been developed which reduce the expense of installing a multiplicity of indi-vidually switched lamp units and make such an alternative more practical Eor larger applications. Low voltage control, however, adds only a limlted amount of ~lexibility to a lighting system. Each lighting unit must be either supplied with full power or turned off. Thus a level of brightness fallin~ between these extremes cannot be selected with such systems.
In res~onse to the need for a ~reater range of control over a lighting system, dimmer circuits have been developed.
Dimming circuits adapted for use with incandescent and fluo-rescent liqhting systems are well known in the art. In addition, a practical dimming circuit which may be used for dim~ing high intensity gas discharge lamps has been invented.
Such a dimming system is disclosed in U.S. Patent No.
3,~16,7~4, entitled "~ligh Intensity Gas Discharge Lamp Dimmer System", and, in improved form, in [).S. Patent No. 3,B94,265, entitled "~igh Int~nsity Lamp Dimming Circuit", both assigned to the same assignee as the present application. This system allo~s for the selective reduction of current through a high h~
intensity discharge lamp to provide dlmminy without damaye to the lamp, by bypassing current around an accompanying bal-last element and thereby achieving a reduction o~ the lamp current for part of a half-cycle of the power cycle.
The use of dimming systems allows a lighting system to be made much more adaptable to the particular lighting re-~uirements to be fulfilledO Consequently, energy savings can be realized through precisely adjusting the light power to the minimum level required for acceptable illumination.
In addition, with a number of dimming units a lighting system may be arranged to provide the optimum light intensity and directional lighting pattern for each point within the lighted area. Additional flexibility may be achieved with multiple dimming controls at remote locations. Such a system, for exampl~, which i5 designed for use with a high intensity gas discharge lighting system, is disclosed in U. S. patent No.
4,144,478 granted March 13, 1979, entitled "Lamp System Take Control Dimming Circuit", assigned to the same assignee as the present application.
Even when using dimming controls, however, the extent to which a lighting system can be adjusting to varying needs is limited. As the size of the system increases, for example, a practical limit is imposed on the number of dimming circuits which can be utilized. As with individually switched lighting units, it becomes impractical to effectively utilize individ-ually dimmed lamps on a large scale. Furthermore, the re-quirement for manually adjusting a lighting system may become inconvenient in a large scale operation.
.~
In addition, other control parameters may be desirable in a lighting system. ~ ~ore efficient system may be real-ized, if dayligt~t i~ available to illuminate an area during certain times of the day. A device which is responsive to light, such as a photocell, could be incorporated into the system to automatically extinguish some or all of the arti-ficial light at times when the natural li~ht provides suffi-cient illumination. Many other useful automatic inputs can be envisioned. ~ 24 hour timer, for example, could auto-matically and reliably reduce lighting levels at times whenregular lighting is normally not required.
The possibilities for more efficient and versatile con-trol of electrical systems have expanded in recent years with the availability of relatively inexpensive digital elec-tronics. tlodern technology enables the production of micro-processors which contain a large number of logic devices, yet occupy a small amount of space. Such devices are also becoming increasingly in~xpensive. A microprocessor can be equipped witll a memory unit to perform a larye number of con-trol tasks. Furthermore, such digital device~ may be readilyand conveniently reprogrammed, maki~ them highly adaptable to chanying conditions~ One example of the application of such a microprocessor to a liyhting control system may be found in an article by McGowan and Feiker, entitled "A New Approach To Lighting System Control", in the Journal of the Illuminating Engin~ering Svciety, October, 1976, at page 3~.
It is therefore a eature o this invention to provide a programmable dimmer control system for high intensity dis-charge lamps.
z~
It is also a feature of this invention to provide a pro-grammable dimmer control system which may be readily and eco-nomically adapted to automatically contr~l any desired number of lamps individually.
It is another feature of this invention to provide a dimmer control system or a high intensity discharge light ing system which may be easily reprogrammed to suit changing needs in the lighted area.
It is another feature of this invention to provide a programmabl~e dimmer control system which will accept inputs from a variety of control sources.
It is yet another feature of this invention to provide a programmable dimmer control system for high intensity dis-charge lamps in which the gate source voltage for the dimmer circuit is controlled by a digital logic component.
.
SIJI'IIIARY OF T~IE INVENTION
~ lamp control system for a high intensity gas discharge lighting system includes a ballast means, with a reactor por-tion, connected to a lamp. A gated~b~pass means is provided for bypassing the reactor portion of the ballast. A detector senses each zero voltage crossing point of the AC power and synchronizes a digital processor, which provides a phase delayed lamp control si~nal to the gated bypass meansO
In a preferred embodiment, the digital processor is a microprocessor operating in conjunction with a read only memory. The memory operates in conjunction with control inputs to the microprocessor to enable the microproce.ssor to z~s compute appropriate phase delayed lamp control signals for each lamp.
single digital processor may be utilized to control a plurality o~ individual lamps through a gated bypass circuit for each lamp.
BRIEF DESCRIPTION OF THE DRAWINGS
.. . . . . . . . . .. .... ..
In order to further describe the features, advantages, and objects of the lnvention~ particular embodimen~s are illustrated in the appended drawings, which form a part of this- specification. It should be noted, however, that these drawings illustrate only ty~ical embodiments of the invention and thereEore should not be considered to iimit its scope, as the inventive concept may be expressed in other equally effec-tive embodiments.
.. .
In the drawings:
Figure 1 is a block diagram of a preferred embodiment of a high intensity gas discharge lamp control system in accord-ance with the present invention. ~
Figure 2 is a schematic diagram showing one embodiment o~ a dimmer circuit for a high lntensity discharge lamp which may be used with the present inven~ion.
Figure 3 is a wave form diagram illustrating the ampli-tude and phase relationships be~ween certain voltages and currents in the dimmer circuit shown in Figure 2.
. , .
DESCRIPTION C)F T~IE PREFERRED EME3ODI~1ENT
Referrillg to the drawings, and first to Figure 1, hi911 intensity discharge lamps 10 are connected to an AC power line 12 through individual dimmer circuits 14. The dimmer circuits 14 receive control signals from a microprocessor 16 through a digital driver 20. Microprocessor 16, which is is sychronized to the pha~e of the AC power line by a zero crossing detector 18, sends a synchronized control signal to each dimmer circuit 14. The appropriate dimming signal for each individual dimmer circuit is selected according to a program provided by a preprogrammed read only memory unit 22 in conjunction with any number of inputs, such as inputs 24, 26, and 28.
The read only memory unit 22 provides the microprocessor with a preselected program, enabling the microprocessor to provide the apyroyriate light level for each lamp when a given set of conditions, as indicated by one or more input signals~ is received. The manual override input 24 typically is a keyboard input allowing manual selection of individual light levels for each lamp, or selec~lon of a preprogrammed lighting pattern such as, for example, a work day lighting pattern for an office, or a night time pattern at reduced levels for a cleanup crew. Other inputs, such as inputs 26 and 28, may be used to provide automatic control. ~he signals from such inputs may be utilized to adjust the lic3hting level according to a particular time of the day or week, or ~o acl~
just the lighting level according to natural light ~vailable, or may be inputs ~rom any number o~ other control sources.
$~
Now refe~ring to Figure 2, a schematic o~ a xero crossing detection circuit 18 which may be u~ilized with the present invention is illustrated, connected through microprocessor 16 to a dimming circuit 14 used with the present invention.
Those skilled in the art will recognize that a single dimming circuit for one hi~h intensi~y discharge lamp is shown, while one such dimming circuit i~ provided for each lamp in a lighting system, as illustrated in Figure 1. TransEormer io steps down the power line voltage, which is connected across the-primary winding of transformer 30. ~he stepped down voltage from the secondary of t-ransformer 30 is full wave rectified by bridge rectiEier 32. This rectified voltage is then applied to monostable multivibra~or 34, which employs a Schmitt trig~er input.
One such multivibrator which may be utilized in this invention is the Texas Instruments No. 74121. The value~ -of the timing resistor 36 and the timing capacitor 38 are appropriately selected to adjust the output of the multi-vibrator 14 to the appropriate pulse width. The output from monostable multivibrator 34 is applied as an input, throuyh line 40, to the microprocessor. rrhe snicroprocessor, by using this reerence timing pulse from the power line, provides a phase delayed control signal which adjusts the lamp current for the desired level o~ brightness.
Now referring to the dimming circuit 14 in Firgure 2, a high intensity discharge lamp 10 is connected ~n series with two inductive ballast elements 42 and 4~, the entire series being connected across power lines 46 and 4~. ~ gated bypass means is provided eor balla~ element 44 in the form of triac 50. The gate source voltage for triac 50 is 5Up-plied to the gate terminal 52 of the triac by the secondary of transformer 54 whith shunt resistor 56 being connected across the secondary leads of transformer 54. A capacitor 58 and a resistor 60 are connected in series between the first and second main terminals of the triac 50 and act as a snub~er device, to prevent the triac 50 from exhibiting false turn on due to commutatin~ dv/dt. The gate source voltage turn on si~nal is received at the primary of trans- ;
former 54 from the microprocessor 16, throu~h resistor S2.
The operation of this dimming circuitry may be more fully understood by reference to Figure 3, which illustrates the phase relationships of the dimming circuitry. When triac 50 is conducting, a complete bypass around element 42 is achieved with a maximum amount o~ current, desiqnated "Full Lamp Currentn, ~lowing through lamp 10. Conversely, when triac 50 is not conducting, a minimum amount of current flows through lamp 10, as indicated ~y the "Dim Lamp Current"
curve shown in Figure 3~ By allowing triac 50 to conduct or part of the power cycler the currellt through lamp 10, and hence the illumination ~herefro~ may be varied between the dim lamp current and full lamp current values. Such an intermediate current value i5 also indicated in Figure 3.
It is apparent, therefore, that merely controlling the period of conduction of the triac 50 will also control the illumi-nation level provided by lamp 10.
Triac 50 should not be rendered conductive until the current throu~h and ~he voltage across element 42 are both of the same polarity. If triac 50 were rendered conductive when the voltage across element 42 ~nd the current there-through were not of the same polariky, a phenomenon known as "hal~ cycle conduction" would occur. In such a situation, the lamp would appear to flash from dim to full bright each half cycle, and would produce an irritating strobe effect to the eye that would also be harmful to the lamp.
Considering the polarity cycles indicated in Figure 3, the current through element 42 does not go positive until point 6~. At this time, the reactor voltage is already positive. At point 66, the reactor voltage goes negative, although the current through the inductive element 42 is still positive. The gate range 68 of time over which ~he gate voltage may be applied is hence determined to be that time lying between points 64 and 66.
The operation of the dimming circuitry described and illustrated herein is similar to that disclosed in U. S.
Patent No. 3 r 894,265, entitled "High Intensity Lamp Dimming Circuit", assigned to the same assignee as the present appli-cation. For a more complete description of the operation of such dimming circuitry, the above patent should be consulted.
Referring now to the operation of the microprocessor 16, each time the microprocessor receives a reference timing pulse from the zero crossing detector circuitry, an interrupt routine is accomplished. In conjunction with data obtained from the various inputs to the microprocessor, the read only memory supplies a program se~uence which enables khe microprocessor to compute an appropriate di~lming signal.
.~
The microprocessor then transmits a gate source voltage slgnal to triac 50, which is thereby sufficientl~ delayed in phase to provide the appropriate current level to the high intensity discharge lamp 10. In this manner, the microproces50r con-trols the brightness level at which the lamp is operating.
The microprocessor used in thi~ invention may be any suitable s~andard model available. For example, one embodi-ment of this invention has been constructed using the Motorola MEK6800D2 evaluation k~t, including the MC6800 microproce~so~
unit. ~ sample program which has been used in this embodiment of the inven~ion is listed în Table ~. This program set~
the data lines to func~ion as outpu~ lines, readies the microprocessor to wait for an interrupt, and initializes the microprocessor registers.
LDA A ., I~
FF
STA A EXT Causes the data line on the B
side to function a~ outputs ~0 LDA A IMM Enables the interrupt by a low to high transition on the interrupt control line STA A EXT
LDS IMM Sets the stack pointer 30. FF
LDX IMM Clears the index register QO
CLI Clears the interrupt m~rk NOP
NOP Wait~ for the interrupt BRA
FC
The program in Table I is used in conjunction with an interrupt service routine, which is set out in Table II.
The interrupt routine delays the gate signal by a predeter~
mined incremellt of time with respect to the zero crossing of the line voltage, controls the gate signal pulse width, and readies the microprocessor to await another interrupt, TABLE I I
CLR A
STA A DIR Clears index register FC
STA A DI~
FD
LDA B EXT Clears the interrupt flag oE the PIA control register LDA B IMM
EF
AND B DI~
STA B EXT Clears the interrupt mask of the CCR
STA A DIR
FE
LDA A IMM
STA ~ DIR
FF
~TI
CPX DIR Compares the index register to memory location bo bo BNE REL
Fb : LDA A IMM
FF
STA A ~x~r Set~ the output lin~s Otl the B side INC ~XT
~$~
LU~ A IMM
Q5 Determines the gate signal pulse wid~h Sus A DIR
b2 ~NE
CLR A
STA A DIR
STA A ~XT Clears the output lines on the B side NOP
NOP Wai ts for an interrupt BRA
FC
A microprocessor is an e~specially advantageous addition to a lighting control system~ A single microprocessor is capable of controlling a large number of lamps individually, and thus a single microprocessor system, ~s here disclosed, may be used to control the entire lighting system for a large area,.t?r even to control an entire building's lighting systems. Furthermore, once such a system is installed, any alterations necessitated by changing lighting requirements can be incorporated very simply. To modify the control se-quence, a read only memory is programmed to meet the new requirements, and the newly proyramln`è~ read only memory simply replaces the memory unit previously installed in the system~ In this fashion, any changes, however extensive, can be readily incorporated into the lighting system. Thus, for example, if a building is remodeled, such a lighting sys-tem would not thereby be outdated. Once installed, the system remains easily adaptable to meét changint3 lit3hting needs, while conserving a ma~imum amount of energy anc3 thereby effectint3 savings in operatiny costs.
While particular embodiments of this invention have been shown and discussed, it will be understood that the inverltion is not limited thereto, since many modifications may be made and will become apparent to tho~e skilled in the art~
For example, although one zero cros5ing detecting cir-cuit has been illustrated, any number of other circuits which are capable of establishing a reference timing pulse from the AC power line can ~e used as well. For example, a phase-locked-loop can be locked to the line frequency and used to provide timing pulses.
It should also be noted that many other inputs may be provided to the microprocessor or obtaining the desired con-trol of lighting in a given situation. In some areas, for example, electric utility users are subject to a demand pen-alty, which imposes a hiyher rate for electricity when the user's consumption of electricity exceeds a certain rate.
In such a situation, the microproces50r could be programmec]
to monitor electrical consumption and automatically reduce lighting levels should tha~ consumption approach the penalty rate.
Claims (21)
1. A high intensity gas discharge lamp control system, including a ballast means connected to a lamp and a reactor portion of said ballast means, comprising:
a gated bypass means for bypassing the reactor portion;
a detector which senses each zero voltage crossing point of the AC power connected to the lamp;
and a digital processor synchronized by the detector, said digital processor providing a phase delayed lamp control signal to the gated bypass means.
a gated bypass means for bypassing the reactor portion;
a detector which senses each zero voltage crossing point of the AC power connected to the lamp;
and a digital processor synchronized by the detector, said digital processor providing a phase delayed lamp control signal to the gated bypass means.
2. The lamp control system of Claim 1, in which the gated bypass means comprises a triac, the gate terminal of said triac receiving the phase delayed lamp control signal.
3. The lamp control system of Claim 1 or 2, in which the detector comprises a Schmitt trigger monostable multivibrator.
4. The lamp control system of Claim 1, in which the digital processor comprises a programmable microprocessor.
5. The lamp control system of Claim 4, in which the micro-processor is operably connected to a read only memory, said memory providing a sequence of program instructions for the microprocessor.
6. The lamp control system of Claim 5, in which the micro-processor may be reprogrammed by replacing said read only memory.
7. The lamp control system of Claim 5, in which the micro-processor adjusts the lamp control signal in accordance with one or more control inputs.
8. The lamp control system of Claim 7, in which one of said control inputs comprises a manual override control.
9. The lamp control system of Claim 7, in which one of the control inputs comprises a light sensitive device.
10. The lamp control system of Claim 7, 8 or 9, in which one of the control inputs comprises a daily time.
11. A high intensity gas discharge lighting control system, including a plurality of lamps, a ballast means connected to each lamp, and a reactor portion of each ballast means, com-prising:
a gated bypass means for bypassing each reactor portion;
a detector which senses each zero voltage crossing point of the AC power connected to the lamp; and a digital processor synchronized by the detector, said digital processor providing a phase delayed lamp control signal to the gated bypass means.
a gated bypass means for bypassing each reactor portion;
a detector which senses each zero voltage crossing point of the AC power connected to the lamp; and a digital processor synchronized by the detector, said digital processor providing a phase delayed lamp control signal to the gated bypass means.
12. The lighting control system of Claim 11, in which the digital processor provides an independently variable control signal to each gated bypass means.
13. The lamp control system of Claim 11 or 12, in which each gated bypass means comprises a triac, the gate terminal of each said triac receiving a phase delayed lamp control signal.
14. The lamp control system of Claim 11 or 12, in which the detector comprises a Schmitt trigger monostable multivibrator.
15. The lamp control system of Claim 11, in which the digital processor comprises a programmable microprocessor.
16. The lamp control system of Claim 15, in which the micro-processor is operably connected to a read only memory, said memory providing a sequence of program instructions for the microprocessor.
17. The lamp control system of Claim 16, in which the micro-processor may be reprogrammed by replacing said read only memory.
18. The lamp control system of Claim 16, in which the micro-processor adjusts the lamp control signals in accordance with one or more control inputs.
19. The lamp control system of Claim 18, in which one of said control inputs comprises a manual override control.
20. The lamp control system of Claim 18 or 19, in which one of the control inputs comprises a light sensitive device.
21. The lamp control system of Claim 18 or 19, in which one of the control inputs comprises a daily timer,
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US89233778A | 1978-03-31 | 1978-03-31 | |
| US892,337 | 1978-03-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1112295A true CA1112295A (en) | 1981-11-10 |
Family
ID=25399810
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA322,439A Expired CA1112295A (en) | 1978-03-31 | 1979-02-26 | Programmable lighting control system |
Country Status (8)
| Country | Link |
|---|---|
| AU (1) | AU525248B2 (en) |
| BE (1) | BE875029A (en) |
| CA (1) | CA1112295A (en) |
| DE (1) | DE2912690A1 (en) |
| ES (1) | ES479083A1 (en) |
| FR (1) | FR2421530A1 (en) |
| GB (1) | GB2018532B (en) |
| IT (1) | IT1113336B (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4287455A (en) * | 1979-12-18 | 1981-09-01 | Erin Engineering (Ontario) Ltd. | Power saving circuit for gaseous discharge lamps |
| EP0046395B1 (en) * | 1980-08-18 | 1985-02-13 | THE GENERAL ELECTRIC COMPANY, p.l.c. | Dimming system for electric discharge lamps |
| AU8929682A (en) * | 1982-01-11 | 1983-07-21 | Cornell-Dubilier Electronics Inc. | Magnetic ballast with thyristor control |
| GB2117192B (en) * | 1982-02-26 | 1986-01-02 | Transtar Limited | Lamp control circuit |
| GB2145587B (en) * | 1983-08-25 | 1987-06-10 | Lutron Electronics Co | Gas discharging lamp dimming system |
| DE3524681A1 (en) * | 1985-07-11 | 1987-01-22 | Trilux Lenze Gmbh & Co Kg | DIMMER SWITCH FOR AN ELECTRONIC FLUORESCENT LAMP CONTROLLER |
| US5078039A (en) * | 1988-09-06 | 1992-01-07 | Lightwave Research | Microprocessor controlled lamp flashing system with cooldown protection |
| CN1162055C (en) * | 1996-10-24 | 2004-08-11 | 恩康股份有限公司 | A power control apparatus for lighting system |
| DE19842761C2 (en) * | 1998-09-18 | 2003-04-17 | Oekolux Gmbh | Process for daylight-dependent dimming of multi-flame luminaires |
| EP1107651A3 (en) * | 1999-12-10 | 2004-12-08 | Otto Diez Elektromaschinenbau | Device with a discharge lamp |
| KR100413216B1 (en) * | 2001-04-06 | 2003-12-31 | 원 호 이 | Apparatus for regulating intensity of illumination |
| JP4115715B2 (en) * | 2002-03-01 | 2008-07-09 | シャープ株式会社 | Backlight device |
| GB2393859A (en) * | 2002-08-22 | 2004-04-07 | Traypoint Ltd | Dimmable lighting |
| DE102006059389A1 (en) * | 2006-12-15 | 2008-06-19 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | Half-night circuit interface for an electronic ballast |
| AU2007357498B2 (en) * | 2007-08-03 | 2013-11-21 | Osram Ag | Method for programming electronic operating devices for discharge lamps and electronic operating device for discharge lamps |
| CN210075638U (en) * | 2019-01-28 | 2020-02-14 | 深圳市鸿远微思电子有限公司 | Application device of LED dimmer combined with reactor |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1024584A (en) * | 1972-03-28 | 1978-01-17 | Carl R. Snyder | High intensity, gas discharge lamp dimmer |
| US4058752A (en) * | 1976-09-09 | 1977-11-15 | Gte Sylvania Incorporated | Dosimetry control method |
-
1979
- 1979-02-26 CA CA322,439A patent/CA1112295A/en not_active Expired
- 1979-03-22 GB GB7910077A patent/GB2018532B/en not_active Expired
- 1979-03-22 AU AU45332/79A patent/AU525248B2/en not_active Ceased
- 1979-03-22 BE BE0/194162A patent/BE875029A/en not_active IP Right Cessation
- 1979-03-27 FR FR7908561A patent/FR2421530A1/en not_active Withdrawn
- 1979-03-29 IT IT21416/79A patent/IT1113336B/en active
- 1979-03-30 ES ES479083A patent/ES479083A1/en not_active Expired
- 1979-03-30 DE DE19792912690 patent/DE2912690A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| IT1113336B (en) | 1986-01-20 |
| GB2018532B (en) | 1982-06-03 |
| BE875029A (en) | 1979-07-16 |
| IT7921416A0 (en) | 1979-03-29 |
| DE2912690A1 (en) | 1979-10-04 |
| ES479083A1 (en) | 1979-11-16 |
| AU525248B2 (en) | 1982-10-28 |
| AU4533279A (en) | 1979-10-04 |
| FR2421530A1 (en) | 1979-10-26 |
| GB2018532A (en) | 1979-10-17 |
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