CA1338476C - Photoelectric control unit - Google Patents
Photoelectric control unitInfo
- Publication number
- CA1338476C CA1338476C CA000564648A CA564648A CA1338476C CA 1338476 C CA1338476 C CA 1338476C CA 000564648 A CA000564648 A CA 000564648A CA 564648 A CA564648 A CA 564648A CA 1338476 C CA1338476 C CA 1338476C
- Authority
- CA
- Canada
- Prior art keywords
- triac
- controller
- relay
- control unit
- chamber
- 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 - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V23/00—Arrangement of electric circuit elements in or on lighting devices
- F21V23/04—Arrangement of electric circuit elements in or on lighting devices the elements being switches
-
- 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
- H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
- H05B47/10—Controlling the light source
- H05B47/105—Controlling the light source in response to determined parameters
- H05B47/11—Controlling the light source in response to determined parameters by determining the brightness or colour temperature of ambient light
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
Abstract
A photoelectric control unit for street lighting comprises control means including a photoelectric sensor mounted on a printed circuit board for switching on a street lamp when the intensity of light falling on the sensor falls below a preset value. Electrical connection means between the P.C.B. and the lamp is provided by three connector pins which are led through a cooling chamber or stem. The pins are cranked to closely follow the contour of the chamber to dissipate heat through the chamber walls. The chamber is also filled with a high thermal conductivity potting compound for heat transfer to the walls of the chamber. One controller for such a photoelectric control unit includes a switching means provided by a relay and a triac connected in parallel.
The triac operates to prevent the relay being subjected to high voltages during switching and hence prevents pitting of the relay contacts.
The triac operates to prevent the relay being subjected to high voltages during switching and hence prevents pitting of the relay contacts.
Description
1 33847~
Back.4.~ld of the In~ention Field of the Invention The invention relates to a photoelectric control unit for - 8 - l:ighting circuit such as a street lighting circuit.
~ 5 More particularly, the invention relates to a controller for such a photoelectric control unit.
De~criPtion of Prior Art In general, street lamps are operated by photoelectric control units comprising a photoelectric sensor and a load switching means. The control unit switches on the lamp when the intensity of incident light falling on the photo-electric sensor is below a pre-set value and switches off the lamp when the intensity of the light is above another pre-set value. Such control units are generally connected to a lamp through connector pins. Heat is generated in these connector pins directly by the current carried by the pins and indirectly by the heat from the lamp. This heat may cause mal-functioning of the control unit which greatly reduces the useful life of such units. One such unit is described in British Patent Specification No.
1,110,263. ~
., , ~ ~ The controllers for lighting control units wbich ~re presently ~vailable are either electro-mech~nical, ellectronic or a combination of both. Electro-mechanical units s~itch power to a load by opening or closing a pair of hea~y duty electrical contacts. Generally the line voltage has a peak value of over 310 volts which causes arc~ng across the contacts as they open and cllDse. The arcing in turn causes pitting of the contact surfaces resulting in a short useful life-span for the ~ontroller.
A Further problem with conventional controllers is that in time, the light-level threshold can drift outside the specified limits due to drift of the threshold reference value and changec in the characteristics of the light detectina sensor which is normally a liaht dependent resistor or LDR. Conventional units employ a thermal switching technique where the LDR
controls the current through, and thus, the temperature of a hi-metallic strip. The threshold point is determined by the force required from the thermal strip to change ov~er spring loaded electrical contacts. The characteris-tics of the spring load as well as those of the bi-metallic strip change with time and this causes the accuracy of the unit to drift outside the accepta61e limits. Also. the LDR is reauired to conduct large currents to heat the ~i-metallic strip and tbe res-ulting self-heating effect causes the LDR to change its characteristics over a period. The LDR units commonly ., .
4 _ used~ in existing controllers gradually break down allowing moisture and impurities to affect the selenium cell. This combined with temperature rise in - the device contributes to further drit of the light level s threshold.
Objects of the Invention - This invention is directed towards providing a photo-electric control unit for a lighting circuit which will have a long useful life.
The invention is also directed towards providing a controller for a photoelectric control unit which will minimise pittina of the contact surface and hence pro-long the useful life of the unit.
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,,,/' ~` ~
- 6 ~ l 3 3 8 ~ 7 ~
As embodied and broadly described herein, the invention provides a controller for a photoelectric control unit, the controller comprising a photoelectric sensor, comparing means for comparing the intensity of sensed light with preset light intensity and switching means operated by the comparing means to switch a lamp, said switching means comprising a relay and a triac, in which the relay contacts and the triac are electrically connected in parallel.
In one embodiment, the lamp is a street lamp.
On switching of the switch, the relay conducts at low voltages and the triac conducts at high voltages.
_ 7 _ 1 3 3 8 47 6 In one embodiment of the in~ention the photoelectric sensor comprises a light sensitive resistor whose resistance decreases with the intensity of incident light.
Preferably the controller includes a capacitor which is charged when the triac operates to keep the relay closed for a short p-eriod to ensure continuous condition.
In a.nother preferred embodiment of the in~ention the photoelectric sensor comprises a phototransistor.
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-1 ' -7(a)-Advcmtaqe~3 of the Invention 1 3 3 8 4 7 6 The-advantage of using a relay and triac combination in the controller to switch the controller greatly increases the useful life and reliability of the controller.
These and other objects and advantages of the invention ~ill be readily apparent from the following description of some preferred embodiments of the invention which are given by way of example only with reference to the accompanying drawings.
- ~ , . ,2 .
~ -8- 1 33 8 47b Brief Descript~on of the Drawings Fig. 1 is an exploded perspective view of a photo electric control unit according to the invention, Fi~. 2 isa perspective view of the photoelec~ric control unit of Fig. 1, ~ssembled, Fig. 3 is a diagrammatic side view illustrating the unit of Figs. 1 and 2 in use, Fig. 4 is a side, partially cross-sectional view of the control unit of Figs. 1 and 2, Fi~. 5 is a perspective view from above of a port-ion of the control unit, Fig. 6 is 2 perspective view of a socket housing attachment for use with the control unit o~ Figs.
1 and 2, 1~ Fig. 7 is a perspect~ve Yiew of a control unit with the housing of Fig. 6 attached, Fig. 8 is a side cross-sectional view of the control unit with the housing attached, and Fig. 9 is a circuit diagram of a controller for a photoelectric control unit, Detcliled DescriPtion Referring to the drawings and initially to Figs. 1 to 5 thereof there is illustrated a photoelectric control unit according to the invention and indicated generally by the re~erence numeral 1. The control unit 1 comprises control means, in this case mounted on a printed circuit board 2 . ,. . =
.. .. .
~or switching ~nd cutput. ln this c~se ~ street lamp 3.
~he cont-rol me~ns as ~ill be described in more deta11 below.
includes ~ photoelectric sensor which causes power to the lamp 3 to be switched on when the ~mount of light falling S on the s@nsor exceeds a pre-5et ~alue, ln this case 55 lux.
The sensor is mounted on the pr1nted circuit board 2 and ~lectrical connection means between the printed circuit board and the lamp 3 is pro~ided by three connector pins 4 which are shaped at their lower ends 5 to engage in a - 10 twis~-socket provided o~l the lamp 3. The connector pins 4 are connected at their upper end 6 to connection points (not shown) on the printed circuit board through flexible connectin9 wires 7- The conn~ctions betw~een the connector pins 4 and printed circuit board 2 are capable of with-st~nding vibrations andJor shudder which would normallybe enco~ntered in use with street l~nterns.
To prevent overheating of the connector pins 4 and con-sequent malfunctior,ing and possible damage to the electrical co~poner~ts mounted on the printed circuit board 2 the pins 4 care led through ~ coolins means in the form of a ste~
which in this case is defined by a cooling chamber 8 where heat geller~ted in the pins ~ is dissipated throush the walls of the chamber 8.
Referring particularly to Fig. 5 the cooling chamber 8 25 comprises a cylindrical side-wall 10 and a disc-shaped base wall 11 which extends radially outwardly of the side wall 10.
A skir~ 12 extends axially downwardly from the outer extremity .., 1 33847~
of the base wall 11. ~he base wall ll 1s formed ~lth three ha,les 13 which are equ~sp~ced ~p~rt at 120 and through which the connector p~ns 4 ~re led. As will be apparent. particulerly from Fig. 1 e~c~ of the connector pins 5 4 is cranked at 15 and 16 to deflne an axially depending leg porl'ion 17, an interconnected radial at base wall portion 18 and an axially extending side wall portion 19. Each of the pin~s 4 is retained in posltion in a retaining hole 14 by a slelf tapping screw 21 which extends through the hole 14 10 to engase in a corr~5ponding hole 22 in the base wall extending portion 18 of each connector pin 4. The connector pins 4 which are sized and shaped so that a large sur~ace area of the connector pins 4 is in contact with the side and basE walls 10, 11 of the cooling chamber.
Conseq~ently heat generated in the connector pins 4 is dissipc-ed throu~h the walls of the chamber 8. To assist heat transfer the cooling cha~ber & is also substantially fille~ with a heat transfer medium, in this case in the form of a p~ttins co~ipouna 2~ which conducts heat away from the pins ~ and intc the side and bas~ walls 10, 11 of the cooling cha~,be r 8. The pottir,g compound used may be any suitable encapsulating compound hzving a high thermzl conductiYity such as a Humiseal 2B74 l 338476 A se~li;ng ring gasket 27 which 1s usu~lly of neoprene materie~l ls provided on the bate wall ll of the cooling chamber 8 to prevent ingress of moisture and dirt throush the joiint between the cooling chamber skirt 12 and the _ 5 socket provided on the lantern 3.
-_ It ~ill be appreciated that the cooling chamber defines - a stem which both ra1ses the assembly from the hot parts of the lantern and minimises the heat carried by the ~onnec~ors to the e7ectronic components mounted on the printed circuit board. In tests, in which the control unit was mounted on a 40Q watt lantern at room temperature, the use of the cooling thamber was found to reduce the temp-erature of the cor,nector pins at the PC~ connection points by up to 10 which represents a large improvement in re7iability.
It h'i ll also be appreciated that the control unit may be used to control the operation of one or a plurality of street lamps or for controlling the operation of any out-side lightina systems.
-~2- 1 338476 ~he pr~nted circuit bo~rd 2 ls mounted 1n ~ printed circuit board houslng 30 which comprises a substant1011y d1sc-shapet basle 31 ~nd a cyllndrtc~l s1de wall 32 extendtng axially upwardly from the b~se 31. Three connector ptn receiving slots 33. equi-spaced at 120 , extend through the t base 31. Three screw receiving plllars 34 extend upwardly from the base 31 adiacent to side wall ~2 and are also equi-spaced at 120 around the housing. Each of the pillars 34 i5 formed ~ith a hole 35 for reception of a self-tappinS 5crew 36 which extends throùgh corre;ponding holes ~7 in printed circuit board 2 for mounting the board 2 to the pillars 34. Reinforcing web5 38 extend bet~een each pillar 34 and the side wall 32.
The upper rim of the circuit board housing side wall 32 is formed wit.h a step portion 39 for receptior, of a comple-mentary st.ep portion 40 which exten~s ~round the lowerperipherY of a translucent conical cover 41 through which light passes to the photoelectric sensor cn the printed circuit board 2. llhe canopy or cover 41 is cf conical shape to prevent accumulation of dirt and also discouraae birds fro~.
perching on the cover. The coYer is typically of a plastics material ~hich is treated to protect against ultra-violet light. For fitting the printed circuit board housing 30 and coolins chamber 8 together the housing 30 is formed with a socket which in this case ~s defined by a skirt 45 which extends axially down~ardty approximately mid-way across the base for reception of a spigot defined by the upper edge of the side wall 10 of the cooling chamber 8.
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~o prevent lngres5 o~ dlrt ~nd mo15ture, the component p~rts ol' the control unit are 5ecurely ~1xed together and the unit ls then coated with ~ se~l1ng compound to provite additional tefens~ve measures against molsture and _5 dirt in~gress. -- One ~tvantage of the invention is th~t the connection ~ means between the control mean5 and the oùtput is arranged to dissipate any heat generated and hence protect the comp-onents o~ the control means. ~hus, a mor~ efficient and reliable switch which has a long life in use is pro~ided.
Referring to Figs. 6 to 8 there is illustrated a modified photGelectric control unit which is similar to that des-cribed above with reference to Figs. l to 5 and like p~rts are assigned the same r~ference nu~,erals. In this c2se the unit includes an electrical socket receiving housing 50 for housing an output socket 51 Which is connected at one end to the connector pins 4 and Which is connected through an outlet cable 52 to the output w~.ich it is desired to switc~, such ~s a street or security lantern. The hGusing 50 ir,c:ludes an upper radial wall 53 and an axially upwardty extending side wall portion 54 Which defines ~ spigot for insertion in the socket defined by the skirt 12 of the cooling chamber 8. A lower cylindrical side wall portion 55 extends downwardly from ~he upper wall 53 of the housing 50.
The lower side wall portion 53 of the housing 50. The lower side wall portion 55 is turned inwardly to define a base wall 56 having a central opening 57 through which the elec-trical connection le~d 5Z is le~d ~rom t~e s5cket 51 ~or connection- to an output- ~he s~cket 51 i5 carr~ed by a mounting plate 60 which is fixed in ~osition by self-tapping screws 61 which engage in corre5ponding 5crew S receiving portion5 62 which extend downwardly from the upper wal~ 53. ~he sealing ring gasket 27 seals the joint between- the cooling chamber skirt 12 and the socket rec-eiving housing ~0.
Mounting means for mounting the control unit on a fixture 10 such as a wall is in this case provided by a mounting flange 65 which is connected to the socket receiving housing side wall 55 by a connecting web 66. The flange 6~ is formed with two axially extendlng slots 67 for ease of mounting to a fixture. ~he particular advantage of 15 the control unit for 2i photoelectric switch according to this em~odiement of the invention is that by using the electri c2il soc~et receiYing housing 2 ttachment 50, the control unit ~ay be used in a wide range of applications includinc, security lighting and in other applications where 20 it ~2y be necessary to ~,ount the ccntrol unit on a fixture such as d w211 rather than directly on a lar,tern.
~ _15_ 1 338476 Referring to F~g. 9 there 1S 111u5trated ~ circu~t diag-ram of -a controller for use with a photoelectr~c sw~tch such as the photoelectr~c switch descr1~ed above with re~erence to F~gs. l to 8. ~he function of the controller _ 5 iS to ~5witch ~ower to a lantern according to the surround-ing brightness. The controller comprises a photoelectric _ sen5~r. comparing means for comparing the ~ntensity of ~ sensed light with a preset light intensity and switching means operated by the comparing means to switch an output.
The photoelectric sensor is in this case provided by a light dependent resistor (LDR) which is used to monitor the lisht level ~nd at s~ecific threshold limits either to close or open the shitCh~ The threshold limits are set to the requirements of the particular user.
The switching means is ir. this case provided by a relay RLl and a triac TRIl connected in parallel. ~'hen it is required to switch the load th~ triac TRIl is engaged and t~;is is followed a short time later by closure of the relay contacts RLl. In this ~ay the r~lay RLl jc not sub-2Q jected to high voltages during the switching action andthe triaC TRIl is not given enough time to heat. When the load is to be switched out the relay RLl is dis-engaged and this is followed a short time later by the switclhing off of the triac TRIl. Again the relay RLl is removed from the ~ircuit while the triac TRIl is hold-ing the Yoltage atalow level and the triac TRIl i5 not B
gi~en enough time to he~t. ln both o~ thP aboYe c~ses the triac ~RIl ~ eose tc ~ndu~t when the relay RLl shorts it out.
The ciircuit operates as follows. A transformer TRFl converts incomi~g 220Vrms (nom) to 24Vrms (nom) and this lower AC voltage is rectified by a bridge consisting of diodes Dl to D4. Capacitor Cl i 5 smoothing capacitor.
24Vdc- is the supply to the re~ainder of the circuitry.
A cent;re tap provided on the transformer TRFl enables llOVrms (nom) supply to be used.
The LDR resistance is monitored by an operational amp-lifier Al through a delay circuit consisting of a ~apac-itor C2 and a resistor RZ. This delay, of approximately 30 seconds. prevents abrupt changes in the value of the LDR recching hl. The operational ampli~ier is used in tt.e comparator ~ode and it co~pares the voltage level on th~ capacitor C2 with a threshold Yalue which is det-ermined by resistors R3, R9 and R6. Resistors R3 and R9 ~orm ¢ potential divider and resistor R6 provides hys-teresis. ~his is to preYent unwanted oscillation duringthe switching action. Threshold calibration is possitle by s~lecting value for Rsot that will cause the unit to switc.h at the correct light levei. FQr high reliability the voltage across the op-amp must be held at a value less than the maximum rating o~ the device. The op-amp 1s rated ~or 36Y, but a voltage of 12Y which is provided by a transistor Ql isused. A 2ener diode CRl and a resi!,tor R10 hold the base voltage on the transistor Ql .
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- 1 3~8~ ~, 1 7 12V below rail result~n~ ln ~n em1tter voltage which is approximately 11.4V below r~ he trans1stor Ql ~lso actS as a regulator, further reduc~ng the possib-i 1 i ty of osc~ tory sw~ tchi ng .
TransistorS Q4 and Q5 ~llow the output of op-~mp Al to _ sw~tch the relay and the triac. A 2ener dlode CR2 is - used to ensure thatthe transistors Q4 and Q5 are swi tched of ~ whlen the op-amp output is 'high'. The LM301 output is unz~ble to come within 1.5 volts of th~ rail v~lJe 10 and woul d not, therefore, be abl e to swi tch off the transilstorS Q4 and Q5. The zener diodes overcome this.
During darkness th~ voltage on pin 2 of the op-amp is low and the op-2mp output is high. Therefore transistorS Q4 ~nd Q5 are switched off during the night and on during the day.
The triac TRIl is shitched through transistors Q4, Q8 and Q9. The trar.sistor Q8 is disabled when the trans-istor Q4 is turned on beca~se its base is held at tne emitt:er voltage. ~'hen the triac TRIl is to be turned on the t:ransistor Q4 ceases to cor,duct allo~ing negative goin~3 pulses from a mains cycle crosso~er detector, con-sisting of two transistors Q6 and Q7, to influence th~
transistor Q8. These pulses occur when the mains sine wave is close to zero volts and cause the transistor Q8 to quickly charge up capacitor C6 throu~h the resis--18- 1 33847b istor IRZ2. The Yclt~ge ~t the b~se of the translst~r Q9 then blecomes hi9h enough to 5wltch on the triac TRil.
The resistor RZ4 whlch i5 connected between the gate of the tr~ac ~RIl and the emltter of the translstor Q9 serves to timit the current through the tr~nslstor Q9 to a rel-iable level. The resistor R22 also lim~ts the peak currentthraugh the transistor Q8 to ~ reliable level. ~'hen the triac rRIl is to be switchedoff the tr~nsistor Q4 starts conductingthus disabling the transistor Q8. The voltage on the ba!;e of the transistor Q9 now begins to decrease as the energy on the capacitor C6 is discharged through the resistor R23. After a time delay the voltage on the transistOr Q9 base will be too low to maintain the triac lRIl in conduction. ~hi5 time delay is needed for the triac/relay sequencing function and it provides 20 sufficient time to allow the relay to disengage ~efore the load voltage increases.
For increased reliability and to reduce radio inter-ference the triac TRIl is switched durin~ the mains zero crossover points. Th~se ~re detected by means of transistors Q6 ~nd Q7. The m2ins is sampled through a resistor R20 and lirr,ited by a zener diode CR3 and a diode D9. The resulting waveform that arrives at the base of the trans-;stor Q6 is approximately square and is further squared by the transistor Q6~ A differentiator network consistirlg of a c;ipacitor C3 and a resistor R14 proYides a negative going pulse e~ch ttme the ~olt~ge on the collector of the tr~nslstor Q6 makes the tr~ns~t10n from ra~l to ground. Thls tr~nstt10n represents the zero cross point when the maln cycle 1s going from negative to _5 positive. In a-s~mil~r manner the trans~stor Q7, capacitor C4 ~nd res~stor Rl6 will ~enerate a pulse during the - posi~ive to negatl~e mains cycle transition. Diodes D7 ~ and D8 ensure that only the negative gcing pulses are transmitted to the base o~ the tran~istor Q8.
~he relay RLl is operated throu~h transistors Q5 and QlO.
The relay RLl is of the normally on type and when the base voltage of the transistor ~lO is low the switch will be closed. ~'hen the relay RLl is to be enga~ed the transistor Q5 will cease to conduct. The volta~e on the capacitor C~ will then begin to decrease as it is disch~rged through the resistor Rl2. After a delay dictated by the capzcitor C5 and the resistor Rl2 the base voltage of the transistor QlO will go below the minimum holding value for the relay RLt and the relay contacts close. This delay is needed to allow the tri~c, TRIl which is being switc~,ed simul-taneously, tim~ to reduce the voltage across the relay contacts to an acc~ptable level. This is part of the triaclrelay sequencing function. When the relay RLl is to be disengaged (at morning) the transistor Q5 again conducts, chargins up the capacitor C5 quickly. The relay RLl i!i then opened quickly before the triac TRIl is dis^
engagl~d, thus protect~ ng the swi tch contacts . Diodes DS ~nd D6 protect the transistor Q10 from the back c~& that normally
Back.4.~ld of the In~ention Field of the Invention The invention relates to a photoelectric control unit for - 8 - l:ighting circuit such as a street lighting circuit.
~ 5 More particularly, the invention relates to a controller for such a photoelectric control unit.
De~criPtion of Prior Art In general, street lamps are operated by photoelectric control units comprising a photoelectric sensor and a load switching means. The control unit switches on the lamp when the intensity of incident light falling on the photo-electric sensor is below a pre-set value and switches off the lamp when the intensity of the light is above another pre-set value. Such control units are generally connected to a lamp through connector pins. Heat is generated in these connector pins directly by the current carried by the pins and indirectly by the heat from the lamp. This heat may cause mal-functioning of the control unit which greatly reduces the useful life of such units. One such unit is described in British Patent Specification No.
1,110,263. ~
., , ~ ~ The controllers for lighting control units wbich ~re presently ~vailable are either electro-mech~nical, ellectronic or a combination of both. Electro-mechanical units s~itch power to a load by opening or closing a pair of hea~y duty electrical contacts. Generally the line voltage has a peak value of over 310 volts which causes arc~ng across the contacts as they open and cllDse. The arcing in turn causes pitting of the contact surfaces resulting in a short useful life-span for the ~ontroller.
A Further problem with conventional controllers is that in time, the light-level threshold can drift outside the specified limits due to drift of the threshold reference value and changec in the characteristics of the light detectina sensor which is normally a liaht dependent resistor or LDR. Conventional units employ a thermal switching technique where the LDR
controls the current through, and thus, the temperature of a hi-metallic strip. The threshold point is determined by the force required from the thermal strip to change ov~er spring loaded electrical contacts. The characteris-tics of the spring load as well as those of the bi-metallic strip change with time and this causes the accuracy of the unit to drift outside the accepta61e limits. Also. the LDR is reauired to conduct large currents to heat the ~i-metallic strip and tbe res-ulting self-heating effect causes the LDR to change its characteristics over a period. The LDR units commonly ., .
4 _ used~ in existing controllers gradually break down allowing moisture and impurities to affect the selenium cell. This combined with temperature rise in - the device contributes to further drit of the light level s threshold.
Objects of the Invention - This invention is directed towards providing a photo-electric control unit for a lighting circuit which will have a long useful life.
The invention is also directed towards providing a controller for a photoelectric control unit which will minimise pittina of the contact surface and hence pro-long the useful life of the unit.
/''~
/
/
,,,/' ~` ~
- 6 ~ l 3 3 8 ~ 7 ~
As embodied and broadly described herein, the invention provides a controller for a photoelectric control unit, the controller comprising a photoelectric sensor, comparing means for comparing the intensity of sensed light with preset light intensity and switching means operated by the comparing means to switch a lamp, said switching means comprising a relay and a triac, in which the relay contacts and the triac are electrically connected in parallel.
In one embodiment, the lamp is a street lamp.
On switching of the switch, the relay conducts at low voltages and the triac conducts at high voltages.
_ 7 _ 1 3 3 8 47 6 In one embodiment of the in~ention the photoelectric sensor comprises a light sensitive resistor whose resistance decreases with the intensity of incident light.
Preferably the controller includes a capacitor which is charged when the triac operates to keep the relay closed for a short p-eriod to ensure continuous condition.
In a.nother preferred embodiment of the in~ention the photoelectric sensor comprises a phototransistor.
/
-1 ' -7(a)-Advcmtaqe~3 of the Invention 1 3 3 8 4 7 6 The-advantage of using a relay and triac combination in the controller to switch the controller greatly increases the useful life and reliability of the controller.
These and other objects and advantages of the invention ~ill be readily apparent from the following description of some preferred embodiments of the invention which are given by way of example only with reference to the accompanying drawings.
- ~ , . ,2 .
~ -8- 1 33 8 47b Brief Descript~on of the Drawings Fig. 1 is an exploded perspective view of a photo electric control unit according to the invention, Fi~. 2 isa perspective view of the photoelec~ric control unit of Fig. 1, ~ssembled, Fig. 3 is a diagrammatic side view illustrating the unit of Figs. 1 and 2 in use, Fig. 4 is a side, partially cross-sectional view of the control unit of Figs. 1 and 2, Fi~. 5 is a perspective view from above of a port-ion of the control unit, Fig. 6 is 2 perspective view of a socket housing attachment for use with the control unit o~ Figs.
1 and 2, 1~ Fig. 7 is a perspect~ve Yiew of a control unit with the housing of Fig. 6 attached, Fig. 8 is a side cross-sectional view of the control unit with the housing attached, and Fig. 9 is a circuit diagram of a controller for a photoelectric control unit, Detcliled DescriPtion Referring to the drawings and initially to Figs. 1 to 5 thereof there is illustrated a photoelectric control unit according to the invention and indicated generally by the re~erence numeral 1. The control unit 1 comprises control means, in this case mounted on a printed circuit board 2 . ,. . =
.. .. .
~or switching ~nd cutput. ln this c~se ~ street lamp 3.
~he cont-rol me~ns as ~ill be described in more deta11 below.
includes ~ photoelectric sensor which causes power to the lamp 3 to be switched on when the ~mount of light falling S on the s@nsor exceeds a pre-5et ~alue, ln this case 55 lux.
The sensor is mounted on the pr1nted circuit board 2 and ~lectrical connection means between the printed circuit board and the lamp 3 is pro~ided by three connector pins 4 which are shaped at their lower ends 5 to engage in a - 10 twis~-socket provided o~l the lamp 3. The connector pins 4 are connected at their upper end 6 to connection points (not shown) on the printed circuit board through flexible connectin9 wires 7- The conn~ctions betw~een the connector pins 4 and printed circuit board 2 are capable of with-st~nding vibrations andJor shudder which would normallybe enco~ntered in use with street l~nterns.
To prevent overheating of the connector pins 4 and con-sequent malfunctior,ing and possible damage to the electrical co~poner~ts mounted on the printed circuit board 2 the pins 4 care led through ~ coolins means in the form of a ste~
which in this case is defined by a cooling chamber 8 where heat geller~ted in the pins ~ is dissipated throush the walls of the chamber 8.
Referring particularly to Fig. 5 the cooling chamber 8 25 comprises a cylindrical side-wall 10 and a disc-shaped base wall 11 which extends radially outwardly of the side wall 10.
A skir~ 12 extends axially downwardly from the outer extremity .., 1 33847~
of the base wall 11. ~he base wall ll 1s formed ~lth three ha,les 13 which are equ~sp~ced ~p~rt at 120 and through which the connector p~ns 4 ~re led. As will be apparent. particulerly from Fig. 1 e~c~ of the connector pins 5 4 is cranked at 15 and 16 to deflne an axially depending leg porl'ion 17, an interconnected radial at base wall portion 18 and an axially extending side wall portion 19. Each of the pin~s 4 is retained in posltion in a retaining hole 14 by a slelf tapping screw 21 which extends through the hole 14 10 to engase in a corr~5ponding hole 22 in the base wall extending portion 18 of each connector pin 4. The connector pins 4 which are sized and shaped so that a large sur~ace area of the connector pins 4 is in contact with the side and basE walls 10, 11 of the cooling chamber.
Conseq~ently heat generated in the connector pins 4 is dissipc-ed throu~h the walls of the chamber 8. To assist heat transfer the cooling cha~ber & is also substantially fille~ with a heat transfer medium, in this case in the form of a p~ttins co~ipouna 2~ which conducts heat away from the pins ~ and intc the side and bas~ walls 10, 11 of the cooling cha~,be r 8. The pottir,g compound used may be any suitable encapsulating compound hzving a high thermzl conductiYity such as a Humiseal 2B74 l 338476 A se~li;ng ring gasket 27 which 1s usu~lly of neoprene materie~l ls provided on the bate wall ll of the cooling chamber 8 to prevent ingress of moisture and dirt throush the joiint between the cooling chamber skirt 12 and the _ 5 socket provided on the lantern 3.
-_ It ~ill be appreciated that the cooling chamber defines - a stem which both ra1ses the assembly from the hot parts of the lantern and minimises the heat carried by the ~onnec~ors to the e7ectronic components mounted on the printed circuit board. In tests, in which the control unit was mounted on a 40Q watt lantern at room temperature, the use of the cooling thamber was found to reduce the temp-erature of the cor,nector pins at the PC~ connection points by up to 10 which represents a large improvement in re7iability.
It h'i ll also be appreciated that the control unit may be used to control the operation of one or a plurality of street lamps or for controlling the operation of any out-side lightina systems.
-~2- 1 338476 ~he pr~nted circuit bo~rd 2 ls mounted 1n ~ printed circuit board houslng 30 which comprises a substant1011y d1sc-shapet basle 31 ~nd a cyllndrtc~l s1de wall 32 extendtng axially upwardly from the b~se 31. Three connector ptn receiving slots 33. equi-spaced at 120 , extend through the t base 31. Three screw receiving plllars 34 extend upwardly from the base 31 adiacent to side wall ~2 and are also equi-spaced at 120 around the housing. Each of the pillars 34 i5 formed ~ith a hole 35 for reception of a self-tappinS 5crew 36 which extends throùgh corre;ponding holes ~7 in printed circuit board 2 for mounting the board 2 to the pillars 34. Reinforcing web5 38 extend bet~een each pillar 34 and the side wall 32.
The upper rim of the circuit board housing side wall 32 is formed wit.h a step portion 39 for receptior, of a comple-mentary st.ep portion 40 which exten~s ~round the lowerperipherY of a translucent conical cover 41 through which light passes to the photoelectric sensor cn the printed circuit board 2. llhe canopy or cover 41 is cf conical shape to prevent accumulation of dirt and also discouraae birds fro~.
perching on the cover. The coYer is typically of a plastics material ~hich is treated to protect against ultra-violet light. For fitting the printed circuit board housing 30 and coolins chamber 8 together the housing 30 is formed with a socket which in this case ~s defined by a skirt 45 which extends axially down~ardty approximately mid-way across the base for reception of a spigot defined by the upper edge of the side wall 10 of the cooling chamber 8.
., , -13~
~o prevent lngres5 o~ dlrt ~nd mo15ture, the component p~rts ol' the control unit are 5ecurely ~1xed together and the unit ls then coated with ~ se~l1ng compound to provite additional tefens~ve measures against molsture and _5 dirt in~gress. -- One ~tvantage of the invention is th~t the connection ~ means between the control mean5 and the oùtput is arranged to dissipate any heat generated and hence protect the comp-onents o~ the control means. ~hus, a mor~ efficient and reliable switch which has a long life in use is pro~ided.
Referring to Figs. 6 to 8 there is illustrated a modified photGelectric control unit which is similar to that des-cribed above with reference to Figs. l to 5 and like p~rts are assigned the same r~ference nu~,erals. In this c2se the unit includes an electrical socket receiving housing 50 for housing an output socket 51 Which is connected at one end to the connector pins 4 and Which is connected through an outlet cable 52 to the output w~.ich it is desired to switc~, such ~s a street or security lantern. The hGusing 50 ir,c:ludes an upper radial wall 53 and an axially upwardty extending side wall portion 54 Which defines ~ spigot for insertion in the socket defined by the skirt 12 of the cooling chamber 8. A lower cylindrical side wall portion 55 extends downwardly from ~he upper wall 53 of the housing 50.
The lower side wall portion 53 of the housing 50. The lower side wall portion 55 is turned inwardly to define a base wall 56 having a central opening 57 through which the elec-trical connection le~d 5Z is le~d ~rom t~e s5cket 51 ~or connection- to an output- ~he s~cket 51 i5 carr~ed by a mounting plate 60 which is fixed in ~osition by self-tapping screws 61 which engage in corre5ponding 5crew S receiving portion5 62 which extend downwardly from the upper wal~ 53. ~he sealing ring gasket 27 seals the joint between- the cooling chamber skirt 12 and the socket rec-eiving housing ~0.
Mounting means for mounting the control unit on a fixture 10 such as a wall is in this case provided by a mounting flange 65 which is connected to the socket receiving housing side wall 55 by a connecting web 66. The flange 6~ is formed with two axially extendlng slots 67 for ease of mounting to a fixture. ~he particular advantage of 15 the control unit for 2i photoelectric switch according to this em~odiement of the invention is that by using the electri c2il soc~et receiYing housing 2 ttachment 50, the control unit ~ay be used in a wide range of applications includinc, security lighting and in other applications where 20 it ~2y be necessary to ~,ount the ccntrol unit on a fixture such as d w211 rather than directly on a lar,tern.
~ _15_ 1 338476 Referring to F~g. 9 there 1S 111u5trated ~ circu~t diag-ram of -a controller for use with a photoelectr~c sw~tch such as the photoelectr~c switch descr1~ed above with re~erence to F~gs. l to 8. ~he function of the controller _ 5 iS to ~5witch ~ower to a lantern according to the surround-ing brightness. The controller comprises a photoelectric _ sen5~r. comparing means for comparing the ~ntensity of ~ sensed light with a preset light intensity and switching means operated by the comparing means to switch an output.
The photoelectric sensor is in this case provided by a light dependent resistor (LDR) which is used to monitor the lisht level ~nd at s~ecific threshold limits either to close or open the shitCh~ The threshold limits are set to the requirements of the particular user.
The switching means is ir. this case provided by a relay RLl and a triac TRIl connected in parallel. ~'hen it is required to switch the load th~ triac TRIl is engaged and t~;is is followed a short time later by closure of the relay contacts RLl. In this ~ay the r~lay RLl jc not sub-2Q jected to high voltages during the switching action andthe triaC TRIl is not given enough time to heat. When the load is to be switched out the relay RLl is dis-engaged and this is followed a short time later by the switclhing off of the triac TRIl. Again the relay RLl is removed from the ~ircuit while the triac TRIl is hold-ing the Yoltage atalow level and the triac TRIl i5 not B
gi~en enough time to he~t. ln both o~ thP aboYe c~ses the triac ~RIl ~ eose tc ~ndu~t when the relay RLl shorts it out.
The ciircuit operates as follows. A transformer TRFl converts incomi~g 220Vrms (nom) to 24Vrms (nom) and this lower AC voltage is rectified by a bridge consisting of diodes Dl to D4. Capacitor Cl i 5 smoothing capacitor.
24Vdc- is the supply to the re~ainder of the circuitry.
A cent;re tap provided on the transformer TRFl enables llOVrms (nom) supply to be used.
The LDR resistance is monitored by an operational amp-lifier Al through a delay circuit consisting of a ~apac-itor C2 and a resistor RZ. This delay, of approximately 30 seconds. prevents abrupt changes in the value of the LDR recching hl. The operational ampli~ier is used in tt.e comparator ~ode and it co~pares the voltage level on th~ capacitor C2 with a threshold Yalue which is det-ermined by resistors R3, R9 and R6. Resistors R3 and R9 ~orm ¢ potential divider and resistor R6 provides hys-teresis. ~his is to preYent unwanted oscillation duringthe switching action. Threshold calibration is possitle by s~lecting value for Rsot that will cause the unit to switc.h at the correct light levei. FQr high reliability the voltage across the op-amp must be held at a value less than the maximum rating o~ the device. The op-amp 1s rated ~or 36Y, but a voltage of 12Y which is provided by a transistor Ql isused. A 2ener diode CRl and a resi!,tor R10 hold the base voltage on the transistor Ql .
,.
~ .
- 1 3~8~ ~, 1 7 12V below rail result~n~ ln ~n em1tter voltage which is approximately 11.4V below r~ he trans1stor Ql ~lso actS as a regulator, further reduc~ng the possib-i 1 i ty of osc~ tory sw~ tchi ng .
TransistorS Q4 and Q5 ~llow the output of op-~mp Al to _ sw~tch the relay and the triac. A 2ener dlode CR2 is - used to ensure thatthe transistors Q4 and Q5 are swi tched of ~ whlen the op-amp output is 'high'. The LM301 output is unz~ble to come within 1.5 volts of th~ rail v~lJe 10 and woul d not, therefore, be abl e to swi tch off the transilstorS Q4 and Q5. The zener diodes overcome this.
During darkness th~ voltage on pin 2 of the op-amp is low and the op-2mp output is high. Therefore transistorS Q4 ~nd Q5 are switched off during the night and on during the day.
The triac TRIl is shitched through transistors Q4, Q8 and Q9. The trar.sistor Q8 is disabled when the trans-istor Q4 is turned on beca~se its base is held at tne emitt:er voltage. ~'hen the triac TRIl is to be turned on the t:ransistor Q4 ceases to cor,duct allo~ing negative goin~3 pulses from a mains cycle crosso~er detector, con-sisting of two transistors Q6 and Q7, to influence th~
transistor Q8. These pulses occur when the mains sine wave is close to zero volts and cause the transistor Q8 to quickly charge up capacitor C6 throu~h the resis--18- 1 33847b istor IRZ2. The Yclt~ge ~t the b~se of the translst~r Q9 then blecomes hi9h enough to 5wltch on the triac TRil.
The resistor RZ4 whlch i5 connected between the gate of the tr~ac ~RIl and the emltter of the translstor Q9 serves to timit the current through the tr~nslstor Q9 to a rel-iable level. The resistor R22 also lim~ts the peak currentthraugh the transistor Q8 to ~ reliable level. ~'hen the triac rRIl is to be switchedoff the tr~nsistor Q4 starts conductingthus disabling the transistor Q8. The voltage on the ba!;e of the transistor Q9 now begins to decrease as the energy on the capacitor C6 is discharged through the resistor R23. After a time delay the voltage on the transistOr Q9 base will be too low to maintain the triac lRIl in conduction. ~hi5 time delay is needed for the triac/relay sequencing function and it provides 20 sufficient time to allow the relay to disengage ~efore the load voltage increases.
For increased reliability and to reduce radio inter-ference the triac TRIl is switched durin~ the mains zero crossover points. Th~se ~re detected by means of transistors Q6 ~nd Q7. The m2ins is sampled through a resistor R20 and lirr,ited by a zener diode CR3 and a diode D9. The resulting waveform that arrives at the base of the trans-;stor Q6 is approximately square and is further squared by the transistor Q6~ A differentiator network consistirlg of a c;ipacitor C3 and a resistor R14 proYides a negative going pulse e~ch ttme the ~olt~ge on the collector of the tr~nslstor Q6 makes the tr~ns~t10n from ra~l to ground. Thls tr~nstt10n represents the zero cross point when the maln cycle 1s going from negative to _5 positive. In a-s~mil~r manner the trans~stor Q7, capacitor C4 ~nd res~stor Rl6 will ~enerate a pulse during the - posi~ive to negatl~e mains cycle transition. Diodes D7 ~ and D8 ensure that only the negative gcing pulses are transmitted to the base o~ the tran~istor Q8.
~he relay RLl is operated throu~h transistors Q5 and QlO.
The relay RLl is of the normally on type and when the base voltage of the transistor ~lO is low the switch will be closed. ~'hen the relay RLl is to be enga~ed the transistor Q5 will cease to conduct. The volta~e on the capacitor C~ will then begin to decrease as it is disch~rged through the resistor Rl2. After a delay dictated by the capzcitor C5 and the resistor Rl2 the base voltage of the transistor QlO will go below the minimum holding value for the relay RLt and the relay contacts close. This delay is needed to allow the tri~c, TRIl which is being switc~,ed simul-taneously, tim~ to reduce the voltage across the relay contacts to an acc~ptable level. This is part of the triaclrelay sequencing function. When the relay RLl is to be disengaged (at morning) the transistor Q5 again conducts, chargins up the capacitor C5 quickly. The relay RLl i!i then opened quickly before the triac TRIl is dis^
engagl~d, thus protect~ ng the swi tch contacts . Diodes DS ~nd D6 protect the transistor Q10 from the back c~& that normally
- 2 0 -cc3mpaln1e5 the swltching of ~ rel~y. A normally ~on~
rel~y 15 u5ed here so that ln the event of f~llure the street lantern being controlled will be s~itched on permanentlY~ It ~5 expected that mo5t fallures w~th1n the controller will result ~n 105S of power to the relay and the controller will thus meet the requ~rement that the lanter-n be 5witched on. Varistor protection is employed in the circuitto prevent large mains bourne spikes and transitionS getting to the cirCuitry. A Varistor, GMl, is ~0 placed aft~r the mains transformer TRFl and takes advant-age of the transformer's secondary resistance. The varis-tor's resistance decreases significantly as the voltage across it increases and this is used to limit the voltage at the transformer secondary. The transformer, TRFl, becaus~ of its inherent winding resistances will not be damage~ by the extra load placed on it during line transientS. A varistor is used here in preference to a zener diode becau5e of its greater speed and current handling capabilities.
LDR self heatin~ is reduced by mini~ising the power dissipation within the controller through the use of high external resistor values. Power dissip~tion is approx-imately lOmw. The use of transistors allows the voltage on the LDR to be measured despite the high source impedance due to the lar5e resistor values. Any suitable LDR may be used alnd preferably the LDR should be hermetically sealed to ensure that moisture and impurities cannot enter the - LDR and alter its charactert;st;cs. Thè particular LD~
^21- 1 338476 chosen ~ the CLM5MGM deY~ce ~hlch h~s ~ St~ble light to resistance relotton5hip ~fter 100 hours burn-in.
All NPNI tr~nslstors ~re typlc~lly type ~t2378-92 ~hile ~11 PNF' transistors ~re typ~c~lly type ~C212B-92. All resistors ~re u.sually ~x~5~ c~rbon. The elements designat-10 ed X are typic~lly solld ~luminium 40Y ~nd those designat-ed ~ ~re usually long life aluminium electrolytic~ ELCO
(Trade-mark) series.
A conformal coating compou~d may be applied to bot~. the board and the components to ensure rigidity of the comp-onents during heavy vibration5 or lantern mast shudder,to protect the electronic circuit from impurities from moisture and dirt ingress and to further protect the board and the components from UV radiation through the conical canopy or CGVer. As ultra-violet tends to break down plastic. both the housing ana the conical are doped with a recommended U.V. inhibitor. The use of a relay acs;cted triac overcomes the proble~. associated with the shitching of heavy loads. When relay contacts open or close arcing will occur between the relay contacts z5 anG thisWill~ in time, cause the contacts to become pitted and eYentually non-operational. The arcing problem could be oYercome using a semiconductor switch in the ~orm of a triac or transistor. HoweYer, such an arrangement because of its saturation voltage dlssipates power result-ing inl heating. This heating ~111 seYerely curta~l the .
C) -~eliability o- the deYice. ~hus, the controlter according to this aspect of the ~nvention i5 part~cularly r~tioble in use ~nd greatly increases the useful life o~ a photo-electric control unit. The method of switching using relay assisted triac has been tested by subjecting a prototype to 40.000 switching operations wh;ch is the equival~nt of over 100 years operation, and when examined after the test the relay was found to be in excellent con-dition ~i~hout any signs of pitting.
A phototransistor may be employed as a photoelectric senC~or instead of the LDR used in the embodiment described abo~e.
rel~y 15 u5ed here so that ln the event of f~llure the street lantern being controlled will be s~itched on permanentlY~ It ~5 expected that mo5t fallures w~th1n the controller will result ~n 105S of power to the relay and the controller will thus meet the requ~rement that the lanter-n be 5witched on. Varistor protection is employed in the circuitto prevent large mains bourne spikes and transitionS getting to the cirCuitry. A Varistor, GMl, is ~0 placed aft~r the mains transformer TRFl and takes advant-age of the transformer's secondary resistance. The varis-tor's resistance decreases significantly as the voltage across it increases and this is used to limit the voltage at the transformer secondary. The transformer, TRFl, becaus~ of its inherent winding resistances will not be damage~ by the extra load placed on it during line transientS. A varistor is used here in preference to a zener diode becau5e of its greater speed and current handling capabilities.
LDR self heatin~ is reduced by mini~ising the power dissipation within the controller through the use of high external resistor values. Power dissip~tion is approx-imately lOmw. The use of transistors allows the voltage on the LDR to be measured despite the high source impedance due to the lar5e resistor values. Any suitable LDR may be used alnd preferably the LDR should be hermetically sealed to ensure that moisture and impurities cannot enter the - LDR and alter its charactert;st;cs. Thè particular LD~
^21- 1 338476 chosen ~ the CLM5MGM deY~ce ~hlch h~s ~ St~ble light to resistance relotton5hip ~fter 100 hours burn-in.
All NPNI tr~nslstors ~re typlc~lly type ~t2378-92 ~hile ~11 PNF' transistors ~re typ~c~lly type ~C212B-92. All resistors ~re u.sually ~x~5~ c~rbon. The elements designat-10 ed X are typic~lly solld ~luminium 40Y ~nd those designat-ed ~ ~re usually long life aluminium electrolytic~ ELCO
(Trade-mark) series.
A conformal coating compou~d may be applied to bot~. the board and the components to ensure rigidity of the comp-onents during heavy vibration5 or lantern mast shudder,to protect the electronic circuit from impurities from moisture and dirt ingress and to further protect the board and the components from UV radiation through the conical canopy or CGVer. As ultra-violet tends to break down plastic. both the housing ana the conical are doped with a recommended U.V. inhibitor. The use of a relay acs;cted triac overcomes the proble~. associated with the shitching of heavy loads. When relay contacts open or close arcing will occur between the relay contacts z5 anG thisWill~ in time, cause the contacts to become pitted and eYentually non-operational. The arcing problem could be oYercome using a semiconductor switch in the ~orm of a triac or transistor. HoweYer, such an arrangement because of its saturation voltage dlssipates power result-ing inl heating. This heating ~111 seYerely curta~l the .
C) -~eliability o- the deYice. ~hus, the controlter according to this aspect of the ~nvention i5 part~cularly r~tioble in use ~nd greatly increases the useful life o~ a photo-electric control unit. The method of switching using relay assisted triac has been tested by subjecting a prototype to 40.000 switching operations wh;ch is the equival~nt of over 100 years operation, and when examined after the test the relay was found to be in excellent con-dition ~i~hout any signs of pitting.
A phototransistor may be employed as a photoelectric senC~or instead of the LDR used in the embodiment described abo~e.
Claims (6)
1. A controller for a photoelectric control unit, the controller comprising a photoelectric sensor, comparing means for comparing the intensity of sensed light with preset light intensity and switching means operated by the comparing means to switch a lamp, said switching means comprising a relay and a triac, in which the relay contacts and the triac are electrically connected in parallel.
2. A controller as claimed in claim 1, wherein the lamp is a street lamp.
3. A controller as claimed in claim 1 or 2, wherein the triac is provided in a triac control circuit which is operated by the comparing means.
4. A controller as claimed in claim 1 or 2 wherein on switching of the switching means, said relay contacts conduct at a first voltage and the triac conducts at a second voltage higher than said first voltage.
5. A controller as claimed in claim 1 or 2 wherein the photoelectric sensor comprises a light sensitive resistor whose resistance increases with the intensity of incident light.
6. A controller as claimed in claim 1 or 2 wherein the photoelectric sensor comprises a photo-transistor.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8525440A GB2166003B (en) | 1984-10-18 | 1985-10-16 | Photo-electric switch |
| US06/903,667 US4791290A (en) | 1984-10-18 | 1986-09-04 | Photoelectric control unit with cooling chamber |
| CA000564648A CA1338476C (en) | 1984-10-18 | 1988-04-20 | Photoelectric control unit |
| GB8810240A GB2203240B (en) | 1984-10-18 | 1988-04-29 | A photoelectric control unit |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IE251684A IE55885B1 (en) | 1984-10-18 | 1984-10-18 | A photoelectric control unit |
| CA000564648A CA1338476C (en) | 1984-10-18 | 1988-04-20 | Photoelectric control unit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1338476C true CA1338476C (en) | 1996-07-23 |
Family
ID=25671855
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000564648A Expired - Fee Related CA1338476C (en) | 1984-10-18 | 1988-04-20 | Photoelectric control unit |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1338476C (en) |
| GB (2) | GB2166003B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4841164A (en) * | 1986-02-11 | 1989-06-20 | Egidio Basso | Light-sensitive switch structure and method with inverse off/on ratio |
| GB2196801B (en) * | 1986-10-24 | 1990-07-25 | Crabtree Electrical Ind Ltd | Electric plugs |
| GB2411971B (en) * | 2004-03-10 | 2006-09-06 | Cableform Ltd | Power factor improvement |
| US7755021B2 (en) * | 2008-02-15 | 2010-07-13 | Tyco Electronics Corporation | Non-toxic photo cells and photosensors including the same |
| CN108045299B (en) * | 2017-12-25 | 2024-03-26 | 中国重汽集团济南动力有限公司 | Automatic automobile light control device with protection function |
Family Cites Families (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB523276A (en) * | 1938-12-30 | 1940-07-10 | Coop Wholesale | Improvements in and relating to electric lighting fittings |
| GB1110263A (en) * | 1966-01-15 | 1968-04-18 | Process Units Halifax Ltd | Improvements in control apparatus for electric circuits |
| GB1180026A (en) * | 1966-06-13 | 1970-02-04 | Lucas Industries Ltd | Vehicle Lamps. |
| GB1196471A (en) * | 1967-04-14 | 1970-06-24 | Associated Semiconductor Mft | Improvements in and relating to Photo-Electric Devices |
| US3602721A (en) * | 1967-11-20 | 1971-08-31 | Malsushita Electric Ind Co Ltd | Photoelectric device with enhanced photoconductive sensitivity and storage effect of input radiation |
| SE348315B (en) * | 1969-02-18 | 1972-08-28 | S Rydborn | |
| CA916944A (en) * | 1969-08-29 | 1972-12-19 | L. Lachambre Jean | Pyroelectric joule meter |
| FR2132990A6 (en) * | 1971-04-05 | 1972-11-24 | Cretien Jean Paul | |
| US3879100A (en) * | 1972-07-07 | 1975-04-22 | Ferdinand E Chabot | Circuit breaker terminal connector, and heat dissipator assembly |
| GB1567306A (en) * | 1976-01-05 | 1980-05-14 | Chilvers G | Light activated control system |
| GB1543735A (en) * | 1976-05-17 | 1979-04-04 | Ind Solenoids Ltd | Photoelectric sensing and control devices |
| GB1557573A (en) * | 1976-11-09 | 1979-12-12 | Whitehead J | Lightsensitive device |
| US4376909A (en) * | 1979-04-13 | 1983-03-15 | Honda Giken Kogyo Kabushiki Kaisha | Automatic light control for automotive vehicles |
| GB2064238B (en) * | 1979-11-21 | 1983-10-12 | Graham C J | Automatic switching unit for vehicle driving lights |
| GB2097918B (en) * | 1981-05-06 | 1984-10-17 | Duport Ltd | Controlling lighting system |
| JPS58145169A (en) * | 1982-02-23 | 1983-08-29 | Nec Corp | Optical semiconductor device |
| GB2119179B (en) * | 1982-04-27 | 1985-07-03 | Lucas Ind Plc | Cooling a terminal of a plug |
| GB2133532A (en) * | 1983-01-10 | 1984-07-25 | Guilherme Ysenbout Mogas | Light sensitive switch |
| US4449074A (en) * | 1983-02-23 | 1984-05-15 | Lutron Electronics Co., Inc. | Excess light turn-off circuit |
-
1985
- 1985-10-16 GB GB8525440A patent/GB2166003B/en not_active Expired
-
1988
- 1988-04-20 CA CA000564648A patent/CA1338476C/en not_active Expired - Fee Related
- 1988-04-29 GB GB8810240A patent/GB2203240B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2203240B (en) | 1989-06-07 |
| GB8810240D0 (en) | 1988-06-02 |
| GB2166003B (en) | 1989-06-07 |
| GB2203240A (en) | 1988-10-12 |
| GB8525440D0 (en) | 1985-11-20 |
| GB2166003A (en) | 1986-04-23 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |