GB2266141A - Hazard light control with hysteresis - Google Patents

Hazard light control with hysteresis Download PDF

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Publication number
GB2266141A
GB2266141A GB9206826A GB9206826A GB2266141A GB 2266141 A GB2266141 A GB 2266141A GB 9206826 A GB9206826 A GB 9206826A GB 9206826 A GB9206826 A GB 9206826A GB 2266141 A GB2266141 A GB 2266141A
Authority
GB
United Kingdom
Prior art keywords
lamp
ambient light
state
comparator
inputs
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.)
Withdrawn
Application number
GB9206826A
Other versions
GB9206826D0 (en
Inventor
Paul Singh Paddan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TILDAWN ELECTRONICS Ltd
Original Assignee
TILDAWN ELECTRONICS Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by TILDAWN ELECTRONICS Ltd filed Critical TILDAWN ELECTRONICS Ltd
Priority to GB9206826A priority Critical patent/GB2266141A/en
Publication of GB9206826D0 publication Critical patent/GB9206826D0/en
Publication of GB2266141A publication Critical patent/GB2266141A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
    • B60Q1/02—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to illuminate the way ahead or to illuminate other areas of way or environments
    • B60Q1/04—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to illuminate the way ahead or to illuminate other areas of way or environments the devices being headlights
    • B60Q1/14—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to illuminate the way ahead or to illuminate other areas of way or environments the devices being headlights having dimming means
    • B60Q1/1415—Dimming circuits
    • B60Q1/1423—Automatic dimming circuits, i.e. switching between high beam and low beam due to change of ambient light or light level in road traffic
    • B60Q1/143—Automatic dimming circuits, i.e. switching between high beam and low beam due to change of ambient light or light level in road traffic combined with another condition, e.g. using vehicle recognition from camera images or activation of wipers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
    • B60Q1/26—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic
    • B60Q1/34—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction
    • B60Q1/38—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction using immovably-mounted light sources, e.g. fixed flashing lamps
    • B60Q1/381—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating change of drive direction using immovably-mounted light sources, e.g. fixed flashing lamps with several light sources activated in sequence, e.g. to create a sweep effect
    • 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
    • H05B39/00—Circuit arrangements or apparatus for operating incandescent light sources
    • H05B39/09—Circuit arrangements or apparatus for operating incandescent light sources in which the lamp is fed by pulses
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q2300/00—Indexing codes for automatically adjustable headlamps or automatically dimmable headlamps
    • B60Q2300/30—Indexing codes relating to the vehicle environment
    • B60Q2300/31—Atmospheric conditions
    • B60Q2300/314—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

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

A flashing hazard light comprising an electric lamp L, a supply terminal T for receiving a supply from a battery B and a photo diode P sensitive to ambient light for controlling the energisation of the lamp L through a lamp controller LC. The voltage from the photo diode P is applied to a comparator CF in which it is compared with first and second references RF1, RF2 which define a range of ambient light intensities whereby, in operation, the lamp remains in the state to which it has been previously set when the ambient light intensity lies within the range defined by the references and only changes its set state when the ambient light intensity moves outside this range. <IMAGE>

Description

IMPROVEMENTS IN LIGHTING APPARATUS The present invention relates to lighting apparatus comprising an electric lamp, a supply connection for receiving a supply from an electrical supply source, and light sensitive means responsive to ambient light for enabling the lamp, in dependence on the intensity of the ambient light, to be set in a first state for energisation from the supply or a second state in which it is prevented from being energised.
Such lighting apparatus is shown and can be in the form of a flashing light employed to indicate hazards such as road works, the lamp flashing at a given rate. The light sensitive means, generally including a photo diode, senses the ambient light intensity to determine whether it is day or night so as to prevent the lamp being energised during the day but allowing it to flash during the night. A problem present with such known apparatus is that around the periods of dawn or dusk the ambient light may fluctuate so causing the state to which the lamp can be set to fluctuate.
It is an object of the invention to provide a safety lamp of the type described in the opening paragraph in which the above problem can be overcome.
The invention provides lighting apparatus comprising an electric lamp, a supply connection for receiving a supply from an electrical supply source, and light sensitive means responsive to ambient light for enabling the lamp, in dependence on the intensity of the ambient light, to be set in a first state for energisation from the supply or a second state in which it is prevented from being energised, characterised in that the light sensitive means comprises a comparator for comparing a signal related to the intensity of the ambient light with first and second references which define a range of ambient light intensities whereby, in operation, the lamp remains in the state to which it has been previously set when the ambient light intensity lies within the range defined by the references and only changes its set state when the ambient light intensity moves beyond the said range.
The light sensitive means may include a light sensitive element from which a voltage can be derived related to ambient light intensity to form the signal, the first and second references being voltage levels lying within the excursion of the signal voltage.
The comparator may comprise first and second differential amplifiers each having first and second inputs of opposite sign, the signal being applied to the first input of the first differential amplifier and to the second input of the second differential amplifier which inputs are of opposite sign, the first reference being applied to the second input of the first differential amplifier whilst the second reference is applied to the first input of the second differential amplifier. The outputs of the first and second differential amplifiers may be of opposite states when the ambient light intensity is above or below the range of light levels but within the said range these outputs have the same state.The comparator may additionally comprise a bistable circuit having as its inputs the outputs of the first and second differential amplifiers, the bistable circuit changing its output state when the states of its inputs have both changed but not when the state of only one of its inputs has changed.
The output of the comparator may be applied to a lamp controller to control the energisation of the lamp which lamp controller may cause the lamp to flash in the first state and to be extinguished in the second state. Such a lamp controller may comprise an oscillator, a frequency divider and a lamp driver for energising the lamp at the required flashing rate.
The light sensitive element, the differential amplifiers, the bistable circuit, the oscillator, the frequency divider and the lamp driver may all be formed in a common integrated circuit.
The invention also provides an integrated circuit incorporating the circuit elements specified above.
The above and other features of the invention will now be described in relation to the accompanying drawings, in which: Figure 1 is a block diagram of lighting apparatus according to the invention, and Figure 2 is a more detailed embodiment of parts of the diagram of Figure 1.
In the arrangement of Figure 1, lighting apparatus in the form of a flashing hazard light is energised from a battery B whose positive terminal (+) is connected to a terminal T whilst the negative terminal (-) of the battery is connected to the light's earth. The supply at terminal T is connected through an on/off switch S and a connection rail to one terminal of a lamp L, here in the form of an incandescent lamp, which is to be energised according to the condition of a lamp controller LC. The supply from the connection rail is also applied to one electrode of a semiconductor photo diode P, which forms part of a light sensitive arrangement, whose other electrode is connected to the signal input of a comparator CF also in the light sensitive apparatus.The comparator CF processes the input signal and compares it with two reference levels RF1 and RF2 derived from the supply line (in a manner not shown) to control the level of the comparator output which is applied to the input of the lamp controller LC. As the safety light of Figure 1 is designed to flash then the lamp controller LC will arrange to alternately connect and disconnect the (other) lower terminal of the lamp L to the supply earth at a predetermined rate during the hours of darkness.
The photo diode P senses the ambient light falling on the hazard light and thus the voltage input applied to the comparator CF from diode P will depend on the level of the ambient light; when it is daylight the voltage will be higher than when it is dark. Ignoring initially the presence of the two reference levels RF1 and RF2, the voltage level input from the diode P will cause the comparator CF to apply an output to the lamp controller LC of a first state when daylight and of a second state at night. This in turn will enable the lamp controller LC to energise the lamp L to flash during periods of darkness but to prevent it from flashing during periods of daylight when it is not required.However at periods of light transition experienced at dawn and dusk, when there are the possibilities of fluctuating ambient light levels, it is possible for the state to fluctuate causing the lamp energising condition to fluctuate. To overcome this problem the signal dependent on the ambient light derived form the photo diode P is compared with the two reference levels RF1 and RF2, which define a range of ambient light intensities, in the comparator CF such that if the level of the signal lies between the two reference levels the output state from the comparator will not be changed from that which it had previously been set.Thus at dawn when the comparator output state has been such as to cause the lamp controller LC to be energised, if cloud is present to cause the ambient light to fluctuate as daylight increases the output state of the comparator CF will not change until the ambient light intensity increases and hence the signal exceeds reference level RF1 and should the ambient light intensity reduce again it would not cause the comparator output state to change again unless the signal level fell below the reference level RF2. A similar situation will also occur at dusk. In this way normal fluctuations in ambient light intensity at these times will not cause the output state of the comparator CF to change.
Figure 2 is a more detailed diagram of that contained in Figure 1 in which the comparator circuit CF is shown in greater detail, corresponding references used in the two figures indicating like components. In Figure 2 the comparator CF comprises an operational amplifier Al whose inverting input (-) is connected to the anode of the photo diode P whilst its non-inverting input (+) is connected to a junction point on a potential divider to be described below.
The output of amplifier Al is connected through a resistor R1 of high resistance to its inverting input such that amplifier Al operates as a transconductance amplifier. This output is also connected to the inverting (-) input of a first differential amplifier A2 and to the non-inverting input (+) of a second differential amplifier A3, the remaining noninverting (+) and inverting (-) inputs of these respective amplifiers being connected to further junction points on the potential divider. The potential divider comprises a field effect transistor FT and four resistors R2, R3, R4 and R5 connected between the connection rail and earth, the transistor FT defining the current through the chain of resistors whose junctions are connected in the manner shown to the appropriate amplifier inputs.The outputs of the amplifiers A2 and A3 are connected to first inputs of respective NAND gate circuits G1 and G2, the output of each gate circuit being connected to the second input of the other gate circuit such that the two gate circuits and their interconnections forms a bistable flip-flop circuit. The output of gate circuit G2 also forms the output of the comparator CF which is applied to the control input of the lamp controller LC.
In operation the analogue signal from the photo diode P representing the ambient light is inverted by the amplifier Al prior to its application to the appropriate inputs of amplifiers A2 and A3. The junction between the resistors R3 and R4 forms the reference level RF2 whilst that between resistors form reference level RF1. For night when the ambient light is at its lowest intensity the signal applied to amplifiers A2 and A3 will be at its highest and exceed both the reference levels RF1 and RF2 causing the output of amplifier A2 to be low '0' and that of amplifier A3 to be high '1'. With these levels applied to the relevant inputs of gates circuits G1 and G2 the output from gate circuit G2 will be low to enable the lamp controller LC to energise the lamp L such that it flashes.During daylight when the ambient light is at its highest intensity the reverse situation will apply with the signal applied to the signal inputs of amplifiers A2 and A3 to be below that of the reference levels RF1 and RF2 to cause these amplifier outputs to be respectively high '1' and low '0' such that the-output of gate circuit G2 is high to prevent the lamp controller LC from energising lamp L such that it will not flash. At dawn with the increase in ambient light a condition will be met when the signal level to the amplifiers A2 and A3 will drop initially below reference level RF2 and then RF1 to initially change the output of amplifier A2 and then that of amplifier A3.However it will be appreciated that the output of gate G2 will not change its state until that at the output of amplifier A3 changes and that once changed it remains in that condition unless the ambient light level fall so far that the corresponding signal falls below the reference level RF2. A similar but correspondingly opposite situation will also apply at dusk when the ambient light level falls.
In the description so far various circuits and components have been described in relation to their operation. The lamp controller LC for providing its flashing function may comprise an oscillator, a frequency divider to bring the oscillator frequency down to the required flasher rate, and a lamp driver for energising the lamp L. Conveniently the photo diode P, the operational amplifier Al, the differential amplifiers A2 and A3, the bistable circuit comprising the NAND gate circuits G1 and G2, the oscillator, the frequency divider and the lamp driver may all be incorporated in an integrated circuit. This would give the advantage that only the battery B, the switch S and the lamp L would need to be connected to the integrated circuit in a suitable housing to provide an operational flashing lamp and thus greatly simplify construction.
Although in the above description reference has been made to particular circuit configurations it will be appreciated that the invention may be performed using other suitable circuit configurations.

Claims (11)

CLAIMS:
1. Lighting apparatus comprising an electric lamp, a supply connection for receiving a supply from an electrical supply source, and light sensitive means responsive to ambient light for enabling the lamp, in dependence on the intensity of the ambient light, to be set in a first state for energisation from the supply or a second state in which it is prevented from being energised, characterised in that the light sensitive means comprises a comparator for comparing a signal related to the intensity of the ambient light with first and second references which define a range of ambient light intensities whereby, in operation, the lamp remains in the state to which it has been previously set when the ambient light intensity lies within the range defined by the references and only changes its set state when the ambient light intensity moves beyond the said range.
2. Apparatus as claimed in Claim 1, in which the light sensitive means includes a light sensitive element from which a voltage is derived related to ambient light intensity to form the signal, the first and second references being voltage levels lying within the excursion of the signal voltage.
3. Apparatus as claimed in Claim 1 or 2, in which the comparator comprises first and second differential amplifiers each having first and second inputs of opposite sign, the signal being applied to the first input of the first differential amplifier and to the second input of the second differential amplifier which inputs are of opposite sign, the first reference being applied to the second input of the first differential amplifier whilst the second reference is applied to the first input of the second differential amplifier.
4. Apparatus as claimed in Claim 3, in which the outputs of the first and second differential amplifiers are of opposite states when the ambient light intensity is above or below the range of light levels but within the said range these outputs have the same state.
5. Apparatus as claimed in Claim 4, in which the comparator additionally comprises a bistable circuit having as its inputs the outputs of the first and second differential amplifiers, the bistable circuit changing its output state when the states of its inputs have both changed but not when the state of only one of its inputs has changed.
6. Apparatus as claimed in any of the preceding Claims, in which the output of the comparator is applied to a lamp controller to control the energisation of the lamp.
7. Apparatus as claimed in Claim 6, in which the lamp controller causes the lamp to flash in the first state and to be extinguished in the second state.
8. Apparatus as claimed in Claim 7, in which the lamp controller comprises an oscillator, a frequency divider and a lamp driver for energising the lamp at the required flashing rate.
9. Apparatus as claimed in Claim 8, in which the light sensitive element, the differential amplifiers, the bistable circuit, the oscillator, the frequency divider and the lamp driver are all formed in a common integrated circuit.
10. An integrated circuit incorporating the circuit elements specified in Claim 9.
11. Lighting apparatus substantially as herein described with reference to Figure 1 or Figures 1 and 2 of the accompanying drawings.
GB9206826A 1992-03-28 1992-03-28 Hazard light control with hysteresis Withdrawn GB2266141A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9206826A GB2266141A (en) 1992-03-28 1992-03-28 Hazard light control with hysteresis

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9206826A GB2266141A (en) 1992-03-28 1992-03-28 Hazard light control with hysteresis

Publications (2)

Publication Number Publication Date
GB9206826D0 GB9206826D0 (en) 1992-05-13
GB2266141A true GB2266141A (en) 1993-10-20

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Family Applications (1)

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GB9206826A Withdrawn GB2266141A (en) 1992-03-28 1992-03-28 Hazard light control with hysteresis

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2309516A (en) * 1996-01-24 1997-07-30 Concept Ind Sdn Bdh Lamp control circuit with selectable brightness level
GB2310491A (en) * 1996-02-26 1997-08-27 Fujitsu Ltd Controlling electronic apparatus in dependence on light level
US7121944B2 (en) * 2001-11-28 2006-10-17 Paul Gauselmann Gaming machine having means to change the brightness of its lights

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1543735A (en) * 1976-05-17 1979-04-04 Ind Solenoids Ltd Photoelectric sensing and control devices
GB2237106A (en) * 1989-07-10 1991-04-24 Brendan James Price Vehicle light management system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1543735A (en) * 1976-05-17 1979-04-04 Ind Solenoids Ltd Photoelectric sensing and control devices
GB2237106A (en) * 1989-07-10 1991-04-24 Brendan James Price Vehicle light management system

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2309516A (en) * 1996-01-24 1997-07-30 Concept Ind Sdn Bdh Lamp control circuit with selectable brightness level
GB2310491A (en) * 1996-02-26 1997-08-27 Fujitsu Ltd Controlling electronic apparatus in dependence on light level
US5844224A (en) * 1996-02-26 1998-12-01 Fujitsu Limited Electronic apparatus and method of controlling electronic apparatus
GB2310491B (en) * 1996-02-26 2000-03-29 Fujitsu Ltd Bar code reader
US6059190A (en) * 1996-02-26 2000-05-09 Fujitsu Limited Electronic apparatus and method of controlling electronic apparatus
US7121944B2 (en) * 2001-11-28 2006-10-17 Paul Gauselmann Gaming machine having means to change the brightness of its lights

Also Published As

Publication number Publication date
GB9206826D0 (en) 1992-05-13

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)