US3789383A - Smoke detector with means for compensating for variations in light source brightness due to line voltage variations - Google Patents

Smoke detector with means for compensating for variations in light source brightness due to line voltage variations Download PDF

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Publication number
US3789383A
US3789383A US00207461A US3789383DA US3789383A US 3789383 A US3789383 A US 3789383A US 00207461 A US00207461 A US 00207461A US 3789383D A US3789383D A US 3789383DA US 3789383 A US3789383 A US 3789383A
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Prior art keywords
voltage
cell
light source
capacitor
photo
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Expired - Lifetime
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US00207461A
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English (en)
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A Vasel
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Kidde Technologies Inc
Graviner Inc
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Pyrotector Inc
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Assigned to PYROTECTOR, INC.; A CORP OF RI. reassignment PYROTECTOR, INC.; A CORP OF RI. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: CHLORIDE INCORPORATED
Assigned to GRAVINER, INC., A CORP. OF DE reassignment GRAVINER, INC., A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: PYROTECTOR, INC.
Assigned to WALTER KIDDE AEROSPACE INC., A CORP. OF DE reassignment WALTER KIDDE AEROSPACE INC., A CORP. OF DE MERGER (SEE DOCUMENT FOR DETAILS). Assignors: GRAVINER, INC., A CORP. OF DE
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/255—Details, e.g. use of specially adapted sources, lighting or optical systems
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
    • G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G08B17/113—Constructional details

Definitions

  • the concentration of smoke at which the device goes to the alarm condition varies with variations in line voltage. This is due principally to the fact that the amount of light reflected onto the photo-cell from smoke particles is a function of the brightness of the light beam, which is dependent on the voltage applied to the light source. With a line voltage higher than normal, the light source will be brighter than normal, and hence the alarm not only will sound at a concentration lower than the predetermined amount, but also will be susceptable to false alarms. With a line voltage lower than normal, the light source will be less bright than normal, a greater smoke concentration will be required to activate the alarm circuit, which could greatly delay the response time of the unit.
  • a smoke detector in which voltage means is provided for varying the voltage applied to the photo-cell inversely with variations in line voltage, to compensate both for changes in brightness of the light source due to the variation in voltage applied thereto, and to eliminate the changes in voltage that would be applied to the photocell in the absence of such voltage varying meansflnexpensive circuit means is provided for increasing the voltage at the photo-cell when the line voltage drops, to make the unit more sensitive and thereby to compensate for the decreased intensity of the light source; and for decreasing the voltage at the photo-cell when the line voltage rises, to make the unit less sensitive, to compensate for the increased brightness of the light source.
  • FIG. 1 is a top plan view, partly broken away, of a smoke detector labyrinth for use with the circuit described herein.
  • FIG. 2 is a view in section taken in line 33 of FIG.
  • FIG. 3 is a schematic diagram of a smoke detector electrical circuit embodying the features of the invention.
  • FIGS. 4, 5 and 6 are diagrams of the wave form of the applied voltage at the input to the neon voltage regulating bulb at low line voltage, normal line voltage, and high line voltage respectively.
  • FIGS. 7, 8, and 9 are diagrams of the wave form of the applied voltage at the input to the detector cell at low line voltage, normal line voltage and high line voltage respectively.
  • a smoke detector which includes a housing 12, a light source 14 disposed outside the housing, and a detector element Cl positioned to view the interior of the housing in a manner to appear hereinafter.
  • the housing 12 comprises a peripheral wall 18 having a pair of end caps 20 and 22 forming an internal dark chamber 24.
  • the end caps extend beyond the periphery of the wall 18 and have inwardly turned flanges 26 and 28 which are spaced outwardly from the wall.
  • Each end of the wall is provided with a series of outwardly inclined spacing lugs 30 which are adapted to engage frictionally the inner surface of the flanges to retain the caps in assembly.
  • the flanges 26 and 28, in conjunction with the spacing lugs 30, form a peripheral opening at each end of the wall to permit smoke to enter the chamber from the surrounding atmosphere.
  • a focusing tube 32 extends through the housing wall on one side thereof, and a light trap tube 34 is disposed in the housing wall on the opposite sign thereof in alignment with the focusing tube 32.
  • a lens 36 may be positioned in the focusing tube to focus the light beam into the light trap.
  • a detector tube 38 extends through the housing wall between the light trap tube and the focusing tube, and is generally perpendicular to the axes thereof.
  • the detector element C1 is mounted in the detector tube with a lens 40 positioned in front of the detector to restrict the field of view of the cell to the medial portion of the light beam.
  • the detector element Cl may be any type of device which is responsive to an increase in light intensity in a reduction in resistance, such as a cadmium sulfide photo-resistive cell.
  • a detector circuit may be connected to the detector element Cl and adjusted to the resistance thereof under normal conditions of no smoke, so that in a predetermined further decrease in cell resistance due to reflected light from smoke in the housing, an alarm will be actuated.
  • FIG. 3 there is illustrated an alarm control circuit for use with the labyrinth of FIGS. 1 and 2.
  • the circuit of FIG. 3 is energized from a 115 VAC source E and is intended to complete a circuit to an alarm device A when a predetermined amount of smoke appears in the housing.
  • the cell C1 is connected across a voltage control circuit VC (connected within the dotted line) in series with a resister R1.
  • the junction J1 between the resister RI and the cell C1 is connected to a neon bulb N1 which is connected to the gate of a silicon controller rectifier SCR.
  • the anode-cathode path of SCR is connected in series with the alarm device A.
  • the voltage at J1 rises to a value high enough to allow the neon bulb N1 to conduct; allowing the voltage at junction J2, between the SCR gate and resistor R2 to rise to a point that the SCR is triggered into conduction in its anode-cathode path to energize the alarm A.
  • the charge in capacitor Fl increases, so that when the neon tube conducts, sufficient energy is present to give an adequate pulse of current through the neon bulb N] to raise the voltage at the SCR gate to the desired level.
  • the resistance of the photo cell Cl will vary with the brightness of the light and therefore, unless some compensation is provided, the smoke concentration at which the alarm will be energized will vary with the supply voltage.
  • percent smoke refers to the drop in light intensity when passing through a chamber of known length. For example, if the light intensity is reduced 3 percent by passing through a column of smoke 2 feet long, it is considered that the column contains 3 percent smoke.
  • the voltage control portion of the circuit, VC is provided. This portion of the circuit provides an increased voltage across the photo-cell when the line voltage is higher than normal, in a manner now to be described.
  • the portion VC of the circuit comprises a neon bulb N2 connected across the voltage source, and a resistor R3, a diode D1 and a capacitor F2 connected in series across the voltage source.
  • the junction J3 between the diode D1 and the capacitor F2 is connected to the photo-cell C1 to serve as the voltage supply for said cell.
  • This portion of the circuit operates in the following manner. Since the supply voltage is 60 cycle alternating current, the voltage at the resistor R3 during a half cycle, (in the absence of the neon bulb N2) would rise from zero to the peak voltage and fall again to zero at the end of the half cycle.
  • the capacitor F2 which receives only half-wave current through the diode D1, would then aquire a charge which would be a function of the peak voltage reached during each half-cycle.
  • the presence of the neon bulb N2 which has a breakdown voltage ofjust below the normal peak line voltage of 150 volts, regulates the voltage appearing at the input of resistor R3 by not conducting until its breakdown voltage of about 150 volts is reached, and then maintaining conduction at a lower voltage level. As shown in FIG.
  • the peak voltage is about 141 volts, which is less then the neon breakdown voltage, and the wave form at the input to the resistor R3 has substantially the shape of the sine wave.
  • the peak voltage is about I62 volts, or just above the firing voltage of the neon.
  • the peak voltage is about I62 volts, or just above the firing voltage of the neon.
  • FIG. 5 it is seen that when the supply voltage reaches the breakdown voltage of the neon, the neon conducts and the voltage across the neon drops to a lower level of approximately 100 volts, due to the voltage drop across the resistor R4 disposed between the neon bulb N2 and the voltage source. A spike of voltage S N is thereby produced during the beginning half of each cycle in the wave form appearing at the input of resistor R3.
  • the wave forms appearing at the resistor R3, illustrated inFIGS. 4, 5, and 6, are modified by the filtering effect of the RC combination of R3 and F2, so that the wave form appearing at the input of the cell Cl and capacitor F2 under conditions of low line voltage, normal line voltage, and high line voltage is shaped as illustrated in FIGS. 7, 8, and 9 respectively.
  • the filtering action of the RC combination in the wave-form of low line voltage is very slight, causing only a slight reduction in peak voltage.
  • the voltage maintained on the capacitor F2 determines the current flow through the cell Cl, which determines the voltage at the junction J1 and the firing point of the trigger neon N1.
  • the charge on the capacitor is a function of the peak voltage appearing at the capacitor input. As shown in FIGS. 7, 8, and 9, it is seen that the peak voltage decreases as the supply voltage increases. Therefore, with a higher supply voltage, the current flow through the cell Cl at a given cell resistance will be less, giving a lower voltage input to the trigger neon N1. However, the higher supply voltage also provides more light output from bulb 14, and with a given amount of smoke in the housing more light falls on cell Cl causing a lower than normal cell resistance. The fact that said higher supply voltage also results in a lower voltage at the input of cell Cl compensates for said increase in light falling on the cells.
  • the compensation afforded by the portion VC of the circuit can almost exactly compensate for the effect of variations in light output caused by variations in line voltage, so that with a given amount of smoke in the housing, the current flow through the cell, and therefore the voltage at junction J1, does not vary with variations in line voltage.
  • the resistor R3, diode D1 and capacitor F2 are included as part of the voltage control circuit, in some cases it is possible to omit these components and still have an operative device with voltage compensation, provided that the impedance of the cell Cl is of the proper value to provide, in combination with the capacitor Fl, the filtering effect previously described, so that changes in the supply voltage will cause opposite changes in the voltage appearing at the neon bulb N1.
  • the impedance value of photo-cells available commercially varies so widely that inclusion of the above mentioned components is necessary to obtain consistent performance.
  • a smoke detector of the type designed to be energized from an AC. source and having a photoresistive cell positioned to view smoke particles illuminated by the light source the improvement comprising means for varying the effective voltage applied to the photo-resistive cell inversely with variations in voltage applied to the light source, whereby the increase or decrease in brightness of the light source with increase or decrease in supply voltage does not appreciably change the alarm point of the detector due to the compensating decrease and increase of voltage across the photocell with the increase and decrease respectively of the brightness of the light source.
  • the improvement comprising means for causing the voltage at the alarm actuating circuit to decrease when the supply voltage increases and vice-versa, said means including a capacitor connected to serve as a D.C. voltage supply for the alarm actuating circuit, means for applying a D.C. charging voltage to said capacitor from the supply voltage, and means for reducing the effective D.C. voltage applied to the capacitor during each half cycle with increases in supply voltage.
  • a smoke detector of the type adapted to be energized from an AC. source and having a light source, a photo'cell positioned to view smoke particles illuminated by the light source, and means responsive to change in D.C. voltage drop across the photo-cell to actuate an alarm, wherein a change in the supply voltage will cause a change in the brightness of the light source and a consequent change in the light received by the photo-cell at a given smoke concentration, the improvement comprising means for causing the D.C.
  • said means including a capacitor connected to serve as the voltage supply for the cell, means charging said capacitor with half-wave current from the same source that supplies the light source, a neon bulb connected across said capacitor to control the effective charge applied thereto, whereby as the supply voltage increases, the neon goes into conduction at an earlier point in the charging half cycle and the high frequency voltage spike formed by the clipping action of the neon bulb filters through the capacitor more readily than the spike formed by the neon bulb at a lower line voltage, and the maximum voltage acquired by the capacitor decreases.
  • a smoke detector as set out in claim 4 in which said means for supplying voltage across said cell and for compensating for a change in the brightness of the light comprises a capacitor and a diode in series across a neon voltage regulator bulb, the voltage supply to the cell being taken from the junction between the diode and the capacitor.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Fire-Detection Mechanisms (AREA)
US00207461A 1971-12-13 1971-12-13 Smoke detector with means for compensating for variations in light source brightness due to line voltage variations Expired - Lifetime US3789383A (en)

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Application Number Priority Date Filing Date Title
US20746171A 1971-12-13 1971-12-13

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US3789383A true US3789383A (en) 1974-01-29

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US (1) US3789383A (https=)
JP (1) JPS4866794A (https=)
AU (1) AU462064B2 (https=)
DE (1) DE2251046B2 (https=)
FR (1) FR2165480A5 (https=)
GB (1) GB1395245A (https=)
SE (1) SE385057B (https=)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3898553A (en) * 1974-04-26 1975-08-05 Rca Corp Circuit for supplying power to a load
US3987358A (en) * 1972-01-26 1976-10-19 The Walter Kidde & Company, Inc. Condition detector circuit
EP0011364A1 (en) * 1978-09-29 1980-05-28 Chubb Fire Limited Heat detector circuit
US4206456A (en) * 1975-06-23 1980-06-03 Chloride Incorporated Smoke detector

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1989007814A1 (en) * 1988-02-16 1989-08-24 Myers Holdings Pty Ltd; Security system for an environment

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2069160A (en) * 1933-09-01 1937-01-26 Kidde & Co Walter Regulated voltage system for detecting suspended matter in fluids
US2415179A (en) * 1944-09-23 1947-02-04 Jr Samuel C Hurley Photoelectric inspection device
US3314058A (en) * 1964-01-13 1967-04-11 Aseco Inc Electronic smoke detector and fire alarm
US3403315A (en) * 1965-10-22 1968-09-24 Smith Corp A O Condition responsive control circuit connected to gate a triggered switch
US3467817A (en) * 1967-02-23 1969-09-16 West Bend Co Temperature control circuit

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2069160A (en) * 1933-09-01 1937-01-26 Kidde & Co Walter Regulated voltage system for detecting suspended matter in fluids
US2415179A (en) * 1944-09-23 1947-02-04 Jr Samuel C Hurley Photoelectric inspection device
US3314058A (en) * 1964-01-13 1967-04-11 Aseco Inc Electronic smoke detector and fire alarm
US3403315A (en) * 1965-10-22 1968-09-24 Smith Corp A O Condition responsive control circuit connected to gate a triggered switch
US3467817A (en) * 1967-02-23 1969-09-16 West Bend Co Temperature control circuit

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
RCA Technical Notes No. 741; Combined Smoke and Fire Detection Circuit for the Home by E. Fischer; 2 sheets; January, 1968. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3987358A (en) * 1972-01-26 1976-10-19 The Walter Kidde & Company, Inc. Condition detector circuit
US3898553A (en) * 1974-04-26 1975-08-05 Rca Corp Circuit for supplying power to a load
US4206456A (en) * 1975-06-23 1980-06-03 Chloride Incorporated Smoke detector
EP0011364A1 (en) * 1978-09-29 1980-05-28 Chubb Fire Limited Heat detector circuit

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SE385057B (sv) 1976-05-31
FR2165480A5 (https=) 1973-08-03
JPS4866794A (https=) 1973-09-12
AU462064B2 (en) 1975-06-12
AU4786672A (en) 1974-04-26
GB1395245A (en) 1975-05-21
DE2251046B2 (de) 1975-08-14
DE2251046A1 (de) 1973-06-20

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AS Assignment

Owner name: PYROTECTOR, INC.; 333 LINCOLN ST., HINGHAM, MA. A

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CHLORIDE INCORPORATED;REEL/FRAME:004094/0656

Effective date: 19830103

AS Assignment

Owner name: GRAVINER, INC., A CORP. OF DE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:PYROTECTOR, INC.;REEL/FRAME:005381/0071

Effective date: 19900605

AS Assignment

Owner name: WALTER KIDDE AEROSPACE INC., A CORP. OF DE

Free format text: MERGER;ASSIGNOR:GRAVINER, INC., A CORP. OF DE;REEL/FRAME:005541/0064

Effective date: 19891018