US4025915A
Expired / Lapsed
US
⏱️ 0.0 years remaining
LED smoke detector circuit
Assignee: SENTROL, INC. A CORP. OF OREGON
•
Filing: 1975-10-06
•
Granted: 1977-05-24
•
Expires: 1995-10-06
Abstract
Abstract A simplified smoke or other particle detector circuit includes a light emitting diode in series with a compensating photocell and a photocell sensing LED light scattered from particles. In parallel with the LED is a high resistance, and in parallel with the photocells is a low resistance, the resistances having a common junction coupled to a threshold circuit input as is the output of the photocells. Sensing smoke produces a photocell output which triggers the threshold device to generate an alarm signal. Failure of the LED produces a voltage at the resistance junction which similarly triggers the threshold device to alarm.
Inventors
- 👤 Robert B. Enemark
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 17:22
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/103; G08B17/107
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
112 words
Apparatus for detecting fluid borne particles comprising: a power supply; a light source; photoelectric means responsive to source light scattered by particles to produce an alarm output, the light source, and photoelectric means being connected in series across the power supply; a threshold circuit having an input responsive to the alarm output to produce an alarm signal; a relatively high resistance in parallel with the light source; and a relatively low resistance in parallel with the photoelectric means, the resistances having a common junction coupled to the threshold device input such that failure of the light source produces a voltage at the junction causing the threshold device to produce an alarm signal.
Claim 2
Dependent Claim
112 words
Apparatus for detecting fluid borne particles comprising: a power supply; a light source; photoelectric means responsive to source light scattered by particles to produce an alarm output, the light source, and photoelectric means being connected in series across the power supply; a threshold circuit having an input responsive to the alarm output to produce an alarm signal; a relatively high resistance in parallel with the light source; and a relatively low resistance in parallel with the photoelectric means, the resistances having a common junction coupled to the threshold device input such that failure of the light source produces a voltage at the junction causing the threshold device to produce an alarm signal.
Claim 3
Dependent Claim
15 words
Apparatus according to claim 1 wherein the light source is a solid state, electroluminescent device.
Claim 4
Dependent Claim
14 words
Apparatus according to claim 1 wherein the light source is a light emitting diode.
Claim 5
Dependent Claim
22 words
Apparatus according to claim 1 wherein the photoelectric means comprises two photoelectric devices in series having an output at their intermediate junction.
Claim 6
Dependent Claim
40 words
Apparatus according to claim 1 wherein the power supply comprises power terminals, the threshold device being responsive to a voltage approaching the voltage of one of the power terminals, and the low resistance being connected to said one power terminal.
Claim 7
Dependent Claim
16 words
Apparatus according to claim 5 wherein the high resistance is connected to the other power terminal.
References Cited (Backward Citations)
US3316410A
Cited
US3534351A
Cited
US3655289A
Cited
US3727056A
Cited
US3922655A
Cited
US3846773A
Cited
US3922656A
Cited
US3882477A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-05-23 | 1980-11-22 | 1981-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-23 | 1984-11-22 | 1985-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-23 | 1988-11-22 | 1989-05-24 | $7700.00 | Window Closed / Lapsed |