Multiwavelength smoke detector using white light LED

• US 7,233,253 B2
• Filed: 04/30/2004
• Issued: 06/19/2007
• Est. Priority Date: 09/12/2003
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Simplexgrinnell LP (Johnson Controls International plc)
• Inventors: Qualey, James R. III
• Primary Examiner(s): Pham; Toan N.
• Application Number:
  US10/835,930
• Publication Number:
  US 20050057365A1
• Time in Patent Office: 1,145 Days
• Field of Search: 340/628, 340/629, 340/630, 324/464, 73/250.1, 250/287
• US Class Current: 340/628
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke

Abstract

A smoke detector includes a smoke detection chamber containing a white light LED and a light detector. The light detector detects light within at least two distinct optical wavelength bands, and generates respective signals indicative of the intensities of the detected light. An analyzer determines, based on the measured light intensities of the different wavelength bands, whether a dangerous smoke/fire condition is present.

Claims

1. A fire alarm control panel, comprising:

communication means for receiving, from at least one smoke detector, information about measured light intensities of different wavelength bands; and

an analyzer which determines, based on the measured light intensities of the different wavelength bands, whether a dangerous smoke/fire condition is present;

wherein the at least one smoke detector comprises

a smoke detection chamber,

a light source having a broad optical spectrum,

a light detector which detects light within at least two distinct optical wavelength bands within said spectrum, the detector generating signals having amplitudes which are responsive to intensities of the detected light, both the light source and light detector being within the detection chamber, and

transmission means for transmitting the measured light intensity information to the fire alarm control panel.

2. The fire alarm control panel of claim 1, further comprising:

an analyzer which determines, based on the measured light intensities of the different wavelength bands, whether a dangerous smoke/fire condition is present.

3. The fire alarm control panel of claim 2, the analyzer comprising an estimator which, responsive to the measured light intensities, estimates a size distribution of an aerosol.

4. The fire alarm control panel of claim 3, the estimator performing its estimation using an inversion algorithm based on equations for Mie scattering.

5. The fire alarm control panel of claim 2, the analyzer comprising a comparator which compares the measured light intensities with previously measured intensity data for at least one aerosol of known composition.

6. The fire alarm control panel of claim 5, the system controller further comprising means for storing the previously measured smoke and aerosol spectral signatures.

7. The fire alarm control panel of claim 1, the smoke detector light detector comprising a photodetector capable of measuring different wavelengths independently of each other.

8. The fire alarm control panel of claim 1, the smoke detector light source being a white light LED.

9. The fire alarm control panel of claim 1, the light source being a broad-spectrum LED.

10. The fire alarm control panel of claim 1, the smoke detector light detector comprising a multi-element photodetector, each element being sensitive to a different wavelength band.

11. The fire alarm control panel of claim 1, the smoke detector light detector comprising a charge-coupled device with wavelength-selective filters applied in various combinations to the detections elements.

12. The fire alarm control panel of claim 1, the smoke detector light detector comprising multiple photodiodes, each photodiode being sensitive to a different wavelength band.

13. The fire alarm control panel of claim 1, the smoke detector light source emitting substantially white light.

14. The fire alarm control panel of claim 1, the smoke detector light source emitting, and at least one of the wavelength bands including at least one of:

infrared light;

visible light; and

ultraviolet light.

15. The fire alarm control panel of claim 1, the light detector detecting at least one of:

scattered light; and

transmitted light.

16. The fire alarm control panel of claim 1, raw measured light intensity values being forwarded by the smoke detector to the fire alarm control panel.

17. The fire alarm control panel of claim 1, the smoke detector further comprising processing means for processing the measured light intensities of the different wavelength bands prior to generating the information to be forwarded by the smoke detector to the fire alarm control panel.

18. The fire alarm control panel of claim 1, the light source emitting, and at least one of the wavelength bands including, infrared light.

19. The fire alarm control panel of claim 1, the light source emitting, and at least one of the wavelength bands including, ultraviolet light.

20. The fire alarm control panel of claim 1, the light detector detecting only scattered light.

21. The fire alarm control panel of claim 1, the light detector detecting only transmitted light.

22. The fire alarm control panel of claim 1, the light detector detecting both scattered and transmitted light.