Forward and back scattering smoke detector and method of use
Systems and methods for smoke detection which utilizes two generally identical light sources and single light detector to compare the ratio of forward and backward scattering smoke particles present in a detection area.
1 . A smoke detector comprising:
a housing comprising a top, a base, and a series of co-axial disks separated by supports; wherein the area between the disks forms slots that allow generally unimpeded, planar flow into said housing and through a testing space;
said housing enclosing a detector component, a circuit board, and said testing space;
said detector component further comprising an optical support, said optical support including a generally planar optical support disk and a plurality of legs, wherein said testing space is above said optical support disk;
said optical support disk further comprising a first light mount, a second light mount, and a sensor mount;
said plurality of legs attached to said circuit board to form a gap between said optical support disk and said circuit board, said gap including said first light mount, said second light mount, and said sensor mount;
the first light mount directing light from a first light source through said optical support disk at a target point in said testing space;
the second light mount directing light from a second light source through said optical support disk at said target point in said testing space; and
a sensor for detecting light scattering from particles in said testing space;
wherein light from said first light source which scatters from said particles at an acute angle passes through said optical support disk into said sensor mount and is received at said sensor;
wherein light from said second light source which scatters from said particles at an obtuse angle passes through said optical support disk into said sensor mount and is received at said sensor; and
wherein said acute angle and said obtuse angle are in different planes.
2 . The smoke detector of claim 1 , wherein said first light source and said second light source produce generally the same wavelengths of light.
3 . The smoke detector of claim 2 , wherein said wavelengths of light are in the infrared (IR) spectrum.
4 . The smoke detector of claim 1 , wherein said first light source and said second light source alternatively illuminate said particles in said testing space.
5 . The smoke detector of claim 1 , wherein said acute angle is between about 45 and about 65 degrees.
6 . The smoke detector of claim 1 , wherein said obtuse angle is between about 110 and about 150 degrees.
7 . The smoke detector of claim 1 , wherein said acute angle is less than half of said obtuse angle.
8 . A method of determining a type of smoke, the method comprising:
providing a housing comprising a top, a base, and a series of co-axial disks separated by supports; wherein the area between the disks forms slots;
providing an optical support, a circuit board, and a testing space enclosed within said housing;
said optical support including a generally planar optical support disk and a plurality of legs, wherein said testing space is above said optical support disk;
said optical support disk further comprising a first light mount, a a second light mount, and a sensor mount;
said plurality of legs being attached to said circuit board and forming a gap between said optical support disk and said circuit board, said gap including said first light mount, said second light mount, and said sensor mount;
providing particles from air, smoke, or a combination of air and smoke;
said particles entering said housing in a generally unimpeded planar flow via said slots and flowing into said testing space;
directing light from a first light source through said optical support disk at a target point in said testing space;
directing light from a second light source through said optical support disk at said target point in said testing space;
detecting light scattering from particles in said testing space through said optical support disk and into said sensor mount at a sensor within said sensor mount;
determining a first amount of light from said first light source which scattered from said particles to said sensor at an acute angle in a first plane;
determining a second amount of light from said second light source which scattered from said particles to said sensor at an obtuse angle in a second plane different from said first plane; and
calculating a ratio of said first amount to said second amount.
9 . The method of claim 8 further comprising, initiating an alarm state when said ratio is above a predefined threshold.
10 . The method of claim 8 further comprising, initiating an alarm state when said ratio is above a predefined threshold and said first amount is above another predefined threshold.
11 . The method of claim 8 further comprising, calculating a total amount which is a sum of said first amount and said second amount.
12 . The method of claim 11 further comprising, initiating an alarm state when said ratio is above a predefined threshold and said total amount is above another predefined threshold.
13 . The method of claim 8 , wherein said first light source and said second light source produce generally the same wavelengths of light.
14 . The method of claim 13 , wherein said wavelengths of light are in the infrared (IR) spectrum.
15 . The method of claim 8 , wherein said acute angle is about 55 degrees.
16 . The method of claim 8 , wherein said obtuse angle is about 135 degrees.
17 . The method of claim 8 , wherein said acute angle is less than half of said obtuse angle.
18 . The smoke detector of claim 1 , wherein said housing further comprises an insect grid that surrounds the periphery of said optical support and defines said testing space.
19 . The smoke detector of claim 18 , wherein particles from air, smoke, or a combination of air and smoke, enter said housing via said slots and flow through said insect grid and into said testing space.
20 . The method of claim 8 , further comprising, providing an insect grid surrounding the periphery of said optical support and defines said testing space; wherein said particles enter said housing via said slots and flow through said insect grid and into said testing space.