Self-calibrating fire sensing device

1. A self-calibrating fire sensing device, comprising:

an adjustable particle generator and a variable airflow generator configured to generate aerosol having a particular particle size and optical scatter properties at a controllable density level;

a first transmitter light-emitting diode (LED) configured to emit a first light that passes through the aerosol;

a second transmitter LED configured to emit a second light that passes through the aerosol;

a photodiode configured to:

detect a scatter level of the first light that passes through the aerosol; and

detect a scatter level of the second light that passes through the aerosol; and

a controller configured to calibrate a gain of the photodiode based on the detected scatter level of the first light, the detected scatter level of the second light, and the controllable aerosol density level.

2. The device of claim 1 , further comprising an additional photodiode

configured to: detect an additional scatter level of the first light that passes through the aerosol; and

detect an additional scatter level of the second light that passes through the aerosol.

3. The device of claim 2 , wherein the controller is configured to calibrate the gain of the photodiode based on the detected additional scatter level of the first light and the detected additional scatter level of the second light.

4. The device of claim 1 , wherein the controller includes memory configured to store the detected scatter level of the first light and the detected scatter level of the second light.

5. The device of claim 1 , wherein the first transmitter LED is an infrared (IR) LED.

6. The device of claim 1 , wherein the second transmitter LED is a blue LED.

7. The device of claim 1 , wherein the photodiode is an LED.

8. A method for operating a self-calibrating fire sensing device, comprising:

generating aerosol having a particular particle size and optical scatter properties at a controllable density level using an adjustable particle generator and a variable airflow generator of the self-calibrating fire sensing device;

emitting, by a first transmitter light-emitting diode (LED) of the self-calibrating fire sensing device, a first light that passes through the aerosol;

emitting, by a second transmitter LED of the self-calibrating fire sensing device, a second light that passes through the aerosol;

detecting, by a photodiode of the self-calibrating fire sensing device, a scatter level of the first light that passes through the aerosol;

detecting, by the photodiode, a scatter level of the second light that passes through the aerosol; and

recalibrating a gain of the photodiode based on the detected scatter level of the first light or the detected scatter level of the second light.

9. The method of claim 8 , wherein recalibrating the gain of the photodiode comprises:

comparing the detected scatter level of the first light to a threshold scatter level of the first light;

comparing the detected scatter level of the second light to a threshold scatter level of the second light; and

recalibrating the gain of the photodiode responsive to the detected scatter level of the first light being below the threshold scatter level of the first light or the detected scatter level of the second light being below the threshold scatter level of the second light.

10. The method of claim 8 , wherein recalibrating the gain of the photodiode comprises:

comparing the detected scatter level of the first light to a previously detected scatter level of the first light;

comparing the detected scatter level of the second light to a previously detected scatter level of the second light; and

recalibrating the gain of the photodiode responsive to the detected scatter level of the first light being less than the previously detected scatter level of the first light or the detected scatter level of the second light being less than the previously detected scatter level of the second light.

11. The method of claim 8 , further comprising measuring ambient airflow outside of the self-calibrating fire sensing device using a sensor before generating the aerosol.

12. The method of claim 11 , further comprising generating the aerosol responsive to the measured ambient airflow being within a particular airflow range.

13. The method of claim 8 , further comprising recalibrating the gain of the photodiode based on settings of a heating, ventilation, and air conditioning (HVAC) system.

14. A fire alarm system, comprising:

a monitoring device; and

a self-calibrating fire sensing device, comprising:

an adjustable particle generator and a variable airflow generator configured to generate aerosol having a particular particle size and optical scatter properties at a controllable density level;

a first transmitter light-emitting diode (LED) configured to emit a first light that passes through the aerosol;

a second transmitter LED configured to emit a second light that passes through the aerosol; and

a photodiode configured to:

detect a scatter level of the first light that passes through the aerosol;

detect a scatter level of the second light that passes through the aerosol; and

transmit the detected scatter level of the first light and the detected scatter level of the second light to the monitoring device.

15. The system of claim 14 , wherein the monitoring device is configured to:

compare the detected scatter level of the first light to a threshold scatter level of the first light;

compare the detected scatter level of the second light to a threshold scatter level of the second light; and

transmit a command to the self-calibrating fire sensing device responsive to the detected scatter level of the first light being below the threshold scatter level of the first light or the detected scatter level of the second light being below the threshold scatter level of the second light.

16. The system of claim 14 , wherein the monitoring device is configured to:

compare the detected scatter level of the first light to a previously detected scatter level of the first light;

compare the detected scatter level of the second light to a previously detected scatter level of the second light; and

transmit a command to the self-calibrating fire sensing device responsive to the detected scatter level of the first light being less than the previously detected scatter level of the first light or the detected scatter level of the second light being less than the previously detected scatter level of the second light.

17. The system of claim 14 , wherein the self-calibrating fire sensing device is configured to receive a command from the monitoring device to recalibrate a gain of the photodiode.

18. The system of claim 14 , wherein the self-calibrating fire sensing device is configured to transmit a message to the monitoring device.

19. The system of claim 18 , wherein the self-calibrating fire sensing device is configured to transmit the message to the monitoring device responsive to the self-calibrating fire sensing device recalibrating a gain of the photodiode.

20. The system of claim 18 , wherein the self-calibrating fire sensing device is configured to transmit the message to the monitoring device responsive to the self-calibrating fire sensing device failing to recalibrate a gain of the photodiode.