Why is there a red light flashing on the roof of the hotel?

The flashing instrument on the ceiling of a hotel room is usually a smoke detector. Its function is to detect whether there is smoke in the room and find the fire in time.

Smoke alarm is something that will automatically give an alarm after the smoke concentration reaches a certain value, so as to achieve the purpose of alarm, that is, flashing red light; There is also a temperature alarm, which means that when it reaches a certain temperature, a red sensor rod will overheat and burst, and then spray fire-fighting water (shaped like a pinion) to achieve the purpose of extinguishing the fire.

Extended data:

principle

The infrared beam of the infrared emission tube is scattered by smoke particles, and the intensity of the scattered light is directly proportional to the smoke concentration, so the intensity of the infrared beam received by the photosensitive tube will change and be converted into an electrical signal, and finally into an alarm signal. The smoke sensing of the alarm is mainly completed by the optical maze, in which a group of infrared emitting and receiving photocells are installed, and the diagonal angle is 135 degrees.

When there is no smoke in the environment, the receiving tube can't receive the infrared light emitted by the infrared emitting tube, and the subsequent sampling circuit has no electric signal change; When there is smoke in the environment, smoke particles enter the maze to scatter the infrared light emitted by the emission tube, and the intensity of the scattered infrared light has a certain linear relationship with the smoke concentration.

If the subsequent sampling circuit changes, the main control chip built in the alarm will judge these changes to confirm whether there is a fire alarm. Once the fire alarm is confirmed, the alarm will send out a fire alarm signal, the fire indicator (red) will light up, and the buzzer will start the alarm.

References:

Baidu encyclopedia-smoke alarm