Realistic alarm experience, fully simulating the entire process of "smoke detection → sound and light alarm → emergency evacuation", children build a real fire alarm system by themselves. Principle of photoelectric tube and resistance capacitance delay circuit. Understand the relationship between smoke sensor sensitivity and false alarms. Secondary development is possible: installing a small fan as a "smoke exhaust fan" or connecting a micro water pump for "automatic spraying". According to the color of the plug, complete the "sensor main control sound and light" circuit. Ignite the cotton swab inside the sealed box to produce smoke, and observe the alarm threshold. Adjust the potentiometer to reduce false alarms and discuss the different needs of the kitchen and bedroom.