สร้างสัญญาณเตือนระยะใกล้

You can read distance, so now react to it. A proximity alarm buzzes the moment something comes too close to the sensor. 🚨

Wire a small buzzer to a digital pin and to ground. Driving that pin HIGH makes a sound, and LOW makes it stop.

In setup, mark the buzzer pin as OUTPUT so the Arduino is allowed to drive it on and off whenever you decide.

Choose a trigger distance, for example 20 cm. Anything closer than this counts as too near and should set off the alarm.

Each loop, take a fresh measurement using the trigger and pulseIn steps you learned, then store the result in a distance variable.

Use an if statement to check whether the reading is below your threshold. That comparison is the brain of the whole alarm.

When something is too close, drive the buzzer pin HIGH. Otherwise drive it LOW so it stays silent until needed.

Remember pulseIn can return zero on a timeout. Skip those values so a missed echo never falsely triggers your buzzer.

Pair the buzzer with an LED on another pin. A visible blink plus the sound makes the alert clear even in a noisy room.

You can make the buzzer beep faster as objects get closer by mapping distance to the delay between beeps, just like a parking sensor.

This pattern, sense, decide, react, is the heart of every smart device. Swap the buzzer for a relay or a message to extend it.

Think about what decides when the buzzer sounds.

You combined a sensor, logic, and an output into a working alarm. That sense-decide-react loop is what real IoT projects are made of. ✅