ボタンが「チャタリング」する理由

You press a button once, but your Arduino may see several presses. This sneaky problem is called bounce, and it trips up almost every beginner. 😅

A button is just two metal contacts that touch when you press. They feel solid to your finger, but at the microsecond level they are anything but.

When the contacts meet, they physically vibrate for a few milliseconds before settling. Each tiny touch and break is a separate electrical event.

During that vibration, the pin reads a burst of rapid HIGH-LOW flips instead of one clean change. Your code can count every flip as a press.

Your loop() runs millions of times per second, far faster than the bounce settles. So it samples the noise again and again.

Picture a counter that adds one per press. One real tap can jump it by three or four because of multiple false triggers.

Bounce strikes when you let go as well, not just when you press. Both edges of the signal can stutter and confuse your logic.

Most bounce settles within about 5 to 20 milliseconds. It is brief, but to a fast microcontroller that is an eternity of noise.

Print a message every time the pin goes LOW and tap once. Seeing several lines in the Serial Monitor proves bounce is real.

You can tame bounce with a small capacitor in the circuit, or with timing logic in code. Software is cheaper and far more common.

The fix is to wait briefly after the first change and ignore the rest. Confirm the button is truly stable before you act on it.

Let's confirm what causes a button to bounce.

You learned that a button's contacts bounce, sending noisy flips that fool fast code. Next you'll silence that noise with simple timing. 🎯