Button input noise, often called "switch bounce," is a common issue in digital electronics where a mechanical button or switch generates multiple erratic signals instead of a single clean one upon press or release. This occurs due to the physical contacts vibrating before settling. Preventing this noise is crucial for reliable system operation. The most common prevention methods are divided into hardware and software solutions.

Hardware debouncing uses passive components to filter the noise. A simple RC (Resistor-Capacitor) filter is a popular method. The capacitor charges and discharges through the resistor, smoothing the voltage transition and suppressing rapid changes. Another effective hardware technique is using a Schmitt trigger, which provides hysteresis, ensuring a clean, fast digital transition once the input voltage crosses a specific threshold. For critical applications, a dedicated debounce IC or a simple SR latch made from logic gates can provide a very robust solution, completely eliminating the bounce.

Software debouncing is implemented in code and is often more cost-effective. The most straightforward method is adding a delay after the initial button state change is detected. The system waits for a period (typically 5-50ms) for the bouncing to settle before reading the button state again. A more efficient and reliable software method is to periodically sample the button state and only register a press after a consecutive number of stable readings. This is often managed by a state machine or a timer interrupt, which doesn't block the main program.

For optimal results, a combination of a basic hardware filter (like a small capacitor across the switch) and robust software debouncing is highly recommended. This approach provides a defense-in-depth strategy, ensuring maximum reliability for any digital input system, from simple Arduino projects to complex industrial controls.