EM04 · Sem 5 · Microcontrollers

Button input with debouncing

Aim: Toggle an LED with a push button and remove contact bounce.

🧪 Live simulation🧊 Real-time 3D bench⚠ Simulated values, not physical measurements

🔬 Virtual lab

Starting the lab…

📘 Theory

A button on an input with pull-up reads HIGH when released and LOW when pressed. Mechanical contacts bounce for a few milliseconds, so the code waits for a stable reading before acting.

debounce time ≈ 20–50 ms

🧰 Apparatus (virtual)

Dev board
button on pin 2
LED on pin 13

📝 Procedure

Run with the default press times
Watch the LED toggle on each press
Add more press ranges
Remove the debounce delay and discuss what real hardware would do

Observations and result (kept on this device)

🎤 Viva questions

Why use INPUT_PULLUP

The pin would float without a defined level when the button is open.

How does hardware debouncing work

An RC filter and a Schmitt trigger smooth the signal.

🛡️ Safety

Virtual board. On real hardware, check supply voltages and pin current limits, and power motors and servos from a separate supply.