Relay + flyback diode

Hold the button to energize the coil; COM swings to NO and lights the LED. The diode across the coil tames the inductive kick.

What's on the bench

• Battery
• Button
• Diode
• LED
• Relay
• Resistor

This project runs prebuilt firmware on the emulated board; open it in the simulator to watch it work and inspect every part live.