Push-Button Code Safe

About this project

Build a 4-digit PIN security vault that physically unlocks a servo latch when the correct code is entered. Three buttons (UP, DOWN, SELECT) let you scroll digits 0-9 and confirm each in sequence, with confirmed digits masked as asterisks to prevent shoulder-surfing. Three wrong attempts trigger a 5-second lockout; six wrong attempts trigger a 30-second lockout -- the same exponential backoff used by ATMs and smartphones. The PIN is stored in EEPROM and survives power-off. A secret admin button combo (hold DOWN + press SELECT on the LOCKED screen) lets you change the PIN without knowing the old one. The WOW moment: hand the box to anyone and tell them to guess the PIN -- the 30-second lockout fires in under 2 minutes. Build time: 2-3 hours. No WiFi, no app, no cloud.

What you get

• Complete, commented source code
• Full components list with quantities
• Pin-by-pin wiring guide and connection table
• Step-by-step upload and testing guide
• Project report (.docx, IEEE style)
• Presentation slides (.pptx)