Keypad Door Lock
Type a code on a membrane keypad to open a servo latch.
Overview
The keypad is scanned as a matrix of rows and columns. A correct code swings the servo to release the latch; a wrong code blinks the red LED and beeps.
Build Steps
Wire the keypad
Connect the eight rows and columns to digital pins and set them as inputs with pull-ups; the library handles the matrix scan.
Read key presses
Accumulate digits into a buffer, with * to clear and # to submit the code.
Drive the latch
On a correct code, move the servo to the open angle, light the green LED, wait three seconds and re-lock.
Handle wrong codes
Blink the red LED, sound the buzzer and require a short lockout after three failures.
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