230 Digital padlock

230 : Digital padlock


How it works

Each buttons press is detected by a rising edge detector, and each button press is decoded into a binary code. That binary code is stored in a shift-register which is continuously checked against a reference value (’the padlock code’).

How to test

Connect a clock generator to the clock input, connect all four buttons with a debounce circuit - the buttons should act as active high.


# Input Output
0 clock none
1 Button A none
2 Button B none
3 Button C none
4 Button D none
5 none none
6 none Button press detected
7 none Code valid