Not a complicated combination lock for arduino using a 1602 display, a membrane keypad and an arduino uno. Anyone can assemble it, you can make changes to the code. You can watch my video in more detail, also under the video there is a link to the description of the device and the code itself with the circuit.
[media = https: //www.youtube.com/watch? v = B0Xr_iLC8iQ & t = 394s]
In standby mode, the display shows an inscription that can be easily changed by yourself, and you need to make some corrections in the sketch.
Using this 3x4 membrane keypad, a pin is dialed, the following characters are visible on the display when typing (****) after the PIN code is dialed correctly, the display will show OPEN
And the relay will work, you can put a servo drive or an electric latch instead of a relay.
The whole scheme is as follows.
On the breadboard there are two LEDs with current-limiting resistors of 150 ohms that signal us that if the lock is open, green is on and red is closed, and the piezo emitter is visible on the top left of the breadboard which serves as a sound accompaniment when you press the keyboard.