4 Digit PIN code

A simple lock with a PIN code to open the door

In this case, the PIN code is 1 4 5 9

You have to enter the code in order, and if you do an error, you have to re-enter the whole PIN code again

This circuit is :

+ a RESET (it's in fact a NOT gate, an inverter, left) to kill the power briefly and start over

+ an AND gate (4 auto switches, top) to "add" the tick coming from the 1, 4, 5 and 9 buttons. Note that the auto switches are connected to themselves, from bottom to right, to keep them ON after one tick (a tick is the little time a button send electricity)

+ a NOT gate (an inverter, right) to open or close the door

+ the keypad (buttons, bottom), blue connected to power, and in red to RESET or AND

In this case : 
+ 1, 4, 5 and 9 are connected in order to the AND (the PIN code)
+ 2, 3, 6, 7, and 8 are all connected to the RESET (all the others numbers)

Simply change the keypad wiring to choose your own PIN code

The official limit of big red buttons in No Man's Sky is 10. Be aware that without glitch, you will use 9 of them in this one build.

You can deport the buttons and hide the circuit with walls, so curious players will not guess the code just by following the wires to the AND.

main source : Beeblebum

Try this circuit live at the No Man's Sky School of Technology (Euclid)