A lockbox that requires a series of push buttons to be pressed in the correct combination in order to unlock has been made without the use of a microcontroller, writes Elecia for Hackaday.
The box opens to reveal a keypad and locking circuitry which activates a solenoid to unlock a drawer when the correct sequence is entered.
Instead of a microcontroller, the box uses capacitors and relays to sequence the correct activation of the buttons and disarm the lock, with incorrect entries resetting the system.
The project highlights the extent of complexity that can be achieved with non-programmable circuitry, and is a good example of how constraints can stimulate creativity.
Further to this, the box also manages power distribution to ensure that each relay is powered in the correct sequence, and does not use a microcontroller.
