Simple and easy build electronic combination lock based on IC LS7220.
The LS7220 is a MOS digital lock circuit. When wired to a ten-digit keypad, the circuit will recognize one four-digit combination out of a possible 5040 combinations.
The LS7220 is configured with the features required for an Automotive Ignition Anti-Theft Digital Lock. These features include Sense input which enables the IC, Save Memory for Valet Parking, Convenience Delay to maintain Unlock condition for short term interruptions of the Sense input and Save Status and Lock Status outputs which can be used for direct drive of LED indicators.