Chapter 8

Building a Keypad Entry System

In This Chapter

arrow Reading a numeric keypad

arrow Using an LED display IC

arrow Actuating a relay

arrow Using character arrays

No self-respecting mastermind would leave his fortress unsecured against intruders. The project steps in this chapter guide you through building a keypad entry system that unlocks a door when you enter the correct code into a standard 10-digit keypad. The system also displays the code on a seven-segment LED display while you are entering it, and when you’ve keyed in the correct code a welcome message is displayed.

The project uses a four-digit (“quad”), seven-segment display — the kind you’ve seen in every spy movie since the 1960s and a widely available standard keypad with a telephone-style layout. The door is secured with an electric locking mechanism that is activated once you type in the correct code.

You can buy systems like this from specialty lock and security suppliers, but it’s more fun to build it yourself and pick up a few Arduino skills along the way. You can also modify the system to accept input from the RFID card reader ...

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