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Basic Electronics for Tomorrow's Inventors by Nick Dossis

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CHAPTER 15
You’ll Never Get In! Build an Electronic Security Keypad
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MANY SECURITY DOORS HAVE A security keypad, which is usually a number of push buttons that a person has to press to activate the secret code to open the door. This stops thieves and snoopers from gaining access to places they’re not supposed to be. This experiment shows you one method of creating a keypad with eight push-button switches that have to be pressed in a certain way to illuminate an LED. The layout for the experiment is shown in Figure 15-1.
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FIGURE 15-1 The electronic ...

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