Introduction

Resistor-Capacitor Timing Basics

Designing and building new electronic devices is quite easy when you know the secret ingredient to rapid design. The technique is to take an existing electronic device and make a small change to it. For example, the Trick Switch project can easily be changed to a noncontact device by adding a sensor. With the right sensor, a hand wave can turn the LED on. The RC timing circuit wired to the sensor signals the Arduino to turn it off. In this chapter, you will build a light sensor circuit to turn on an LED with the wave of your hand and automatically turn it off. Figure 2-1 shows the Sunrise-Sunset Light Switch device.