Table of Contents
In this example you will learn to use a photocell light sensor with the XBee Zigbee Gateway to sense and take action based on the amount of available light. You use light to tell if it’s day or night of course, but you can also determine if a cabinet is open or closed, or if someone is currently occupying a hotel room. Because light changes at the speed…well of light, it’s a great sensor to use when want to prototype using changes that happen instantaneously rather than only over a longer period of time. Best of all, these sensors are cheap—at about a dollar a piece, they’re a great component to use when deploying sensors in large multiples.
The resistance across the two leads of the cell varies according to the amount of light hitting the cell. With our circuit, the brighter it is, the lower the voltage that is passed to the XBee’s analog-to-digital converter (ADC). This reading is then sent via Device Cloud to the XBee Zigbee Cloud Kit’s online dashboard application. Now you can monitor the brightness from anywhere right in your web browser.