A discreet enclosure box sits in the sun, seeming to innocently soak up the rays abound. Two solar panels sit on top, recharging a Nickel–metal hydride battery contained within. You’ve seen this before in garden lights, motion lights, and similar outdoor appliances. But this black box has an ulterior motive!
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Solar Cricket is the latest addition to our Weekend Projects series of beginner-friendly electronics builds. With over 40 projects to choose from that you can start and finish in a weekend, if you build or modify any of these projects please send us pictures and a story of your experience. Use hashtag #WeekendProjects on either Google+, Twitter, or Facebook to post your progress and we will find you.
While the solar panels are used during the day to keep the Arduino active and recharge the battery, they’re also used as a sensor to detect light levels. Simpler builds could implement a light dependent resistor to detect when light drops below a certain level, but using the panels in conjunction with an Arduino Micro gives us more semantic control over when the circuit knows it truly is after sunset:
In other words we can compensate for cloud cover during the day, because crickets do not typically start chirping until after a genuine sunset!
But back to the circuit for a minute. We want to both keep the circuit operating during the day but also sense when to begin chirping at night (at which point the battery power kicks in). This is done via a simple charging circuit that ensures a steady supply of voltage is delivered to the Arduino, while the battery acts as a reserve for any excess power. This is done using a small number of common components. In the end all we are doing is running the sketch code and chirping a piezo buzzer [kudos to the builder for the 2600 reference -Ed.]. This may be overkill for some, but it’s a great introduction to the jeelib library for power management and this process of charge during the day, switch on at night, could easily be modified to power other projects.