[Carl] recently installed solar panels in his house. This system supplements the electricity it draws from the grid by charging a battery bank with cheap energy (like beer) from the sun. The system featured a simple meter that actually only showed the total amount of electricity produced by the modules. [Carl] wanted to extract more data from his system. He managed to build his own monitor using an Arduino.
The trick with this build is how the system works. The panel contains an LED light that flashes 1,000 times per kWh of electricity. [Carl] realized that if he could monitor the rate at which the LED was lighting, he could roughly determine the amount of current produced at any given time. We have seen similar projects in the past.
Like most tech newbies, [Carl] built his project by gathering other examples he found online. He began using a sketch originally intended to calculate the speed of a vehicle by measuring the time taken for the vehicle to move between two points. [Carl] took this code and modified it to use a single photoresistor to track the LED. He also built a sort of VU-meter using LEDs. The meter increases and decreases in proportion to the reading of the electricity meter.
[Carl] continued to improve his system over time. It added an LCD panel so you can see not only your current and accurate reading, but also your highest reading for the day. He put all the electronics in a plastic tub and used a ribbon cable to move the LCD panel to a more convenient position. He also asked his friend [Andy] to clean up the Arduino code so others can use it as they see fit.
