Low Cost Pure Sine Wave Solar Inverter Circuit ECE Capstone Design Project, Spring ‘14 Cameron DeAngelis Luv Rasania Advisors: Professor Yicheng Lu and Rui Li Introduction Ever thought about what goes on behind the scenes when you simply flick the power switch to on? There is an entire process as to how this electricity is created to help power on your lights and devices. In todays world most of the electricity is generated through the use of electromechanical generators which are driven by heat created from chemical combustion or nuclear fission. This process however, exerts pollution into the air and small amounts of radiation. Motivation The world today is slowly transforming into a green world where pollution is going to be at an all time minimum. A solution to cut down pollution created by these generators is to have an alternate form of energy production. Through the use of solar panels, energy from the sun is almost always readily available to be harnessed into electricity. This energy, however, is in the form of DC voltage and needs to be inverted to an AC voltage to be compatible with our electrical grid. This is where a solar inverter circuit becomes necessary. Design In order to invert the DC voltage, the group made use of a 555 timer IC, a decade counter IC, and H-bridge circuit, and a passive filter circuit. The 555 timer is responsible for generating a clock voltage input for the decade counter at the correct frequency. The decade counter provides an optimized square wave for triggering the transistors in the Hbridge circuit. The H-bridge inverts the input signal into a modified sine wave, which then enters the filter where it becomes very similar to a sine wave. The filter is a 3rd order low pass design which values were chosen by trial and error. Results The circuit produced a relatively good output signal at the required frequency and amplitude, so the project was an overall success. The design came out to a total cost of $45.71. The pure sine wave output is shown below.