thenextbilliononline / freifunk-open-mppt

Open hard- and software solar maximum power point tracker

These are preliminary sources and CAD files from the Freifunk-Open-MPP-Tracker project.

SOME LICENSE-FOO:

This is a Open-Source and Open-Hardware project under General Public License v2 and Creative Commons - Attribution - ShareAlike 3.0. For more information, check out the LICENSE file.

A QUICK OVERVIEW OF THE DIRECTORIES:

AVR-FUSES

Contains a XML configuration file to program the fuses of the AVR. I am using the AVR dragon board and AVR-Burn-O-Mat software to program the fuses.

SCHEMATIC AND BOARD

Electronic CAD files and component libraries, made with KiCAD. KiCAD is a free and open ECAD tool. Due to the intend to provide a open hardware and open software project for DIY home-brewers, I have decided to use a free and open source ECAD software tool, too. It is my first project with KiCAD, though.

uC-SOURCECODE

AVR-GCC source and Makefile.

SOME NOTES ABOUT THIS DESIGN

Basically this hardware has two building blocks: The MPP controller section and the buck converter.

At the moment, the buck converter section is based on the el cheapo and low-fi MC33063 controller chip. It can easily be replaced by a faster and more fancy switch converter IC to construct a more powerful and slightly more efficient buck converter section. However, with the external powerful P-MOS switches, the efficiency was already around 94% with the first prototype (measured at 2 Ampere output current).

One reason to replace the MC33063 might be noise. Under low load, the MC33063 will skip pulses of the PWM, so the switching frequency becomes audible.

External references

• https://wiki.freifunk.net/Freifunk-MPP-Tracker
• https://wiki.freifunk.net/Freifunk-Mast