QElectroTech. QElectroTech, or QET in short, is a free software to create industrial complex electric diagrams. But you can also even do plumbing, geothermal, air-conditioning, layout, hydraulics, pneumatics, domotic, PID, photovoltaic, swiming pool plumbing, ect...! On last version 0.100 devel the collection contains over 8000 symbols...