Electronic sensor circuits convert light, temperature, sound, and other signals into a form that can be processed by electronic circuits. Learn about solar cells, photoresistors, thermistors, and magnet switches. Then build circuits that respond to heat, pressure, light, and more. This Engineer's Mini Notebook is a compilation of three of Forrest Mims's notebooks: Sensor Projects; Solar Cell Projects; and Magnet & Magnet Sensor Projects.