Tank Float Switch Schematic - Microcontroller Interfacing: Due to my ladder logic compiler, I often get questions on how to build hardware to connect a micro to the outside world. I have not been able to find a good reference to suggest. Much of the material online is wrong or incomplete, or reflects good practice circa 1970.. How to Size Wiring for Your System - The Manual Method. Also see the Easier-to-Use Wire Sizing Calculator. Properly sized wire can make the difference between inadequate and full charging of a battery system, between dim and bright lights, and between. Description of the Charging System: (includes some troubleshooting & problems much more later in article) The BMW Airhead charging system is basically the same; with only modest variations, on all models from the introduction of the 1970 /5 series, to the end of production in 1995-1996..