2nd January 2011 - High/Low Voltage warning system

A voltage low warning light is mandatory for all aircraft in the UK. Commercial versions are available but quite expensive so I constructed one. This flashes a warning light slowly when the system voltage drops below 12V and then after a period leaves the light on to avoid being too much of a distraction. It also flashes the light fast if the voltage rises above 15V. In addition the unit outputs the voltage on a opto isolated serial output so it can be read into the system monitor I've also built. The circuit and program is very simple and uses a Picaxe 08M microprocessor to do all the hard work. If you want to copy it and don't need the serial output just omit the optocoupler.