Power Line AC Voltage Presence Sensor
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-01
This circuit arrangement provides a single zener diode to simultaneously monitor proper voltage on a poly-phase AC power supply to a system. The zener is on the high voltage side of the supply and is biased to provide a stable reference. A threshold detector operates by switching the zener bias current through an optical isolator. The optical isolator output is coupled to a circuit designed to be consistent even with variations in the optical isolator. AC Voltage Presence (ACVP) sensors are used to detect if the AC voltage at a given point is below a predetermined value. Such sensors are invaluable for isolating faults in power systems. When placed inside a power supply for example, this sensor can be used to tell if the power supply has enough voltage to operate or not.