Circuit for intrinsically safe pilot light

摘要

An electric circuit for energizing an intrinsically safe pilot light having a cluster of light emitting diodes arranged in a pattern and visible through a lense cap located in a hazardous area. The pilot light has terminals connected through the circuit that includes a rectifying bridge and a current regulator to the diodes to optimize the light output of the diodes and make the pilot light insensitive to the polarity of an A.C. or D.C. intrinsically safe electrical supply to the pilot light and limiting the current to the diodes to a constant value in event one or more of the diodes is destroyed or shorted. A pair of printed circuit boards are spaced by a plurality of conductive supports with one of the boards mounted on a base of the pilot light and carrying the rectifier and current limiting components which are connected to the terminals. The other printed circuit board provides a support for the diodes and has a printed circuit thereon, portions of which provide a reflective surface for light emitted by the diodes. The pilot light includes a translucent lense cap formed of material that transmits light frequencies matching the light frequencies emitted by the light emitting diodes and optionally may include a fuse that replaces one of the conductive supports and limits current to the hazardous area.