Abstract: A method includes forming a housing having a ceiling portion and a smoke permeable wall portion. The ceiling portion of the housing has a first aperture and a second aperture. The method includes mounting a circuit board to the housing so that the housing and the circuit board collectively define a smoke chamber that is bounded by the ceiling portion, the smoke permeable wall portion and the circuit board. The method includes placing an emitter in the first aperture and placing a detector in the second aperture. The emitter defines an emitting region in the smoke chamber and the detector defines a detecting region in the smoke chamber. In a typical implementation, the detecting region at least partially intersects the emitting region in the smoke chamber, and the emitter and the detector are disposed substantially outside the smoke chamber.

Abstract: A method of reducing variation in optical power levels across a group of light emitting diodes includes testing each respective one of the light emitting diodes to determine an optical power level produced by that light emitting diode when connected to an electrical power source. During testing, the electrical power source delivers a substantially identical amount of electrical current to each respective one of the light emitting diodes. The optical power levels from the test all fall within a first range of values. The method includes connecting an electrical resistance in parallel with at least some of the light emitting diodes to reduce an amount of optical power produced by those light emitting diodes. After the electrical resistances are connected, all of the optical power levels produced by the light emitting diodes fall within a second range that is narrower than the first range.

Abstract: A device and method for manufacturing an integrated smoke cell are presented. The smoke cell includes an integral housing with a ceiling portion and a smoke permeable wall forming a chamber when mounted on a printed circuit board. An emitter and detector are mounted above apertures in the chamber ceiling so the emitter and detector are mounted substantially outside the chamber while detecting smoke present within the chamber without blocking ingress of smoke through the chamber wall.