throwing some light on LEDs

Light-emitting diode (LED) lamps are replacing incandescent filament lamps in a variety of indicator applications, as they offer improved reliability and performance at a comparable price. A bewildering variety of LEDs of different shapes, sizes, colours and prices is now available, and the amateur constructor may find it difficult to choose a device for a particular project, especially if the parts list simply says that a `LED` should be used, with no indication of type. This article aims to dispel some of the mystery surrounding LEDs, so that the constructor can choose the most suitable type for his requirements, and calculate the operating conditions.