High Intensity Discharge (HID) lighting contain a capsule of gas. The emission of light takes place from an arc discharge of two electrodes which are closely spaced which is tightly sealed within a small tubular capsule. HID lights need ignition that is often provided by an additional metal part I.e third electrode or a voltage pulse supplied to the capsule of gas. Once lit the electrical arc begins to evaporate the metal salts within the bulb increasing light efficiency and luminous power. The consumption of power is less and the quantity of light produced is greater than regular bulbs.
The light is produced through the metal vapour by passing current through it. On the first ignition, HID bulbs produce 5 % of output and require 10-15 sec to reach their full potential.
Light-Emitting Diodes (LED) light source consists of a semiconductor diode which has p-n junction in the centre. When current passes through the diode it emits light. Unlike Ordinary bulbs like incandescent, they don’t have a filament. LEDs are lit only by the movement of electrons in a semiconductor diode, making them energy efficient over long periods of time.
HID lamps are more delicate and usually take warm-up time during ignition. Whereas LEDs lamps are “instant on” and convenient on frequent on-off cycle. LEDs consist of semiconductor diode than filament to break or burn out gives them a longer lifespan than conventional bulbs. HIDs are less durable as compared to LEDs due to the mechanical nature of the substances used.