ACCEPTANCE SPECIFICATION FOR LIGHT EMITTING DIODE TYPE
SOLID-STATE PILOT INDICATION LIGHT

Introduction

Light Emitting Diodes (LEDs) are basically comprised of P-N junction diodes that have a dimension of approximately 0.4mm square. This junction (chip) is composed of semiconductor materials such as Gallium Arsenide Phosphide, Gallium Aluminium Posphide, Silicon Carbide etc. The chip is bonded to a lead wire frame and encapsulated in ep-oxy resin of a suitable refractive index. Chips emit light at various intensities - which are measured in millicandela (mcd) - and in different wavelengths, depending on the impurity injected into the chip at the time of manufacture. The outer epoxy is often tinted (coloured) with various colours to provide enhanced contrast while burning; however, this tinting reduces the intensity of the light emitted by the chip. The chips are usually encapsulated into the standard LED dimensions of 3mm, 5mm or 10mm diameter.

  • Electrical parameters: LEDs can have an absolute forward current rating of up to even 50mA (except in blue), de-pending on the composition of the P-N junction. Furthermore, LEDs - being diodes - have a forward voltage drop ranging from 1.6 volts to 2.4 volts (or 3V to 3.3V for blue) and a maximum peak inverse voltage of 5V.

  • Life: The diodes are rated for a life of 100,000 hours (considered completed when the light intensity depreciates to 75% of the initial rating). This is subject to maintaining the operating current within the absolute maximum forward current ratings (after temperature derating, if any), and with adequate protection for PIV.

  • Glow sensitivity: LEDs are highly sensitive to the applied voltage, and will glow as soon as the voltage across the di-ode exceeds the rated forward voltage of the P-N junction.
    Physical:

  • Body: The LED Module body shall be of fire-retardant glass-filled thermosetting resin, capable of providing adequate electrical insulation even after absorption of moisture. The fire-retardant property should be adequate so as to with-stand the UL94-V2 test.

  • Terminals: Terminals will be of brass construction, each capable of holding two pin type or spade type cable lugs.

  • Lens: The lens shall be constructed of fire retardant (UL-94V2) polycarbonate material and should have high spectral transmission for any particular colour.

    The colour of the lens shall have the following spectral wavelength transmission:

Colour Wavelength
(Nanometers)		 Colour Wavelength
(Nanometers)
Blue 430-450Nm Amber 590-595Nm
Pure Green 550-560Nm Orange 605-610Nm
Green 560-570Nm Red 630-660Nm
Yellow 575-585Nm Deep Red 690-695Nm


  • Adapter dimensions (for fitting into panel cutout): The diameter of the adapter shall be as follows (depending on the diameter of the panel cutout the Module is to be used in):
    22 mm +/- 0.5 mm
    25 mm +/- 0.5 mm
    30 mm +/- 0.5 mm

    The thread shall be of metric standard.

  • Lock nut: This shall be of adequate thickness to cover a minimum of three threads and shall have no appreciable looseness when fitted.

  • Gasket: The rubber gasket shall be of adequate thickness, and shall not be loose in the body. It must be of mini-mum 1mm thickness to satisfy IP54 requirements

  • Bezel: The metal parts of the bezel shall be of brass, chrome-plated to a shining finish, and shall withstand corro-sion.

  • Salt Atmosphere requirements: The Module shall withstand Salt Spray Test for ensuring no corrosion under salty atmospheric conditions.

  • Marking: Industrial type Modules shall be bipolar (except for 220V DC operation).

  • Internal Protection: The Module will be designed to IP 54 requirements.

    Optical and Electrical

  • Luminosity: The axial light intensity shall be minimum 80mcd for standard Intensity types and 100mcd for high in-tensity types (except blue).

  • Viewing Angle: Viewing angle of the LED Module with lens shall be a minimum of 45 degrees on all sides of the axis of the lens (viewing angle is the angle at which the light intensity falls to 50% of the axial).

  • Current: The rated current shall be 30mA (maximum) at the rated voltage.

  • Diode: The Light Emitting Diodes used in the Module shall have an absolute maximum forward current rating of at least 40% in excess of the rated operating current.

  • PIV: Adequate protection shall be provided for Peak Inverse Voltage (which is 5V maximum for all LEDs).

  • High Voltage Test: The Module shall withstand a voltage of 2.5KV between body and terminals for 1 minute.

  • Insulation Resistance Test: The insulation shall be minimum of 50 megohms when tested with a meggar at 500V DC.

  • Relative Humidity Test: The LED Module will be kept in a humidity chamber at RH 95% and temperature 40 degrees centigrade for 24 hours. The Module will withstand insulation test as per clause 2.7 (after wiping off any moisture).

  • Salt Water Boiling Test: The bare Module body will be subjected to boiling in salt water for one hour. The insulation resistance will be the same as per clause 2.7 (this will be a type test).

  • Fuse: A fuse shall be provided in the Module to protect on-line equipment in case of a short circuit.
    NB: This has been introduced since 1997 at the insistence of KRIBHCO Hazira. They had experienced damage to very valuable equipment due to a short circuit inside the LED Module. Since this is a remote possibility, we are incorporating this feature so users can be free from worry.

  • Low Voltage Glow Protection: The Module shall be provided with circuitry so that LED will not glow below 25V. This voltage is generated inductively due to long runs of adjacent cables; whereas a 240V filament lamp does give any indication below 60V, LEDs begin to glow at a very low voltage unless protection against this possibility is provided.

  • Power Consumption: (A) 0.75 watts maximum for AC (B) 1.75 watts maximum for DC

    Life

    The LED Module shall be rated for a life of 1,00,000 hours

    Ten samples shall be tested in an oven at a temperature of 80 degrees centigrade for 16 hours in burning condition at rated voltage. There should be no failures.