Can I Replace LEDs With A Fluorescent Tube In An Emergency Light Project

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Light emitting diodes (LEDs) and fluorescent lights use two different technologies for producing light. So, the short answer is no.

A fluorescent light is a type of gas discharge tube that contains inert gas within the glass casing while an LED is based on a PN junction diode, a solid-state device. Fluorescent tube produces ultraviolet (UV) radiation that is converted to visible light. LEDs emit electromagnetic radiation across a small portion of the visible light spectrum.

Further, fluorescent tube light requires a ballast circuit to stabilise the internal current that produces light while LED can be directly connected to a DC source through a current limiter to produce the light.

Fluorescent tube is coated with a layer of phosphor, which glows when it comes in contact with UV radiation. Although most UV radiation stays within the tube, some does escape into the environment. This UV light can potentially be hazardous, while a normal LED does not produce any hazardous UV light.

A fluorescent tube is almost always powered with AC. The tube’s driver or ballast consists of a transformer along with other passive components. The transformer’s primary coil current induces a current in the secondary coil, producing a voltage of approximately 230V that makes the fluorescent coating glow.

When power is first applied to the tube, a high voltage discharge is needed to start the flow of current. However, once this discharge takes place, a much lower voltage is sufficient—usually under 100V for tubes under 30 watts and 100V to 175V for tubes of 30 watts or more.

The fluorescent starter is a time-delay switch that opens after a second or two. During this time, the high voltage across the tube allows a stream of electrons to flow across the tube and ionise the mercury vapour, which makes the tube to glow. Some modern fluorescent tubes do not require a starter because they come with a ballast that has extra windings and energy to initiate the light.


 

2 COMMENTS

  1. I will make the observation that, where a fluorescent lamp generates ultraviolet light through the excitation of the mercury vapor in the glass envelope; white emitting LEDs do not directly emit white light. All of the white/off-white emitting LEDs (as well as many LEDs used to emit amber light for automotive uses) that I have used are an ultraviolet emitting LED which has the top surface of the PN junction die coated with a phosphor (very similar, if not identical, to that used in fluorescent lamps) which emits the desired combination of light frequencies,, in response to being illuminated by the ultraviolet light generated by the LED PN junction.

    Irrespective of the proposition of a “drop-in replacement’ of one technology for the other,, both technologies produce the desired light output in a final similar step in the process of light production, while having very different underlying methods of generating the ultraviolet light to begin with.

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