What Is a Neon Lamp?
A neon lamp is a lighting device that emits light when a glow discharge occurs in a glass tube filled with neon gas.
The lamp can emit light in a variety of colors by combining it with argon gas or by using a transparent tube and a fluorescent tube. Two electrodes are mounted inside the glass tube, and glow discharge is generated by externally controlled voltage.
In recent years, LEDs have become the mainstream lighting device, and neon lamps are used in the same way. The advantages of neon lamps include low power consumption, long life, no heat generation, and resistance to shock.
Uses of Neon Lamps
Neon lamps are lamps that emit light by filling a glass tube with neon gas. They are used for various effects and lighting, with entertainment district lighting being a typical example. In recent years, neon lamps have also been used for interior decoration.
Another application is the neon light-emitting detector. This detector uses the current from a neon tube that flows through a human being to the ground. It has the advantage of not requiring batteries, but it should be noted that it cannot be used when wearing insulated gloves, and there is a risk of electric shock.
The glass tube itself, which is filled with gas, can be processed by bending and stretching to be used as a text expression. By adjusting the thickness of the glass tube, the luminous intensity of the neon tube can be adjusted. Because of their low power consumption and long life, neon tubes are sometimes used for long periods as all-night lights, indicator lights (pilot lamps), and other lighting applications.
It was one of the most popular lighting devices until the advent of LEDs and is still used in the situations described above.
Structure of Neon Lamps
It consists of a glass tube with two electrodes made of iron or nickel and filled with neon gas at a low pressure of about 10~15 mmHg. The glass tube may be transparent or coated with fluorescent paint on the inside.
Neon gas emits red light in transparent tubes and pink or orange light in tubes coated with fluorescent paint.
Other Information on Neon Lamps
1. Neon Lamp Emission
When voltage is applied between the electrodes, the electrons between the electrodes are accelerated by the electric field and collide with neon gas, ionizing it into positively charged cations and electrons.
The resulting cations collide with the cathode, which emits secondary electrons. The emitted secondary electrons move to the anode, causing a large electric current to flow. This phenomenon is glow discharge.
This current (flow of secondary electrons) has enough energy to excite the neon atoms in the glass tube. As the excited atoms return to their ground state, they emit light with a wavelength corresponding to the energy difference between the energy bands. In the case of neon atoms, this light is observed as red light.
2. Characteristics of Glow Discharge
When glow discharge begins, some of the gas is ionized and generates more electrons. When this is repeated, an electron avalanche causes a steady current of about 0.1~10 mA to flow between the electrodes. The sustained discharge in a low-pressure gas is a characteristic of glow discharge.
The glow discharge start voltage in neon lamps is about 70 V and the discharge end voltage is about 60 V. A stable voltage must be supplied to continue stable discharge. Therefore, like fluorescent lamps, neon lamps are generally used in combination with ballasts.
Further raising the voltage between the electrodes results in an arc discharge, which makes neon gas more unstable. The light observed at this point changes to a blue-white color. Arc discharges generate very high heat, as evidenced by their use in arc welding, so care must be taken.