Neon glow lamps are a sort of components that are quite old, simple and cheap. They are widely used as main voltage monitors. The most interesting characteristics are the very low current needed (even less than 1 mA) and the relatively high nominal voltage (60..80 V).
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The most common lamps are composed by a glass bulb filled with low pressure neon
which contains two cylindrical electrodes. When a current flows though the lamp a
red orange glow appears on the negative electrode. If the current is alternative
both electrodes will glow.
The current may vary between 0.1 and 10 mA depending on the desired
brightness and the type of the bulb. The voltage drop is about 60..80 V and
is rather independent of the current.
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Special models supporting higher voltages (110 or 230 Vac) can be easily found, since they just include a series resistor.
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The color of the light is usually orange, and to obtain different colors (typically green) the bulb is usually filled with mercury and on the internal surface of the bulb is covered with a fluorescent material. The electrical characteristics are similar to normal neon bulbs.
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