Electronic – Why does a neon lamp indicator on a power strip switch flicker in the dark

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Neon lamp indicators embedded in power strip switches indicate whether the switch is ON or OFF.

When the neon lamp is ON in a dark environment (lights of the room are off), the lamp begins flickering and it sometimes goes off for a few seconds.

When I switch the lights of the room on, it stops flickering and remains bright. Even when I unlock my phone in the dark near the lamp, it stops flickering!

Is the light-making-mechanism in neon lamps affected by the light intensity of the surrounding environment?

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UPDATE: I captured my observations with my iPhone and uploaded it to YouTube. Here is the link of the video:

All the lights of my room were turned off. There were no plugs connected to the power strip. The only source of light was the screen of my MacBook Pro, which was not plugged in. I increased and decreased the brightness of the computer screen during the video. I then produced two additional light environments using my phone.

Best Answer

This is a common phenomenon: neon pilot lights have a limited lifetime, and after many years of use, they begin to flicker, then they finally go dark. They no longer can operate at line voltage, but instead require a higher voltage for stable operation.

Also, neon pilot lights can act as photosensors. Try this with a flickering neon bulb: shine a red LED on it. Then shine a blue LED on it. If both LEDs are roughly the same brightness, then the blue LED should have a much greater effect. You're seeing the same photoelectric effect that won Einstein the 1921 Nobel, leading to the "photon" concept.

All gas-discharge tubes suffer from a common problem: the gas atoms tend to become embedded in the metal surface of electrodes, so over many years the gas pressure falls as well as the gas mixture being altered.