How a Neon Light Bulb works?

Thread Starter

HighVoltage!

Joined Apr 28, 2014
142
I do not want to get to scientific, but more on electric technical side. Does it conduct at certain voltage (short). Why do some have resistors (To limit current?)?
 

BobTPH

Joined Jun 5, 2013
2,345
A neon bulb does not conduct at all, up to a certain voltage. Then the gas in the tube ionizes and it starts conducting. At that point, it pretty much looks like a short circuit, so the current must be limited by a resistor or it will blow up. Once the gas is ionized, it will conduct at a lower voltage than was initially needed. This is called negative resistance, since an increase in current was accompanied by a decrease in voltage across the bulb.

Bob
 

MaxHeadRoom

Joined Jul 18, 2013
20,407
Does it conduct at certain voltage (short). Why do some have resistors (To limit current?)?
Does it conduct at certain voltage (short). Yes
Why do some have resistors (To limit current?)? yes.
Neon tubes were used for counter indicators, voltage regulators, and firing tubes for mercury pool switches, (Ignitrons).
Max.
 

crutschow

Joined Mar 14, 2008
24,710
Because of the negative resistance you can make a simple relaxation oscillator with just a neon bulb, a resistor, and a capacitor, that will cause the bulb to blink.
 

Thread Starter

HighVoltage!

Joined Apr 28, 2014
142
A neon bulb does not conduct at all, up to a certain voltage. Then the gas in the tube ionizes and it starts conducting. At that point, it pretty much looks like a short circuit, so the current must be limited by a resistor or it will blow up. Once the gas is ionized, it will conduct at a lower voltage than was initially needed. This is called negative resistance, since an increase in current was accompanied by a decrease in voltage across the bulb.

Bob
I have recently experimented with one and applied 120VAC only to one side without completing the "loop"; The bulb was "dim".

The bulb "glows" (shorts) when circuit completed.

Why was bulb "dim" when only one side was energized?
 
Top