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I'm organizing a lot of components and don't know what this is. Hooked up to PS at low voltage and nothing happened. I can't tell the anode from the cathode. What is it?

photo of unknown component

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  • \$\begingroup\$ Looks like a lightbulb to me... \$\endgroup\$ – Eugene Sh. May 31 '17 at 16:16
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    \$\begingroup\$ A neon lamp, as your diagram says there's no filament. \$\endgroup\$ – TonyM May 31 '17 at 16:17
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    \$\begingroup\$ Often seen in continuity testing screwdrivers.. or used to be... \$\endgroup\$ – Trevor_G May 31 '17 at 16:24
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    \$\begingroup\$ I have one of those :D \$\endgroup\$ – what is this May 31 '17 at 16:24
  • \$\begingroup\$ Looks a heck of a lot like a neon bulb to me. Note that, in addition to being regular lights, these can be used for crude voltage sensors/regulators, as a part of a primitive oscillator circuit, etc. By playing with the gas mixture/pressure some significant variation in the operating voltage is possible. \$\endgroup\$ – Hot Licks May 31 '17 at 18:37
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Looks like a neon light. They need a fairly high voltage to light up.

Like, 90Volts or more. You can use them on 110VAC with just a small series resistor.

This is an example:

enter image description here

This guy gives a lot of info about the ne2.


A quick look at a datasheet for the NE2 says it needs 95VAC or 135 VDC to light up.

So, you can run it on DC, but you'd need an unusual power supply to do it.

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  • \$\begingroup\$ thanks very much! can i power it with a dc supply? \$\endgroup\$ – what is this May 31 '17 at 16:22
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    \$\begingroup\$ @whatisthis, Yes, you can power it with DC, but note! Those resistors are important. A neon bulb requires a high voltage to start, but its operating voltage is much lower. You'll let the magic smoke out if you hook it directly to a constant-voltage supply without a ballast resistor. \$\endgroup\$ – Solomon Slow May 31 '17 at 19:00
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    \$\begingroup\$ Also, on DC power, only one of the two electrodes will glow. With AC, they both will glow. \$\endgroup\$ – Solomon Slow May 31 '17 at 19:01
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Looks like a neon lamp to me. You need higher voltages to light it up. enter image description here

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    \$\begingroup\$ and a resistor in series to avoid the spark shorting out the circuit. \$\endgroup\$ – ratchet freak May 31 '17 at 16:19
  • \$\begingroup\$ that's exactly it; i also included a real picture in my edited original post. thank you! \$\endgroup\$ – what is this May 31 '17 at 16:22

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