What is bulb type called in attached pic

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1. In attached pic what is this bulb. In circuit it is directly connected to 220Vac manis via a 470k resistor as you can see pic.
It has two filaments is it as you can see. What ac is applied it both glows. But when ac is given by clipping negative half by a diode, only one filament glows.

 

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Looks like an NE-2 neon lamp.

 

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Yup: https://en.wikipedia.org/wiki/Ne...

 

The glowing portion in the lamp is a thin region near the cathode

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It has two filaments is it as you can see

FYI, those aren't filaments.  They are electrodes.  They glow by ionising the gas within the bulb, as opposed to incandescent lamps which glow by heating a filament until it is at a high enough temperature to emit light.

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Thanks, pic shows it also
https://en.wikipedia.org/wiki/Fi...

 

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Seems shocking that there could be electronics people who never saw one of those. NE2 "relaxation oscillators" were one of my first projects, and indeed, a first project in my first electronics class.

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That is a Neon light.

 

The Neon gas begins conduction at about 60 volts.  Make sure you limit the current with a resistor, starting at about 100,000 Ohms, more or less!

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Interesting how the pcb symbol is for a diode. A neon is far from a diode.

I once had to test these bulbs with a multimeter - they all failed.

 

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I once had to test these bulbs with a multimeter - they all failed.

LOL!

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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Not quite as funny as the thermal fuses that died after soldering! True story! I don't think the person involved shared my humour with the situation especially after I explained that the soldering iron is like 300C and the fuses were 90C! I did remark that the fuses worked well.

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You evil, evil person!

 

But I am glad you didn't work in the hand grenade factory.

 

Ross McKenzie ValuSoft Melbourne Australia

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The other interesting feature of the small neon bulbs is that the conduction voltage is a function of the ambient lighting.

 

That means they start conducting at a different voltage level based on whether the bulb is in the dark, or in a brightly lit environment.

 

Like Torby, I think a string of flashing neon bulbs was probably one of my first projects.

With different R's and C's the "fireflies" all flashed at different rates.

The current draw was so low that the circuit would essentially flash for the static shelf life of the battery!

(no on/off switch required)

 

JC

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Neons... battery... what voltage Jay?

Ross McKenzie ValuSoft Melbourne Australia

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I think the practice was to use 90 volt 'B' battery 8) 

 

Does anyone know how 'old' the NE2 is?  I found them

inside some of my surplus WWII radio equipment as

overload protection in receiver antenna input circuitry.

 

 

Tom Pappano
Tulsa, Oklahoma

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Yes, as Tom mentioned, one used to be able to buy a 90 V battery at the hardware store.

 

JC

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Ohh... I was never that wealthy laugh

Ross McKenzie ValuSoft Melbourne Australia