Help on how a Tesla coil excites a neon bulb / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Help on how a Tesla coil excites a neon bulb

previous 1 2 3 next

Move Thread

LAN_403

Ash Small

Thu Sept 03 2015, 10:07AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Gases like neon and argon are much easier to ionise than gases like oxygen and nitrogen (air), and at resuced pressure are again even easier to ionise (see Paschen curves for more detail).

When placed in an electric field, the neon ionises due to 'capacitive coupling', rather than 'inductive coupling' (at least, this is the conventional thinking. I think TC's are capable of inducing currents as well as the secondary winding is an inductor, so maybe it's not so clear cut, but it's generally accepted that it's capacitive coupling that does all the work here.)

Generally, with capacitively inducted plasmas, the atoms of neon (in this case) are pulled apart by the rising electric field, with electrons pulled in one direction, and Ne+ ions pulled in the other direction. These ions and electrons can collide with more neon atoms to create more ions. When the field reverses they are pulled in the other direction. The light is produced as neon ions and electrons re-combine to produce atoms again, When this happens a photon is released.

Inductively coupled plasmas, on the other hand, tend to cause the ions and electrons to move in circles or spirals, first in one direction, then in the other.

Basically, as the voltage on the topload rises the electrons in the neon bulb are attracted to the topload and the positive ions repelled. As the voltage on the topload reverses, the electrons are repelled and the ions are attracted, and light is emitted as these ions and electrons re-combine, producing photons.

I hope I got it all 'the right way round', I've at least supplied a few other terms for you to google

EDIT: Looks like Udo posted while I was writing.

TeslaIsBae

Fri Sept 04 2015, 08:30AM

Registered Member #55171 Joined: Fri Jun 05 2015, 06:44AM
Location:
Posts: 9

Thank you guys, it still took me quite a while to understand everything even with your great explanations. But I would just like to confirm what I understand:

So a neon bulb is always excited through capacitive coupling, no matter if it has an electric arc jumping to it or if it's further back in the electric field of the TC. The only difference is that the electric arc

Uspring wrote ...
causes the high electric field of the TC top to be transported into the vicinity of the tube.

?

Thanks

Uspring

Fri Sept 04 2015, 09:55AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

TeslaIsBae wrote:

So a neon bulb is always excited through capacitive coupling, no matter if it has an electric arc jumping to it or if it's further back in the electric field of the TC. The only difference is that the electric arc
Uspring wrote ...
causes the high electric field of the TC top to be transported into the vicinity of the tube.
?

Yes, and the field drops off at larger distances from the TC top. At sufficiently large distances the neon bulb will stop emitting light.
I should have said more accurately, that the charge of the top of the TC is transported near to the bulb, if an arc hits it. The charge of the top is causing the field and a conductive path like an arc will transport it close to the bulb increasing the field there.

If the other side of the tube is grounded, you'll have a direct current path from the top through the tube to ground. In this case capacitive effects are negligible and the tube will become very bright.

TeslaIsBae

Fri Sept 04 2015, 10:21AM

Registered Member #55171 Joined: Fri Jun 05 2015, 06:44AM
Location:
Posts: 9

Ok, that answers all my question, for now

Thank you everyone!

dexter

Wed Sept 09 2015, 05:53PM

Registered Member #42796 Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195

well this is interesting

also works with the LED floating in the air

Ash Small

Wed Sept 09 2015, 06:20PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

dexter wrote ...

well this is interesting

also works with the LED floating in the air

I know it's still a bit early, but wireless Xmas tree lights, maybe?

E.TexasTesla

Fri Nov 20 2015, 03:35AM

Registered Member #4362 Joined: Sat Jan 21 2012, 03:44AM
Location: Texas
Posts: 98

I placed a small laser pointer on top of my toroid once and the laser diode fired right up.
It only worked for a short time so I'm not sure what was actually going on.

Art

Mon Jan 04 2016, 04:14PM

Registered Member #57369 Joined: Fri Sept 18 2015, 01:24PM
Location:
Posts: 66

When a coil illuminates a bulb youâ€™re holding itâ€™s because a circuit is completed through the bulb, continuing through your body (mainly the surface of your skin), which is also capacitively coupled to ground. When this is happening, the bulb and your body is the path of least resistance (or in this case impedance) to ground. If you want to take your body out of the equation, you can do so by connecting one side of the bulb to some foil sheet sitting on the ground, and suspending the bulb near the coil.

TwirlyWhirly555

Mon Jan 04 2016, 07:14PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

i tried it with a Bunch of neons on a pice of 5mm acrylic sitting on top of a SSTC @ 24V halfbridge

IMG_0683[1] by TwirlyWhirly555, on Flickr

Perezx

Tue Jan 05 2016, 05:45AM

Registered Member #54263 Joined: Thu Jan 15 2015, 09:54AM
Location: Perth
Posts: 35

Guys, thats just a radio transmission. If your neon tube has any electrodes - they work like antennas. If not - gas itself, especially when ionised, is conductive.
Try to touch one electrode by hand (which means grounding) or attach a wire (antennae) to it - bulb will ligh up brighter / on a longer distance.
Spark between bulb and coil acts like a wire.
LED acts like a rectifier, its terminals - like antennas.

previous 1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob