Demonstrating The Photoelectric Effect Using Neon Lamps

August 28, 2024 by Dave Rowntree 30 Comments

Neon lamps are fun to play with. These old-school indicators were once heavily utilized in many types of equipment for indication purposes but now seem largely relegated to mains voltage indication duties. Here’s a fun video by [Ashish Derhgawen], discussing the photoelectric effect of neon lamps with some simple demonstrations.

[Ashish] demonstrates the well-known photoelectric effect by triggering a sub-biased neon lamp with visible light from an LED. Neon bulbs work on the principle of voltage-induced ionization, creating a visible glowing plasma. If the applied voltage is high enough, around 60 to 80 V, electrons get knocked off the neutral neon atoms. The now free electrons, roaming around highly energized, will eventually come across a neon ion (missing an electron) and recombine to make it neutral again.

The results are a lower total energy state, and the difference in energy is resolved by the emission of a photon of light, which, in the case of neon, is a dull reddish-orange. Nothing unusual there. However, nothing will happen if the applied voltage bias is just below this device-specific threshold. There’s not enough energy to strip electrons.

Apply an external light source, and this threshold can be exceeded. The photons from the LED are just energetic enough to strip a small number of electrons from the surface of the electrodes, and this causes a cascade, or avalanche effect, lighting up the plasma and turning on the neon lamp. ~~Take away the external light source, and it dies down and goes dark.~~

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The History Of Neon Lights

May 17, 2021 by Al Williams 12 Comments

We always enjoy history videos from [The History Guy] but they don’t always cover technology history. When they do, though, we enjoy them twice as much as with the recent video he posted on the history of neon signs. Of course, as he points out, many neon lights don’t have actual neon in them — they use various noble gasses depending on the color you want. Sure, some have neon, but the name has stuck.

The back part of the video is more about the signs themselves, but the early portion talks about [William Ramsay], a Scot chemist who started extracting component gasses out of the atmosphere. The first one found was argon and then helium. Krypton and neon were not far behind. The other noble gas, Xenon, also fell to his experiments. He and another scientist won the Nobel for this work.

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Hackaday Podcast 077: Secret Life Of SD Cards, Mining Minecraft’s Secret Seed, BadPower Is Bad, And Sailing A Sea Of Neon

July 24, 2020 by Mike Szczys 3 Comments

Hackaday editors Mike Szczys and Elliot Williams are deep in the hacks this week. What if making your own display matrix meant a microcontroller board for every pixel? That’s the gist of this incredible neon display. There’s a lot of dark art poured into the slivers of microSD cards and this week saw multiple hacks digging into the hidden test pads of these devices. You’ve heard of Folding@Home, but what about Minecraft@Home, the effort to find world seeds from screenshots. And when USB chargers have exposed and rewritable firmware, what could possibly go wrong?

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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A Nixie Clock With Neon Bulb Logic

September 29, 2014 by Brian Benchoff 27 Comments

This is an oldie, but oh, man is this ever good. It’s a Nixie clock made without a microcontroller. In fact, there aren’t any logic chips in this circuit, either. As far as we can tell, the logic in this clock is made with resistors, diodes, caps, and neon tubes.

The design of this is covered in the creator’s webpage. This clock was inspired by a few circuits found in a 1967 book Electronic Counting Circuits by J.B. Dance. The theory of these circuits rely on the different voltages required to light a neon lamp (the striking voltage) versus the voltage required to stay lit (the maintaining voltage). If you’re exceptionally clever with some diodes and resistors, you can create a counting circuit with these lamps, and since it’s pretty easy to get the mains frequency, a neon logic clock starts looking like a relatively easy project.

This clock, like a lot of the author’s other work, is built dead bug style, and everything looks phenomenal. It looks like this clock is mounted to a plastic plate; a good thing, because something of this size would be very, very fragile.

Video below, thanks [jp] for sending this one in.

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High Voltage Plasma Lamp Is Also Tasteful Steampunk

August 18, 2011 by Brian Benchoff 21 Comments

Instructables user [Admiral Aaron Ravensdale] just finished a high voltage plasma bulb build that makes creative use of off-the-shelf parts. As a self-described steampunk, [Adm. Ravensdale] also earned some cred by included working gears in his build.

The heart of the build is a “flicker flame” candle light bulb. These light bulbs have two flame-shaped plates inside the bulb to act as electrodes. Instead of the Argon that normally fills an incandescent light bulb, the candle bulb is filled with Neon. When excited, Argon gives off a rather unnatural purple glow – not very convincing for a simulated candle and certainly not steampunk. The Neon in the flickering candle bulb gives off a brilliant orange, perfect for simulating a flame and will surely impress the duchess during afternoon tea.

After the right plasma bulb was found, [The Admiral] scavenged the rest of the high voltage electronics from disposable cameras. Attaching three electrodes to a brass gear, the entire mechanism was made to spin using parts from an old clock and a CD drive motor. We’re always impressed with the scavenging abilities of steampunkers – we’d still be waiting for our gears to arrive if we attempted this. Check out the video of this really cool and very inexpensive plasma bulb after the break.

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