Drawing on a plasma display with a laser pointer

An orange plasma display will retain an image caused by incident near-UV light. This is an interesting visual combination of photoelectric, hot carrier injection, plasma, and charge trapping effects.
Correction: The orange display is running at 700Hz, 130V in the video. Also, the laser emits no 365nm light. I measured some as low as 380, but the tail isn't as long as I implied! Thanks Matthew King for pointing this out in the comments.
I realize that I may have conflated the issues of one-resistor-per-pixel and the display's ability to maintain an image throughout row scanning. They are separate problems that are both addressed by designing the panel to work on AC. Each pixel can maintain its state (on or off) by being supplied constantly with a lower "sustaining" voltage, and can be set or cleared by giving it a momentary higher or lower amplitude. The sustaining voltage allows the pixel to be emitting light or not, and its state remains because of its own impedance until updated on the next scan. In color plasma displays, separate electrodes are used for sustaining and addressing pixels, and the discharge may be sustained between coplanar electrodes instead of plane-to-plane, as in this display.
It's also a possibility that the dielectric and MgO layer only exists on one electrode (the metal), and the ITO is bare. I don't know.
On this display, if all rows are electrically connected together, and all columns are connected together, and AC is applied to rows and columns, this effect does not work -- no light is emitted at all! At least some of the electrodes (ie every other column) must be left floating to emit any light, and to show this memory effect. So, driving AC plasma panels requires more waveform tricks that I do not fully understand.
Photo of the TFT LCD with funny attribution: en.wikipedia.o...
Applied Science video with rotating, flashing neon light:
• Flashing Light Prize 2...
Prior art patents:
patents.google...
patents.google...
Physics coffee mug in opening shot: www.atomstoast...
Refs:
sci-hub.se/htt...
sci-hub.se/htt...
sci-hub.se/10....
sci-hub.se/10....
www.nature.com...
sci-hub.se/10....
patents.google...
www.slideserve...
patents.google...
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[@Muonium1]

Several things amaze/surprise me about this video. First, that you are able to come up with topics so consistently novel, fascinating, and non-intuitive that I never would've thought to investigate such things on my own if given about a thousand years to do so. Second, that people are still finding use for images that I uploaded to wikipedia 15 years ago, like that reflection microscope image of a Dell Axim PDA's TFT at 8:40 - this is greatly pleasing to me. Thirdly, that there is 365nm radiation coming out of 405nm laser diodes as you mentioned at 5:20. Can that be right? I've measured the spectrum of these cheap laser diodes before and while they're obviously not as clean and monochromatic as a gas laser, they're still way narrower than an LED and have a FWHM of only a couple nm - I'd like to hear more about this because I know you have a spectrometer too so I guess you've seen it firsthand. And fourthly, that nobody ever even knew about this throughout the entire heyday of the neon plasma display during the 80s and early 90s and no one ever made a product exploiting it! Anyway, you are my fav science youtube channel for many years now and I hope the new videos never end!

[@AppliedScience]

Thanks so much for your photo! I might have gotten the attribution wrong, but it was taken verbatim from Wikipedia, and I added a link in the description. People were asking about the "forklift driver" ;) Also, I was indeed playing too fast and loose regarding the 365nm from a 405nm laser. I just measured it, and found some 380nm, but definitely no 365. I updated the description.

[@jeremoisde9928]

So @Muonium you are Not the Gabelstaplerfahrer? Oder doch?

[@RealNovgorod]

Powerful solid-state UV emitters (or even lasers) weren't really a thing until quite recently, so there was no practical way to make it into a consumer product back then unless you want kids at the arcade to fool around with high-voltage mercury lamps and get eye cancer from the hard UV.

[@zyeborm]

​@@RealNovgorod .... do you not?

[@eyescreamcake]

One time a coworker was trying to explain something about a particular part, and she brought up an image from Wikipedia to show me, and it was a photo I had submitted to Wikipedia lol

[@account0199]

I don't think you need to worry about your video output schedule, we, your crowd, appreciate your "quality over quantity" approach...

[@rehoboth_farm]

When I worked for a large chip manufacturer who makes processors for computers... You know the guys. We just used SiO2 for the ILD, inter-layer dielectric, material which separated the layers of metal lines. So essentially just glass. I don't think it was any special recipe of any kind. I think that it is pretty standard semiconductor tech. We just used silane gas and oxygen at specific temperatures and mixtures to grow SiO2 if my memory serves correctly. Now, the chemistry to keep copper from diffusing into it and the techniques to get nice square bottomed etched lines was extremely sensitive and I don't believe that I can discuss that. Glass is a really easy to manufacture dielectric material with suitable properties. It also etches really easily and predictably with HF. It would seem that manufacturing panels like this would be very similar in process techniques.

[@derrekvanee4567]

All I know is I wanna get to know you and bring my styro, explosions n ire, and Neil friends.

[@rehoboth_farm]

@@derrekvanee4567 We all need to have dreams.

[@zashbot]

BIG HINT 🤣🤣

[@agentgreengnome]

During my first night flight while training for the my pilot's licensee, in the school's beater C172 from the 70's, the radio's orange display quit working when we needed to be changing and monitoring Air traffic frequencies. The radio still worked, we just couldn't see what channel we were on or what channel we'd be changing to. Having an unknown electrical issue in the air at night was pretty nerve racking, hoping it is not the beginning of a bigger systematic failure. Even the CFL was unable to troubleshoot the issue. After a couple rounds of troubleshoooting and restarting the avionics to no avail, I shined my LED head lamp near by and the display lit up! I don't remember if the screen was refreshing properly, but I remember for the remainder of the flight, I'd have to "reignite" the display with the LED light every now and then. I always wondered what the phenomena was, I always assumed the display was just barley being driven below some some energy state threshold and the LED photons gave it just enough kick to change states. I thought the display was an orange cold cathode, but maybe it was a plasma display as show in this vid. Very cool video as always!

[@saad3677]

Wow.

[@whatevernamegoeshere3644]

Okay that's a situation where piss would pour down my ankles

[@jk-video2716]

If the display was neon, then as it ages, sputtering can lower the gas pressure so that it needs more voltage to ionize (ignite) a spot to get light emission. Shining a light on it adds energy to the neon atoms with the same effect as increasing the supply voltage.

[@coloradostrong]

_Barely_ and _barley_ are 2 different things.

[@muwatter]

The radio was a KX-155 right? Most of those King radios have a little photoresistor under the plastic next to the display which is connected to an automatic dimming circuit. As the display ages and becomes dimmer the dimming becomes non-linear and the display gets very dark /off at higher dimming levels (when the light on the photoresistor is low). By shining light on the display you illuminated the photoresistor and temporarily decreased the dimming level and the display lit up again for a while.

[@HuygensOptics]

Another reason for making the back electrode from metal (except price) is that metals are generally reflective and send additional light in the direction of the viewer. Anyway, superb video again Ben!

[@RingingResonance]

It might work similar to the old Tektronix storage tubes. They use flood guns to flood the whole screen with electrons, but the phosphor does not glow because it's not enough energy to excite the electrons until you get a more intense beam of electrons to "activate" the phosphors by giving them an extra charge so that the energy of the flood gun is enough to get the electrons over that charge state and produce light in that spot.

[@hfuy8005]

I was going to say that. I'm not that clear on exactly how those worked, but it immediately occurred to me that this might be related physics.

[@RingingResonance]

@@hfuy8005 I'm not sure either, but I think it has to do with energy states of the phosphors. It's as if they have some sort of hysteresis.

[@thenoblerot]

Yes! Came here to say that. Glad someone was able to say it before it got lost in comments.

[@rdyer8764]

Back in the 80s I worked with people like your colleague (and you). They invented a microwave chamber that heated a cup of coffee (not patented) a discrete-logic version of the Pong game (not patented) a laser-based digital data storage/retrieval device using a photographic plate and LASER (patented), which later became the basis of the CD-ROM. These were fun people, often a bit eccentric, but usually quite humble. The best job I ever had primarily because of the people!

[@CuriousMarc]

Interesting effect. Are you sure you are not just simply ionizing one of the UV lines of the argon or neon? One way to find out is to try it in a regular neon bulb. If you can strike it by shining the laser in-between the electrodes, it’s ionization, if it works inly by shining it on the metal, it’s photoemission. But if it were really photoemission, it would make more sense to me that it comes from the MgO, not from the ITO or metal layer buried under a dielectric. Just don’t see how you can have an electron current nearly high enough to strike a neon plasma coming through a dielectric. Just talking out of my rear-end since I have not researched the subject properly…

[@Muonium1]

I think the purple photons are too feeble aren't they? 405nm is equal to 3eV per photon but argon's first ionization energy is like 15-16eV.

[@ramjetross]

You're on the right track, the real explanation is that F (oxygen ion vacancy) and F+ (oxygen ion vacancy + one electron) defect centers in MgO crystals are located at 3.0 and 2.96 eV above the valence band maximum (VBM), respectively. This means that the 3.1eV 405nm laser light is exciting MgO valence electrons into the F level or maybe even exciting an electron in a F+ level into the conduction band as well and that is main reason for increasing the free carrier density in the device. The reason there is an asymmetry in the dot brightness is because the excitation of carriers in those defect levels are populated and depopulated on one side of the device for each polarization of the AC electric field. So you can imagine you have a box of balls and you raise one side and lower the other. The balls will go back and forth. This is the displacement AC current and you're not having a charge pass through the dielectric. So then the laser power is attenuated when it reaches the bottom layer of MgO because it had to travel through the first layer of MgO. Normally the high voltage AC is enough to excite these defect levels or rip them out of their position, but he is operating it in lower voltage where only the laser gives it enough energy to excite the states. The gas in the middle that becomes plasma is used as the luminescent source with a threshold limit minimum it seems. Like there needs to be enough voltage between the MgO layers to start the plasma going. The dielectric is still too insulative to pass enough charge through it. Most metals have a work function higher than 4eV and wouldn't even get excited at 365nm. The amount of 365nm light is miniscule as well. You should be able to do the same effect with regular AC EL displays with MgO too. It's all about the defect states in MgO, that is where the excited carriers start.

[@Muonium1]

@@ramjetross is this the F for farbzentrum / color centers?

[@ramjetross]

@@Muonium1 F (oxygen ion vacancy) and F+ (oxygen ion vacancy + one electron)

[@CuriousMarc]

@@ramjetross That is a very convincing and knowledgeable explanation!

[@daic7274]

7:26 Brings back memories of my childhood,first multimeter and a mains socket.. Hmmm,my meter has a 20 amp range.. This is a 13amp outlet.. Let's measure the current! Lesson learnt,multimeter fixed and socket replaced.

[@matthewellisor5835]

And trousers washed... We've all been there.

[@Polite_Cat]

At the risk of sounding like a dummy, why cant you do this? I would imagine that this essentially causes a short circuit in the outlet because the meter has little resistance, but why cant the outlet handle it? From what I understand, outlets can handle something like 1800 watts, so why would a short circuit hurt it? Wouldn't it just be limited to it's max power as if you were running a power hungry room heater? (Which I know has a lot of resistance). Basically I think my question is... why exactly cant you short circuit a plug, and why would it explode? Finally, why would it hurt your meter as long as you had it in the correct current mode?

[@Jmoneysmoothboy]

@@Polite_Cat The voltage that comes into your house is 240v and the current that comes into your house is effectively infinite. V=IR so if you have an outlet that supplies 120v or 240v and you short it with a resistor of ~0 ohms the outlet will do its best to supply infinite current. Very few things are capable of handling effectively infinite current and they don't include multimeters or wall sockets. In theory the only thing that should happen when you short a socket is the circuit breaker popping but in reality outlets are never terminated properly and they behave more like resistors which is where the magic smoke is stored.

[@williamgreen5575]

Funny you mentioned neon bulbs. I noticed the output of a neon bulb can be affected by the amount of ambient light. I have a power on indicator neon on our boiler that's usually in a dark room, and it has a slight AC flicker to it. When I shine a light on it the flicker stops and its light constantly.

[@alexanderthomas2660]

Indeed, I also noticed this on a simple mains power block with neon indicator. The bulb would flicker in the dark and be steady when sunlight hit it. Unfortunately that bulb died a long time ago…

[@Broken_Yugo]

I recall reading that neons for logic applications had a touch of some alpha emitting radioisotope in them for that reason.

[@samot1808]

Maybe it's just more difficult to perceive the flickering when not in the dark. In the dark you would get the maximum amount of 'dynamic range' and thus easier to notice.

[@samot1808]

After reading further it seems what OP is referring to is an actual thing.

[@corn322]

I've got an old power strip with a neon indicator... sure enough, it flickers with lights off and steady with lights on.

[@bronsonstephens5799]

Man. You continue to impress me with every video you upload.

[@newtonbomb]

He definitely provides a unique treasure of priceless informative video content, unparalleled not just on this platform but on the entire internet. He's long since impressed me to the point where I can't even measure it anymore.

[@anesthetized7053]

hes like the golden goose of weird science ideas. dude never misses

[@cobralyoner]

there’s just nothing like the glow of these old plasma displays. miss them. they looked just so cool!

[@hellterminator]

You actually can sort of get away with neon bulbs in parallel. Yes, initially, one will hog all the current, but over time (weeks to months, in my experience) it will degrade until they even out. But then, they won't light up all at once, no, instead, on each half-cycle, a random one will light up (and then a different one and then a different one). If you connect about a dozen of them in parallel, after the initial burn-in, they create a really nice dancing light effect.

[@voltare2amstereo]

Big Clive did make one in a video a few years ago very cool effect

[@joshuagibson2520]

You, Quint, and Grady are 3 of my top fav channels to watch.

[@joejane9977]

hey do you channel names so i can find these ppl

[@joshuagibson2520]

@@joejane9977 practical engineering is Grady's channel and Quint Builds is the other.

[@roro1640]

@@joejane9977 Would also highly recommend 'Breaking Taps', 'The Thought Emporium', 'Nile Red', 'Action BOX', and 'Codys Lab' (if you aren't already subscribed) for similar content

[@Zanaki113]

This is so cool, I wonder what the other comments think! *I can't understand a word of what they think*

[@AC9BXEric]

Plasma TV sets have a property like this. If you look closely, generally only seen in a dark room, when turning it on, before the set starts making a picture, the screen will show a blotchy approximation of what was last displayed when powered off.

[@interferon4800]

I sure am glad Ben takes the time to publish his endeavors so we can all enjoy them. Lots of people talk about theory, few make practical implementations.

[@cashewABCD]

Glad I listened till the end, your intuitions are genius. The patent surprise is a fun twist. Thanks for another great discovery!

[@1kreature]

It is a sad twist that just serves to highlight the issue with the patent system. Protecting investment in research yes, stumbling on something no. And not being able to utilize an idea because someone patented it "just because", and not actually protecting a product they would be producing is just sad. The person who stubs his toe on something first should not be allowed to collect royalties on the dispersal of rocks.

[@aronbjr]

This is part of the optogalvonic effect, in which the discharge changes it’s resistance due to incoming light. If you sweep a continuous spectrum of laser light (like from a dye laser), you can measure the resistance change of that gas filling the discharge. I used this as a calibration standard (neon lamp - also argon or other gasses that have emission spectra peaks at important calibration wavelengths), and as you tune / sweep the dye laser (in my case a grazing incidence R6G pulsed dye laser) thru the spectrum, when the due laser matches a peak emission of the gas, the resistance dips… and so you know the dye laser is at that exact frequency / spectrum. I would partially power the discharge lamp, and when the laser wavelength matched a strong emission peak, the lamp would light. There are a few other related phenomena to this, one used for deep space photography, by CCD deep-discharging using deep UV from the sun.

[@brainlicker1]

I can imagine a legendary crossover event with How to make Everything, Cody's lab, Nile Red, and Applied Science if HTME ever makes it to the modern era.

[@stdorn]

I worked as a biomedical. equipment technician for 18 years and this was one of many devices I worked on. if memory serves me correctly this is from a Propaq Encore patient monitor. I wonder if I ever serviced the one this came out of.

[@simon_far]

I noticed it was a patient monitor at 11:22, where you can see the burn-in of the most common readouts. It looks like their patients' SpO2 was consistently in the 90s.

[@stdorn]

@@simon_far 90's is pretty typical unless your having serious lung issues. I have tried holding my breath until im ready to pass out and havent ever dropped below 95%

[@stdorn]

its pretty typical to be 98 or 99%

[@williamogilvie6909]

Fascinating. Those plasma displays I have hoarded for 15 years have suddenly become useful.

[@sommelierofstench]

this is one of the most creative channels ever. well done man. this is so cool. you’ve made and demonstrated some crazy stuff, but this is so rad. i love how humble you are and how you share all this cool stuff constantly.

[@Kalanchoe1]

i cannot express how cool this channel is!

[@w_M_w]

Find all your videos interesting. Your Channel is Probably the best Electronics channel on KZbin, wish there were channels with your high level of detail, quality, and professionalism.

[@marksmod]

Hooray, it is a new Applied Science video! The best, most interesting and in depth science channel on KZbin!

This is great, as usual. This is truly the level of nerdiness you cannot get elsewhere.

[@marvin19966]

you want to buy my friend

[@alexitoyt1130]

If this is activated by high energy photons, would it work for detecting radiation gamma sources? If it worked like the old fluoroscope x-ray machines, could you use it as a portable x-ray machine? Since scotch-tape being unrolled produces intense x-rays, could that flash the image of your bones in your finger overlayed on the screen?If this is activated by high energy photons, would it work for detecting radiation gamma sources? If it worked like the old fluoroscope x-ray machines, could you use it as a portable x-ray machine? Since scotch-tape being unrolled produces intense x-rays, could that flash the image of your bones in your finger overlayed on the screen?

[@RavenLuni]

Other things of note : The ITO and metal conductors will be at opposite ends of the triboelectric series. Also: Are you sure the dotted effect is due to the AC cycle and not PWM output from the laser? (I've noticed this when waving laser pointers around especially ones with single cell power supplies which rely on a DC-DC converter to power the diode)

[@inothome]

I was wondering if it was possible PWM causing it too.

[@ramjetross]

Pretty sure it's because the F and F+ defect centers in MgO crystals are located at 3.0 and 2.96 eV above the valence band maximum (VBM), respectively. This means that the 3.1eV 405nm laser light is exciting MgO valence electrons into these defect levels and that is what is increasing the amount of electron density in these defect states. The reason there is an asymmetry in the dot brightness is because the excitation of carriers in those defect levels are populated and depopulated on one side of the device for each polarization of the electric field. So imagine you have a box of balls and you raise one side and lower the other. The balls will go back and forth. This is the displacement AC current. So then the laser is attenuated when it reaches the bottom layer of MgO because it had to travel through the first layer of MgO. Normally the high voltage AC is enough to excite these defect levels, but he is operating it in lower voltage. The dielectric is still to insulative to to pass enough charge through it. Most metals have a work function usually higher than 4eV and wouldn't even get excited at 365nm. The amount of 365nm light is miniscule as well. It's all displacement current still. You can do the same process with regular AC EL displays with MgO too. It's all about the defect states in MgO, that is where the excited carriers start.

[@gordo8189]

I'm guessing most of Ben's audience would've had that thought.. I'm sure he tried sweeping the laser over some laser-sensitive phosphor like a CRO screen to discount that..

[@stephanieparker1250]

I love seeing your investigation process, the questions you ask going through the tests etc, so interesting! 🙌

[@Chriss120]

i like that small rant at the end about never wanting to stop discovering and researching a topic.

[@SeanJonesYT]

Ben it's amazing how consistently you make videos that are just absolutely fascinating. Hilarious that a coworker just happened to have patented the observation. Brilliant stuff, I hope I'll make it to the ranks of your fascinating, brilliant people.

[@pdrg]

I've never been disappointed by one of your videos, stay curious for the rest of us who can't delve as deeply!

[@foundparts6301]

PLATO's 1970's terminals had plasma displays. There's a good technical deep dive on how they worked in "The Friendly Orange Glow"

[@cwollak]

Thank you for the quality content.

[@frizzby-x]

No other channel on KZbin brings me so much positive emotions as this one.

[@JCWren]

Nixie tubes are sometimes driven with some similar biasing. The -120V is constant, and the +60V is switched on and off, so you're alternating between 120V and 180V across the element. This results in faster ignition of the plasma, and also helps eliminate any afterglow.

[@ahmadalhwejh9026]

I like your channel not only because you're full of knowledge but also because you're quit humble. Thank you for posting

[@slashz0r]

thanks for always including the journey of how you got to the final result. it's really enlightening to learn how you look at things, amazing content as always.

[@adrianram5524]

This guy breaks my brain so often.... I can't stop watching

[@hell7sing]

Amazing video. I don't quiet understand everything but the comment section is very helpful. Many examples and discussions help. This is by far the best comment section of any channel. I know you mentioned this in a previous video.

[@mased-v2j]

Great video! The modern would wasn't built by a few dozen "Eureka!" moments but rather millions of accidental discoveries like this.

[@tolipydob]

Thank you for the fun viewage. Perhaps there is a DC offset changing 1/2 pixels? alternately perhaps the pixel stack ends up being diode-ish? Silly boomer EPROM anecdote follows: I used to (re-)program a lot of EPROMs. I had an erasure enclosure that could hold dozens of devices. I called it a Barbie Tanning Spa.

[@initialb123]

Learnt so much from this, what a rabbit hole indeed. Thanks for taking the time and effort to upload these videos Ben!

[@pe4958]

Anyone with any kind of medical degree watching this instantly recognized the burn-in pattern on that plasma display All the time I've spent looking at these I don't think I ever realized (some of them) were plasma technology 🤷‍♂️

[@ke6gwf]

No medical degrees needed to recognize it either! Lol

[@AndrewGillard]

It was only once I saw the burnt-in image that I finally had any idea what a "plasma display" was! (I have no medical qualifications, but I've seen those displays enough to recognise them.) I don't think I've ever heard that term before, and I wasn't aware that those displays were a different technology to the display types I'm more familiar with. I'd never really thought about what kind of display they were, but I probably would have just assumed them to be some kind of backlit LCD tbh.

[@lobsterbark]

@@AndrewGillard Most displays that looks like that are just backlit LCDs. It actually has been that way for quite a while. During the transition period of actual plasma displays and backlit LCDs, there were quite a few displays that do a very good job of looking like plasma displays. To the point you would have to take apart the device to see that it wasn't plasma. Not quite sure why they put so much effort into hiding the fact that it wasn't plasma.

[@vevenaneathna]

i remember when plasma screen tv's were a big deal and cost 3000$ and people would freak out about turning them off if you paused something or left the room to get something. idk. those things were impossible to see from more than one narrow angle and basically self exploded after owning them for a year or two. sounds like the perfect type of tv to make lots of money with. guess our new tech must be a lot cheaper idk

[@SeanHodgins]

Not all teaching moments are injury moments, but all injury moments are teaching moments.

[@speedstor]

These youtube videos are like the tv show Dr. House. But instead of diagnosing a patient, Applied Science learns about a new technology/thing. And instead of Dr. House and a team of doctors, we have Ben Krasnow guiding us through the mystery, discovering new detail, and solving the puzzle. Thanks for the videos :D

[@SarahKchannel]

I think its a bit like gas in laser gets excited, where valence electrons get pumped to a higher energy state when being excited by a photon. When the laser excites the gas, the break through energy required for it to glow get lowered. Add to this the AC current and the laser pointer, then depending on which position of the sine wave the effect is higher or lower. To prove the later, when scribing fast when power is off, the pattern is not supposed to show.

[@johnyoungquist6540]

We used plasma displays in our aircraft instruments for years. They had neon, mercury vapor and KR85 gas in them. The Krypton 85 is radioactive and kept the display ionized a little in the dark and the cold. They often had a keep alive electrode that had a few uA of DC continuously flowing for the same purpose. Some neon bulbs like those HP used in their voltmeter chopper circuits probably had some help to switch quickly in the dark. Some neon bulbs were made with green glass (radioactive uranium glass) for the same reason. Fascinating discovery you have here.

[@gudenau]

This is fascinating, oddly enough my first thought on how that worked was the one you mentioned last. It's cool that a coworker had a patent for this.

[@Alexander_Sannikov]

I sometimes wonder if I should at some point rewatch applied science videos from the very beginning, because it's been a while and I might have forgotten some stuff

[@andrewlorona7360]

If you use a camera flash on magnesium carbonate, you get a short duration blue glow. Something I found through experimentation and though you might find interesting. So maybe the MgO layer is excited by the laser to release electrons into the plasma.

[@joshuagibson2520]

So happy for a vid from you. It's been a while!

[@supernumex]

For the large dot small dot trail, perhaps you could set up a high speed camera and also try to visualize the AC waveform in the same shot (perhaps something as simple as a red/green led to show positive/negative) to see if if the positive cycle consistently produces the larger/smaller dot.

[@linhthai75]

AS :" I suspected the driver is not totem pole, but open collector type..", this quote define why we all enjoy this channel (who doesn't respect they spirit of the First Nation People (aka. Native American where I'm from)). Another fact is reading those who had commented, look like thay all have a quantumm computer brewing up at some stage in their garage.

[@AlexRetsam]

I really love these technology videos you do. Thanks!

[@efkastner]

Not only are the dots big/small/big/small, the distance between them changes. It looks like the small is closer to the big that came before it than the one after it.

[@xxportalxx.]

Yeah that's true, I feel the simplest explanation would be that his function generator isn't producing a perfectly symmetrical drive current, or that the panel behaves nonlinearly. However I wonder if it's bc 'freeing a hole' isn't strictly possible, i.e. it's always the electrons that actually move. So possibly you can eject electrons from the metal surface, but can't effectively eject electrons from the gas, therefore the e field has to be weak for the electrons to be ejected from the metal in the reverse polarity (but close enough to the peak to actually cause ignition) therefore shifting the reverse polarity dots to the raising edge of the reverse polarity curve.

[@NicleT]

Could it be an artefact due to interferences between the A/C frequency of the plasma and the one of the UV light?

[@drew6017]

If you do make your own driver, try increasing the drive voltage and frequency such that power is kept constant. I'm interested to see if the higher electromotive force on the high side of the AC waveform would lower the photon energy required to liberate electrons from the metal layer (possibly permitting this effect at longer wavelengths, maybe visible?). Thanks for the vids!

[@clynesnowtail1257]

I was also gonna add, could the AC be made non-symmetrical to compensate for the differing brightness of which end is positive and negative? Instead of 50/50 positive and negative in reference to 0, could you do 60/40 or 40/60 and give it the additional power on that side of the waveform so it comes out even?

[@firstmkb]

So many rabbit holes, so little time!

[@notapple6053]

Thanks for comming back! This one was something else man

[@jomiar309]

This was incredibly fascinating, and your ability to explain it clearly is admirable! You've given me a lot to think about!

[@Veptis]

I usually don't catch up with your videos in my watch later before your next video is released. So it's probably coming out soon with a really interesting topic!

[@Ts6451]

Gas discharge lamps do tend to be sensitive to external illumination, It is not that uncommon for neon indicator bulbs to be brighter in a lit environment than in the dark, presumably because the illumination lowers the striking voltage, so it strikes earlier in the waveform. Radiation can also affect the striking voltage, a Geiger-Müller tube is pretty much a neon lamp with some added stuff to tune detection and ensure the ionization is quenched quickly, perhaps your display will show a sensitivity to radiation too? I suppose the glass is too thick for alpha and beta, but I suppose that gamma and X-rays might have an effect. I also seem to remember reading something about neon indicator lamps being used as detectors for microwaves at some point, but I don't really remember what that was about.

[@D3ltaLabs]

You have single handedly renewed the plasma display. Maybe one day will will see a scanner or signature panels using this tech. Love your videos

[@alexitoyt1130]

There any readable difference when it's brighter/darker IE voltage/resistance? That difference between acrylic & polycarbonate would be a nice way to detect plastics that's exceptionally hard to do. You try it on a solar cell? I know they emit light when you drive them in reverse and have the same sort of tech inside them. (more in the IR range though IIRC)

[@mleko5procent]

Definitely one of the best placates over the whole internet.

[@belg4mit]

This was very cool. You mentioned the idea of using it for I/O, but I didn't see anything about reading the laser-scanned image out of the display. Is it too basic to cover?

[@kp5343]

Probably terrible res

[@albertweber1617]

If it's possible to read, it would be revolutionary. You could turn any old plasma tv into an incredible artistic device

[@narayanbandodker5482]

One way would be to stick a CCD behind the display

[@MatthijsvanDuin]

The resistance of the pixel changes, so that should definitely be detectable through current measurement

[@sanjeawaut]

@@albertweber1617 like to know more details about, how to do that. I have plasma TV with me. Wanna convert it as drawing panel.

[@PrescoFlex]

I find the laser effect is always dotted when swiped across a surface. Try it on your wall back and forth. It’ll leave a pattern, not a clean line. At least on my cheap laser it seems to be pulsed despite being a battery operated diode, possibly they’ve developed a micro inverter for cheap lasers

[@peterjameson321]

Yes Prescott, I had considered that the laser might be pulse driven. The large and small dots could result if the waveform of its driving circuitry is asymmetric.

[@roberthickoxjr]

Thank you. I absolutely find your videos entertaining while informational. I appreciate all of the detailed thought you put into your topic.

[@ARVash]

The off state going dark when the laser hits it reminds me of how glow in the dark stuff gets dark when you shine a laser at it. I wonder if the power being on when shined is caused by the change in conductivity that happens with plasma, whereas the off state going dark is about the electrons being dumped. very cool

[@DextersTechLab]

Absolutely fascinating video as always Ben!

[@thromboid]

What great timing - I recently used a UV flashlight on glow-in-the-dark material and found that I could doodle pretty well on it. I've since been thinking about painting a ceiling or feature wall with glow paint and using a computer-controlled UV laser pattern scanner to make a big phosphorescent/fluorescent vector display...

[@PovlKvols]

That is indeed one deep rabbit hole. Thank you for sharing!

[@JasonOlshefsky]

This reminds me of those CRTs with high-retention phosphorus that were used as display "memory" in some early terminals. I only saw one in the 1990s and back then we didn't have UV lasers at the ready, but I imagine the phosphorus could be excited the same way and retained by the bias voltage (I think that's how they worked).

[@edward17829991]

I'm very interested in the idea of reading the marks scribed by the laser. If u drive the pixels in sequential fashion, then u can monitor the current changes synchronously to figure out the lightened pixels. Very interesting, please keep investing! I'm looking forward to the follow-ups.

[@Quickened1]

Fascinating stuff there! Man, you reminded me of when I was about 7 and decided plugging a 9v dc motor into a 120v ac outlet would make a great miniature fan. My results were the same as yours, BOOM!

[@jotatsu]

Isn't this similar to the principle of Image intensifier tubes? The ones the military use in NVGs.

[@rdyer8764]

And weren't the old digital-storage oscilloscopes (phosphor-based) also similar?

[@xxportalxx.]

I would say that the effect is dominated by the freeing of electrons by the photoelectric effect in the metal, and that when the polarity reverses the bias decreases the freed carriers (rather than you 'freeing holes,' as that'd essentially require you to free electrons from the gas which isn't likely absorbing much of the incident light, unlike the metal). This may also be the cause of the apparent shifting in the low intensity dots.

[@bjmcculloch]

But if that were the case, then the “stored” visible intensity should never go to the background level in between the peaks. It would have periodicity, but it should always be brighter than the pixels that were not lazed. My guess is that in one polarity, the photoelectric effect is operating on the metal, and in the other polarity the photoelectric effect is operating on the ITO.

[@xxportalxx.]

@@bjmcculloch my interpretation was that in between the peaks the e field was close to zero, and therfore not strong enough to maintain a plasma even with injected carriers. I.e. near the zero crossing point there wasn't enough current to ionize the gas sufficiently while photoelectrons were providing activation energy, no matter the source of the photoelectrons.

[@fonkbadonk5370]

I love how you always come up with every possible angle to anything. After about 2/3 of the video I thought: Mhhh, I have an old plasma TV in my basement I haven't used in some years. Wonder what this will do to it. And sure enough, you went there :) Thanks for yet another super fascinating video!

[@MVVblog]

Would it work the same if the power supply had only positive half-waves? Or is a polarity reversal necessary to properly power the display?

[@isusteve7]

I noticed a similar phenomenon recently with a green laser pointer - a quick sweeping motion produces a dotted pattern similar to what you observed. I think it could be an artifact of the laser itself, not so much the display. The alternating bright/dark dots could match up with differing optical properties of the mirror/output coupler in the optical resonator within the laser, or perhaps a difference in the linear distance of the excitation source from either end of the resonator itself. Love the content - Stay Classy, San Diego!

[@ke6gwf]

That looks like the display from an old hospital vital signs monitor. (and by old, I mean, it probably finally got upgraded last month... Lol) SpO2 is Peripheral capillary Oxygen Saturation, or O2 Sat. Looks like most of the patients it served where in the high 90s where we should be! Another fun video!

[@wa4aos]

I wish I had had KZbin in my college days for my EE studies but now channels like this is part of my ongoing education. Applied Science is at the top of my list for Enovation and Inspirational. Thank You Ben for your clever, educational and sometimes humorous videos. Only you would go to the trouble of designing a complex machine to crank out cookies. I hope you still use that system from time to time. LOL

[@alexitoyt1130]

Brilliant demo, still amazed the UV from these lasers and the glass barriers don't diminish the effect. Been using this to trigger a plasma in a bottle lately. If you could read back the written data from the array maybe it could make a cheaper X-ray imaging panel. :-)

[@paulkocyla1343]

I guess that the effect is caused by direct excitation of the gas by the laser. Once "ignited", the resitance drops, and the idle drive current of the display keeps it excited. The off-state pixels don´t look completely dark, there must always be some idle current flowing.

[@ipsofaxmachine4716]

I've gone through several Line 6 DL4 guitar effects pedals and many have died on me only to be revived by replacing the EPROM. I never realized what that thing was doing to the state of the board until now!

[@markkrutzmann6862]

I have another theory: The laser light ionizes the gas a bit, thus lowering its firing voltage. This would also explain the dots when panning quickly as firing voltage is only enough at the peak voltage. In gas discharge voltage references of old (fancy neon bulbs basically) they put slightly radioactive stuff in the tube to achieve a lower firing voltage. After some years the material is not as active anymore and can cause malfunctions, as the firing voltage may not be met. There are two possibilities to test this hypothesis that I can think of now: 1.: Try to use something radioactive or x-rays to ignite the pixels 2.: Alter the driving voltage and pan the laser quickly around. The "duty cycle" where it works would be different as well. Now, actually, when thinking about it the two methods would not prove the hypothesis, also the fact that illumination without powering the display has an effect is not explained by this idea. Nevertheless it might be a combination of several effects and may be food for thought for you, so I commented anyway.

[@robbystokoe5161]

My initial hypothesis was that the laser was being absorbed by the gas itself, ionizing it and lowering its resistance. I think that possibility might still be worth considering. This reminded me of something called a laser-driven light source which uses a focused laser to create a compact pocket of luminescent plasma between the electrodes of an arc lamp. The laser makes the plasma pocket smaller than an ordinary arc, allowing a less-divergent beam after collimation. I think most of the energy is supplied by the electrodes still, the laser just makes the plasma only ignite in a compact region. It looks like Hammamatsu/Energetiq may be the sole supplier for those.

[@tramsgar]

This triggers an old memory of me plaing with a laser pointer to make "permanent" lines on a plasma TV. Discovered by coincidence, forgotten by stress, but now I can recall the excitement and surprise. The TV was on, for sure, just as described here.

[@josiaboy]

what happened at 18:12 is absolutely hilarious 😂 the sheer luck that you work with one of the only people in the world who can say "I actually did that over 10 years ago, see I have proof" is astounding

[@dancoulson6579]

I must admit, I immidiately assumed the UV was lowering the ionization voltage of the gas, as you said right at the start. I'm leaving this video paused in the background and will come back to it later when I can pay more attention. I can tell it's going to be an interesting one :)

[@VuULF]

I've got to look through my junk for an old amber display now 🤔

[@mas5.545]

absolutely fascinating ! Ben, thank you for the amazing content and your explanation about the physical/working principles.

[@swilwerth]

Can a laser replace the heater function on a vacuum tube, but by photoelectric emission?

[@QuanrumPresence]

Checkout photomultiplier tube, not exactly a vaccum tube. But it is designed to be activated by single photon and multiply the signal

[@Superkuh2]

The first stages of electron accelerators (that generate the electron bunches) for x-ray lasers sometimes do this.

[@whitcwa]

Video cameras with vacuum tube pickups use a photocathode in the image plane in addition to having a thermionic cathode in the electron gun.

[@projectartichoke]

Also interesting is that neon lamps may not strike in total darkness. Some need at least some photonic excitation. And if you have an old power strip where the neon light is going bad and it is blinky, shining a weak flashlight on it will cause it to glow steadily.

[@adamdapatsfan]

I hadn't thought about that - if I can nerd-snipe myself with just pen and paper, being in a garage like yours must only amplify the potential!

[@federicoae7671]

Something similar to the neon bulb incident happened to me, but with a christmas tree light. I was no more than 7 or 8 at the time and figured that if 50 lights could go on the outlet, surely one could go as well. I had yet to learn about series and parallel.

[@zebo-the-fat]

I did the same thing but with an led, they were very new at the time and I didn't know you needed a resistor... connected directly to a power supply and it just exploded... bits of the plastic body all over the desk!

[@maximivanov8467]

If the electrons are indeed knocked out from the conductor and not from the gas, the alternating brightness of the dots can be simply explained by the fact that the upper electrode is transparent, i.e. does not absorb as much light, and therefore not as many free electrons can be produced from it.

[@michaelmoorrees3585]

7:20 - Shades of Electroboom ! Emphasis on "boom". 16:30 - EPROM (UV erasable). Haven't used one of those in years. I have a UV eraser around here, somewhere. Been buried for decades !

[@alexitoyt1130]

For the large dot small dot trail, perhaps you could set up a high speed camera and also try to visualize the AC waveform in the same shot (perhaps something as simple as a red/green led to show positive/negative) to see if if the positive cycle consistently produces the larger/smaller dot.

[@alexitoyt1130]

I have another theory: The laser light ionizes the gas a bit, thus lowering its firing voltage. This would also explain the dots when panning quickly as firing voltage is only enough at the peak voltage. In gas discharge voltage references of old (fancy neon bulbs basically) they put slightly radioactive stuff in the tube to achieve a lower firing voltage. After some years the material is not as active anymore and can cause malfunctions, as the firing voltage may not be met. There are two possibilities to test this hypothesis that I can think of now: 1.: Try to use something radioactive or x-rays to ignite the pixels 2.: Alter the driving voltage and pan the laser quickly around. The "duty cycle" where it works would be different as well. Now, actually, when thinking about it the two methods would not prove the hypothesis, also the fact that illumination without powering the display has an effect is not explained by this idea. Nevertheless it might be a combination of several effects and may be food for thought for you, so I commented anyway.

[@robertpeters9438]

Wow, how tiny that eprom was. My old 512kbyte eproms were larger than the whole window! Another great video.

[@nochan99]

The dots are not only asymetric in brightness, but also in phase. It looks like the dim dots are triggered slightly earlier than midpoint between bright dots.

[@ITpanda]

Cool stuff. Hoping to see a small Etch-A-Sketchish product soon! A small power distribution board and 18650 holders with a holder for a small laser pointer.

[@ceaderdoodog57]

You are amazing and I love you. Your channel has changed my life. Thank you.

[@Skunkola]

Love your vids, they're always interesting and you never know what part of your brain is going to get lit up but it's always so rewarding. Ty.