The decorative lamp that's built wrong on purpose

This video contains a heckuva lot of flickering imagery throughout, and if that is a problem for you, you probably shouldn’t watch this one. Hello and welcome to No Effort November, a series of — what? It's December‽ Oh no, I'm not prepared for this! Uh, uh, uh OK well... mmmhmm I'm not doing that thing where I paint Christmas lights like some kinda madman. I know, it’s devastating to me, too, but in light of the season I will talk about a certain kind of light of the season. Some folks like to

decorate their homes all subtle-like with a candle in the window sills. But real candles are annoying and also a fire hazard so some people will use these definitely convincing and not-at-all tacky light sockets on a stick! put a little night light bulb up there, and have electric candlelight. And honestly, on the right sort of house it does look pretty festive. At least from outside. But what if you want something that's just a little less subtle? Well, you get yourself one of these things. Ain

’t it a beauty? It replicates the bright orange glow and incessant flickering of a real candle just perfectly! I mean, take a look at this side-by-side comparison. I can’t tell the difference! OK, I’m being a little hard on it. This thing is actually pretty cool, if not exactly faithful to what it’s attempting to mimic. This is a “flicker flame” lamp, though I’m not sure if it even has an official name. It’s a rather clever exploitation of a flaw that can occur in neon indicator lamps. This is

one such lamp. It’s dead simple, just a glass envelope filled with a bit of neon (and often a hint of argon), with a pair of electrodes floating in the middle. Put a fairly high voltage across these electrodes, something a bit north of 100 volts, and you’ll get current to flow between them. And thanks to neon being neon that will cause a visible glow discharge on the cathode. Why exactly that happens we don’t need to get into but importantly, once you have exceeded the striking voltage and you g

et that glow discharge, you need a current-limiting resistor to keep the current in check. Without it, the lamp will basically short circuit and often explode. Fun! Wanna see that happen? Why not! Good thing I’ve got those switched outlets in this room so I can do this from a distance. Contact! That was significantly less violent than I was expecting. OK, we're doing this one more time. Contact! [rattling as glass bounces on table] Much better. Now because AC line voltage exceeds the striking vo

ltage of these lamps, all you need is that resistor to keep ‘em from, y'know, splodin' and they’ll work. They also have very long lives and consume very little power. So, they are often used as indicator lights in simple devices hooked up to mains power. Since LEDs are so stinking cheap now we don’t see these quite so often as we used to, but they’re definitely not gone. Simple kitchen appliances without electronics, for example, will often still use them because if you don’t need a low-voltage

power supply for logic circuitry, you might as well not bother with driving an LED. Oh, and there are also versions of these filled with other gasses which produce different colors of light, including a bit of UV which when combined with a phosphor coating on the glass means you can make pretty much any color you like. Blue and green are quite common. As a matter of fact here’s a blue one in the switch of my cheap Walmart kettle, and there’s a green one in this hot plate. These are not LEDs -

they’re tiny little discharge lamps. Another fun use of this principle is in novelty lamps like this. Here we find electrodes which are shaped in novel ways to entice tourists to buy it. I mean... it worked! And in here we don’t find neon but instead something else. I’m leaning towards mostly argon but I’m not sure. Anyway, whatever it is produces a violet discharge on the turtles which conveniently also causes a phosphor on the Hawaii script to fluoresce green so we get two colors! Could have e

ven more if we wanted. Anyway, back to the neon ones. Earlier you might have caught me saying that the glow discharge occurs on the cathode. But here, both electrodes appear lit. That’s because this is powered by AC, so which electrode is the cathode keeps flipping back and forth really fast and both appear lit. If I put a diode in series with the lamp we’ll keep one of them from glowing, and by reversing the polarity we can make the other half glow. Making cathodes in a bunch of different shape

s, then stacking them together with a space in between and running high voltage DC to them is how Nixie tubes happen, by the way. How have I not done a video on Nixie tubes yet? That’s weird. Uh, anyway, as these indicator lamps age they can start to become a little unstable. If driven lightly they can last practically forever, but if they’re overdriven by a resistor that’s too low in value the electrodes can become damaged with time. Sometimes doing this is OK; for appliances which only get use

d occasionally, it’s not the worst thing to squeeze some extra brightness out of the lamp in exchange for longevity. You just don’t need it to last that long. But for something like the switch of a power strip which may be turned on forever, you’ll start to get problems eventually. The glow discharge will often become unstable with damaged electrodes, causing the indicator to flicker. Wait a minute… This thing flickers! It flickers a heckuva lot! And if we look at it a little more closely, we’ll

see that this is effectively the same thing as a neon indicator. We’ve got two electrodes separated by a gap connected to wires leading out of the envelope. Really the only thing that makes this different from an ordinary indicator is the shape of the electrodes. They’re meant to mimic a flame, so they’re shaped like a flame. The shape of the glass itself is also evocative of a flame. And inside the base of the lamp is that current limiting resistor so we can operate this from ordinary AC power

without — that. So why does it flicker? Because it was built wrong! On purpose! The electrodes in here are not trying to create a uniform glow, as a matter of fact that’s exactly what we don’t want. Now, details into how exactly this is made flickery are sketchy. I’ve found conflicting information in a few places, for instance a patent for this lamp design claims to use a barium azide coating in order to enhance the flicker effect but an earlier patent for an unrelated device claims the same su

bstance increases discharge uniformity. That doesn’t make sense! Plus the turtles in the novelty lamp appear to have a very similar coating, yet they don’t flicker at all. A different source I found claims the sides of the electrodes that face each other inside the lamp are coated with an insulating varnish in order to force the glow discharge onto the outside surfaces. And, y'know, I suppose makes a little sense but that patent doesn’t mention the need to do that. Plus, it’s not like the electr

odes on the indicators only glow on the halves that face each other so I don’t see why that's necessary. Wait a minute, Through the Magic of Buying Ten of Them, I can afford to sacrifice one of these and find out! [pop] Nope, there doesn't appear to be a difference at all between the two sides. Though interestingly, these electrodes quickly turned white once exposed to air. I don’t know what exactly I was just touching so you can bet I washed my hands pretty thoroughly after this. Oh, uh, if the

re was an insulating varnish on one side (which again - doubtful) the leads on my multimeter scratched through it so, you know, I don't think it's there. Given that information around these is contradictory and apparently sometimes flat-out wrong, my explanation here on how it works is more than a little bit speculative and synthesized from stuff I’ve observed and read online. If we have any subject matter experts in the audience who can confirm or challenge this please do chime in. Whatever the

coating is on the electrodes, it’s not uniform. That’s clear just by looking at it. And this is probably going to change how easily a gas discharge can happen on any individual point across its surface. In fact, we can see that the pattern in the flickering often follows those imperfections so clearly those affect what regions will glow. When the lamp first strikes, then, only some parts of the electrode can light. The electrodes are not, I guess, pure enough for a neat, uniform glow. But I don

’t think that’s the only thing going on. Looking back at the novelty lamp, the sea turtle-shaped electrodes are not perfectly coated either, however, they do glow uniformly and (importantly) stably. Perhaps this is a better coating than in the flame lamps but there are a few key differences here. Firstly, this ain’t neon. So the gas composition is different. But I think more importantly, this is a very large envelope and the electrodes are nowhere near as close to each other as in the flame lamp

s, and in fact they don’t even overlap. In the flame lamp not only do they completely overlap but there’s only a tiny gap between the electrodes, and that is probably causing instability due to Paschen’s law. Or "pass-kins?" However you pronounce that. See, once lit the area near the glowing discharge will heat up. And the electrodes are sandwiching a small quantity of gas between them. That gas is going to get warm very quickly once there’s a discharge, so it will expand and sort of jet out the

sides. And thanks to science reasons, the voltage required to maintain the discharge changes based on the gas pressure. That’s going to cause the area that’s most likely to glow to move once the gas expands, but every time it moves that next area gets warm, too, so the gas in that region expands, and the spot most likely to glow gets pushed somewhere else. This just keeps happening over and over again, and while it is somewhat random it is also very clearly cyclical. And again, these patterns s

eem to follow the imperfections on the electrode surfaces, so while I don’t think that’s the only factor here, it probably matters a lot. I think the strongest argument for that comes from the fact that very old, worn-out indicators exhibit this same phenomenon. And luckily, I have one right here! After looking over all my power strips I finally found one with a flickery lamp. I had to destroy the switch to get a good look at it but hey, For Science! Speaking of science, this lamp’s flickering i

s so borderline that it only flickers in the dark. Believe it or not, photons entering the glass envelope can help the neon gas to ionize, and even just a tiny bit of light from my phone flashlight gets this to stop flickering. Ain’t that neat? Anyway, if we look at this thing up close we can see that it’s darkened. This lamp was almost certainly being over-driven at least a tad, though to be fair it’s probably been on for well over a decade at this point so it still did quite well. Now, though,

one of the electrodes can’t quite maintain an even discharge and sure enough, at least with the lights out, the spots that glow move around in a similar fashion to the flicker flame lamp. With the darkened glass a sure sign of material loss from the electrodes, it’s likely that the instability is being caused by damaged and thus imperfect electrodes - which seems to give more credence to the uneven coating theory for the flame lamp. However, it might not simply be the electrodes causing the fli

cker - the original patent for the flame lamps claims that the gas composition affects how the lamp flickers, and that could also explain what’s going on with the flickery indicator. Perhaps after years of service the gas mixture has become impure or damaged somehow. But regardless we know for sure that neon lamps are not *meant* to do this, but over time they often start. So in a sense, the flicker flame lamp is an exercise in perfecting the imperfect lamp. Through some combination of a non-uni

form electrode coating, the shape and spacing of the electrodes, the size of the envelope relative to them, and even the specific composition of the gas mixture, this thing is deliberately bad at being a neon lamp. That just happens to look kinda like a flame, so make the electrodes flame-shaped and you’ve done it! But I had one more theory which I thought to test. What if the current-limiting resistor of this lamp is deliberately too restrictive? Maybe it simply doesn’t have enough current flow

ing through it to cover the entire electrodes with that glowy goodness and so the spots moving around is just a side-effect of that. Well, I rigged up these indicators in this definitely OSHA-approved testing device so we can find out. You can see that they decrease in brightness from left to right. The first lamp is powered through a 33 kiloohm resistor, which is too low of a value so it’s being over-driven. It glows quite brightly, which is nice, but it would likely become damaged over time a

nd darken like we saw with the power strip. Generally, you want to drive this size of lamp with about a 100 kiloohm resistor for 120V AC power. The next lamp is driven at that correct value (or close, anyway, I don’t have a resistor of that exact value on-hand). But the next two lamps have very high-value resistors, with the one on the right having about 500 kiloohms of resistance in total. Although it is glowing very dimly, it’s not flickering and the glow around the electrodes is mostly comple

te. So it appears increasing the resistance value mainly affects the brightness of the discharge, and not how complete it is. In fairness, these are really tiny indicators with a small fraction the electrode surface compared to the flame lamp, so this may not be conclusive. Honestly, this entire video isn’t conclusive. There’s things about these lamps that seem to make perfect sense yet other things don’t make any sense at all. But given how they’re built to behave essentially exactly like the

failure mode of a neon indicator, I think the most likely explanation is simply that they’re deliberately made kinda wrong. It’s probably not the best idea to put two flat electrodes right next to each other. The gas mixture might be just a bit off to ensure the glow discharge is uneven. And the coating on the electrodes is certainly less-than-perfect. But I do know there’s one thing we can learn from this: Sometimes things that are a little bit broken have a beauty all their own. Thanks for wat

ching. ♫ inconclusively smooth jazz ♫ Hey, so I had forgotten that I have this other novelty bulb where the glowing electrodes are in front of one another, but here there's a substantially larger gap than we find in the flicker bulbs. That could just be because whatever factory made these didn’t have great tolerances, but the electrodes going through the stem are deliberately quite well spaced. Perhaps if these were too close to each other we’d get that flickering - and maybe that happens becaus

e the glowing areas can meet? I dunno, but I thought I’d bring this up. Aloha! Sometimes doing this is OK. For appliances which only get used occazzzzzzioonally what the heck was that? [coughs] So, this might no be concplusive. Conclusive! These are really tiny indicators with a small fraction the electrode surface compared to the flame ramp... Did I say "frame ramp?" I did, didn't I? So, of course *after* I made the video I find out Big Clive covered these a while back. I mean, that seems so ob

vious in hindsight and why didn't I look for that? Although we're mostly on the same page - he also thought there was an insulating coating on one side but destroying the lamp put that into question. However, a higher resistance did make the glowing spots smaller so that probably has something to do with it. Anyway, Happy Decemberween!