You’ve no doubt seen plenty of fluorescent lights,
but have you ever seen one like this?
It may not seem all that strange at first glance,
after all\hthere have been plenty of weird fluorescent lamp designs over the years.
But this one’s missing a\hpretty crucial part:
the electrical connections.
Your typical fluorescent tube has little wires\hattached to pins which stick out of the glass at each end,
and they connect to electrodes inside the tube.
Those wires are then connected to a ballast and starter which together place a voltage on\h the electrodes
to pump electricity through the lamp which makes it glow.
But this… this is\hjust a glass tube.
How’s that supposed to work?
Well, with these.
The tube is designed to\hbe held in place by a pair of…
let’s call them electromagnets.
That’s not exactly the\hright word which will become clear in a moment
but each one of them is formed by wrapping a\hwire around a ferrite core several times.
With the help of electronics inside this driver\hunit,
a high-frequency alternating current is sent through the wires
which then causes a\hmagnetic field to repeatedly form, collapse, and form again inside the ferrite cores.
Now, if\hyou know a little bit about power transformers,
then if we take the tube out of the picture\hfor a moment and look at a core by itself,
then what we’re looking at appears to be a toroidal\hpower transformer that somebody forgot to finish.
See, usually we’d have at least two coils\hof wire wrapped around one of these cores.
When we run alternating current through the\hfirst coil of wire, called the primary winding,
it will induce a rapidly changing magnetic field\hthrough the core
which in turn induces a voltage on the other coil of wire known as the secondary\hwinding.
When that secondary winding is part of a circuit, current will flow
and the upshot is that\henergy is transferred from the primary winding, through the core, and into the secondary winding.
We often do this because the secondary winding will produce a different voltage
when it has\ha different number of turns around the core compared to the primary.
But here, there isn’t\ha secondary winding!
It just doesn’t exist.
That is, until I put the tube back.
This\hlamp isn’t a literal wire, of course, but once I have it enclosed by the core
it\hdoes indeed form a loop in the exact same way a single turn secondary winding would.
It\hlooks a little strange because it’s going way over there before looping back to the core, but\hthat’s what it is.
Now, because this lamp is so large, we need a second core positioned on the other end of the tube,
but they’re wired together and so act as one.
When the alternating current being sent through the\hwires by this driver unit induces magnetic fields in the cores,
those fields then induce a voltage\h inside the fluorescent tube.
And, because it’s formed in a loop, that results\hin current flow which causes the lamp to light.
For that reason, this is known as an\h induction lamp.
The actual light it produces is the result of the exact same\hprinciple as an ordinary fluorescent tube:
a low-pressure arc discharge is produced by\hpassing current through an ionized mixture of mercury vapor and a noble gas such as argon,
and\has electrons collide with the mercury atoms the mercury emits ultraviolet light
which is then\hconverted to visible light by the phosphors coating the glass.
But rather than use electrodes\h reaching inside the tube in order to pass current through the gas,
current flow is generated\h externally via electromagnetic induction.
Why would we want that?
Well first, it’s\hpretty cool!
But also this particular lamp has a power rating of 200W and a light output in the\hneighborhood of 16,000 lumens.
That is unusually powerful and bright for a fluorescent lamp,\h especially given its relatively small size.
But brightness, power, and coolness weren’t really the\hmain reasons these appeared - operating life was.
Getting rid of the electrodes would mean getting\hrid of the weak point of the fluorescent lamp.
In a conventional tube, the electrodes slowly\h wear out in a process known as sputtering.
This happens the most at lamp start-up, but sputtering\hstill happens throughout continued operation.
Over time this causes the ends of the tube\hto darken -
the dark spots are the material which used to be the electrodes, but as\hit sputters off it becomes deposited on the glass.
That reduces light output\hslightly but the bigger problem is that as they wear away
the electrodes lose\htheir ability to emit electrons.
That makes it more difficult for the ballast and starter\hto initiate the arc discharge across the tube,
and eventually they will wear to the point\hthe tube is no longer able to start and the lamp has failed.
As the technology developed we\hgot pretty good at making electrodes which could last a good while,
and fluorescent lamps would\h typically have a rated life of 10,000 hours.
But if we could do without the electrodes,\h the lamp could in theory last forever.
And, well, that’s the point of this technology.
There’s nothing to the lamp but a phosphor-coated tube filled with some argon gas
and a pellet of\hmercury amalgam chilling in this little glass appendix.
It has no electrodes to wear out and\h this means the tube itself has a theoretically unlimited lifespan.
Nothing truly lasts forever,\hof course, and due to phosphor wear and mercury absorption
these will lose light output over\htime,
but these lamps have a rated lifespan of 100,000 hours - a tenfold increase over\hconventional tubes.
Operating dusk-to-dawn, that would mean this should last nearly\h23 years before requiring replacement.
Now, obviously, that’s a pretty phenomenal\hlifespan and so it might be surprising how uncommon this technology is.
I mean, there’s not\ha whole lot to this thing
and it operates on the fundamentals of electromagnetism that have been\hunderstood since the 19th century.
Sure enough, electrodeless lamps which operated via\hinduction had been demonstrated many, many times in the past.
Nikola Tesla was\hplaying with it because of course he was.
But a practical and effective application\hof the technology was surprisingly elusive.
It wasn’t until 1967 that John Anderson filed\ha patent for a lamp like this one,
and then it took until 1990 for it to actually be commercialized\hinto a finished product.
What took so long?
Well, despite how simple the overall\h idea is on the surface,
it turns out there were a LOT of different problems that needed solving\hbefore this could actually become a reality.
For one thing, inducing current flow in\ha loop of gas, even if it is conductive, is a lot harder than a solid metal wire.
To sustain the arc discharge in the tube, the magnetic field generated by the cores has to\hswitch back and forth very a lot,
so the frequency at which this thing operates needed to be very\hhigh.
You’ll notice the patent shows the driver as “converter to radio frequency”
and Anderson\hlists a preferred frequency range of 100 to 500 kilocycles.
That’s almost reaching the AM radio\hbroadcast band.
By 1967 it was relatively trivial to produce high-powered oscillators which ran at\hthat frequency,
but that wasn’t the main issue.
Because of the required high frequency,
wrapping wire\haround an ordinary iron core as found in most power transformers wasn’t feasible.
At those\hfrequencies, the eddy currents which form inside the cores would cause it to get extremely hot.
That’s the mechanism by which induction cooktops work.
But the problem is, that would both limit\h the efficiency of the power coupling
and how much power you could feasibly transfer into the tube\hbefore the cores started to melt.
This meant ferrite compounds, which are extremely magnetically\hpermeable but not electrically conductive
and therefore don’t form eddy currents inside,
were required\hfor high-frequency power coupling.
They weren’t invented until the 1930’s and even though they\hwere fairly common by the time Anderson filed his patent,
ferrite was still an expensive material.
In fact, that’s the main reason this lamp gets narrower where the cores attach:
making the tube diameter\h smaller requires less material in the cores.
But here’s where the story gets a\hlittle weird.
Although this patent is nearly a spot-on description of\h this lamp both in form and function,
the first commercial products using the\htechnology were very different from this.
The QL line from Philips was the first commercial\hinduction lamp and they looked…
pretty much like an ordinary incandescent light bulb.
They\hweren’t - they were in fact fluorescent lamps which worked by induction similar to this.
But compared to this tube and its external cores, they were constructed inside-out.
I don’t have\hone to show you, but thanks to a donation to the channel from Jeff, a long-time Patreon\hmember,
I do have this variation which was manufactured by GE.
This Genura lamp was released\hin 1994 and it is designed to replace a reflector flood bulb
but it works on the same basic\hprinciple to the original Philips QL lamps.
Here, the discharge tube isn’t so much a\htube as it is...
a vessel.
And a single coil, once again in the form of a wire wrapped around a\h ferrite core,
protrudes from the base of the lamp into a hollowed-out section of the glass vessel.
This evacuation stem holds the pellet of mercury amalgam which is required to produce ultraviolet\hlight
and it rests inside the ferrite core when assembled.
An oscillator circuit in the base\hof the bulb sends high-frequency pulses through the wire wrapped around the ferrite core
which in\hturn creates a rapidly fluctuating magnetic field around it.
That field reaches well inside the discharge\hvessel.
As the field changes in intensity, current flows through the gas inside,
and our desired mercury discharge occurs.
In this lamp design, the single coil protruding\hinto the vessel produces a magnetic field in a toroidal shape around its perimeter.
That’s why\hthe QL lamps from Philips look a lot like an ordinary light bulb.
It’s not a linear discharge\hrunning through a tube but more of a fuzzy donut of ultraviolet light surrounding the induction\hcoil,
which a bulb-shape happens to encapsulate quite well.
The phosphors on the glass convert the\hUV to visible light
and the result is a compact yet very bright light source with an extremely\hlong life.
The original QL lamps ran at 85 watts and had a rated life of 100,000 hours.
Now,\hthis GE lamp isn’t quite so optimistic but that’s likely down to the fact that its drive\helectronics are built into the lamp itself.
This was sold as a drop-in replacement light\hbulb,
so everything had to get crammed into here.
And since these are generally\h operated with the base facing up,
heat from the discharge would rise right\hinto the electronic components
which shortens their operating life, especially\hcapacitors.
The QL line from Philips used an external driver muck like this thing does
and the lamp itself was\hlittle more than a glass orb on a stick.
Still, it wasn't quite as simple as it looks.
Because the induction coil was shoved up the middle of the lamp, it gets pretty hot -
particularly\hin the case of the QL lamps which operated at 85 watts.
This was a problem because as the\h ferrite material increases in temperature,
its magnetic permeability decreases which\h limited the strength of the magnetic fields it can produce
and thus the amount of\hpower it can send into the gas discharge.
That reduces both brightness and energy\hefficiency.
Philips solved this by incorporating heat-conducting material into the design of\hthe ferrite core’s stem,
which by the way they referred to as the antenna.
From what I can tell\hlooking at patents, GE didn’t solve this at all,
but since the lamp only operates at 23 watts\h the induction coil probably never got hot enough to matter.
But another issue with the single-coil designs is that\h it require an even higher frequency to function:\h\h
around 2.5 megahertz.
And because these are\hoperating at radio frequencies and pumping dozens of watts or more into the discharge vessel,
well radio\hfrequency interference was a significant problem.
To try and help solve it, the glass is coated with a transparent yet\hconductive material, such as indium tin oxide,
which absorbs radio frequency energy and\h keeps it from escaping.
And in this lamp, the underside of the discharge vessel also has a metal shield which was\hbonded to this copper ribbon
that allows the absorbed energy to return to the circuit ground.
But, it’s clear that GE at least wasn’t making the strongest promises about its effectiveness.
They warn specifically against using these on boats as they could disrupt maritime communications.
And, uh,\hgiven that they provided a phone number for interference complaints...
well I think it’s\hsafe to say this was very much a beta test.
Now, it might seem a little odd that\h the basic idea for this later design was patented in 1967
yet induction lighting didn’t get\hcommercialized until after Philips and GE released their single-coil designs.
But it\hmight make more sense if you consider that these external-coil lamps...
really aren't that\hdifferent from conventional fluorescent tubes.
In fact, many lower-power versions of this design\hincorporated circular tubes which look a whole awful lot like a standard circular fluorescent\hlamp.
They did offer higher light outputs, but the form was still very familiar.
The fact that\hneither the QL lamp nor this Genura lamp look anything like a fluorescent tube is probably why\hthe technology was first commercialized like this.
Consider the GE bulb:
the resulting discharge\hinside this vessel produces a compact but powerful ring of UV light just under a relatively\hflat piece of glass.
This meant fluorescent technology could not only mimic the appearance\hof an incandescent reflector
much more faithfully than sticking a coiled tube inside a\h fake bulb but it was also much more effective.
This flavor of induction technology was able to\hcreate much more powerful yet also compact light\hsources than a linear fluorescent tube
while\hstill offering similar energy-efficiency.
That was compelling enough on its own to\h pursue not only for aesthetic purposes
but because it allowed the use of fixtures\hwith optical systems that produced much more directional light.
To a point at\hleast - I’ll touch on that more in a bit.
Induction technology also solved one of\h fluorescent lighting’s little annoyances:
a slow warm-up.
High-efficiency fluorescent\htubes in particular only produce a fraction of their light output at first
due to lower vapor pressure\hwhen cold and thus they can take several minutes to warm up.
This lamp also starts with a lower\h vapor pressure and thus reduced light output,
but the warmup time is just a few seconds.
And the large external-coil lamp is similarly quick - it’s at full brightness in only\h10 seconds.
You can actually observe the mercury discharge migrating away from the amalgam\hpellet as the tube heats up and the pressure builds.
But… well, that was at room temperature,
and these lamps were sold to go outdoors.
In fact street lighting is one of the most likely\h places you’re going to find these in the wild.
And I live where the outside air sometimes\hgets colder than a freezer,
so I put this whole thing inside a freezer overnight to see\hhow quickly it would warm up from truly cold.
The lamp had no issues starting but, like\hmost fluorescent lights in this temperature,
the mercury was barely contributing anything and we could\hsee the purple glow of the argon starter gas.
Interestingly it initially did the same thing\h where the light output seems to grow from the mercury pellet,
but before long that bright spot\hdisappeared and it all averaged out to a very dull grey.
It took about 10 minutes to attain\hfull brightness so it looks like cold-weather performance is only improved slightly.
But at least it had no trouble starting!
Speaking of starting, well now it’s time to\hcome clean here -
I don’t really understand the mechanisms by which these lamps start.
See, the gas mixture in these tubes isn’t electrically conductive until it’s ionized.
The\helectrodes in a traditional fluorescent tube emit electrons when heated and/or when a sufficiently\hhigh voltage is placed across them,
and those electrons collide with the gas molecules inside\h and ionize them which causes dielectric breakdown.
But with these, all we got is magnets.
The 1967 patent mentions the use of electrodes in contact with the glass that, when a sufficiently\hhigh voltage is placed across them,
will ionize enough gas inside the tube to initiate dielectric\hbreakdown.
But this device has no such electrodes.
A later patent filed in 1995 describes this device\hnearly perfectly,
and it even has a diagram which more clearly illustrates the rather confusing\hway the wires are wrapped around the two ferrite cores.
But it also mentions a conductive strip\hin contact with the glass specifically for the purpose of creating ionization points for\hstarting the lamp.
But again, this lamp doesn’t have those.
All the information I could find on\hhow this lamp gets started was quite handwavey,
but my best understanding is that the driver\hcircuitry initially sends a much higher than usual voltage through the wires
which produces a strong\henough electric field that free electrons in the gas mixture are sort of thrown about,
causing\hsome ionization.
Basically it’s the same way that fluorescent tubes can start glowing when you hold them near a Tesla\hcoil.
And once some of that gas is ionized the discharge across the tube can be completed
after which the driver can switch to its normal operating voltage.
That may also further explain why the internal\hcore lamps were commercialized first.
Based on readings of patents, it was initially thought\h that a secondary winding would be needed on the ferrite core
to produce a high voltage capable of initiating a glow\hdischarge,
but that feature seems to have gone away once it was decided to use the very\hhigh frequency found here.
This patent filed in 1982 seems to suggest that simply by inducing\hthe magnetic field at a frequency of 3 megahertz,
a sufficiently strong electric field is produced\h inside the vessel which can ionize the gas.
But I still haven’t gotten a truly satisfactory answer,\h here, and would welcome one in the comments!
It might have something to do with the metal\h mesh found here,
and a closer look up the middle of this Genura’s discharge vessel shows a\hpiece of wire at the top of the evacuation stem.
But truthfully, I gave up trying to find an answer.
So, with their extremely long operating life\h and newfound applications for energy-efficient\hfluorescent lighting,
it might seem strange\hthat this technology is so obscure.
I mean, today we have LEDs and this technology is\hobsolete
but knowing that back in 1990 we had a lighting technology with a lifespan that\hessentially matches the best LEDs we have today,
you would think it would have\htaken the world by storm.
Yet it didn’t.
Why?
Was there another one\hof those light bulb conspiracies afoot?
Yeah, no.
See, here’s the thing - the tech is\hreally cool and opens up some new possibilities,
but not that many and it also came with some\hsignificant downsides.
For one, cost.
The QL line of lighting from Philips was very much a\hspecialized commercial product and I’ve been having a heck of a time finding original pricing,
but you can bet it was quite high.
Not only had they created a new kind of fluorescent lamp,
but\hthey had to manufacture specialized electronics and the power couplers.
The lighting system really\honly made sense in applications where relamping was an operational headache
or its operating\hmethod offered improved safety -
apparently they saw success in the oil and gas industry due\hto regulations concerning explosion-proof lighting.
GE’s take on the technology was sort-of\hconsumer focused,
and the Genura bulb retailed for about $30 in 1994, equivalent to\h$65 today.
But that’s a pricey light bulb especially considering its expected life\hisn’t all that great.
It’s certainly much better than the 1 or 2,000 hours you could\hexpect out of an incandescent flood bulb,
but it was barely an improvement over existing\hfluorescent technology.
You needed to really, really want fluorescent lighting in this specific\hform-factor,
and I find it interesting that GE really didn’t bother to explain what’s so cool\habout this technology on the box.
They're just calling this an electronic compact fluorescent lamp.
Which is true but certainly underselling it.
But the biggest issue, and what I think is likely\h the main reason this technology never took the world by storm,
is that it’s still fundamentally\hfluorescent lighting.
Yes it was longer-lived, but it still had kinda meh light quality.
And,\hbecause fluorescent lights are very much not point-sources of light,
it was hard to direct\hthe light these emitted.
This 200W lamp was originally housed in this flood fixture,
and while you could point this in a direction, it still casts a very wide beam of light.
I don’t\heven think you could describe it as a beam.
The QL lamps were more compact, but they still emitted\hdiffused light which is difficult to control.
Take street lighting as an example.
I've\hencountered a few induction street lamps in the wild,
but they all have about as much beam\hcontrol as a circline fluorescent light stuck in the middle of the kitchen ceiling.
Because that’s\hpretty much what they are.
And the inverse square law means that you can’t place the lamps too\hhigh above the street or they just won’t offer effective light output.
This ultimately means you\hneed many more of them placed closer together.
High-intensity discharge lamps like high pressure\h sodium and metal halide produce all their light in a small arc tube
which allows fixtures\hwith optical systems to focus the light they produce into a narrow beam,
permitting the use of\hfewer fixtures by placing them higher in the air.
And actually, the Genura lamp demonstrates\hthis downside quite well.
While it mimics the basic appearance of an incandescent BR flood very\hfaithfully...
at least from the face of it,
there’s no directionality to the light it produces.
Even a\hfrosted lamp like this produces a somewhat narrow beam of light thanks to fact that the filament is placed far down the reflector
and that is very important to both the character and effectiveness of the light it produces,
especially when recessed in ceiling can fixtures.
This lamp simply cannot recreate\hthat directional light,
and I would imagine that presented problems from both an\h aesthetic perspective and a functional one,\htoo.
It may be the same number of lumens,\h but when fired in all directions and not mostly downward,
the room might\hbe underlit compared to before.
And let’s not forget that conventional fluorescent\htechnology saw lots of innovation, too.
If any of the lighting nerds out there have been\hwondering why I never touted the flicker-free light output created by the high-frequency drivers\hin these things,
that’s because electronic ballasts for traditional tubes did the same thing.
They\hdidn’t operate anywhere near these frequencies,
but they were fast enough for the persistence\h of the phosphors to produce truly continuous light output.
That also increased the\henergy-efficiency of fluorescent lighting.
As a matter of fact, a bog-standard T8 tube is\h more energy-efficient than either of these induction lamps.
And then of course there’s the CFL.
Those, too, got\helectronic ballasts and all the benefits thereof
and they were available in much more modest\h power outputs than induction lamps.
Sure, the Genura lamp is a more elegant solution\h than sticking a coil in a fake bulb,
but… is its elegance worth the extra cost?
The\hmarket clearly decided no it wasn’t.
I mean, this lamp was sold long before the old curly-q\hCFL went mainstream.
Once we figured out how to make those cheaply, small induction lamps\hlike this just hardly made any sense at all.
And when ordinary fluorescent lights already had a\h10,000 hour lifespan,
well frankly you just had to be extremely committed to the idea of a lamp\hwhich could last 20 years without being touched.
That is, if it makes it that long.
The\hweak point in the induction lamp isn't the discharge tube, it's the electronics inside this box.
And while it certainly is possible to produce electronic circuitry which lasts\h100,000 hours,
well let’s just say there are never any guarantees.
Honestly props to\hGE for being so realistic with these lamps.
The QL line from Philips probably had the best\h quality drivers of any commercial system
and since they were separated from the lamp they didn’t have\h to deal with heat.
But had this tech gone mainstream, we’d no doubt have the same race to\hthe bottom that plagues so many things.
But of course now this is all moot.
The\hLED has trounced every lighting technology that we’ve ever made on energy efficiency,\hquality of light, and flexibility.
We still have the same race-to-the-bottom nonsense\hgoing on, unfortunately,
and it’s not like there haven’t been some high-profile issues with LEDs (such as purple\hstreetlights)
but in general lighting is now just solved.
We’re there.
Aside from some cheap\hbuilder-grade light bulbs I still have kicking around,
I personally haven’t needed to replace a light\hbulb in several years.
That’s no doubt helped by the fact that I generally only buy high-quality\hbulbs
and I use dimmers nearly everywhere so rarely are any of my lights at full-brightness,
but yeah.
I’m certainly not pining for the days of old.
But luckily our path to get here was\h filled with all sorts of wacky nonsense like this.
♫ electromagnetically smooth jazz ♫
And because it’s formed in a loop,
that\hinduced voltage results in current flow which causes the lamp to light.
Except it\hdidn’t.
Probably because… you need to be secured in place.
Hopefully I didn’t just\hkill ya, that would be very problematic.
For that reason, this is known as\han induction lamp.
And I cannot be sitting here with this in front of my eyes.
…chilling in this little glass appendage.
Is that the right one? Nope. I pointed at the wrong one.
I mean, there’s not a not… not a… dada da!
And in this lamp, [glass scraping sounds] the\hunderside… that I’m sure sounded horrible.\h
…have been demonstrated many many\htimes over the past.
In the… in… ugh.
One would have to call this technology...
totally tubular, amirite?
That one hurt to the core.
Both of them, actually.
Hey did you know that Michael used to be a taxi driver?
He switched to a career in science since he only got one fare a day.