I’m not one to toot my own horn, but I think you’ll find this video…
quite touching.
There’s a good chance you’re watching this video on a device with hundreds of little
touch sensors designed to sense your touch.
We take the touch screen for granted these days
unless, of course, you’ve got a Macbook,
but it wasn’t that long ago that we thought touch sensors were the bee’s meow.
And actually, longer ago than that, a peculiar kind of lamp was trendy as all get-out.
Here’s one of them now.
And how do you turn it on?
Why, you simply touch it.
Anywhere!
Well, anywhere that’s metal.
And built-in to the lamp is a dimming function emulating the good ol' three-way bulb with
bright,
Brighter,
BRIGHTEST!
Off.
These lamps were everywhere in the 1980’s.
Well, mostly nightstands and desks.
and they seem to have largely disappeared.
But why?
And how do they work?
And who invented them?
And when?
All these questions and more will be answered after this sentence.
Let’s start with a bit of history as well as a lesson in internet literacy
and thorough research.
If you ask The Google when the first touch lamp was invented,
you’ll get the rather on-the-nose result of 1984.
Now I mean that seems plausible, after all
they were all the rage in the age of beige,
new age raves and Nicolas Cage’s coming-of-age,
but if we follow the source of this “helpful”
snippet, we’ll see it references this patent.
Now, while Scott M. Kunen does indeed have the patent
“Touch controlled switch for a lamp or the like” in his name,
and while it was indeed filed in its original form in 1984,
it doesn’t take much reading, in fact only to the third paragraph of the description
to find
“At the present time several 'touch controlled lamp dimmers' are commercially available
[whispered strenuously] (which means they already existed)
in which touching an electrically conductive
part of the lamp causes the power level to the bulb to change, either continuously or
in discrete steps.”
So clearly Mr. Kunen did not invent the concept of the touch lamp in 1984,
in fact the patent in question is for a device allowing you to touchify an existing lamp
with a simple plug-in module.
So who did invent it?
And when?
Well, right there for you in that patent are citations of other patents.
That’s how patents work.
Of particular note is this 1953 patent held by Sylvania which, and I quote,
“relates to a capacity operated control system, and more particularly to control systems employing
a metal conductive plate simulating a push button, in which the control is exercised
not by pushing on the plate, but by bringing a finger or other part of the body close to
or upon the plate.
Such systems have been called pushless push button control systems.”
Now I don’t know about you, but I think we really oughta bring "pushless pushbutton"
back into fashion.
And the other more directly relevant patent citation is this one, an invention of
Norman Green, owned by the Aladdin Lamp company.
Their genie-ous idea was, and I quote,
“to provide an improved lamp which an operator may light or extinguish simply by moving his hand
or some other part of his body into proximity with the lamp.
A further object is to provide a lamp having improved switching means operable by body capacitance.”
This patent is from nineteen-FIFTY-four
which seems to suggest touch-lamps were available all the way back then.
And, sure enough, we can corroborate this finding with a search in Google Books for
“touch lamp” in magazines from the mid-1950’s and boom, there it is, in an issue of
Kiplinger’s Personal Finance from 1955.
A
♫ swanky 1950's big-band ballad begins as highlighted section is read with intoxicating enthusiasm ♫
The eleventh Nashville is of course the best.
Oh, and adjusted for inflation, this was a $340 dollar lamp.
So, I hope we’ve learned here two things; one,
Don’t take everything you read on the Internet at face value, and two,
Google takes everything it reads on the Internet at face value.
I don’t wish to get into the debate over what the consequences are of Google shifting
its mission from providing information to providing
"answers,"
but here we are.
Anyway, better get back on track here before this tangent gets any more inflammatory.
This apparently first-of-its-kind touch lamp, though crude in its electronics, used the
same exact principle as this newer-but-not-quite-modern one.
It uses the capacitance of the human body to activate a switch.
See, all it takes to make a capacitor is a pair of conductive things with a gap of some
sort of dielectric material in-between them.
You can then store a charge between the two conductors.
Fun fact, if you take a potato, cut it in half, stick electrodes in each half
and bring them close together but not quite touching,
then you’ve made a capacitater!
Since your body is a veritable hodge podge of different stuff
like skin and fat and muscle and bones and whatnot,
you are actually a capacitor of about 100 picofarads.
And that means you’re useful!
Let me now state that I am no Big Clive and my understanding of the theory involved in
most electronicals is limited at best, but I shall do my best to describe what
Aladdin’s lamp does when you touch it.
Lucky for me the patent describes this in fairly basic terms.
Links to this patent and other information are available in the description for those
wishing ;) to look for yourself.
Norman Green’s Fantastical Lamp used a pair of vacuum tubes, a latching relay,
a selenium rectifier (an early kind of diode), some coils, a resistor, some capacitors, and finally -
you!
Both of the tubes were triodes, one of which acted as an oscillator.
This created a voltage across the resistor.
This served to limit the amount of current that could be produced between the two triodes.
That current was directed through the relay coil, and in the ordinary state not enough
current is produced to actuate the relay and thus turn on or off the lamp.
Now, one side of that resistor is attached to a sensing ring.
When you touch that, your body’s capacitance affects the circuit.
You increase the capacitance between the sensing ring and circuit ground,
which thanks to a whole bunch of phenomena that are really frankly outside my ability to comprehend,
cause the oscillation in the first triode to stop, which causes an increase in current produced by
the triodes together, which will then energize the relay and actuate the ratcheting switch mechanism.
The lamp will thus turn on.
Once you stop touching it the oscillation starts again and the field in the relay mostly collapses
so it no longer produces actuating force.
Touch it again and we repeat everything, this time with the lamp turning off.
Frankly I am astonished that touch lamps existed in the age of vacuum tube electronics.
But they apparently did.
I am also slightly terrified by the fact that the sensing ring is separated from mains voltage
merely by the relay coil and resistor on one side, and the grid of a tube on another.
Doesn’t sound particularly fail-safe, though the ring could actually be insulated with
the device still functional depending on its sensitivity.
Still, the patent seems to suggest the intent was for it to be bare metal.
Neat.
These lamps were apparently marketed as “Magic Touch Lamps,” and my favorite part of the
patent, immediately following a section on the value of being able to simply touch it
and not find the switch in the dark, reads
“Furthermore, the fact that the lamp can be controlled merely by moving the hand
close to the base lends a magical or mysterious quality to the lamp,
which greatly increases its commercial value.”
Yeah, the vacuum tube circuitry of the lamp was actually sensitive enough that you didn’t
even need to touch it directly, you could instead get close enough to it and it would
switch the lamp on or off.
Now, for those unfamiliar, vacuum tubes are generally not known for their energy efficiency.
Most rely on thermionic emission of a heated cathode, and the tubes in this lamp were no exception.
It likely consumed 10 or 20 watts all the time, and combined with the overall expense
of the lamp, it’s no wonder these early touch lamps are incredibly rare.
You can’t even find a good picture of one online, though in fairness
“Aladdin lamp” leads to some rather animated results.
So if these were around in the 1950’s,
well how come they seem to be a product of the 1980’s?
Well, almost certainly because that was when basic electronics started to get dirt cheap.
Until then, adding touch functionality to a lamp would dramatically increase the cost,
but by the late ‘70s we had mastered integrated circuits to the point that the module needed
to add touch sensing was… pretty cheap,
and also small enough that it could be incorporated in virtually any lamp.
We could also easily add dimming functions with the help of a triac.
And best of all, these solid-state electronics wouldn’t consume much power of their own.
This particular lamp is from somewhere around 1986 or ‘87, the golden age of golden touch lamps.
Its three-level behavior is pretty typical of touch lamps of the day,
and while it’s not sensitive enough that you don’t need to touch it,
touching it literally anywhere but the glass will make it change brightness.
If I plug it into a Kill-a-watt we can see that it consumes about half a watt of standby power,
not ideal but also not enough to notice on an electric bill.
At least, if you’ve only got one.
If we open the bottom we can see the base hides a small circuit board.
The lamp cord is connected via wire nuts to the hot and neutral input of the board, and
the hot and neutral wires from the lamp socket get attached to a red wire coming off the
board and another neutral lead.
A small yellow wire attaches to the stem of the lamp.
That’s the sensing wire of the circuit.
There’s a sixteen pin chip here which I could unfortunately not find a datasheet for
but it’s pretty clear that this is the brains of the operation.
Most of the components you see on the board are there simply to derive a power supply
from mains voltage for that chip.
And over here you can see a triac.
This serves as a high-speed switch for the lamp socket, like a solid-state relay.
Triacs are fast-enough at switching that they can be used to dim a light bulb by cutting
off the power mid-wave on each AC cycle with high precision.
Most dimmer switches use triacs so it’s no surprise to find one here.
The benefits of using an integrated circuit like this are numerous but chief among them
are its ability to self-calibrate,
flexibility in programming and thus behavior,
minimal power consumption,
and added safety.
With a microprocessor at your disposal, you can actually measure the apparent capacitance
on the yellow wire and track that over time.
All it needs to do is repeatedly put a tiny charge on that yellow wire and observe the resulting discharge.
No need to have it directly coupled to line voltage.
When it suddenly changes thanks to a human touching the lamp and increasing its capacitance value
and thus the total charge, it will trigger some sort of event.
In this case, the next stage on the bright, brighter, brightest, off routine.
The IC will simply put control voltage on the triac as necessary for the given brightness.
Doing it this way means that the module can be used in pretty much any lamp you can think of.
When it first powers on it establishes its baseline capacitance which could change depending
on lamp's design or even other things you have near to the lamp.
It’s only when that value changes a lot that it interprets an input.
The original Aladdin touch-lamp’s circuitry was probably calibrated and tuned to each
specific lamp since it operated essentially on a threshold of capacitance values,
and indeed any analog circuitry designed to accomplish this task would need similar calibration.
But this?
It'll just figure it out.
You can actually observe this self-calibration when you plug it in.
The lamp shines a brief pulse and it won’t respond to touch for a few moments.
Most likely as a part of its boot sequence, it takes multiple capacitance readings to
establish a baseline before it enters a ready state.
And it likely also adjusts that baseline as time goes on,
which helps minimize erroneous triggers.
So what happened to the touch lamp?
This certainly don’t seem to be all that popular anymore.
Well, I’m not sure, but they’re not dead!
You can still buy them.
You can even go to the lamp repair section of your favorite hardware store and pick up
one of these puppies for somewhere between $5 and $10.
This is essentially the same exact thing as the module in the base of this lamp,
it even has the same wire colors!
Though it has gotten a bit smaller…
Want to look at the actual circuit board?
Well, thanks to the magic of buying two of them, I have an already-taken-apart-one
right here!
As a matter of fact you barely have to do anything to take this apart.
The board is just sitting in a little plastic box, it’s not even attached to anything.
Listen.
[sound of rattling in the box]
But sure enough, we find essentially the same things we did in the original lamp.
Though, since this is much more recent, I can in fact find the datasheet for the chip.
And, well, yeah.
It does all the same things as this other one.
Detects a change in capacitance on the yellow wire (and it claims to be superbly sensitive)
then it goes between bright, brighter, brightest, and off.
Though it calls the darkest setting “night” mode, which is probably a lot darker than this.
The beauty of these little modules is that you could really add touch functionality to virtually any lamp.
In fact this ring is on the yellow lead with the idea that you’ll clamp it between the
base and stem of an ordinary lamp.
Though there’s nothing stopping you from extending this lead to somewhere else
so you could, oh I don't know, turn on a lamp by touching your fridge or something silly like that.
Or, a little less preposterously, you could connect this to a fancy stainless steel stud
and use it to control bookcase lighting with a futuristic pushless pushbutton.
Since these use a triac for dimming, in general they seem to play nicely with dimmable LED bulbs.
Even this old one works just fine with a modern LED in there.
As with anything dimmers and LEDs there’s always the potential for some compatibility
weirdness but this Philips WarmGlow 40 watt equivalent bulb operates silently and flicker-free
with this pretty old lamp.
And to bring this all back to the start, your smartphone uses the same method this lamp does
to tell where your fingers are.
Built into the screen is a grid of electrodes designed to detect a change in capacitance
brought about by the presence of a fleshy digit.
We seem to have decided that this is the best way to do it as you don’t need to exert pressure
on the screen like with some alternative technologies which can help with pointing accuracy.
Flirtations with using multiple screen technologies at the same time for high positional accuracy
and force measurement were abandoned for reasons.
The greatest downside of capacitive touch screens is that ordinary gloves prevent your
fingers from furiously fighting fictitional fantasy foes,
but thankfully extraordinary gloves are available to mitigate this drawback.
Still, Aladdin was right.
There really is something magical about just touching a lamp and having it light.
Maybe these will become fashionable again, though we might want to focus a bit on
reducing their standby power a little.
For now though, while your desk lamp may not bring you the touching experience that this one does,
rest easy knowing that you can have a similar experience
simply by turning your smartphone’s flashlight on and off.
Thanks for watching, and a special thanks goes out to both patron of the channel Anachronistic_Tendencies
for suggesting this video topic, and also my dad for reminding me that this touch lamp is in the family.
Since I grew up with this, it’s not really something that I thought of as novel but actually
yeah, I mean this is pretty neat!
Maybe they’ll see a resurgence some day.
Then again, we seem to prefer talking to our lights these days.
Oh well.
♫ capacitively smooth jazz ♫
Well mostly nightstands and desks. And seem to have been... largely dis--
seem to have BEEN largely disappeared!
Emulating the good ol' three-way bulb with bright, brighter, brightest!
Off.
Shhhhh
[distressed laughter]
I don't wish to get into the debate over the...
That's a... that's a very;
I don't wish to get int
idon'twishtogetintothedebate, that's very, like...
staccato.
I don't wish to get into the debate over what the consequences are of Google shif... [laughs]
Again, idon'twishtogetintothedebate.
How many... [counts syllables aloud]
Ten syllables!
Is a pair of conductive things with dehbudebubude
be be be be
bop.
Its three-level behavior is pretty typical of touch lamps of the day,
and while it's not sensitive enough that you don't need to touch it,
touching it literally anywhere but the glass [immediately bonks the glass with a clunk]
With a microprocessor at your disposo, you can actually measure the...
Disposo.
Disposal.
I'm saying "disposo" aren't I?
Dispozo's quite an interesting clown...
You've made a capacitater!
[breaks] I can't believe I'm doing that
Doesn't this just seem like a weirdly modern thing, but from decades ago?
What happened?
Anyway, hey google, turn off the lights.
And also learn how to do proper research!