One of my favorite things in life is when
I discover an unexpected piece of technology
in everyday household items.
Many of us have so many interesting things
around us that may go unnoticed.
Take kitchen appliances, for example.
They’re often a lot simpler than at first
they seem, but in at least one particular case,
that simplicity is accomplished with
wondrous ingenuity.
I’m talking, of course, about toasters.
Yes, the toaster, perhaps the silliest household
appliance.
A single-purpose receptacle in which you place
sliced carbohydrate media to be partially
burned for your enjoyment.
Delicious.
Electric toasters have come a long way from
their 19th century roots--
good grief that’s terrifying--
wonder no more when the toast
will pop up.
The jumpscare potential has been completely
eliminated with this digital display.
And wanna toast more than bread?
What about a bagel?
Be amazed as the side elements turn off, toasting
only the cut side.
Innovation at work!
Of course, if you actually go back a mere
70 years in time, you’ll discover a toaster
that is better than modern toasters in nearly
every single way.
You’re right, sally, it is like magic.
But ignoring the surprising backward steps
we seem to have made in the tantalizing territory
of toaster technology, let’s get to the
point of this video, shall we?
This toaster was a mere $8.88.
That’s only $4.44 per slice!
Now, perhaps it’s not surprising to you
that a toaster can be manufactured so cheaply.
It is after all simply a small box with a
bit of nichrome wire
(that’s an alloy of nickel and chromium)
forming bread-singeing
heating elements.
How complicated can it be?
All it has to do is turn on the heating elements for a while,
then shut them off and lift the bread.
Ah, but see, it’s the way the simplicity
is accomplished that’s so ingenious.
First, have you ever tried to push the lever
down while a toaster is unplugged?
If you do, you’ll notice that it simply
won’t stay down.
No matter how hard you force it, the lever
simply springs back up.
Why is that?
Well, it turns out that this single lever
is performing the roles of bread lowering
and lifting mechanism, power button, switch
contact, retention latch, circuit breaker,
and thing-that-moves-the-little-bread-squeezing--centering-things-in-and-out.
Uh, to explain how it does all those things,
we’ll need to take this apart.
And through the magic of buying two of them,
I have an already-taken-apart one right here.
Under the plastic covering is a sheet metal
box containing the heating elements, as well
as a small circuit board.
This circuit board doesn’t do all that much,
but the way it has been integrated into the
device as a whole is simply fascinating.
First, notice these two pairs of contacts.
These are what actually provide power to the
toaster.
In this state, there is no completed circuit.
If you look at where the power comes in on
the board, it goes right to this contact,
and then it’s got nowhere to go.
This contact must be pushed down to complete
the circuit.
Actually both pairs of contacts must be, as
the other one breaks the connection on the
neutral side as well, a smart move to protect
against the potential for a power outlet with
the hot and neutral wires reversed.
If, when it’s plugged in, I manually engage
the contacts using these
high-tech insulated poking devices, now power can flow through the toaster.
You’ll hear a slight buzz and see that the
heating elements begin to glow.
[buzzing of toaster]
Not only do the elements
receive power, but so does the rest of the board.
But what is responsible for normally engaging
those contacts?
Why, the lever of course.
Also, I’ve just realized this isn’t technically
a lever.
Why do we call it a lever?
Wait, do we call it a lever?
Let’s double-check that Sunbeam ad.
Yeah, lever.
Hmm.
Anyway when the lever reaches the bottom,
a set of its own insulated poking devices
press the contacts down, and thus complete
the circuit.
That’s not the interesting part, though,
ho no.
The interesting part is how it stays down.
Remember, with the toaster unplugged, the
lever refuses to stay in the down position.
It just pops right back up.
But with it plugged in, now it will.
How?
Well, watch closely.
Did you see that metal plate suddenly stick
to the yellow thing?
Watch again.
That yellow thing is an electromagnet, and
so long as it has power,
it will hold the lever in place which keeps the contacts pushed in
and allows power to flow through the heating elements.
Now you may have already figured out the double
whammy of genius here.
If the only thing holding the lever down is
an electromagnet, and the only way the toaster
will work is with the lever held down, then
by shutting off the electromagnet, it will
let go of the spring-loaded lever, shut off
the power, and of course eject the bread,
now toast, in a violent fashion without warning.
Fascinating.
Which brings us to the other stuff on the
circuit board.
Though we don’t need much in the way of
circuitry in here, we do need a way to determine
how long to hold down the lever, and thus
how long to toast the bread.
These days it’s handled with specialized
components, like this
(in a high-pitched, altered voice)
“MULTIPLE FURNACE DISABILITIES TIMING IC”,
which features
such marvels as CMOS, TO-94, and Bagel.
Google Translate wasn’t much help here,
but in any case we do know this is suitable
for all types of toaster, and it appears to
support a bagel mode but I can’t see exactly
how the chip itself is going to handle a bagel
mode given that it only has the one output.
In any case, the main thing this chip is doing
is looking at the output from the potentiometer
here to determine how long to stay on.
And as we know from the datasheet, roast the
development of the time interval: 0-300 seconds.
Also, let’s just get it out of the way that
these numbers do not correspond to minutes.
Tom Scott already did a video on this, but
this should give you further proof because
if the max time is 300 seconds, that’s 5
minutes, not 6, so these are just arbitrary numbers.
And funnily enough the box suggests there
are only 6 settings, when in reality there
are probably 300, as this is not a 6-position
switch, it is an infinitely variable potentiometer.
But I digress.
Anyway, most of the other stuff on the board
is support equipment for the main IC, such
as its power regulator and smoothing capacitors,
though surprisingly there is a diode connected
straight up to this yellow lead going into
the toaster body.
This might be designed to halve the available
current to part of the element through half-wave
rectification, and indeed the middle section
doesn’t glow as intensely as the outermost
sections so perhaps that connects to the middle
section, but I can’t say for sure.
If I’m following my traces right, the actual
electromagnet is connected to this little
transistor on the bottom, which is itself
connected to the output of the main IC we
were looking at earlier.
So, the IC is in control of the electromagnet
and when it decides the toast is done, it
kills the output to the transistor, which
kills the power to the electromagnet, which
kills the power to the everything.
Oh, and this little switch here, activated
by turning the darkness dial all the way to
the left, will interrupt power to the electromagnet
and immediately release the toast.
There’s a bit of a poetic sadness to the
way this circuit works.
When you press the lever down, it comes to
life and says “Oh!
Hello world!
Let’s see, first I’ve got to send power
out on pin 1.
It looks like I’m getting 2.4 volts in on
pin 3 so I’ll just count to 137.”
And then 137 seconds pass and it says “Time’s
up!
Now I’ll just stop sending power out on
pin 1 and…”
Before we were putting self-aware digital
circuits in toasters, mindless analog circuits
would do the same thing but more crudely.
Often the timing was accomplished through
charging a capacitor, and the setting of the
darkness dial, being a potentiometer, would
change the rate at which this capacitor was charged.
Once it’s past a certain voltage level,
the power gets cut to the electromagnet via
a transistor, and pop goes weasel.
And before that, a simple mechanical clock
timer would suffice.
And I haven’t even gotten into this complication;
some toasters use more than just time, or
don’t use time at all!
Sometimes there’s a bimetallic thermostat
near where the bread sits, and adjusting the
darkness adjust the temperature at which the
thermostat would open the contacts.
No timer required.
Newer toasters with digital circuits can use
use a thermocouple to determine if the toaster
is cold and thus if it will need more time
for the first toast, and less time for subsequent ones.
The sky’s the limit when it comes to today’s
totally technical temperature-tied toaster technology.
In fact, if you’re looking for something
to read, check out the description for a patent
on time-based temperature compensation circuits
from 1982!
This design uses a second capacitor that is
charged up fully whenever the toaster is used,
and slowly discharges after the toaster has
finished toasting.
If the toaster is immediately used again,
it won’t have discharged much at all.
The charge on this secondary capacitor effectively
gets transferred into the main timing capacitor
and thus will shorten the overall toasting
time,
helping to compensate for an already-hot toaster.
If it hasn’t been used in a while, the capacitor
will be fully discharged, and thus the toaster
runs for the normal period of time.
You may have spotted the “chip with temperature
compensation” earlier, so even our $8.88
toasters probably have a similar hot-toaster-taming-timer.
If anyone wants to look at this schematic
and reverse engineer how it could do that,
be my guest, but I’ll throw my supposition
into the ring and suggest that the chip probably
can stay awake for a while between toasts
thanks to energy stored in one of these capacitors,
and thus can keep track of how long it’s
been between toasting sessions.
Anywho, I think I’ve had enough toast for
one day.
Actually, I don’t even really like toast.
I haven’t used my toaster in close to a
year.
In fact, I’m pretty sure the last time I
used it was to hold up the multi-colored flashlights
in the “these are not pixels revisited”
video.
Yikes.
And of course, I’d like to raise a toast
to the wonderful people on Patreon who keep
these videos and my terrible puns coming.
With the support of people like you, Technology
Connections is about to see a pretty major upgrade.
I’ll fill you in on the details pretty soon
but for now, if you’d like to support the
channel with a pledge of your own and get
perks like early video access, occasional
behind-the-scenes footage, as well as find
out what that upgrade is I’m talking about,
please check out my Patreon page.
Thanks for your consideration, and I’ll
see you next time!
♫ toasty smooth jazz ♫
And, through the magic of buying two of them,
I have an already taken apart one, right here!
(cord hits the microphone) That went really
badly!
Often the timing was accomplished through
charging a capacitor.
[toaster pops up]
So it definitely is temperature
compensated.
We figured that one out.
Before we were putting self...
[toaster pops
up]
(bleep) it’s that fast!
Ah, but see it’s the way that simplicity
is accomplished that’s so ingenious.
First, have you ever tried to push the lever
down while the heater is unp….
Toaster….
Often timing was accomplished through charging
a capacitor, and the setting of the darkness
dial, being a potentiometer [toast pops up],
would change the rate…
Yeah I shoulda known…
