LEDs are really cool.
They have low voltage, low power.
They last a really long time.
and they are really physically tough.
They're not like incandescent.
That's why we have that filament that you bump
and it breaks and also burns out
you don't have mercury like you do
in the fluorescent light switch
if you break becomes a huge mess
and with halogen, it's so hot that if you touch it,
you'll not only burn yourself,
You break the light bulb.
So, LEDs in almost every way are fantastic.
But they are different.
You have to work with them a little bit differently
and you can still break them if you treat them wrong.
So today, we're gonna look into how to use
LEDs and we're just going to use some of these
standard LEDs to go over to concepts
and then from there, you can extrapolate
into bigger or smaller LEDs.
So, right here, I have a couple of different LEDs.
I actually have white, blue, green and red
and we're going to talk about the difference
in the voltage level of those
and how the forward drop is different for those
and also just how they work in general.
So, LEDs are light emitting diodes.
So in essence, they are diodes that just happen
to produce light at the same time.
So, on all of these they are hooked up
in a very specific way.
If you flip them, they're not going to work
and that's true with any LED
because diodes are one direction only.
LEDs are actually pretty straightforward because
I have an extra one right here,
They give you some clues on how to tell the difference.
You notice, one of these is longer than the others
and then if you actually look inside
which you can't look inside all of them
but if you can look inside,
one of the sides is significantly bigger than the other.
So, the short lead goes with the big side
which means it's the negative terminal.
So, in this particular one,
current will flow from this side, the longer lead,
through out to the shorter lead.
If you put it the other direction,
it's not going to work.
Since LEDs are diodes,
the voltage and current relationship is not linear.
It's not like a resistor
where as you increase the voltage,
the current goes up linearly.
What happens with the diode and LEDs
is that you increase the voltage,
you increase the voltage and no current flows
And then you hit a certain point
where you get to that forward voltage
that the LED starts to conduct
and then a tiny increase in the voltage
drastically increases the current
until basically you overcurrent the LED
and it explodes which I'm hoping to do
in a couple of minutes.
So, as I mentioned earlier
these LEDs with their different colors
have different forward voltages because
they're based on different semiconductor materials.
So I'm actually going to use this voltage supply
and increase the voltage slowly
so you can see as they turn on
and then see also as the current goes up
and as I do it, I'll probably have to take
some out so they don't blow
because the green and the red
with their lower forward voltages
will actually probably explode
before the white and the blue
even start to show any light
because they have significantly higher forward voltages.
So let's do that now.
So here, we have the LEDs hooked up
and they're being directly driven
I don't have any resistors in there,
which is not normally something you want to do
But we're just doing this for demonstration's sake.
So I'm not expecting anything until we get over 1.5 volts.
Before we will see even a flicker.
So as we jump up to one,
there is still nothing whatsoever.
Now, I'm at 1.3
I think I just saw it turn on.
Yep. If you look, you can see it flicker
at 1.7, 1.8 volts on the red.
Still nothing on the green that I can see.
Oh, actually there is.
It's just very dim.
As we get up to now a 1.9
I can see the green better
but still nothing from the white and the blue.
We're currently at also
Fluctuating between 8 and 15 milliamps.
It's obviously brighter.
There's no question that these two are on.
Still absolutely nothing from there.
Now, these are rated to only be able to conduct
about 20 milliamps before you start
to cause any damage.
That doesn't mean they're gonna explode
if they're at 25 milliamps
but anything over 20 milliamps will shorten the life
and technically could explode but that's not likely.
They can usually take quite a bit more
before you have any catastrophic immediate damage.
So let's keep going up just a little bit more
So now we are at almost 40 milliamps.
So these are probably both about at their limit
of how bright they are and the voltage you can put
across them without any damage.
And notice we're only at 2.25 volts.
And again, these haven't even started.
So I'm gonna unplug these
so we don't damage them right now
and we're gonna see what we have to do
to get the blue and the white up solo.
2.2, 2.3.
Okay, I just saw the blue flicker on
At about 2.3, 2.4 ish and the white also.
So, white and blue have very similar forward voltages
and to get them to about the same forward current,
you're actually closer to 3 volts.
There we go.
We got 3 volts and now we're doing
Oh 20 actually
We can go higher 3.2 volts
and now there's about 20 milliamps going through
both of them and is also pretty bright.
So that just shows you different chemistries
inside different semiconductor material
causes them to conduct at different levels.
If we still had these other two plugged in at this voltage,
there would be some serious damage.
And again, we're gonna do a demonstration
I've only seen an LED blow up once
I want to do it again because it was interesting.
One other thing while I have this is
LEDs compared to the other lights,
are much more directional.
So from my angle looking down on it,
the white LED is enough to kind of give me some stars
But it's not nearly as bad as if I bring my face
right in front of it which is just blindingly bright.
Now, LEDs have that focus like this
Unlike incandescent switch are more like that
but you can get LEDs that have
a little bit wider viewing angle.
So it depends on what you're trying to do,
depends on what you want.
We have a Christmas tree that we use
and we put up LED lights and the problem with that is
my wife puts up so many LEDs that it doesn't matter
where you are, there's at least one
pointing directly at your eyeball at all time.
So that is definitely a drawback
in certain circumstances.
But other times, you don't want to waste light
putting it in all directions
and you do want it directly where it is.
So, it depends on what you want, but just know
that in general, LEDs are much more focused
and in their viewing angle.
So, look into that see what you want to do.
Okay with that. I'm going to turn this off
and I'd actually now like to set it up so that we are going
to drive just one red LED and see what happens.
So, I'm gonna put that together really quick.
Okay, so I just set this up.
I actually put this back here
for better contrast so you can see it better
but we have the LED that's going to be driven directly
by this power supply and I've also been using
the multimeter to get a more precise
reading on the voltage.
But I think we're ready to go to see what happens
as we turn it up.
Hopefully it's interesting, visually
and hopefully it doesn't hurt me.
With that in mind,
I actually do want to grab some safety goggles
because I like my eyeballs
and even though they're not incredibly fashionable,
It's better safe than sorry.
So let's start cranking this thing up.
and we know that it starts conducting at 1.7 volts
All right. We're at 1.7 and there we go.
Now I'm starting to see some current flow.
We're getting close. There we are.
We are now over the maximum recommended value.
And again, just even at this,
this will decrease the lifetime
Even though, there's nothing catastrophic
going on right here.
But let's see what it takes to get up
to catastrophic levels.
Let's crank this thing up.
We're now at 3 volts and we are almost four times
the current that is supposed to be through there.
I think I want to lean back just a little bit.
I am surprised at how long this is lasting.
So, we are now at a hundred and ten milliamps.
This is being driven about six times more current
than it is rated for and we are almost to four volts.
It doesn't even look like it's getting any brighter.
This is really interesting.
I'm wondering if this is ever going to explode
or if it's just going to fail and not do anything.
Too interesting.
So we're at 160 milliamps.
This must just be a really tough LED
because the other one did not take nearly as much
voltage to explode 150 milliamps.
Now I'm just highly impressed.
Oh, but now it's just dead.
So if anything happens, if it explodes,
it's because it's too hot because right now
we're getting 150 milliamps through there.
So it is probably burning things even though
there's absolutely no light being produced anymore.
So, I'm smelling something.
Something is definitely cooking.
I do not want to start a fire in here.
Explosions, I can handle.
Fires, not so much.
Wow, I don't wanna get my face too close to that.
But I'm thinking that it's just melting on there.
Oh, I have a thermometer.
Gary lent me a thermometer.
Let's see how hot this thing is.
Turn that on, see how precise this is.
81
100 degrees
107 degrees
95
104 degrees
So, yeah that got pretty hot it did not explode
like I was expecting but it got really hot
which is kind of a bummer
I kind of wanted it cook, wanted it to explode
but as you can see it, it did fail.
So I mean it doesn't work anymore.
Had all these.
What the heck it's working again.
I don't even know what to say.
I have no idea what to say.
LEDs are super tough. This is fantastic.
And my whole experiment did not go as planned,
but I think I'm ok with that.
Even though an explosion would have been nice.
Okay, so I'm just gonna turn this off.
I'm not gonna push my luck.
And I'm hoping that it doesn't like explode
from the heat behind me and get me
in the back of the head somehow.
And again really an explosion,
is it just cracking and sometimes it pops
pretty far away and frankly again,
I've only seen one explode once
and it did go a couple of feet.
But it's not gonna actually hurt you
unless it hits you in the eyeball.
So, that is the LED.
I think I've rambled on far enough.
You've seen how tough it is.
You've seen the different forward voltages.
You've seen, well, I guess you couldn't smell it
Like I couldn't I'm gonna take no
I'm gonna leave these glasses on.
because I still don't know if that's gonna pop.
Yeah, it took a lot of current and it started to melt
started to smell bad, but it was great.
So I hope that gave you an idea of what it is like
to deal with an LED and hope you found this interesting.
I'm sorry. I wanted to give you guys an explosion
something to see, something exciting
but this LED is just too darn tough.
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As it is. Have a great day.