To figure out duty, look at the last frame. Measure the last tip of the led to the second led. I got 12mm, second measure the led (rice). I got 5mm, now devide. Roughly 40% duty. LEDs start showing light around 3.2v. Your spinning that strip of LEDs at around 2 rps. I counted 28 frames in 2 revs. Each frame consistently shows 5 led dots so it shows they are in sync.
I really like this, complete to the point, and subtle with some open ended questions. You remind me of a physics teacher I had in high school. Keep up the good work.
And about frequency - if you see a slow-mo you will notice that at each frame there are two traces for each light - one is dim and the second is bright. From this I can assume that for one frame of filming the LED blinks two times. Knowing that the frequency for most cameras is 24 or 30 fps, i would say that these lights operate at frequency either 48, or 60 hertz. Of course, its just my supposition. And by the way - how do you figure out the voltage?
this is my second semester in electrical engineering, i'm dying to finish my prologue to electrical engineering course, so i can fully understand what you are talking about. be prepared to be showered with questions..
9:21 DUDE WTF I THOUGHT I WAS THE ONLY ONE! I still see tail light leds from a 'couple frames ago' too when I move my eyes quick. Thanks for clearing this up bro. subscribed!
You remind me of my self. I love real and raw unscripted content. Means you ACTUALLY know what you are talking about and not pretending. GJ! I am going to investigate your channel to see if you deserve my love or not.
IR LEDS CAN be seen with the aid of a video camera/smart phone camera. If you notice at 5min8sec into the video, when he pushed the button with the IR facing toward the camera you see a faint pulse of ir light. You can also take your tv remote and record the led as you press Any button and will see the same pulse from your smartphones LED screen. Thanks for the video!
Kalvin Morrison Yeah. Watched this thing before on some life hack channel, I guess, but I forgot it, thinking it might be a scam. It's interesting that IR is translated into a bluish white.
Sorry for being late to the LED party but to answer your little test, duty cycle is around 40% judging by the spacings (less than 50% anyways) and the break down voltage is at most 2.2 - 2.4V depending on whether your line voltage is 110V or 120V (that of course is if you simplify this to the DC equivalent) but this is 60Hz AC so if you were to measure across one of the LEDs with an Oscilliscope you would see a half rectified waveform but you would only see the top part of the half sine wave. The peak voltage would actually be (sqrt(2)*120V)/50 = 3.39V. Now if we say the duty is 40% the turn on would be at 5% time of the cycle (because half wave) so turn on voltage is actually sin(0.05*pi)*3.339V = 0.53V. If the duty is less the turn on voltage is higher.
True since I actually know that the forward voltage of white leds is like 2.2 - 2.8V (1.5 - 1.8 for red leds) so if we say the the turn on volts is 1V then the duty is probably closer to 30% --> sin^-1(1/3.39)/pi = 9.25% (turn on time) --> 50 - 2*9.25 = 31.5%!!
Hey buddy! Since Doc hasn't posted that yet, I'd suggest u watch the vid from Khan Academy-India. Sir Mahesh Shenoy has explained it really really well, with an enthusiasm similar to that of Doc!😄
What happens to the hole and the electron after they meet? And are there new holes or are the same ones reused? If new holes are made where do they come from?
Annihilation. And yes, new holes are created all the time as electrons leave the left side and get sucked into the battery by its applied electric field. It's the exact opposite of the right side, where new electrons are being dropped off at the same rate.
"... But somethings interesting. If I move it back and forth - oh no that's not interesting - maybe that's a little interesting." Oh my word he's so funny.
Woh..actually I'm french (yeah we don't care but ) , and all the french explanations of How does a LED work were some kind of hard to understand, and I found out your video and I understand all of it ! I want you so much to be my electronics teacher xD thank you
Doc I love your teachings. You really make an effort to keep everything moving fast and visually interesting forr the modern student. Keep making videos man! Id love to see some electrician level 2 math, trigonometry and vectors videos!
I think you can calculate the cycle duty by measuring the percent of dark length and bright length. Also the video might be 30 fps or so and there are around four bright periods which means the frequency is 30 * 2 = 60 Hz.
You're in the states because mains electricity is 120V and has a line frequency of 60hz, the video you have is 30fps, so the two are in sync and you don't get that rolling shutter effect that you would normally see if you were recording this in England.
@ 3:00 Look at it. What does the green thing look like? If you said a two dimensional toradol field...... and/or.....a two dimensional plasmoid burst....
As of 2015, consumer available LEDs have reached >41% efficiency (radiation in the visible spectrum), a vast improvement from 15% as stated here in the video.
Anybody noticed that when you move your head the blue LEDs of a billboard move while the other colors don't? This has been confusing me for a long time. I wear glasses. Does it matter?
Although it is infrared LED you can see it if you turn on the camera of your cell phone and press any of the buttons of the remote while looking at the screen of your cell phone. Unless the LED is bad you should be able to see it turn on. Now you know!
Which of the following statement is true? A) A PN junction in diode emit light in visible region B) A PN junction in diode emit light in infrared region C) A PN junction in diode emit light in microwave region Please tell the which one is true
Nice video but in the first minute you make an incorrect statement. Electrons jump over the barrier because are thermally excited (as estimated by Fermi-Dirac distribution) - not because of an electric field.
Well, they wouldn't be inclined to recombine at all without the electric field (you'd just have a happy depletion region), so I don't think my statement is incorrect. I've noticed that my LED's don't light up unless I hook up a voltage source.My statement might be incomplete, though. Are you suggesting that the efficacy of LED's goes down as temperature decreases?
Hi nice one. Probably the band diagram is a bit oversimplified but I guess it does the job for the large audience. We've published a video on a the bandstructure design principles of LEDs. Have a look!
I still don't understand how they work. We just got bulbs all over our house replaced by leds today. Very bright light. The bulbs are made of pastic, and give off no heat. Very interesting.
+Kevin Olesik Most digital cameras or phone cameras can see IR light from IR remotes/IR LEDs. When I am working with IR LEDs in my lab I have my Pentax digital camera handy to view the IR LEDs to see if they are on. Or I use an IR phototransistor sensor in a circuit I made just for testing IR LEDs. It just senses when an IR LED is lit and then drives a visible LED to indicate that it sees IR light from the IR LED.
Best educational physics video ever.
I'm totally baffled by your awesomeness.
Wow you are a fantastic teacher!
To figure out duty, look at the last frame. Measure the last tip of the led to the second led. I got 12mm, second measure the led (rice). I got 5mm, now devide. Roughly 40% duty. LEDs start showing light around 3.2v. Your spinning that strip of LEDs at around 2 rps. I counted 28 frames in 2 revs. Each frame consistently shows 5 led dots so it shows they are in sync.
You explain things extremely well. Great vid.
Thanks, yo.
I really like this, complete to the point, and subtle with some open ended questions. You remind me of a physics teacher I had in high school. Keep up the good work.
And about frequency - if you see a slow-mo you will notice that at each frame there are two traces for each light - one is dim and the second is bright. From this I can assume that for one frame of filming the LED blinks two times. Knowing that the frequency for most cameras is 24 or 30 fps, i would say that these lights operate at frequency either 48, or 60 hertz.
Of course, its just my supposition.
And by the way - how do you figure out the voltage?
Would you mind posting a video on transistors? I'm facing a bit of a problem with them.
"You can get Nacho cheese, OR you can get ... COOL RANCH. So depending on what colour flavour you like, you can win."
Please make more educational videos. Your "erratic" enthusiasm and speed of explanation is infectiously great to watch.
Dude, you need more shares and likes, what an amazing video!
6:50
Are those fringes moving across your table?
Did you just break your stereo remote?
You don't how good kick-ass physics teacher you are. I just love you I can pay over 500$ to study from you. May God bless you
this is my second semester in electrical engineering, i'm dying to finish my prologue to electrical engineering course, so i can fully understand what you are talking about. be prepared to be showered with questions..
i love your enthusiasim, i adore you way of understanding things and i love your videos, you are officially my new role model
9:21 DUDE WTF I THOUGHT I WAS THE ONLY ONE! I still see tail light leds from a 'couple frames ago' too when I move my eyes quick.
Thanks for clearing this up bro.
subscribed!
You remind me of my self.
I love real and raw unscripted content. Means you ACTUALLY know what you are talking about and not pretending.
GJ!
I am going to investigate your channel to see if you deserve my love or not.
IR LEDS CAN be seen with the aid of a video camera/smart phone camera. If you notice at 5min8sec into the video, when he pushed the button with the IR facing toward the camera you see a faint pulse of ir light. You can also take your tv remote and record the led as you press Any button and will see the same pulse from your smartphones LED screen. Thanks for the video!
Kyler Edward You rock! Thanks!
Excuse me, what's "band" you have mentioned in video?
5:06
Your camera can detect Infra Red!
+Mohammed Zaid Every modern camera can. Point your remote at your phone camera.
Kalvin Morrison
Yeah. Watched this thing before on some life hack channel, I guess, but I forgot it, thinking it might be a scam. It's interesting that IR is translated into a bluish white.
Sorry for being late to the LED party but to answer your little test, duty cycle is around 40% judging by the spacings (less than 50% anyways) and the break down voltage is at most 2.2 - 2.4V depending on whether your line voltage is 110V or 120V (that of course is if you simplify this to the DC equivalent) but this is 60Hz AC so if you were to measure across one of the LEDs with an Oscilliscope you would see a half rectified waveform but you would only see the top part of the half sine wave. The peak voltage would actually be (sqrt(2)*120V)/50 = 3.39V. Now if we say the duty is 40% the turn on would be at 5% time of the cycle (because half wave) so turn on voltage is actually sin(0.05*pi)*3.339V = 0.53V. If the duty is less the turn on voltage is higher.
I think the duty must be less, since white LED's require quite a bit more than a volt. Or maybe the number in series is not what you supposed?
True since I actually know that the forward voltage of white leds is like 2.2 - 2.8V (1.5 - 1.8 for red leds) so if we say the the turn on volts is 1V then the duty is probably closer to 30% --> sin^-1(1/3.39)/pi = 9.25% (turn on time) --> 50 - 2*9.25 = 31.5%!!
You should've pointed the first remote control @ the camera to show that you can see if an IR led works by using a video camera or camera phone.
Please do some videos on transistors!
thanks, doc. Can you please make lectures on transistors and logic gates?
so ur remote control is a multiplexer right?
Oh cool, remotes have infrar-- is he? yeah he just ripped open the remote.
Best teacher ever. 10/10 cups of coffee.
Crazy but a great explanation
Hey! Could u please please please make a video on transistors? Lots of love from india! Thanks
go to veritasium he explains them very better than this
Hey buddy! Since Doc hasn't posted that yet, I'd suggest u watch the vid from Khan Academy-India. Sir Mahesh Shenoy has explained it really really well, with an enthusiasm similar to that of Doc!😄
What happens to the hole and the electron after they meet? And are there new holes or are the same ones reused? If new holes are made where do they come from?
Annihilation. And yes, new holes are created all the time as electrons leave the left side and get sucked into the battery by its applied electric field. It's the exact opposite of the right side, where new electrons are being dropped off at the same rate.
Thank you Doc, you are an amazing teacher.
"... But somethings interesting. If I move it back and forth - oh no that's not interesting - maybe that's a little interesting." Oh my word he's so funny.
Woh..actually I'm french (yeah we don't care but ) , and all the french explanations of How does a LED work were some kind of hard to understand, and I found out your video and I understand all of it ! I want you so much to be my electronics teacher xD thank you
why do we see waves on the sheet of paper when led bulb is on? i know it only catches the camera but anyway, what and why is it?
This lad is a legend
You should consider putting a Not Safe For Work disclaimer on your video. Thanks.
Doc I love your teachings. You really make an effort to keep everything moving fast and visually interesting forr the modern student.
Keep making videos man! Id love to see some electrician level 2 math, trigonometry and vectors videos!
Thanks! Interesting ideas...trig might be fun and very useful for my local students. What would you want me to do with vectors?
Vector relations between motor and generator parameters.
And AC trigonometry in electrical calculations
Thanks!
i like your physics dude!
so it is a battery linked to a magnet instead of a filament(wire)?
TheRoidemortetfleur Not much magnetic going on. Did you watch the series of videos?
I think you can calculate the cycle duty by measuring the percent of dark length and bright length. Also the video might be 30 fps or so and there are around four bright periods which means the frequency is 30 * 2 = 60 Hz.
You're in the states because mains electricity is 120V and has a line frequency of 60hz, the video you have is 30fps, so the two are in sync and you don't get that rolling shutter effect that you would normally see if you were recording this in England.
What is a Zener diode ??
Go look it up, man!
you skipped some words in the Lumberjack song !
BTW, WONDERFUL demonstration on PWM and duty cycle !
+boB Gudgel Oh no! Sorry.
they are in parallel sequence, arent they?
@ 3:00
Look at it. What does the green thing look like? If you said a two dimensional toradol field...... and/or.....a two dimensional plasmoid burst....
O man, I just love your lecture ................
Doc Schuster can you make a video on rectifiers please ? AC to DC i guess.
weirdest video but actually made me understand finally lol. Thanks!
I'm a bit confused, what exactly are "holes"?
Ethan Novacane Where an electron ought to be.
Bro.......teach about transistors also.....it would help my studies
Nice video I learned from this one keep it up!
Just curious, hope someone can share some information, it is material of panel solar solar and LED is same from p-type and n-type
The positive holes are the most confusing part. Is it literal ? A bubble ? A hole with positive materials around it ? What is it ?
As of 2015, consumer available LEDs have reached >41% efficiency (radiation in the visible spectrum), a vast improvement from 15% as stated here in the video.
+Garden Tower Project DANG! 41% is extremely good. Where do you get this figure?
i finally know how you look like
thank you so much for your help
You remind me of the 11th doctor:)
they dont recombine they combine, they dont reunite they unite!
***** That's a great point! It's statistically impossible that they've even ever met before. Thanks!
yer thought you’d like that :)
cool teacher :)
why does LED glow even current passed in any direction where as a diode allow current only in one direction
But it doesn't!
oh ok
Anybody noticed that when you move your head the blue LEDs of a billboard move while the other colors don't? This has been confusing me for a long time. I wear glasses. Does it matter?
Those LED's,i guess would be in a parallel combination
Although it is infrared LED you can see it if you turn on the camera of your cell phone and press any of the buttons of the remote while looking at the screen of your cell phone. Unless the LED is bad you should be able to see it turn on. Now you know!
U r so unique!
Are you in fb or other social networking site???
You are the next Bill Nye!
....Anyway, who need remote controls nowaday… At least this sacrifice allows us to see better what is behind the scene of LEDs… Thank you
Which of the following statement is true?
A) A PN junction in diode emit light in visible region
B) A PN junction in diode emit light in infrared region
C) A PN junction in diode emit light in microwave region
Please tell the which one is true
Zaheer Iqbal visible
Nice video but in the first minute you make an incorrect statement. Electrons jump over the barrier because are thermally excited (as estimated by Fermi-Dirac distribution) - not because of an electric field.
And how do we suppose they are thermally excited?
Well, they wouldn't be inclined to recombine at all without the electric field (you'd just have a happy depletion region), so I don't think my statement is incorrect. I've noticed that my LED's don't light up unless I hook up a voltage source.My statement might be incomplete, though. Are you suggesting that the efficacy of LED's goes down as temperature decreases?
Hi nice one. Probably the band diagram is a bit oversimplified but I guess it does the job for the large audience. We've published a video on a the bandstructure design principles of LEDs. Have a look!
you are the best
Thanks!
I still don't understand how they work. We just got bulbs all over our house replaced by leds today. Very bright light. The bulbs are made of pastic, and give off no heat. Very interesting.
awesome !!
a simple IR Night Vision security camera also sees the IR emitted from a remote control ...
+Kevin Olesik Most digital cameras or phone cameras can see IR light from IR remotes/IR LEDs. When I am working with IR LEDs in my lab I have my Pentax digital camera handy to view the IR LEDs to see if they are on. Or I use an IR phototransistor sensor in a circuit I made just for testing IR LEDs. It just senses when an IR LED is lit and then drives a visible LED to indicate that it sees IR light from the IR LED.
Time marches on.41% is great.
Woohoo face reveal
You're the classiest lumberjack ever
good but the gun stuff is a little weird
Nice
lol you can actually see the light wave in the video
I'm just as confused about LEDs as i was before watching this video :/
About LED taillights (on and off mode) here is a good example, taillights of a 2015 mustang th-cam.com/video/uN6VsV8cCgY/w-d-xo.html#t=428
Are u like doing an ad or smthing
those are in parallel !
Less coffee please......
Holy mother of Newton! He's singing Monty Python to his class (I suppose), I'd love to be at one of his classes!
thumbs up !!
Obnoxious, I'll seek answers else where.. Thanks for Nothin!
0.24 volt lights, duty cycle is 75%
Kevin Olesik Check that duty cycle again. I'm sure they're on less than half the time.
Instructor or comedian? Chose! Great for ages 17-23 with corresponding mentality!
you are a lot to handle
Hahah awesome!
wired in parallel
CÓMO ?!!
Up the Ritalin dosage, Chief.
Cool ranch. lol...
YOU have luke skywalkers voice
I mean connection
*when ADHD teaches*
you're so lovely 🙈
Ten dollars for one lighbulb? Are you kidding me cheap? What planet are you from?
dude wtf r u on about? right from the start?