Your LED Questions Answered! (Part 2)
Ask an Electrical Engineer is a series where frequently asked questions from non-engineers will be answered by an engineer. For this video, our main topic is all about LEDs (Light Emitting Diodes).
Hey guys, welcome to Ask an Electrical Engineer part two. What happened was, we got so many questions that the video was getting crazy long so we've split it up into three parts. And so we're going to jump back into more questions that non engineers have for us electrical engineers about LEDs.
00:18 Are LEDs better than HIDs?
I believe this question must be directly related to cars if I'm not mistaken. So LEDs are better than HIDs (high intensity discharge) if I'm not completely off my rocker. Old school headlamps were halogen and then they switch to HID, which is a gas discharge type. Now the newest, most expensive (and inexpensive) cars have LEDs. The reality is yeah, they're better. They are more directional, which can be a good or bad thing. Some people don't like the way LEDs look. And so that's a more subjective thing, but they last longer, they're going to be more robust, especially in a car that's getting jolted around. There's no gas and no filament to be bounced around or to be broken. And so, yeah, other than the subjective, "do I like the way it looks" and "is it blinding me in a way that I don't enjoy", LEDs are quantifiably better than HID car lamps.
01:29 Are LEDs good for growing "plants"?
So LEDs are good because you can get them to emit exactly the spectrum you need for a plant to grow. Now if you're going to just grab some random LED off the shelf that you use for lighting your house, it's probably not going to work...it depends on which led but there are some out there specifically for growing plants and those make sure they hit the the lines of the spectrum that plants need. So they do definitely have LEDs that are great for growing plants. Use them responsibly.
02:18 Are LEDs directional?
Yes, actually, that could be considered a strength and weakness. LEDs are very directional. My wife loves Christmas lights and so our Christmas tree has literally thousands of lights on it. And I hate the fact that I cannot walk by the Christmas tree without at least one if not three or four LEDs blinding me and shining directly into my eyeballs because they're pretty inexpensive lights and so they're pretty directional – and that's not ideal. However, other times like when I replaced my fluorescent tubes in my kitchen by having a string of LEDs instead of a fluorescent tube, I was getting light that's flying right up into the ceiling and reflecting a little bit, but that's not as efficient as having LEDs that are pointing directly downward. One solution is to use a diffuser and stuff like that to make it so you don't have to stare at individual LEDs.
03:17 Are LEDs environmentally friendly?
Yeah, for the most part, they're environmentally friendly. Now, I think this is a matter of comparison. So compared to the mercury in some gas discharge or in fluorescent light, yeah, they're super environmentally friendly, because mercury is really fun to play with and extremely bad for you and the environment. So in that way, yeah, they're great. They're environmentally friendly, because they also use way less energy, they're just much more efficient.
Now, I do want to say that there are certain drawbacks, and I don't want to go too crazy into this, but anytime something's made, it takes energy. So if you you take a huge box of fluorescents and say, "hey, these are 5% less efficient than my LEDs", and you chuck them in the trash and then you buy a bunch of LEDs, you just threw a bunch of things away that it spent energy to create. And now these new things also needed energy to create them. Even though the LEDs are pretty good, they are electronic and like everything we produce, nowadays, it does have a negative environmental impact. But I don't think that should be a reason to not buy them. But sometimes it makes sense to think, "hey, I've got something that's doing 95% of what I need it to, let me just wait until its end-of-life". And if you wait a bit longer, LEDs are probably going to be more efficient, require less energy to create and costs less and so you'll be doing everybody a favor. So yes, LEDs are great. Just be reasonable about any upgrades you do. But if you're doing new construction or just need a new bulb, yeah, I'm all for LEDs. Man, I feel like I was just on my high horse...
05:07 Can LEDs be made from Silicon and Germanium?
What the heck? Uh...sure?
05:16 Why do LEDs blink or flicker?
LEDs do not blink or flicker, it's the electronics behind them that are driving them that have issues that causes them to blink or flicker. It would be like asking "why do cars crash" and thinking "well, it's because people driving them are human beings like me, so they're idiots and they crash into things, so that's why cars typically crash"...except that's not exactly true because sometimes your CB joint comes off and your tire falls off and you go into a ditch and you should have been maintaining your vehicle.
So LEDs blink or flicker because the power that's coming in needs to be modulated needs to be changed in such a way that the LED can use it properly. And that's usually where the issues lie – you get some cheap electronics in there or part that's going bad or some other issues and then it's not giving the LED a constant clean voltage, and that's causing it to flicker.
06:17 How do LEDs produce white light?
So that can be done in a couple of different ways. The first one, the original one was, you just had red LEDs, green LEDs, blue LEDs, and you stick them close enough together and you put kind of a phosphor coating on the the bulb itself and voila, you have white light. They've actually been doing some other stuff that I'm not as familiar with, but they're actually figuring out a way so that the semiconductor material itself shoots out photons of varying wavelengths to create white light in one LED, and honestly, I don't know that much about it. I know much more about how you use an RGB to make white but that isn't as good of a color because you even though you have a white light to our eyes, you stick it through a prism and it comes out a very clear red, green and blue (instead of a more blended spectrum) and so it's not super great. It doesn't get the full spectrum. It just hits those three parts of the spectrum really, really well. That's how LEDs produce white light. The newer ones again, I'm not so sure.
07:22 How can LEDs be used most effectively in a bear attack?
[silence] I have no idea.
07:42 Are LEDs waterproof?
It's a good question. LEDs are pretty low voltage so they don't typically...you don't have much problem with current going through the water unless it has a huge amount of minerals in the water. So if it doesn't have an enormous amount of minerals in the water, it's not going to be enough resistance to really cause problems, more of what you're going to have issues with, is again, the electronics that are supporting the LED that are going to have issues with the water. So this LED, I could hook it up to a battery and throw it in a swimming pool. And I'd be super surprised if that did not work. But if I were to take this oscilloscope and the LEDs that are probably scattered around it for illumination, or whatever, and threw that in the swimming pool, yeah, that wouldn't work anymore. So the LEDs themselves should be fine. It's usually everything that's around it that is going to cause problems when you introduce water.
What is the difference between COB, CSP and CREE lights?
CREE is a very popular brand of LEDs, kind of like GE or Lumiled are brand names. COB stands for "Chip on Board" which indicates that the LEDs are integrated together more tightly and, as I understand it, earlier in the manufacturing process. Sharing a semiconductor substrate rather than sharing a PCB. CSP stands for "Chip Scale Packages" and is a way of packaging discrete LEDs into something smaller so that you can fit more of them onto a PCB. It basically is getting rid of all of the "unnecessary" plastic and metal that surrounds the LED itself to make the unit as small as possible.
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