Why all solar panels are secretly LEDs (and all LEDs are secretly solar panels)

Part 2 - explainer video is here: • How diodes, LEDs and s...
LEDs and solar panels are both made of diodes. A diode is just designed to allow electricity to flow in one direction but because we make them out of semiconductors they can do all these other things.
Video produced in cooperation with Merck ( / merckgroup . Merck is known as Merck KGaA, Darmstadt, Germany in the United States.
Here's the link to the curiosity report (interactive): www.merckgroup...
And here it is as a PDF:
bit.ly/StateofC...
Animations by Dom Burgess. His brilliant channel, Every Think, is here:
/ @domburgess
Thanks to these amazing patrons on Patreon for supporting my channel:
Glenn Watson
Joël van der Loo
Patreon: / stevemould
Twitter: / moulds
Instagram: / stevemouldscience
Facebook: / stevemouldscience
Buy nerdy maths things: mathsgear.co.uk

[@error1022]

1. electric motor generator 2. mic speaker piezo 3. solar panel diode led

[@keelo-byte]

galvanic cell Electrolytic cell Beer Hangover Hair of the dog...

[@jimmyjohn8008]

Now I'll waiting for the next generation of phones to have a solar panel screen charging button

[@rwatson2609]

roomy's toothbrush toilet cleaner cattle corn car fuel condoms rifle protectors crazy glue wound sealer microwave oven hair drier Lol, maybe not the last one but I liked this video.

[@FrankHarwald]

ceramic microphone ceramic capacitor buzzing ceramic caps

[@patrikgubeljak9416]

Diodes are not necessarily LEDs. Depends on the band structure, e.g. silicon makes solar cels and diodes but will never electrically emit light.

[@moth.monster]

Resistors can also emit light but only once

[@SeanBZA]

They also emit smoke for quite a long time before starting to become light emitters.

[@clementdel2776]

@@SeanBZA pretty unique design!

[@rivencraft1734]

@@SeanBZA All computers run on smoke, thats why when the smoke comes out they stop working.

[@PenPeng]

@@SeanBZA Every machine is a smoke machine if you operate it wrong enough

[@hebl47]

Resistors actually emit light all the time, the problem is we can't see it because it's around 6000nm in wavelenght. But you're right - visible light is usually a one time event.

[@ZeldagigafanMatthew]

So, should we call solar panels Light Absorbing Diodes (or LADs) instead? I think so.

[@AbdullahBilik]

or LSD : Light swallowing diodes. Sounds better to me.

[@DASyam-tb7qt]

Smart LAD

[@sandylengerich2304]

Funny Tad

[@dyingofcringe8839]

lad lol

[@billkillernic]

Nope because a) all diodes are light absorbing (so there is no reason to distinguish that property of them by a different name for the particular ones used in a solar panel) b) the diodes are only a component of the *panel* hence we name the entire *panel* according to what it does so a *solar* **panel**

[@jpopelish]

I had a long career as a circuit designer, and several times, with high gain circuits, with diodes, I had to take the light sensitivity of the diodes into account.

[@mrwess1927]

Neat!

[@mrwess1927]

Care to share what you know?

[@jpopelish]

@@mrwess1927 Any opamp circuits with high gain can be affected by diodes connected to the inputs. I think an audio preamp with a pair of clamp diodes (glass encased 1N4148) across the inputs, for static protection picked up a hum from room lighting. and a high gain DC amplifier (for a seismograph) connected up as an absolute value circuit, had offset problems, if operated in the light. In both cases, either switching to a black epoxy cased diode, or using a black plastic transistor as the diode, cured the interference.

[@Cooliemasteroz]

That’s interesting, a lot can be learned from experience.

[@gorilladisco9108]

Aren't they usually encased in non-transparent mold?

[@positronundervolt4799]

'You can use a speaker as a microphone.' Hello, CIA.

[@heroslippy6666]

Hello CIA my old friend...

[@Yorgarazgreece]

*NSA joined the chat*

[@TheFoodnipple]

LEDs can also act like a pixel from a camera 😉

[@vincentrobinette1507]

If you take a microphone apart, and a pair of head phones, you will find the diaphragms look very similar.

[@RennieAsh]

Vincent Robinette depends on the mic. Dynamic microphones are closest to speakers

[@JohnnyX50]

I first had that eureka moment when I was sat playing with an LED and was reminded of the 'equal and opposite reaction' law. I thought if LEDs emitted light when a voltage was passed through them, would they create a voltage if light was shone at them. To my amazement this was true as I also connected a volt meter across an LED and shone a bright light at it. It was a few years ago when I did this, and now I have discovered this video and it has made me smile! Thank you! True scientific discovery and learning :)

[@Kokurorokuko]

That feeling must be amazing

[@stargazer7644]

So if I push my car the tank will fill with gasoline?

[@zneebaby]

@@stargazer7644 🤣🤣🤣 I wish 😛😂😂

[@Fine_i_set_the_handle]

yea now hook a load up to an oven burner and see if it powers your device by pulling heat out of the air

[@markthornemarmaduke]

@@stargazer7644 and if someone pushes you..

[@SteveFrenchWoodNStuff]

I spent over 35 years of my life in electronics; how did I not know this until now? Thanks for another eye-opening, insightful video!

[@DakCuh]

The energy companies would lose money probably

[@berekexer8158]

Maybe you worked in the warehouse?

[@tekamanurag6065]

@@DakCuh No this way is not efficient i think, all diodes contains this property but I think there is a reason we don't really use them like this.

[@kristopherlee81]

I have forgotten so much of my electronic knowledge from the late 80's ...seeing this video makes me want to learn everything again.. Ty

[@desertodavid]

I also learned Electronics in the late 70s and 80s. I'm not sure what type of diode they use in solar panels. But I always thought they were made up primarily from what we knew as LCDs light-collecting diodes versus LEDs light emitting diodes.

[@sethsims7414]

I saw a video by a professor who researches solar cells. He talked about how LEDs get some amount of their energy from the heat of the crystal lattice. He said if you could get the efficiency of the LED high enough (80ish percent of electrical power into light) they would actually act as refrigerators rejecting heat as entropy in the light emitted. He talked about putting such a super LED across the vacuum of a Dewar flask from a high efficiency PV cell to make a heat pump from the inner wall to the outer wall. All this is pretty well known by people who study PV cells and LEDs, but I had no idea and find it super interesting.

[@MushVPeets]

I imagine a massive bank of these super LED's would make for a nice cooling system for a spaceship.

[@BrokenLifeCycle]

Wait. Are you saying that LEDs at a high enough efficiency can actively absorb heat in molecules and emit it away as visible light? So is it theoretically possible to pump heat away out of a spacecraft in vacuum just by shining a spotlight with this super LED in a direction?

[@sethsims7414]

@@BrokenLifeCycle yep. It has been demonstrated in laboratory settings but isn't practical at the moment. It's infrared light not visible light though. www.wired.co.uk/article/230-percent-efficient-leds

[@healthytamilnadu8816]

Man, thanks for sharing thats so cool to know...

[@sethsims7414]

@@sunmoon1234 Peltier modules are certainly semiconductors that act as heat pumps. But they don't turn the heat into light, they work on a different principle.

[@lucasbhogal3790]

we just learned that in school, but with this video I understand it

[@Hallowed_Ground]

@@jatre5938 You're stupid.

[@fantaisiechopin8240]

@@Hallowed_Ground Dud just gave the man an advice..tf is ur problem?

[@nalyddoow9295]

@@fantaisiechopin8240 You're stupid.

[@Derpuwolf]

nalyd doow you got him there

[@Derpuwolf]

Mantresh perhaps they’re not a native speaker, but hopefully it improves!

[@Tocsin-Bang]

The first observation of the led dates to 1907 when Henry Joseph Round noticed for the first time that when a potential of 10 volts was applied to a carborundum crystal, it emitted yellowish light.

[@trippytrev1421]

I love how you get right to the point and explain it in a way everyone can understand

[@Syncromatic]

“Diodes are really simple electrical components “... my electronics textbook thoroughly disagrees...

[@goncaloaguiar]

The Shockley equation is quite simple ;)

[@KuraIthys]

I've seen someone that was determined enough to make their own semiconductors, and I have to agree. What a crazy process. And she was just about capable of making transistors... Maybe at a stretch an integrated circuit consisting of about 3 components. When you see it as small-scale improvised production it still looks nuts, but not quite as crazy as the real methods. And of course this improvised stuff was using commercially available wafers, which are really difficult to produce in their own right...

[@Improbabilities]

My textbook on the physics of electrical components also thoroughly disagrees.

[@poptartmcjelly7054]

@@KuraIthys It's Jeri and we all know her. She wasn't "close" to making transistors, she actually *made* transistors.

[@PhiTonics]

They are super simple, just like every other element in modern electronics, its confusing due to the scale(small) and materials used (compounds) but in actuality every peace is just an arrangement of positive, negative, and dielectric materials, even rocks have these various properties, everything dose to some degree, when arranged properly you get what we call electricity. Look into how all these components are made: transistor, diode, compactor, battery, you will see it's just various arrangements of P,N, and dielectric.

[@time-lapserpro4370]

Solar panels should be used as outdoor lights. OLED screens should trickle charge your phone. Thanks for coming to my Ted Talk.

[@nopparuj]

I’m sorry but solar panels emits Infrared which is invisible to human’s eyes, also power generated from OLED is not enough to charge your phone as it is so low it turns into useless heat when charging.

[@nopparuj]

Also thank you for hosting a TEDTalk.

[@Jay-kc2pm]

r/wooosh

[@time-lapserpro4370]

Cole Ikr

[@EzeePosseTV]

@Nopparuj r/wooosh

[@tomasdahuabe]

This video gave me the idea to test old film camera shutter speeds for servicing them. I made a really simple device which is just an LED soldered to an input jack connected to an audio interface to my PC and then on the other side of the camera shutter I put a laser pointer pointing to where the LED would be on through the shutter, shoot the camera while recording the "audio" signal and then see the audio clip to check the interval. And it works perfectly :)

[@polymetric2614]

holy shit. that is absolutely fucking mad genius

[@lucasheffield7838]

this comment is extremely underrated

[@ChrisThomasBone]

In case anyone's wondering, the term that encompasses both microphones and speakers is "transducer", or a device which converts between acoustic information and an electrical signal

[@MedlifeCrisis]

So why don't they just plug in solar panels so they light up and power themselves? I can't believe I'm the only person to think of this. Engineers with their fancy degrees pfft

[@SteveMould]

Bloody medics.

[@drewadkins4099]

STOOPID IT DONT WORK THAT WAY

[@mr2octavio]

@@drewadkins4099 hey man good luck in the Wooshlands

[@wierdalien1]

@@SteveMould Hey! The medics our thing (biomeds/nurses) to lay into

[@davidwilliston1209]

Entropy

[@leonmanetana7987]

This reminds me that the earlier Raspberry2 B models had a single diode that caused the computer to reset when a sufficiently powerful light hit the board. For example, a photo flash... this is why those earlier models were called "camera shy". Fun stuff.

[@vitordanieleal]

Wow thats true

[@melgibson6331]

Daniel Leal it happend with risc proccessors.

[@opensourcememes116]

Sometimes the led right in rpi begins to glow with our any external power supply

[@photonicpizza1466]

It wasn't a diode, it was the power IC (component no. U16), which was a WL-CSP chip. Basically an integrated circuit without any packaging, attached directly to the board. Still caused by the photoelectric effect, so the principle is the same, but it wasn't a diode.

[@NazD10]

Realistically this applies to any component, but as far as i know risc is extremely low power, so essentially it's much easier to overvolt.

[@BertGrink]

Steve Mould: "I like to have my old projects at hand" Me: "I'm a pack-rat too"

[@atinyknobofbutter9015]

Coming up next :how your fridge can work as a tv and your tv as a fridge

[@pbody6678]

Hahahahaha!

[@seraf8297]

After that: How your toaster can be used as the pc that runs all my teammates computers

[@arthurlouisamv6176]

Well you can use a fridge to be a heater and a heater to be a fridge

[@alexb__4133]

I mean with a Samsung smart fridge you can do at least the first one

[@workhardism]

I can drive my car forwards and in revverse.

[@QuantumFluxable]

hey Steve, I'm studying electronics and I gotta say, pretty well made video! if you want to look at other "reversable" electromechanics stuff here's a few examples: Peltier-/Seebeck-Effect (voltage creates temperature differential, but temperature differential also creates voltage), Piezo-Effect (voltage -> crystal lattice deforms, crystal lattice deforms -> voltage), or coupled inductors (current in one coil -> voltage in the other, but also it affects itself. pretty weird.)

[@karlkastor]

Also some motors and dynamos. I was very happy when I found out you can wire two Lego Mindstorms motors together and control one directly by turning the other.

[@IceMetalPunk]

I mean, he touched on the reversibility of the piezoelectric effect when he demonstrated that microphones and speakers are interchangeable :)

[@QuantumFluxable]

@@IceMetalPunk oh yea that's true, i kinda forgot about that video until he mentioned it and even then the memory is foggy...

[@GRBtutorials]

IceMetalPunk Actually, that’s not really the piezoelectric effect at play, it’s EM induction on the speaker and something more complicated (that has to do with capacitance) on the microphone.

[@mr.lasonyer1280]

There is no single correct answer to this. There are many different techniques to build a microphone. You can use a magnet attached to a membrane. This membrane is vibrating when you speak on it and the magnet induces a current in a coil. Other microphones use a capacitor with one electrode being a charged isolator (electret). The electret electrode is attached to a membrane similarly as in the previous example. The sound waves make the membrane move again which causes the distance between the electrodes to change. This movement causes a change in capacitance and eventually a change in voltage across the capacitor. Microphones which use the piezoelectric effect exist, but they have a rather bad sound quality. But they are mechanically sturdy which makes (or made) them useful for some applications.

[@TommoCarroll]

As always Steve...this was _illuminating_ ! 💡 But for real you’re by far one of the best Science communicators on this platform chap! 🙌

[@kuro13wolf]

That's interesting considering you commented this 3 minutes after this 5 minute video was uploaded. And every other science video I've watched today. Hmmm...

[@TommoCarroll]

Rhyme Bito Aha I type comments whilst watching the video bud :) Nice to see you’ve got a similar taste in Science KZbinrs though!

[@protoborg]

This guys simply does not understand the physics involved here.

[@NetRolller3D]

_Illuminati confirmed_

[@safir2241]

Aspect Science You’re great as well!

[@RandmAnimal]

"LEDs are solar panels" By that logic, I can make a solar panel by only using christmas lights

[@marcelosantos5683]

Actually, if you search you can find projects of homemade solar panels using only LEDs

[@RabbitholeIsrael]

YES, AFTER CHRISTMAS YOU PUT YOUR TREE OUTSIDE in the sun to provide electricity until the next christmas

[@AshutoshShelkeP]

@@RabbitholeIsrael dayum!

[@santiagocortez9554]

But a very inefficient one

[@DarkDucky79]

What about old LED TVs? Maybe a way to recycle them instead of sending them to the trash pile. Saving the planet one TV at a time.

[@antoniomaglione4101]

The reversibility of PN junction is a classical well known into engineering labs. I remember as a young experimenting with the germanium OC71 transistors, some manufacturers used a glass case painted with black varnish. By removing some varnish from the top of the transistor with a razor blade, the OC71 behaved just like a phototransistor. I built an electronic rooster, a control system for model railways, an RPM counter and a motorised gate control, all with scraped transistors. Thank you for the inspiring video; the electronic as an hobby has disappeared almost completely (especially the analog parts, which are erroneously considered obsolete), so a video like your is able to recall the spirit and the curiosity of experimental electronics, which appears nowhere along the Internet. Regards, Anthony

[@Anton-cv2ti]

It's also the same for electric motors and generators. Heh, it's a fun world we live in.

[@jolomies]

also peltier elements, put a power in one, and one side gets cold and other hot, create a temperature difference and you get power out of it.

[@allanrichardson1468]

And piezoelectric crystals!

[@rivencraft1734]

All I heard was, you reverse the polarity to solve all your problems.

[@TheAngelsHaveThePhoneBox]

And unlike diodes or speakers/microphones, electric motors are actually quite often used as generators as part of their normal operation. Eg. regenerative braking in electric vehicles (cars, trains) or pumped-storage hydroelectric power plant. They can be designed in such a way they're effective at both.

[@GRBtutorials]

NoLlama Yeah, in fact most motors are also good generators, and vice versa.

[@Wecoc1]

In my next concert I will sing on a speaker powered by a LED

[@kokorobertco]

That would be LED Soundsystem

[@ze_rubenator]

Don't forget your solar power microphone!

[@wave1090]

Make sure to use a generator as a fan for wind effects

[@arsenymakarov6961]

that would be a massive waste of energy! )

[@GRBtutorials]

Well, technically the speaker used as a microphone also produces a voltage across it. What you mean is an amplifier connected to a speaker all powered by an LED.

[@zorgatron8998]

Light Emitting Solar Panels! Amazing. Seriously, I always wondered how you know if the solar panels on cheap garden solar LED lights are good or not, without testing and benchmarks and stuff. This is a super easy way to test them. This could probably even be done "in the field" which is while you're at the shop, so you pick out only the good ones.

[@rtmordecai1]

One of the best physics demonstrations I’ve seen was when Mr. O’Neil put a wire coil between two plastic cups, strung them to an led, and played music through them by shining a laser he had hooked up to his ipod on it.

[@kikivoorburg]

First CGP Grey uploads and now this video? Today keeps getting better!

[@matacusa]

Within 30 minutes of each other. What a time to be alive.

[@awitcheskid]

Now if only vsauce would upload I'd be in heaven.

[@Azivegu]

dont forget Tom Scott

[@aaroncameron1494]

Quick! Someone calculate the odds.

[@althaz]

Hah, I came here straight from CGPGrey's vid :).

[@robertwilliams3457]

So my LED tv is not only a microphone but a 70” camera? Hello big brother!!

[@superjeffstanton]

Woke

[@blackturbine]

Life=lie

[@erichmarkmann6332]

@@superjeffstanton c

[@phasm42]

LED TVs are just your usual LCD with LED backlighting instead of the usual CCFL bulbs.

[@texasinfobroker]

LG=Looking Glass?

[@okboing]

One thing I noticed about solar cells is that covering them from one side, even just a little bit, caused the voltage to drop dramatically, but covering from either adjacent side, even a lot, doesn't lead to as much voltage drop.

[@EVRLYNMedia]

that is so cool. i never thought about how you can literally reverse the roles of solar panels and leds

[@dnzssrl]

2:59 here you go, your daily dose of nightmare fuel. You're welcome.

[@kawsakiTV]

Great video! I remember using my cheap on-ear headphones as a microphone when I was a young teen in the late 90s! I always found that whole idea cool :)

[@jordanbensen5209]

This guy just explains stuff in a way that I immediately understand.

[@axelelmfeldt4540]

Imagine having your phone screen act as a solar panel to charge your phone

[@jamesdeegan7365]

well apple did upgrade there firmware so you can charge your phone in the microwave

[@stargazer7644]

You could do that, but you’d need infrared vision to read the screen.

[@bruhmoment1835]

@@jamesdeegan7365 It's faster than using their chargers too!

[@naraydaniels7832]

@@jamesdeegan7365 screw you guys because of you not just did my Phone not charge but i wrecked it and my microwave and my phone now i have to buy a new one Screw you Nah im just kidding

[@archie2934]

@@fayenotfaye you ever heard of a window lol

[@TheDIYScienceGuy]

This is one of those channels which always makes me so happy when there is a new upload! Put myself in knowledge absorption mode! 🤯

[@matthewgiles5757]

Every diode is a light emitting diode, but sometimes only once!

[@GRBtutorials]

Same applies to almost any component!

[@nopparuj]

Also smoke emitting diode as well.

[@GRBtutorials]

Nopparuj Oh, yeah, the SED

[@pentachronic]

Yeah and after that once, it becomes a Dark Emitting Diode !!

[@SamuelLing]

*ElectroBoom agrees

[@SchioAlves]

Does that mean that a led panel with lots of led under the sun (like those on road signs) are constantly sending a reasonable amount of power when off?

[@intixshintei5429]

yeah, but not enough to induce a change/imbalance in the circuit

[@parthgulati4675]

But you have a good point :)

[@stargazer7644]

The problem with your statement is the word “reasonable”. LEDs are optimized to emit light, and that makes them poor solar cells. Solar cells are optimized to generate electricity, and that makes them poor LEDs.

[@vince77Z]

When I was little I plugged a microphone into a sound system, and when the microphone made noise, I thought I had made a scientific discovery

[@GRBtutorials]

Well, you still call it infrared “light”, so yes, IREDs (including those designed for that, like those in a remote controller and solar panels) are also LEDs.

[@0MVR_0]

Indeed, most light is outside our visual spectrum.

[@GRBtutorials]

Omar Omokhodion Yep, though we can still see some NIR from remotes and perceive FIR with our skin as “heat”.

[@inteuniso]

@@0MVR_0 light, electromagnetic radiation, same difference.

[@melodyqueen6432]

Cellphone makers listen up - I wanna charge my phone by leaving it in the sun. Make it happen

[@einHOCHaufWISEGUYS]

except the display heats up pretty signifigcantly by absorbing all the light heat degrades overall lifetime of any electronics, but especially for the battery :/ I had my phone shutting off due to overheating (on a relatively hot day, mind you) after I left it in the sun for a while

[@marcusfred4480]

You can get USB power banks that have solar panels to charge them.

[@Unerty]

@@marcusfred4480, that solar panels on powerbanks aren't made for charging them, but only for keeping energy

[@marcusfred4480]

@@Unerty What??? Lol! I can assure you that the solar panels absolutely put charge in the batteries.

[@Charlesincharge42]

But then they will want $3500 for a phone.

[@zoned7609]

I do this every day at work - load up a module into the (pitch black) EL chamber and run a current through it, and use a camera with special aperture and exposure/ISO settings to capture the pattern and check for any cracks. They become very obvious under these conditions. Oddly enough, some of the extremely cracked modules sometime still produce an OK amount of power. Depends on how the damage happens. If you have solar panels, clean any leaves that fall on them. If they shade the exact percentage of a cell needed to cause a 'kink' in the electrical flow, heat builds up and it can literally catch fire. We do a test called the "hot spot" test that puts various sizes of square tape over a section to find the magical % of a cell that causes the "kink" so the manufacturer can put it in their specs/manual.

[@josefhula9811]

Hey there, my father (village mayor) has issues with a company providing public illumination powered by solar panels. We would like to apply this method to check if are some panels faulty. Could you give more practical insight? How much current and what voltage is needed and is a laptop camera or front facing Iphone camera (lacking UV filter) sufficient? We tested both cameras on a TV remote and they worked just fine. Thanks

[@josefhula9811]

They use Victron Energy SPM150-12/3a 150W-12V Mono. Optimum operating voltage of 17.86 and opt. operating current of 8.399 A

[@zoned7609]

@@josefhula9811 While I am a somewhat knowledgable tech when it comes to solar panels, my expertise ends at testing and identifying problems. I can tell you a good resource: kzbin.info/www/bejne/bpnYhqaebsqobrc At around 7:20 ish he starts explaining what is needed to capture an Electroluminescence (EL) image. This video shows how to use a multimeter to measure volts and amps, which you can compare with the info sheet on the back of the solar panel. kzbin.info/www/bejne/m5mZma2Dl5tsnbs I haven't had the opportunity to vet everything from these videos, but they seem like a good starting point. Sorry I can't be of more help.

[@shakibm1558]

2:53 my 13 year old emo self would've created a KZbin channel just so I can upload videos with visible light filtered out

[@snakeru1]

Filtering out visible light is easy. Just put the lens cap back on.

[@josephdestaubin7426]

"I know there is no one there" LMAO. You're my new favorite human being, at least on KZbin. :)

[@mananvarma5944]

So basically, solar panels , when connected to a voltage source, emit light but we can't see it because they do this in the infrared region and not in visible wavelengths. Good! Thank you.

[@Phantom-el6oe]

Manan Varma No, it's just heated up absorber that emits light and wears off in process. After few minutes of that solar panel loses effectiveness and dependig on type and absorber it could completely stop working

[@mananvarma5944]

@@Phantom-el6oe So, doing that isn't advisable. LOL I was thinking of doing this. Thanks for saving my solar panel :-)

[@Phantom-el6oe]

Manan Varma Always to your service sir

[@mananvarma5944]

@@Phantom-el6oe Roger That! Thank you sir!

[@patrikgubeljak9416]

@@Phantom-el6oe No, it's not true, and that is not how diodes generate light! If you had a GaAs or a direct gap semiconductor panel, it would glow, once you apply voltage bigger than the bandgap. But it would not emit IR. In the case of Si diodes, they will not emit light because they are indirect bandgap semiconductors.

[@quetzalcoatl-pl]

I love the speaker-microphone analogy!

[@blugerdude]

I worked in a Solar Panel Factory for some time and we used the exact Infrared method shown here to diagnose faults and cracks before we sent them out the door! The crazy thing is that I didn't understand how it worked until I watched this video nearly ten years later!

[@AlRoderick]

Film scene idea, geeky hero jury rigs a blinking infrared beacon on the roof of a bad guy building by feeding a voltage into the solar panels that their backup can spot on night vision.

[@heroslippy6666]

Now that would be cool.

[@PyarMatKaro]

Can you explain the bandgap, and why efficient blue LEDs require other elements in addition to gallium nitride? (But I can't promise a Nobel prize)

[@FatboySim]

BitDancer easy. Circle.

[@playaspec]

As an old EE who *thought* he had seen it all, this was AMAZING! Thanks!

[@patjustpat5014]

yes, check out "silicon devices", they were invented some years ago after the vacuum tube.. ;P

[@technowey]

I'm an electrical engineer. You can use many kinds of microphones as speakers, but not all. Condenser microphones, which use capacitance, won't function as a speaker. Virtually all speakers can be used as microphones. Speakers usually use magnetism. Some crude speakers use the piezo-electric effect. Both of those will work in reverse as microphones.

[@seansiquig]

*_why don’t we just use redstone?_*

[@ronnor1579]

can you light up a LED just with shining a light on a different LED?

[@LeonidasSthlm]

Yes! It's not very effective but it should work.

[@liammargetts]

Yeah, though you'd need multiple LEDs to power the one LED to a good enough standard That is if you're not artificially powering the LEDs, but then again you'd probably need quite a few LEDs

[@karlkastor]

Yes! It's similar to an optocoupler.

[@SeanBZA]

Yes but you generally need to have a lot of light shining on the first LED and the second must have a lower voltage drop. done it shining a blue LED onto a green GaAsP led and using the voltage generated to light a hyperbright red LED. You generally will have to shield the blue LED and the green one, as otherwise the light from the red is nearly invisible in the glare, the efficiency overall is so low. You also have to couple the blue and green together well, so flat top ones are best with some tubing joining them.

[@DanteYewToob]

Wouldn't that just be using a solar panel to light an LED? Hahaha

[@kaptein1247]

Its interesting how every informational video regarding electricity somehow makes me understand electronics even less

[@daneast]

One thing that should have been mentioned is that the various corresponding combos (speaker microphone, etc) differ in that they are engineered for optimal performance in one way or another. A large diaphragm works better for emitting sound efficiently over a small spectrum, while smaller diaphragms work better for absorbing sound across a wide spectrum. A lens for a camera is larger so it can collect more photons over a greater physical area, while a lens used for a flashlight that emits light can use a much smaller lens since the light source is concentrated. So while many things can work both ways, it will work very poorly in the reverse manner it was not designed for.

[@rushthezeppelin]

BTW cameras with the IR filter removed might not be able to do thermal imaging BUT they can act as a digital night vision.

[@jelteklaswijnja4055]

And it's super easy to modify most webcams!

[@sidharthcs2110]

But needs IR illumination

[@JefeInquisidorGOW]

@@sidharthcs2110 you can do that with your remote control led

[@stargazer7644]

No video camera will do thermal imaging. Glass lenses wont even pass the light.

[@minkyone]

where did you find that concentrated solar cell? Thanks for the awsome video

[@feynthefallen]

Wow. Mind blown. 20 years of hobby electronics, and I never knew. Always just took LED, diodes and solar panels for granted.

[@desalegnsimon6671]

Serious topics like this with real life application and example is what I am here to watch.

[@adamlyduch9365]

the same goes for electric motors and alternators, every motor can be used as an alternator and other way round

[@rogerbarton497]

No it can't, a motor with a commutator acts as a dynamo ie it has a DC output. If you put a DC voltage across and alternator* it will just twitch and not rotate. Some types of washing machine pump motor will act as an alternator. * I mean a basic alternator, not an alternator with a rectifier &/or regulator built in.

[@modernkennnern]

1:52 Solar Panels, they don't make great LEDs ~ Steve Mould 2019

[@Nico-jc8fw]

FWIW, the applications aren't limited to imaging cracks for the failure analysis of PV cells: a decade or so ago, I helped a colleague use images for PV cells when reverse-biased at different voltages, to compute the efficiency of the PV cell at individual points in there, and help characterize those cells but also help improve the fabrication process.

[@wilbur9416]

That was really cool and informative thank you for taking apart your camera so that we can see that

[@puffinjuice]

I feel like I've lost all curiosity at work. how do I fix this? Is it because my work and hobbies overlap too much? I used to do so much experimentation at home. now I can't bear to look at technical things in my spare time. I know I haven't lost my interest because I get excited whenever I see videos like this.

[@krap101]

I go through the same thing. If I'm too concentrated on work or am deeply engaged in something, I don't feel like working more at home. When I am bored at work, I can't wait to come home to my projects

[@zachburke8906]

puffin juice it sounds like burnout to me! It happens to everyone, your best bet would be to separate your job from your hobby as much as possible. That’s not to say they cannot be the same type of work, it’s just having them be different helps keep things interesting. If you are working on one type of electronics at work do something else at home.

[@enoughofyourkoicarp]

Her: "Did you put the Christmas lights up?" Me: *looks at solar panels* "Get a camera." (I am so lazy) Her: (He's so intelligent) Me: *Buys Steve a drink*

[@Phantom-el6oe]

*Wears off solar panel that cost more than whole Christmas*

[@bradfader691]

I worked for a solar panel manufacturer and we used an EL machine that charged the solar panels with 70v dc and took a infrared picture to check if all the connections were made an if cells were damaged.

[@UltimateBargains]

I remember as a kid in the late 1960's or early 1970's I had a power transistor, which was about the size of a Kennedy silver half dollar, encased in thick metal. Applying brute force with pliers and vice grips, I tore off the top to expose the inner wiring. I connected a voltage meter and measured a voltage as I exposed the inner wiring to light. That power transistor acted like a solar panel, but it was very inefficient as such.

[@_Dylanm]

I had to check this wasn't a troll video after the speakers and microphones fact

[@-book]

When you find a really cool KZbinr and you're like: Ohhhhhh this awesome dude!

[@fr89k]

It's a long time since I had to learn about semiconductors, but one thing I remember is that you cannot build LEDs from silicon, because it is an indirect semiconductor. To emit a photon, these semiconductors don't only need exited electrons, but also a phonon is required. And this is basically where my physics knowledge ends, because I can't properly explain what a phonon is or does...

[@jamesb2291]

I remember reading a Robert Heinlein book or story that had basically foretold PV solar panels and described them as emitting light when fed electrical current or producing energy when exposed to light.

[@PierreThierryKPH]

Is there a link between the frequency of light emitted by a diode and how it would absorb light? That is, for example, do solar panels absorb near-IR better than other frequencies when they emit near-IR?

[@Rudxain]

This is related to resonance. My hypothesis is that if a solar panel is "tuned" (like a string instrument) to resonate at a specific frequency or wavelength, it should be very efficient at absorbing it AND emitting it. However, ultraviolet light has *A LOT* more energy than infrared, and more than visible spectrum. This is why the sun is used as source, because it generates more energy without the need for "tuning". Quantum Dots have the special ability to be "tuned" (only at build time), so if you make a QD solar panel with a lot of QDs tuned to multiple frequencies (specially UV) you get A LOT more energy than traditional panels!

[@hellboystein2926]

Ever heard anything about the difference between Direct- an Indirect-Semiconductors?! Propably not! In fact it's quite difficult to get any kind of 'effective' electroluminescense from Silicon, regardless of other 'tricks' like doping, structuring,..and regardless of the desired wavelength!

[@patrikgubeljak9416]

Thank god, finally someone in the entire comment section who knows something.

[@Exitof99]

Before clicking on this, my first thought was how microphones and speakers are the same thing too, something I figured out as a kid with my Radio Shack electronics kit with all those springs and such. I did the "AM pirate radio" thing when I was maybe 10 and used an early 80s earbud as my mic to DJ between songs. Those were the days.

[@JesusJuenger]

Fun fact about digital cameras picking up infrared light: the Game Boy Camera (accessory) had no filter for infrared so you could see the light from your TV remote control and such using it. I guess it wasn't a problem for it because the picture quality was so dreadful anyway that the infrared didn't make a big difference.

[@jesusjesus2807]

2:04 yes you can call it an LED even if it emits IR. Any diode that emits any wavelength of the electromagnetic spectrum is an LED. Look out for those gamma emissions though OUCH!

[@vincentrobinette1507]

I wouldn't worry too much about gamma rays. Most PN junctions are monochromatic. They emit in a very narrow spectrum. If you can't see the light, because it's outside of the visible spectrum, you might just want to check. (I was going to say: "Look into it", but that might be a bad idea!)🤣😁😝

[@neurhlp]

The semiconductor bandgap (1-10eV) limits the photons energy, so you will never get gamma photons (100keV) . The only way to get gamma or X-ray if you put millions of amperes in the diode and it explodes very violently, resulting in lots of UV photons, some X-ray photons, and maybe some gamma photons from excited nuclei.

[@vincentrobinette1507]

@@neurhlp Is that what they call a gamma ray burst?🤣😁😝 As far as sending and receiving at the same time, to illuminate, you have to apply enough voltage to forward bias the diode junction. If the LED is exposed to light, than if the voltage is reduced below forward bias, there will still be voltage across the terminals. You just need to load the diode, so it stays just below junction voltage, to get maximum energy back out of it. As far as efficiency, it's actually quite high, considering the very small area of the LED Vs a solar cell. A screen has millions of them, giving them the surface area of a solar panel, and producing close to similar efficiency. The only thing that makes the idea impractical for now, is that each pixel, represented by each LED element, needs a push-pull pulse width modulator, with an inductor. The magnetics would be very difficult to scale down that many into something the size of a lap-top, let alone a smart phone. in theory it can be done, but not practical for now.

[@HelamanGile]

solar panel camera next

[@jjmcook]

When I originally found this out about solar panels the first thing I thought of was Heinlein's short story "Let There Be Light" where the solar panel the protagonist invents also functions as a light if you run current through it.

[@KJfourIPS]

I vaguely remember seeing a write up of a display that exploited this principal. It was interlaced, and the currently dark diodes we're used to measure reflected light from the line that was currently active.

[@tuns4life342]

Does this mean that you can turn a led tv screen into a solar panel for off the grid purposes?

[@drlegendre]

No. While all LEDs do exhibit the photovoltaic effect, to some degree, they are not at all optimized for this purpose and as such are extremely inefficient.

[@turbopokey]

I KNEW IT! The government technocracy has us all ensnared! lol

[@zrxdoug]

I was hip to this at the age of 12 back in 1975...I had read "Let There Be Light" by Robert Heinlein a few years before, and did the experiment with a fried digital watch and my first multimeter that summer.. Smart Feller, Heinlein..he wrote that story in 1940..

[@greggv8]

in 1940 a short story titled "Let There be Light" by Robert A. Heinlein (as Lyle Monroe) had solid state panels that were equally efficient at making light from electricity as they were at making electricity from light. That's a 'holy grail' of semiconductor technology that has yet to be achieved. Heinlein used a lot of pseudonyms when submitting stories to the magazines in the 1940's, often at the request of the editors so it wouldn't look like he was writing nearly half of the stories they published.

[@RobertCole1981]

just a quick question, does this mean Infared leds will act better than regular leds as solar panels?

[@johnlocke9609]

Great question! Didn't even think of that.

[@andrewnetherton652]

Infrared LEDs can absorb a broader range of the solar emission spectrum than visible LEDs, yes. But both IR and VIS LEDs are bad solar cells.

[@liammargetts]

Better clickbait would've had the title the other way around

[@stabgan]

This channel should be shown in every school in all STEM Unis

[@mdmkoopman]

Thank you so much Steve! A college asked me for a tachometer today to measure fan speed. We don't have one, but thanks to you i now know led's are solar panels. With a scope and flashlight I made the day :D

[@araozuco]

"I know there's no one there" 😂

[@williamschmidt-hansen6311]

What was that solar cell at 4:00? I would like to find more information about it.

[@intptr]

google hcpv

[@g1998k]

Amazing video Steve. Being a Civil Engineering I can confirm that this video was a great CPD for myself.

[@geoschmo]

Heinlein published a short story in 1940 called "Let there be light" set in a future where there was a technology called "Light Panels" that generated light from electricity more efficiently than conventional incandescent bulbs. The plot of the story was about a scientist who discovered that these panels could be used to generate electricity from sunlight and ran afoul of the corporate power generating interests. This was written in 1940. Seven years before the invention of solid state devices.

[@noviksstory3325]

Nobody: Steve: LEDs are solar panels

[@Samantha-jv6xu]

Mind-blowing

[@waspbulgasari4498]

This is some some genius sh*t over here

[@DNAinstinct]

This format needs to die.

[@oldcowbb]

@@DNAinstinct these youtube memes literally take zero effort to make and they aren't even trying to be funny. They just exist and super annoying

[@user-ki2wm5hd4e]

Sorry, but it was more than 3 years ago in this video: kzbin.info/www/bejne/jJTUo6KKesRpaKM

[@michaelscott1800]

So if I leave my deadflash light in the sun, diodes up, it should recharge my batteries?

[@ernestsmith3581]

You can charge those dead 1.5 V cells right up to 0.25 V. LOL

[@jeffmccrea9347]

You can also use your phone camera to test you IR TV or any other remote. Point it into the camera, press a button and look for a pale blue glow. You don't even have to remove the IR filter. This is how I discovered that part of my DVD recorder's remote had failed. Some buttons worked, some didn't.

[@tonyrking]

What could have been a good addition to the microphone/speaker analogy would be the TV Remote control diode and the receiver unit diode. Both units have a diode, one sends the pulses of IR light- one receives those pulses of IR light.

[@rakeshvishwakarma2205]

Super one bro, you kind of superman the way your voice and briefings its all awesome, you rock and einstein

[@tttITA10]

Aren't the circuits' schematics at 0:13 reversed in relation to what the battery is doing in the experiment behind?

[@time-lapserpro4370]

Shorter is positive.

[@stickyfox]

@@time-lapserpro4370 might wanna look that one up again. (yeah, they're reversed)

[@MuhammadAhmed-gm1bv]

i was wondering the same

[@AppliedCryogenics]

Diodes can also be used to detect ionizing radiation. They output picoamps when irradiated by say, a radiotherapy machine. They're less sensitive than ionization chambers but can form denser detector arrays.

[@8amonas]

A good example is the piezo discs i believe, they can be used as pressure sensors, microphones, speakers and much more