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

DavidEF · 2019-03-13T17:40:30.000Z

I ran across this today and thought it was interesting. I know TK and others have already talked about LEDs generating a small voltage when a light is shined on them. There was a little bit of talk about using this feature of LEDs as a way of flashing configuration options into the UI. But, in this YouTube video, the guy in the video shows how solar panels are also diodes, and will emit light when a voltage is applied to them. I had never heard about this. Do you guys know anything about it?

Enderman · 2019-03-13T17:52:45.000Z

And microphones can be used as speakers, and speakers as microphones, etc etc etc.
These things are just made to do one thing very well with some side effects.
It’s pointless to use something for another thing it’s not intended for.

Muto · 2019-03-13T18:03:57.000Z

Enderman:

And microphones can be used as speakers, and speakers as microphones, etc etc etc.
These things are just made to do one thing very well with some side effects.
It’s pointless to use something for another thing it’s not intended for.

Way off base man.
Didn’t the Walkman headphones use a variant of mic drivers?
Just because something wasn’t originally intended for another use does not mean it is pointless.

Many medicines were not made for the thing they became useful for.
Lot’s of Men (and Women) are grateful for Viagra and it was developed for high blood pressure.

Schoki · 2019-03-13T18:35:32.000Z

Haven’t watched the video, but…

Yes solar panels can be used as LEDs, they emit light, but they’re not made for it. Also, solar panels emit infrared light, not visible light. That means you could use it as an infrared heating plate, or whatever, you could play this game further (Enderman’s comment isn’t far off).
I think it was even common practice to test solar panels like that for cracks after manufacturing, or after reliability testing. They just power them up and look after dark spots with an infrared camera.

Enderman · 2019-03-13T18:44:32.000Z

Muto:

Way off base man.
Didn’t the Walkman headphones use a variant of mic drivers?
Just because something wasn’t originally intended for another use does not mean it is pointless.

Many medicines were not made for the thing they became useful for.
Lot’s of Men (and Women) are grateful for Viagra and it was developed for high blood pressure.

Using an LED as a solar panel or a solar panel to emit light is pointless because of how bad they are at doing that.
They are specifically designed and intended to do the opposite.
Which is why you buy an LED if you want light, and a solar panel if you want energy.

Boaz · 2019-03-13T19:24:10.000Z

Well that still doesn't mean Enderman isn't way off base .

Ground control has tried and repeatedly fail to make contact.

It appears he may be drifting aimlessly forever .

Doesn't mean we don't care...

Unfortunately there aren't any rescue plans being considered other than turning a solar array on a satellite into a butterfly net.

Muto · 2019-03-13T21:05:02.000Z

LOL Boaz

MascaratumB · 2019-03-13T21:38:50.000Z

Wait… What? Viagra can be used as Leds and Leds as Viagra?
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DavidEF · 2019-03-13T21:51:32.000Z

MascaratumB:

Wait… What? Viagra can be used as Leds and Leds as Viagra?
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No, Viagra doesn’t produce any emissions. But it does help with the aim.

MascaratumB · 2019-03-13T21:58:04.000Z

DavidEF:

MascaratumB:

Wait… What? Viagra can be used as Leds and Leds as Viagra?
.
.
.
.
.

No, Viagra doesn’t produce any emissions. But it does help with the aim.

DavidEF · 2019-03-13T22:01:49.000Z

Well, I (sorta) agree with Enderman and others. This is (sorta) useless for the most part. But, that doesn’t mean that the (now useless) feature won’t someday be implemented in a new product in a useful way. I already mentioned the idea of using the main LED in a flashlight to receive configuration options. We don’t do that here YET, but it has been mentioned as a serious possibility and several members have shown interest in it one day becoming a reality.

Actually, I’m surprised you guys don’t know that on two-way radios, the speaker IS the microphone! So, these things do become useful eventually, when someone inevitably figures out how to make it work well enough both ways. I don’t know what that will look like with solar panels and LEDs. But remember that the LED was first invented because someone discovered that a diode leaked out some energy as “useless” light.

DavidEF · 2019-03-13T22:02:53.000Z

MascaratumB:

DavidEF:

MascaratumB:

Wait… What? Viagra can be used as Leds and Leds as Viagra?
.
.
.
.
.

No, Viagra doesn’t produce any emissions. But it does help with the aim.

NOT that I would know personally. :innocent:

Enderman · 2019-03-13T23:37:18.000Z

DavidEF:

Actually, I’m surprised you guys don’t know that on two-way radios, the speaker IS the microphone!

Um, they are two separate things.

Lightbringer · 2019-03-13T23:54:26.000Z

Old old old wired intercoms (1 master, N slaves) used 1 speaker for speaker+microphone in all the slaves. That’s all they were, in fact, the box with speaker and PTT switch (optionally a call-button). Plenty of circuits online showing how to do that.

Older less-efficient LEDs make better photodiodes than modern more efficient LEDs. In the latter, the emitting volume is thinner and nearer the surface to let more light escape, but provides very little “collecting” volume for incoming light. Like trying to catch photons with a butterfly net, and lousy at it, but where it’s sheer enough to let photons slip through easily when emitting light. The former had lots of that, and were able to collect more incoming photons to act better as a photodiode, but emitted light had a harder time getting out of the chip.

CdS cells (variable resistance) would emit yellow-green light when hit with enough high voltage… and only if DARK, else its resistance would be low enough for the HV to fry it instantly.

So… nothing earthshattering. It works, to a varying degree.

DavidEF · 2019-03-14T00:13:29.000Z

Enderman:

DavidEF:

Actually, I’m surprised you guys don’t know that on two-way radios, the speaker IS the microphone!

Um, they are two separate things.

https://www.radiotronics.co.uk/media/wysiwyg/motorola/dp4400/motorola-dp4400-diagram-features.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Motorola_hand-held.jpg/200px-Motorola_hand-held.jpg
http://dealers.yaesu.com/LMRMktgEmail/image/HX400%20noise%20cancel.jpg
https://ae01.alicdn.com/kf/HTB1qa.WIpXXXXcyXVXXq6xXFXXX5/XQF-Heavy-Duty-Speaker-Microphone-Mic-PTT-IP54-Waterproof-for-Kenwood-Baofeng-HYT-Hytera-Two-Way.jpg_640x640.jpg

Huh. So they are. I thought I knew something and I was wrong. Sorry about that. :person_facepalming:

hank · 2019-03-14T00:17:29.000Z

I believe this is why there was talk many years ago (around the time of early development of Gransee’s Arc Flashlights) of building a walkie-talkie feature into his flashlights. So you could aim your light at a distant flashlight and the LED would convert the incoming light into an audio signal for 2-way communication.

Didn’t happen. Could have. Noted the idea as prior art.

Enderman · 2019-03-14T00:36:04.000Z

DavidEF:

Huh. So they are. I thought I knew something and I was wrong. Sorry about that. :person_facepalming:

Mics are so small they are just hidden right beside the main speaker haha

DavidEF · 2019-03-14T01:25:56.000Z

Enderman:

DavidEF:

Huh. So they are. I thought I knew something and I was wrong. Sorry about that. :person_facepalming:

Mics are so small they are just hidden right beside the main speaker haha

Well, not only that, but it seems like I was told that two-way radios used the speaker as the mic. It’s probably one of those things that used to be true.

Lightbringer · 2019-03-14T02:14:03.000Z

DavidEF:

Well, not only that, but it seems like I was told that two-way radios used the speaker as the mic. It’s probably one of those things that used to be true.

They did, and it was.

Early choices were only dynamic and piezo, both relatively big and rather delicate.

Nowadays, electret (permanantly polarised ceramic) elements can be made into small dots that hide behind the teeny tiny hole you’d otherwise miss unless you were specifically looking for it.

Swib · 2019-03-15T00:37:46.000Z

Well the hailing horn speakers on our vessels act as both speakers and microphones and surprisingly they work rather well as both.