Transmitting Sound using Sunlight - The Photophone

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How to make a photophone to transmit sound using sunlight. This invention by Alexander Graham Bell works by reflecting sunlight off a mirror, which is attached to a speaker, to a solar cell and from there to an amplifier.
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See also:
How to Make Crystal Radio Amplifier for Speaker
• How to Make Crystal Ra...
Pyramid Hologram - How to Make/How it Works with Princess Leia Hologram
• Pyramid Hologram - How...
How a Prism Works to Make Rainbow Colors
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The inspiration for this was a comment by Michael Meadows under my video Hand-Cranked Laser - TEA Laser Powered by Wimshurst Machine • Hand-Cranked Laser - T... . Thanks Michael!
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14 окт 2024

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Комментарии : 136

@GoRepairs 9 лет назад

It's always amazing what discoveries were made in the past, considering what tools they had available.

@tobortine 9 лет назад

That's the best practical explanation of modulation that I've ever seen. Well done.

@MoondancerRec 8 лет назад

The problem with this transmitter is that the mirror is glued to the speaker rim, not the cone itself. That is why the sound at the receiver is muffled. I used to experiment with photophones in the 1980s. I removed the paper cone completely, flattened the cone holding frame, and attached the mirror directly to the voice coil. The sound is great that way. Enjoy the mod!

@RimstarOrg 8 лет назад

Oh, thanks for the tip! I might just try that. I'd have to find a different speaker though - the one I used is part of a set.

@JaysNotebook 9 лет назад

I've just got to say... You're AWESOME, RimstarOrg! I love watching your videos and all the cool stuff you can do. They have definitely inspired me to actually try things instead of just learning about them. Thanks again!

@RimstarOrg 9 лет назад

JaysNotebook If I've inspired you to actually try things then my work is definitely done! I couldn't ask for a better result. Thanks!

@JaysNotebook 9 лет назад

RimstarOrg What do you think would happen if the mirror was concave? I'm sure there'd be issues trying to focus the light onto the PV cell, but when the focus is just right, any ideas? Better quality sound? Weird noises?

@RimstarOrg 9 лет назад

JaysNotebook If you're already capturing the majority of the sunlight on the PV cell then focusing it wouldn't help. However, Alexander Graham Bell did do focusing to gather larger areas of sunlight onto his small Selenium cell receivers (PV cells weren't invented yet) and they worked fine. So focusing doesn't negatively affect the fluctuations.

@Lechoslowianin 9 лет назад

Very interesting way of sending information. well shown

@GREENPOWERSCIENCE 9 лет назад

AMAZING!

@RimstarOrg 9 лет назад

GREENPOWERSCIENCE Thanks Dan!

@RimstarOrg 9 лет назад

Transmitting sound using sunlight - and a mirror attached to a speaker with a solar cell to receive it. Enjoy!

@RimstarOrg 9 лет назад

***** Thanks. Yeah, it's summer here in Canada so I can take the camera outdoors. :)

@GianniPirolaFaidate 9 лет назад

Super my friend ;) !!!!!!

@RimstarOrg 9 лет назад

Gianni Pirola GP Fai Da Te Thanks!

@Tech_Planet 9 лет назад

This is cool, good stuff as always RimstarOrg. Is this how fiber optic cables work?

@thunderbolt997 9 лет назад

J.D. Rock they pulse a laser acordingly to the binary data and then recieve it via a light sensitive detector

@Slider2732 9 лет назад

Really enjoyed this, am sure it will be on many projects playlists. Could be used with your pizza box portable crystal radio and homemade amplifiers, for a bigger project start to finish.

@RimstarOrg 9 лет назад

slider2732 Thanks. Glad you enjoyed it. I'm also glad you used the plural form of homemade amplifiers. The pizza box portable crystal radio's output would have to be amplified to get the transmitter's speaker to vibrate in the first place.

@mylove1618 2 года назад

That’s amazing

@RimstarOrg 9 лет назад

+MAK Yes, but you'll have to plug the microphone into an amplifier and connect the amplifier to the speaker. The rest is the same. I've already done this but instead of a speaker and sunlight, I've connected the output of the microphone/amplifier to a small circuit and a laser (extra circuitry is needed for the laser approach) and it works great. Hopefully that'll be in Friday's video. PS There's no Reply button under your comment because of your Google+ settings. - go to your Google+ page, - in the top, right corner click on your thumbnail icon, - in the popup that appears, click on "Settings". - for the 2nd question down "Who can comment on your public posts?" set it to "Anyone".

@ArkiverUnifiedEnergy 9 лет назад

Nice demonstration! Some cool stuff going on there. Surprised to see todays solar cells pickup the modulation. Well done.

@trailkeeper 9 лет назад

I noticed on your laser vid that the beam width is small and concentrated on a small spot of the solar cell, hence having a good transmission effect, and I mentioned using a magnifying lens for when the beam is spread out wide, but didnt make the connection that a magnifying lens could also be used in this instance also, with your photophone, however people should be careful they dont burn a hole in their solar cell, by keeping the focused area as large as possible (depending on the distance and light intensity) prevents damage to the solar cell, and still have good audio. Its worth a try, and the results may not be as good as expected, unless the solar cell is small, and the light can essentially pass on and off the solar cell a bit due to the movement of the light beam.

@RimstarOrg 9 лет назад

trailkeeper That's a good point re damaging the solar cell. I think as long as the mirror is flat and small like mine and the spot on the cell is spread out then at most you'll get double the sunlight. If, however, you concentrate the light using a lens or concave mirror then you could get concentrated sunlight on the cell and then possibly cause damage.

@trailkeeper 9 лет назад

RimstarOrg Usually if the spot is 1/4 to 1/2 inch or less, it seems, damage will happen, a burn spot. I have done it once so I know it can happen. I was testing the output of a solar cell with concentrated light on it. Basically, you can put all the concentrated light onto the solar cell area, there is no need to have it more concentrated than that. But for the communication circuit, and with a small mirror like for the photophone, it could be concentrated if the the beam has spread out alot, and then concentration of it will probably not damage the solar cell, or atleast keep the light 1/4 to 1/2 inch or larger size on the solar cell. In fact a large solar cell may also capture more stray light, hence hindering the reception a little, put you could also put something like carboard, etc over it with just an opening for the sunlight. Good to paint the tube flat black and stuff also.

@TechVentions 9 лет назад

This is awesome i understood it but my mind still refuses to belive it's real i haven't seen such a thing like that ever before along with the wireless electricity transmittion your channel is cool and it deserves more subs

@TechVentions 9 лет назад

Transmission*

@PatrickStar-lu3ot 9 лет назад

The Doppler shift in action...Cool! I like this.

@keithking1985 7 месяцев назад

This is so awesome 👍

@OdedCnaan 9 лет назад

Very nice project. I am wondering, since solar panels output about 9V, how did you connect it to the LM386 circuit that runs on very low voltage. Does the capacitor filter out the 9V DC and leaves only a low voltage for the sound or did you use a load to reduce the voltage?

@Ludvictv 9 лет назад

Amazing project man! Thank you for sharing!

@sohamgumaste 9 лет назад

Did you get a new mic? The video sounds way better than the previous ones! Next, you should do the same process with a laser.

@RimstarOrg 9 лет назад

Soham Gumaste No new mic - I had a bit of a cold or throat infection when I recorded it so my voice was deeper :). And prompted by all these comments about lasers, I'm putting together some ideas.

@weshare03121984 2 года назад

Awesome video I very like this.

@digvijaysingh325 2 года назад

amazing brother

@Joshuanorton999 Год назад

Thank you very much. ❤❤❤❤❤

@younscrafter7372 5 месяцев назад

1:12 I figured you'd have to use more complex electronics to filter out the non-signal "background", maybe even something like an arduino, but I guess a capacitor works as well

@USWaterRockets 9 лет назад

You can do the same thing with a cheapo laser and a photodiode. If you do that the vibrations will be more apparent as you can see the point moving around on the target. The best part is you don't have to constantly adjust the angle of the "transmitter" to keep it on target as the sun moves. I imagine that this was quite annoying while trying to record this video!

@RimstarOrg 9 лет назад

USWaterRockets Nope, the sun wasn't moving fast enough and the test runs weren't long enough for the sun's movement to be a problem. But for longer runs it certainly would be.

@ull893 4 года назад

Wow. Thank you

@SpontaneityJD Год назад

This video is amazing..

@andyjones7121 9 лет назад

This blows me away! I don't quite get it though. Isn't the light always being reflected to the pv cell? Even if its vibrating? I don't see how the vibration is picked up?

@andyjones7121 9 лет назад

I'm also suprised the pv cell is so responsive and sensitive. Thanks for this video! I have some old speaker, a stack of pv cells and plenty sun! You're awesome!

@RimstarOrg 9 лет назад

Andy Jones Glad you like it! Yes, the light is always being reflected to the pv cell but the amount of light varies. The variation isn't noticeable to you or me unless you look at it far away like I do at the end of the video, and mostly at the edges, though at around 2:35 I think you can see it varying on the green plastic just to the right of the base of the amplifier. The solar cell does a better job of "noticing it" and the amplifier amplifies the resulting electrical variation further to make audible sound. Another way to think of it is to imagine you're standing outdoors holding a big mirror and reflecting sunlight onto the wall of a building. Now imagine you keep moving the mirror closer to you and farther from you and you keep doing this over and over, while keeping the light more or less centered at the same place on the wall. The amount of sunlight will vary by a small amount all over the spot on the wall, though it'll be most noticeable at the edges.

@RimstarOrg 9 лет назад

Andy Jones I took the round mirror from a woman's compact mirror normally used for applying/checking makeup which you can by at a dollar store. Have fun, and let us know how it goes!

@andyjones7121 9 лет назад

RimstarOrg Thanks! The sensitivity is really amazing! I wonder if instead of the mirror being on the speaker, if 1 side of mirror was fixed, and other side attached to speaker, so the mirror pivoted at an angle instead of in/out, maybe there would be more motion at the pv cell? You're making the world a smarter place! Unfortunately everyone's watching Caitlin Jenner right now, so you've got lots of work to do!

@aslimlines3069 9 лет назад

Andy Jones well I be a Jimmede cricket

@michellegriffith113 6 лет назад

I’ve been trying to come up with an application for this. Kind of a hassle for live sound (say playing outdoors) and the measures that must be taken in order to convert the sound into reflected sunlight is enough to defeat the purpose right there, you have a speaker playing music with a mirror on it that is focused on a solar panel off a short distance that requires a separate amplifier with a fair amount of low end reductions..... a 1/8” audio line about 20’ Long would produce WAY better sound quality. I’m not saying that it is not really neat (cause it is) and I will most definitely build one myself, I’m just looking for practicality so I can justify the time and effort.

@DadBodDrumming 3 года назад

Literally Sound at the speed of light!

@ercost60 2 года назад

The mirror is thick and poorly mounted to your speaker. You will get much better range & performance from a thin, first surface circular mirror mounted in a tube, like a diaphragm. Lightly hold the circular edge so the speaker vibrations flex the mirror to go concave/convex. Really works great.

@Oinikis 9 лет назад

The technical flaw of this (besides relying on sunlight) is that the beam is changing direction, rather than intensity, so part of it has to be off the panel in order for the change in direction of the beam to have an effect. Then, the mirror is mostly moving back and forth, not sideways. It can be improved by attaching one side to a speaker, other to a firm surface, so it will be deflected, but the best option would be attaching the wire to a resistor and connecting a directional lamp or a laser, so you can have the intensity changing really wide. Cool device nevertheless! and works good enough for a prototype.

@RimstarOrg 9 лет назад

Oinikis Yeah, the sunlight issue is why it never took off back in the 1880s. As for the beam having to be part off the panel for the effect, I'd think so too but that's not the case. I didn't include it in the video put I tested from a greater distance where the solar cell was entirely in the bright portion and it still works. I guess the intensity gradient from the exact center of the beam and outwards is enough for a solar cell to count as what you and I would think of as being part off. The spot looks homogenous to us but isn't I guess. It would be neat to do as you describe with a laser and see the projection of the point moving on a wall.

@mak4346 9 лет назад

Cool..... Im a big fan, i had made a vandegraff generator using ur tips and i like this tooo, i will try to make this also

@Grizzly_Lab 9 лет назад

Ok, now you blown my mind, totally O.o I wanna try... oh how much I wanna try it! ^_^

@jowarnis 9 лет назад

"TAKING CARE OF BUSINESS EVERY DAY! TAKING CARE OF BUSINESS EVERY WAY!" I love that song :D BTO ftw!

@RimstarOrg 9 лет назад

jowarnis I'm with you on that. I got lucky with that one for sure.

@RimstarOrg 9 лет назад

+Oded Cnaan The solar cell I used outputs around 0.5 volts in full sunlight. A solar panel is made up of multiple solar cells connected in series to get higher voltage. Just how much voltage a solar panel outputs therefore depends on the individual solar cell voltage and how many the manufacturer connected in series. I guess very small solar panels used for camping and such are around 9V or less. Larger solar panels for powering cottages and houses are manufactured to output 14V or higher. You can see where I've connected 6 of these solar celled in series to get around 3.22V in full sunlight on my webpage here rimstar.org/renewnrg/diy_homemade_solar_panel_simple.htm. PS There's no Reply button under your comment because of your Google+ settings. - go to your Google+ page, - in the top, right corner click on your thumbnail icon, - in the popup that appears, click on "Settings". - for the 2nd question down "Who can comment on your public posts?" set it to "Anyone".

@MoondancerRec 8 лет назад

I used a TCG 3033 PIN diode and a lens. It also outputs .5v at full sunlight, but if you reverse bias the diode with a resistor in series and apply high DC voltage it will get higher voltage swing as it will work as a voltage divider circuit. just add a DC blocking capacitor and have fun!

@gouthamkrishna3565 9 лет назад

Great Videos.Good job sir

@Phenurb 7 лет назад

Never thought that the main principle behind it was so simple!

@KylesYTU 9 лет назад

wow i really want to do that

@JDtheEE 9 лет назад

Hey RimstarOrg , Have you thought about making a solenoid engine before? I would love to see and i think that would make a cool video!

@RimstarOrg 9 лет назад

Hmmm... this is the first I've heard of them. They look like fun!

@JDtheEE 9 лет назад

Just built one. They can go pretty fast!

@VintageElectronicsGeek 9 лет назад

This is cool!

@nand3kudasai 9 лет назад

Awesome project! and also you explain what a modulator is. you made a solar analog modem ! (i think) i once heard of a device that used a laser to pick up the vibrations on remote objects and translate that into sound, to hear from far away. i do not know how well that works. (oh i see someone already commented on the laser one)

@RimstarOrg 9 лет назад

Jerónimo Barraco Mármol Thanks! Now that you mention it, I guess I made two halves of a modem. My transmitter is the modulator, the MODem part, and my receiver is the demodulator, the moDEM part. A full modem would be one that can both transmit and receive i.e. both modulate and demodulate.

@nand3kudasai 9 лет назад

RimstarOrg Thanks for the correction, i said it too quickly. Yes your answer is more correct. A Mo-Dem has both components inside to have communication in both ways. Either way is an excellent way to explain how modulation works :)

@two_number_nines 9 лет назад

try lightweight mirror and put the solar cell in the end of a tube. you should calculate the lenght and diameter

@mm-fi4ne 5 лет назад

Hi RimstarOrg, I saw your video and your explanations on your website but I don't understand why you connect a capacitor between your photo cell and your speaker. Is that in order to smooth the voltage ? And why 22 nF ? Thank you in advance

@huffenstein4116 2 года назад

My understanding is the capacitor is being used as a filter to remove excess signals (i.e. the sun not from the mirror). As far as why he choose 22 nF? My best guess was that he tried a few different ones and found the one that worked best.

@caproneamandriano6025 4 года назад

Complimenti

@sketchyssk8shop 9 лет назад

That is wild.

@waterandafter 9 лет назад

Would AG Bell have had solar cells and if so would they have been sensitive enough to pick up the light's small vibrations? What else would he/could he have used as a receiver?

@RimstarOrg 9 лет назад

waterandafter He used a few different things but mainly selenium, a material which changes its electrical resistance depending on the intensity of the light it's exposed to. If you use a battery to put a voltage across the selenium, then as the changing light changes the resistance the current also changes. According to ohms law, current = voltage / resistance (I = V/R). That current then changes according to the original sound, so when he ran that current through whatever he used as a speaker, it reproduced that sound.

@waterandafter 9 лет назад

RimstarOrg awesome.

@brfisher1123 9 лет назад

This is pretty much like LiFi which is like WiFi but uses visible light (like your photophone) instead of microwaves which are basically just high frequency (small wavelength) radio waves hence "MICROwaves", would this work with indoor artificial lighting?

@RimstarOrg 9 лет назад

Brandon Fisher LiFI :D Or what about ViFi for the Visible part? I tried indoor artificial light first, a 26W CFL, but it didn't work as far as I could tell. It's hard to beat or even match sunlight for intensity.

@brfisher1123 9 лет назад

RimstarOrg Lol I know you were joking but sorry "ViFi" wouldn't work; it'd be like calling the BluRay format "VioRay" (for the 405nm violet laser diode BluRay uses in case you were wondering) though I supposed "V-Ray" wouldn't sound too bad.

@tastyfish4890 8 лет назад

Can you use an incandescent bulb or an LED torchlight to transmit wireless music ?.

@RimstarOrg 8 лет назад

+Tasty Fish I would think you could. The volume may be less since they're not as bright as sunlight, but they should work.

@trailkeeper 9 лет назад

The vibration isn't really modulating/adjusting the intensity of the light beam being sent, very much at all except for a slight angle, of sun angle of incidence and reflecteion, and of angle of incidence on the solarcell, although it is changing its direction a bit, so perhaps focus only, say 1/2, of that light beam onto the solarcell receiver, that way the light may shift both onto, and off, the solarcell receiver, effectively modulating the intensity received. The farther out the solarcell, the better the effect, but less light intensity on the solarcell. Just an idea. In a way, Bell had the first "wireless" audio communication device. If this project inspired some, there are several other good sites about Heliography and Light communication (such as with led's and lenses, or just plain old mirrors, like a small "signal mirror", some have communicated over 50 miles, but with a easy to learn Tap code, or Morse code often used for wire/radio).

@RimstarOrg 9 лет назад

trailkeeper Yeah, I didn't say it was adjusting the intensity of the light beam being sent but I guess what I said can be interpreted that way, probably more so than what I actually intended. The direction is fluctuating, not the intensity. The intensity of what the solar cell is receiving is fluctuating. I should have been more precise with my wording. I guess taken with the animation I'd hoped that it was clear I was talking about the direction fluctuating.

@chemicalbombgang 9 лет назад

fantastic love it :D

@mygaffer 8 лет назад

Earliest example of wireless technology that I'm aware of.

@shazizz 9 лет назад

That's cool! I already see many other uses for this concept.

@RhetteLawe 9 лет назад

Nice... If you use lasers and photodiodes you would instantly have something that would transmit in a single color, and would only receive in a single color, for miles at a time. for a short range you might be able to use regular LED's.

@RimstarOrg 9 лет назад

RhetteLawe Thanks. A DIY laser one would be fun to try, maybe between two buildings.

@TheMrPeteChannel 7 лет назад

Where can I buy this wonderful product!

@RimstarOrg 7 лет назад

Good idea! It would make a fun product wouldn't it!

@rayr1444 7 лет назад

Transmit your spoken voice, like the original Photophone. That would be more amazing to those unfamiliar with this effect, and was Bell's discovery and intention.

@RimstarOrg 7 лет назад

Hmmm... good point. I would have been great to have my voice travel on a sunbeam. I did, however, send it via laser in my follow-up experiments ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-yZ7PrWUVWP8.html.

@woopenne6851 9 лет назад

Hi RimstarOrg, I came upon your photophone video on RU-vid and is currently building it. However, I am using a 7.7V solar cell and built the crystal amplifier you created. However, the whole photophone doesn't work. What could been the problem? We are using a torchlight as the light source. Thanks and appreciate your reply soon.

@RimstarOrg 9 лет назад

+Woo Penne A 7.7V solar cell sounds like a solar panel with multiple solar cells. Is that what you have? If so, make sure your light covers all of the solar cells completely. If you don't then some of the solar cells will be fighting the others. Do you gets any variation in sound if you just wave the torchlight on and off the solar panel?

@woopenne6851 9 лет назад

+RimstarOrg Thanks! No, I will change to a 3 V solar cell and test it out soon. However, there is no output sound from the speaker embedded in the crystal amplifier you created while using the 7.7V solar cell. What could be the issue?

@RimstarOrg 9 лет назад

+Woo Penne You'll hear a sound only when there's a change in light on the solar panel. Steady light won't do anything. That's why I say to move your torchlight on and off it repeatedly. Try different volumes on the amplifier of course too. Also, make sure you have the solar panel wires hooked up correctly. If you're not sure then try the other way around.

@woopenne6851 9 лет назад

+RimstarOrg It is working however there is too much noise in the speaker and makes it inaudible. What can be done to reduce the noise

@woopenne6851 9 лет назад

+RimstarOrg It is working however there is too much noise in the speaker and makes it inaudible. What can be done to reduce the noise?

@Breslinmusic 8 лет назад

GENIUS :)

@sharetoyourfriends6817 3 года назад

Thnks

@juggernautsvaderdmunchkinland 9 лет назад

Wow!

@KowboyUSA 9 лет назад

Amazing 135 year old tech.

@accidentalengineering 9 лет назад

This is nice, but it would be more impressive to transmit light using sound waves :)

@hyperloopbeats 3 года назад

..or to transmit/recieve money using a microwave.

@leticia06408 2 года назад

@@hyperloopbeats lol, but talking about microwaves themselves, we kind of have digital bank

@hyperloopbeats 2 года назад

@@leticia06408 we also have microwaves

@lambda4931 6 лет назад

Very 👍

@kkece41 9 лет назад

good

@francoisbelangerboisclair 8 лет назад

If I stick a mirror to a window (with the glass vibrating due to noise inside) and shoot a laser to it. Would a solar cell get the modulation if the laser is reflected on it?

@RimstarOrg 8 лет назад

It should. I tried it but with a car window and the radio playing inside the car and it didn't work, but there could be a number of reasons why a car window would be a bad choice. It was my only option though.

@RimstarOrg 8 лет назад

@VideoVegetable 9 лет назад

Nice. Today we can use lasers with or without fiber optics to do the same.

@RimstarOrg 9 лет назад

VideoVegetable Yup, I just got it working with a laser this morning. It took me around 15 minutes. A video about it will take longer though since I have to play around with it and make something pretty. But it worked!

@mak4346 9 лет назад

instead of radio can we use microphone????

@teravolt1195 9 лет назад

There were no PV cells in the late 1800s i don't think, so how was the sunlight demodulated?

@RimstarOrg 9 лет назад

Tera Volt ***** Bell primarily used selenium, whose electrical resistance varies with the intensity of light. He used a lens to focus the incoming light onto it. However, surprisingly he also found that a lot of other materials would directly placed a sound when the concentrated varying sunlight hit it, including hard rubber. You had to put your ear close to it to hear it.

@cristianocostasilva8591 3 года назад

Top

@alexpdr92 2 года назад

wow

@InnovationBlast 9 лет назад

They had solar cells in Alexander Graham Bell's time?

@MisterTalkingMachine 9 лет назад

Blast As far as I know, Bell's Photophone used a photoresistor, since old drawings I've seen of it show a battery connected in series with the receiver and the earpiece. -As a matter of fact, it's said that Bell was so proud of this device, that he attempted to name his daughter 'Photophone' at some point, yet his wife stopped him.