Instructables
This is a neat project I picked up about a month ago. It's a simple project allowing you to transfer sound across a space on light with little quality loss. The credit of this project goes here
 
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Step 1: Gather Your Materials

Picture of Gather Your Materials
Things You Will Need:

Two Mono Jacks
1 Audio Transformer
1 Solar Resistor
1 Laser
1 Single AA Battery Clip (for reciever)
1 Triple AAA Battery Clip (for laser)
Batteries (1 AA, 3 AAA's)
Some wires and tape

A breadboard is optional, but I chose to use one to save time.

Step 6: Using the Circuit

Now that the transmitter is built, you can use it. Simply connect an audio source (such as a CD player) to the mono jack and turn on the laser. The modulations of current produced by the audio device causes the laser to modulate accordingly. It will get slightly dimmer and brighter, depending on the music. However, this is very difficult to detect by the human eye, and it isn't particularly useful. In order to make the circuit useful, we need build a reciever.
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frogjake94 years ago
I can't seem to find a solar resistor anywhere. Where can I get one?

if u cant find cds then find ldr . both are same

you can search for LDR(light dependent resistor)... i think....
where can i get AUDIO TRANSFORMER at home?what are the appliances using audio transformers?
RAYED3 years ago
HOW CAN I IDENTIFY AN AUDIO TRANSFORMER
I began this project a while ago (have yet to finish) and I found one at Radio Shack for around $2.70. The catalog number is 273-1380. Good Luck!
pratikreddy2 years ago
I tried this experiment. Everytime I tried, my laser is weakening and losing strength. Sound is not trasmitting. If I connect directly to speakers from Audio and battery it's working. I lost few lasers so far $15 energizer and couple of regular lasers. Can you please help?
kamathln4 years ago
Oh Boy! This reminds me of a funny happening. When in college, my classmate had done this very project at home. One early morning he brought it to the college's electronics lab to show off.

The electronics lab is soundproof, so we should not actually hear the morning prayer which is loudly sung using a loudspeaker. But on that day, we did hear it faintly! We guessed the door was not completely closed. Anyways, with respect for the prayer, we all stood up. After a while our ears were able to finally locate the sound and realize the door was closed after all. The prayers were coming from the reciever!

What actually happened completely stunned us! The college used a loudspeaker/amplifier which induced the signals strongly back into the lighting power supply. It was a cloudy day, and we had switched on the lights in the electronics lab. So we got the "signal" that was being "transmitted" by the speaker/amplifier !

ross33 kamathln3 years ago
thats pretty funny how clear was the sound?
ZenX3 years ago
instead of using a single laser, could this function with many LED's?
rejsps4 years ago
I built a laser pointer modulator many years ago using a power FET instead of a transformer.  I biased the gate using a voltage divider with one leg being a potentiometer.  The audio was coupled in through a capacitor (0.22 microF).  With no signal, the bias was set to have the laser partially on.   Then the audio modulation was in a fairly linear part of the laser diode's I-V characteristic.  The resulting audio is very high fidelity when picked up by a good photodiode.  FYI, the power FET came from Radio Shack, but they no longer carry it.
jules154 years ago
can u replace the audio trans. with something?
akinich4 years ago
hey nice instructable
is it possible to get the audio transfrmer out of any items then just buying
i kinda the recycling type
If I connect the transformer with the lower ohm side being the laser side, what differences would it make?
I am using a phototransitor and the receiver doesn't work. I don't know if it could be the laser. Is there any special laser that will work great with this project. On another topic: other than radioshack, is there any other good store to get my electrical components from even if it is a web store?
saites2001 (author)  Theinventor945 years ago
Without knowing more specific details about your problem, I would venture to guess that it's not the laser. Any general purpose laser should do. I find it more likely that you don't have something hooked up correctly. As far as an electronics store, online is probably your best bet. I like Jameco, but Digikey is also a good and popular supply company.
What laser did you use?
bing2you5 years ago
I, like ReCreate, would also like to know what model of transformer you are using. I'm a beginner, maybe it isn't very important, but I thought I'd ask anyway.
He is using a RadioShack Catalog No. 273-1380.
kyles895 years ago
you can use phono jack to, just do it the same way have both channels going to the same place, and then ground to ground still. id use the phono jack cause sometimes the mono ones do not get all of the such as in fat bottom girls by queen, also with the phono one you could technically have the sound go to different places at the same time, for a different experience.
ReCreate5 years ago
what kind of transformer is this? from how many volts to what?
Quick stupid question. I got the mono jacks, and I don't know how to wire them. Any help would be greatly appreciated. Thanks TAK
saites2001 (author)  aesopiankitty5 years ago
There should be only two leads on the jack. Connect a wire to each one of these leads. Next, add the mono jack to the breadboard according to the instructions and pictures above. Hope this helps.
i don't think my jacks have leads. did i screw up?
saites2001 (author)  aesopiankitty5 years ago
No. The jack should have a couple of places to solder wires to. In a sense, one of these is positive and one is negative. You'll be connecting these to one side of the transformer. It's been a while since I've done this project, but IIRC, it doesn't matter to which you connect each wire (of course, they can't be connected to the same lead). If you still are having problems, post a picture of the jack and we'll see if we can get this taken care of.
I think I see one lead. It's inside the jack, and when i shined a light into the jack, I saw it glimmer. Where do I put the other one?
saites2001 (author)  aesopiankitty5 years ago
I'm confused. You shouldn't have to shine a light into anything. Please post a picture so I can see what you're seeing.
hope this is helpful. where do i find the leads?
Photo 1.jpg
saites2001 (author)  aesopiankitty5 years ago
It looks like it has a covering on it. If I'm right, you'll have to remove that first. I was actually kind of expecting a picture from the side. Where did you get this jack? Did you buy it or harvest it?
I bought it from some store online. I'll look for the covering. What's it look like? Sorry about this and thanks for all your help.
saites2001 (author)  aesopiankitty5 years ago
On the jacks used in the project there is a sort of covering that screws over the jacks. The top of the jack is still exposed (to be inserted into a device), while the bottom (where the wires have been soldered on) are covered (to prevent electric shock). There is likely some sort of cover obstructing your view. There should be two distinct and obvious places on the jack itself to which you may attach wires (if it were a stereo jack, there would be three contact points). You don't have to apologize -- this is what Instructables was made for.
well after a long break i found them. thank you so much for all your help and one more question :P there are two leads: one in the center of the cavity of the bottom of the jack. and the others on the wall. which is positive and negative.
saites2001 (author)  aesopiankitty5 years ago
If I'm not wrong, it shouldn't make a difference. And if I am wrong, you can probably just reverse the wiring (as in no harm to the project). Sorry that I can't be more specific or directive than this.
believe me, after all that i'm more likely to kiss the ground you walk on than to be sad about specifics. i'll let you know how this turns out. thanks so much AK
wee_man5 years ago
for this what types of diaodes is it leds red one or proper lasers or could i substitute the leds or ir leds and with add a lot of them and have a range of like 1km or so would this would be possible gradly apprishate some info please.
what kind of laser you used for it? a laser diode? and can i ask for the circuit design please...thank you,
rrrmanion6 years ago
could you forget the receiver and use it to control stage/party lights? e.g. control 4 lights with a 4 channel (quadraphonic) sound system and add a dmx output?
saites2001 (author)  rrrmanion6 years ago
It sounds like it would work, but I'm not sure about the power requirements.
tdhelder6 years ago
Concerning the wireless Ethernet, rather then switching the laser on and off why not bias the laser on and then just bump the voltage to change the intensity. The lag should be greatly reduced then. Effectively AM.
saites2001 (author)  tdhelder6 years ago
Well, though that may or may not be true (to be honest, I'm not exactly sure), I still wouldn't try it. Interference would be to great, and electromagnet waves (radio waves in this case) also move at the speed of light (light is electromagnetic energy). Therefore, wireless communication via radio waves just makes more sense. Using a laser would not theoretically be any faster, and would be more prone to interference and other issues.
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