WARNING: this project involves the use and modification of laser devices. While the lasers I suggest using (store-bought red pointers) are relatively safe to handle, NEVER LOOK DIRECTLY INTO A LASER BEAM, BEWARE OF REFLECTIONS, and be EXTREMELY CAREFUL when MODIFYING a laser product. Also, I am not liable for anything stupid you do.
Here is yet another thing to do with those promotional laser pointers: send music (or data) from point A to point B over the laser beam using amplitude modulation. All it takes is pointing the moded laser at a detector, and music can be heard from an attached amplifier. The range and quality (or data speed) can vary, but I have gotten a HALF MILE of range with excellent audio quality and around 300bps of throughput.
The image shown here is the transmitter and receiver working across my desk during a test.
TO SEE HOW TO USE TWO LASERS TO TRANSMIT TWO MUSIC CHANNELS AND MIX THEM WITH A PAIR OF SUNGLASSES, check out the blog post here.
A video of the system working can be found here: http://video.google.com/videoplay?docid=6895048767032879458&hl=en
Much inspiration for this project came from http://sci-toys.com/scitoys/scitoys/light/light.html#laser_communicator
Here is yet another thing to do with those promotional laser pointers: send music (or data) from point A to point B over the laser beam using amplitude modulation. All it takes is pointing the moded laser at a detector, and music can be heard from an attached amplifier. The range and quality (or data speed) can vary, but I have gotten a HALF MILE of range with excellent audio quality and around 300bps of throughput.
The image shown here is the transmitter and receiver working across my desk during a test.
TO SEE HOW TO USE TWO LASERS TO TRANSMIT TWO MUSIC CHANNELS AND MIX THEM WITH A PAIR OF SUNGLASSES, check out the blog post here.
A video of the system working can be found here: http://video.google.com/videoplay?docid=6895048767032879458&hl=en
Much inspiration for this project came from http://sci-toys.com/scitoys/scitoys/light/light.html#laser_communicator
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Signing UpStep 1: Gather Materials
To send music over a laser beam you will need the following parts, most of which can be gotten for less than 5 dollars at radioshack total (besides the pointer, which probably costs $15). If you are on a tight budget, try replacing the laser with a red LED and a 100ohm resistor attached in series.
for the transmitter:
a laser pointer
batteries (D-cell work best)
potentiometer (variable resistor) 50k ohm or less
audio source (iPod, cd player, mic preamp, PC line-out, etc.)
some wire (cat5 aka ethernet cabling works best)
toggle switch (a turbo switch from an old PC works well)
audio transformer (can be pulled from audio equipment)
1/8" audio jack (can be gotten from the end of a headphones cable)
for the reciever:
phototransitor (photodiodes or IR detectors also work)
1/8" audio jack
some more wire
high-gain amplifier (laptop with mic input, or mic preamp plus amplifier)
magnifying glass (helps at great distances)
tools:
wire cutter/stripper
soldering iron and electronics solder
tape (clear and/or electrical)
digital multimeter (can be useful... not realy required)
tripod (helps for aiming laser at a distance)
empty pizza boxes with white backs (for finding beam and for adjustments)
some assistants
for the transmitter:
a laser pointer
batteries (D-cell work best)
potentiometer (variable resistor) 50k ohm or less
audio source (iPod, cd player, mic preamp, PC line-out, etc.)
some wire (cat5 aka ethernet cabling works best)
toggle switch (a turbo switch from an old PC works well)
audio transformer (can be pulled from audio equipment)
1/8" audio jack (can be gotten from the end of a headphones cable)
for the reciever:
phototransitor (photodiodes or IR detectors also work)
1/8" audio jack
some more wire
high-gain amplifier (laptop with mic input, or mic preamp plus amplifier)
magnifying glass (helps at great distances)
tools:
wire cutter/stripper
soldering iron and electronics solder
tape (clear and/or electrical)
digital multimeter (can be useful... not realy required)
tripod (helps for aiming laser at a distance)
empty pizza boxes with white backs (for finding beam and for adjustments)
some assistants
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This one featured at the link here will probably work:
http://www.mouser.com/ProductDetail/Xicon/42TU120-RC/?qs=sGAEpiMZZMv0IfuNuy2LUU2nVj3GMLUawQykJuAOLGA%3d
And Link OR a Site to buy a suitable Audio Transformer???
Hope quickly response as soon as possible....
I've got the laser wired up to the batteries and that turns on. If I test for sound now (even though no sound is hooked up) I'll hear a click noise every time I turnt the laser on and off.
Now when I wire everything up with the transformer all I can get to come out is the click. No other audio.
For the reciever I'm using a .5v 6watt solar cell.
If anyone could help I'd be thankful. I can also upload pictures of the project if that would help.
Another way to think about it is that the the photo cell is 8 W but your laser is in the milliwatts so it's your laser is way less than one watt to the signal from the laser is going to be very weak in comparison to the total signal from the photocell
Sorry if this comment doesn't make any sense I'm typing it with Siri
I'm really thinking that my problem is the wiring on the audio transformer.
Cheers,
Chris
Are you using a mic input on the receiver side? A solar cell is self-powered, so it may not work well in a PC mic jack, which is expecting a varying resistance. Honestly I just don't know -- ive never tried it.
What you can do is, build or use a preamp after the solar cell but before the main amp. Be sure to use the "line in" jack on the main amp, not a mic jack.
If you want more help, I suggest you draw a schematic of your setup, and/or use pictures.
Again thanks for your help.
This is mainly because laser diodes only conduct electricity in one direction - that is, they work with Direct Current (DC). However, (most) audio outputs have alternating directions of current (AC). So when you hook up a laser diode to the audio output, you only get half of the waveform.
Furthermore, laser diodes have a minimum voltage required to turn them on. So you will actually get less than half of your waveform if you attach the laser diode directly to the output.
That is why there is a battery pack involved: the batteries provide the direct current bias needed to keep the laser on. The audio output (via the transformer) subtly changes the strength of that direct current, and is therefore manifest in the laser's output brightness.
Hope that helps.
Long answer: if you knew exactly what resistance(s) to use, you could substitute the potentiometer(s) for fixed resistor(s). However, these resistances depend on your laser pointer and the voltage of your battery pack, so it is really convenient to use the pots. (They are inexpensive too.... and useful in other projects, so I'd recommend buying/salvaging some.)
Also, I realize now I didn't address your second queston "can you use a photocell instead of a phototransistor". I assume you mean either a Cadmium-Sulfide passive cell or an active solar panel (generates electricity from light). The issue with the photo-cells are that they (typically) have a slower responce-times as compaired to a phototransistor or photodiode. The result is that a photo-cell-based circuit does not pick up on the higher frequencies as well, if at all. It might sound like music through a wall (only bass).
But, you can always try origional designs! Do let me know how you get along with this!
Chris