Instructables

Send Music over a Laser Beam

Step 1: Gather Materials

Picture of 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
 
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lazer1554 years ago
 Is the potentiometer absolutely necessary?  I dont have one on hand so I want to know if I can use just a resistor.  Can I use one of those photocells instead of the phototransistor?
navaburo (author)  lazer1554 years ago
Short answer: YES.

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.)
 What is the potentiometer for?  I got it working without a pot or a resistor.  Does the pot filter out static and background noise?
navaburo (author)  lazer1554 years ago
Lasers often have a non-linear response. That is, their brightness depends on the power-supply voltage in a complicated way. The potentiometer(s) along with a control of the input audio amplitude (mp3 player volume) allow you to select which section of the psv-brightness curve to use. So, you should be able to select a linear portion, and get great audio quality. Using a non-linear portion will result in nasty sounding distortion.

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
chewie50005 years ago
what phototransister did you use (some have 2 contacts some have 3) and how was it connected to the mono jack
this is awesome... but i already spent like a buch on a dock sadly... is there anyway to get this to work with a guitar? i don't like cables... and i have a 1/4 to 1/8 inch cable transitor thingy.. it takes those huge things into little small things like the headphones of an ipod... that would be awesome if there was someway to do this with a guitar with the same quality as a cord...
You'd need to be still, though to use it. Radio waves would be better.
navaburo (author)  i r teh panda7 years ago
sure, you can use a guitar. I would suggest either using a guitar with a battery (active) or going through an effects petal first. tell he how it works.
gesiwuj7 years ago
The only Audio Transformer I can seem to find is a 1200Ω step down to 32Ω, will that suffice? If not, where can I find one cheaply on the internet (sent off from the UK, no US imports :p)?
navaburo (author)  gesiwuj7 years ago
just about any transformer will work actually, you will just have to play with volumes.
what kind of equipment has audio transformers I can take from ;ie cd players,speakers, stereo receivers??
gesiwuj cronzer6 years ago
I found mine on an old electronics kit, but that was just lucky. Try finding an AM radio or something on Freecycle.
cronzer gesiwuj6 years ago
ohh, ok thanks oh and does this work with green lasers??
gesiwuj cronzer6 years ago
Not sure... I've just got a red laser. I'm not an expert but I don't think it'll make a difference. It's measuring the variance in intensity of the light at the receiving end, not the wavelength. Why not try it :p
girrrrrrr27 years ago
what case is that on your Irectangluar object( formarlly known as ipod)
Ian018 years ago
You will also need a telescope.
navaburo (author)  Ian017 years ago
if a tripod is used to aim, retroreflectors (like those on bike tires) can be used to aid in targeting with out a telescope.