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Author Topic: Data transmission with a modulated LASER  (Read 2835 times)
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Hi everyone,
For a project at uni i've been given the task of transmitting information through space using a modulated laser. I think an Arduino would be a great tool for the project and was wondering if anyone had any advice as i'm a complete beginner. My thinking so far is that i'd convert a file into a binary string of 1s and 0s (not too sure on the details of how to do that yet) and then using the Arduino, modulate the laser on and off accordingly. Then have a photodiode as a receiver to re-create the binary string which can then be used to convert the file back to its original format. If anyone has any info or advice it'd be really really appreciated.

Thanks in advance

Paul
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stuff to look at

http://sci-toys.com/scitoys/scitoys/light/light.html

http://www.scitoyscatalog.com/mm5/merchant.mvc?Screen=PROD&Store_Code=SC&Product_Code=LASERVOICEKIT&Category_Code=L

http://www.ramseyelectronics.com/downloads/catalog/201201w-21.pdf

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Thanks for the reply.
I've come across a few ways of using a laser to transmit an audio signal, i was just wondering if it was possible to transmit something more complex like a computer image or any type of file in general. As far as i know a file is essentially composed of a binary string of 1s and 0s that could be used to modulate the laser and read by a receiver. Would an Arduino have the ability to do this?

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Lots of hits on google for 'arduino laser communication'.  In theory it's not too hard to send digital data of any sort over a laser-photodiode link.  In practice, there are lots of interesting variables you'll have to tame: noise, precision alignment, and slow photodiodes to name a few.

To send a file you might look into SD card support.  Do not expect to achieve megabit per second speeds; you'll be doing well to get into the kilobit per second range with reliability using off the shelf parts.

You might want to start by building a little test rig to send and receive data over a short distance and work it up from there.

Here are some guys who take this stuff to the limit for fun: http://www.modulatedlight.org


-br
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You can use a laser in lieu of an IR LED and perform remote control protocols quite a distance. This worked for me at ~40 feet with no trouble. I couldn't go any farther because my house isn't that big smiley-wink. For a general purpose communication you can use serial. You just need your laser on the TX line (powered via transistor, etc.) and a phototransistor on the RX line on the other side.

If you do buy a laser look for one that can be focused. When you're testing it's problematic getting that little red dot aimed properly and it's nice to be able to widen it.
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There are many different wireless optical technologies, including ones that use lasers.  If your project allows it, you could simply borrow from some of the already proven technologies.  IIRC, there are digital and analog solutions.  I worked for a budding technology startup years ago, before the big .com bust.  Our major focus was finding ways to provide very high speed data connections in existing construction areas (dense urban, etc) without the expense and trouble of tearing up streets or tunneling under things.  Optical wireless was something we spent a lot of time on... but it's been about 14-15 years so my memory is a bit fuzzy smiley-wink
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i was just wondering if it was possible to transmit something more complex like a computer image or any type of file in general.
File yes,
Image no. - Not because of any difficulty with the laser but the arduino is too limited in memory and slow to transfer an image in a decent amount of time.

Do not use on / off to modulate the laser for binary 0 and 1, use Manchester encoding.
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Or use what ever they use in the fiber optics cables. Seems to work well there.
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Or use what ever they use in the fiber optics cables. Seems to work well there.
You might not have noticed that fibre optics is not air.
There is no alignment problem and no light interference.
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You might not have noticed that fibre optics is not air.
There is no alignment problem and no light interference.

Is that better or worse? Line of sight does not have bends and twist like cables, and clean air may have better optical clarity than the tranamission material used in the fiber cables.
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bends and twists are nothing compared to an uncontrolled environment like open air. 
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It is much worse in free air. Bends are not noticed in an optic cable, it is a closed environment. It is always aligned. You can get away with simple on / off modulation in a cable.
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http://blog.makezine.com/2008/08/13/laser-modem-with-an-ardui/
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bends and twists are nothing compared to an uncontrolled environment like open air. 

It is much worse in free air. Bends are not noticed in an optic cable, it is a closed environment. It is always aligned. You can get away with simple on / off modulation in a cable.

i didn't say anything about better or worse transmission or transmission materials, I was refering to the tramsmission methodology. 
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clean air may have better optical clarity than the tranamission material used in the fiber cables.
i didn't say anything about better or worse transmission or transmission materials
It seems like you did... either way, the two aren't very comparable.  purpose-built fiber and open air are worlds apart.  It's still doable, though.
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