25 thoughts on “RS-232 Serial Laser Link

  1. I’m saying this as nicely as possible, but wasn’t it obvious this would happen when linking to a geocities site?

    PS love the site, been reading a long time (but i think this is my first comment)

  2. Back in the late ’90s I built a laser link based on a design by a guy in Melbourne (Derek Weston’s UPN-LT, you can still find it with google). Roughly similar, except that it used IrDA protocols (and modulator/demodulator chip) instead of running async serial directly over the optical link. I gather they had a small city network going there for a while using these transceivers. Unfortunately the big difficulty in laser comms is aiming, not modulation. There are more things than you think that can put your link out of alignment. You really need some sort of self-adjusting optics to do this for any length of time.

  3. This guy has a simple analog laser pointer setup:
    I’ve built it and it transmits sound quite well. It could also make for a good start for data transmission. For higher data rates, I think a photodiode might be a good idea.
    I’ve found places (can’t find the link right now, sorry) that sell laser diodes with collimating lenses for under $3 each, although all you get is the diode, the lens, a small thermalsink that the laser’s mounted on, and a resistor soldered onto the laser leg. But they make for a cheap laser spotlight, when you get about 20 of them and drill a bunch of matching holes in a bit of metal for them to all press into.

  4. This is cool. We made something like this for our TI-85’s using a laser LED back in the day so that we could transfer programs without linking with a cable. One of the other students tried to turn us in for cheating but the professor was so impressed that he said that if we could come up with something like that we knew enough to pass his exams anyway so he let it go.(it was an electronics class.)
    Keep up the great work

  5. Oh! Forgot to mention it. Try bouncing it off your sister’s(or whoever’s window) when she’s on the phone to her boyfriend with no modulation input and just output it straight to an audio amp. Oh wait, no don’t do that its illegal. :p


    By the way, we used a cheap set of mini binoculars with our sensor at the focal point mounted in our xciever box, we just cut the binoculars in half to make two trancievers.

  6. Hah. Both the hex shmitt trigger ic, and the rs232 driver arrived today. And guess what: The rs232 ic was shipped from Germany in a envelope, pretty banged up.
    But the shmitt trigger arrived from texas, usa, by priority air mail, in a big arse box! Wonder who lost the most to satisfy a non-paying customer…

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