[Laser] 5mw laser tranceiver kit

[Chuck Hast]

On Tue, Sep 28, 2010 at 23:56, Mike <mikecouture at bellsouth.net> wrote:
> Group,
>
> Check out this page as another example of things we might want to
> incorporate into the subject kit:
> http://www.modulatedlight.org/optical_comms/using_laser_pointers.html
>
> Lots of good ideas. They even use one of those cheap pointers modulated with
> 40kc etc....
>
Back before I lost my job (and my free time) I was doing some work
on digital optical links. I had come by some 250mw DVD write lasers,
the neat thing about them was that you could run them at low power
and not have to worry about blasting them into permanent LED status.

I started out trying to figure out how to modulate the things, I ended
up driving them with the 74hc05 open collector hex inverter. I was
switching the laser with no issues at 10mhz (that was as high as my
source went) the modulating wave form I have a optical power meter
and was able to set the max current through the diode such that I did
not go above 5mw. (not much for that diode, I have yet to loose one
due to over current, as these will handle a whole lot more) I got the
laser and driver part done and got no further, but I realised that once
I had tested the 74hc05 out, that it would be easy to modulate this
thing with wave form that could drive the 74hc05.

Note of caution and responsibility, do NOT succumb to the urge to
run these things at full power over open space, or even in a room,
they can burn holes in stuff (I use one to remove warts) there is a
reason they use them in DVD >>BURNERS<<, to put little holes in
the media. But they can put little holes in your eye balls too!!

As long as you limit the power out these lasers should last forever,
and you will not have to worry about over currenting one. They can
be found in any old DVD burner, and generally they are still in good
shape as it is usually something else that has died in the thing.

Same thing goes for the CD writing laser, only it is worse as you can
NOT see it so, you will not see a flash or there will not be bright spots
on the walls to remind you that you are working with a real working
but invisible laser. Also when working with these things get your self
a set of goggles I have found green or blue ones that do a good job
of knocking the optical power down but were designed for other things
to generally work just fine at the normal powers we are running at. If
you are working with the high power diode and decide to run the power
up IN YOUR LAB be sure you have real and proper laser goggles a
burn is forever.

For another part of the spectrum the Blue Ray diodes can let you
play with light at +/-405nm. Same thing goes here as far as safety.
Again they have been out on the market long enough that you can
find bad ones at the local computer repair emporiums.


Most computer repair shops have a stack of old DVD writers and in
many cases are happy to have someone haul them off, otherwise
they probably have to pay to get rid of them, and have to take them
to the recycling depot for such items.
-- 

Chuck Hast  -- KP4DJT --
When the righteous are in authority, the people rejoice: but when the
wicked beareth rule the people mourn.  Prov 29:2 KJV
---
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