[Laser] 5 mw laser transceiver kit

[Chuck Hast]

On Mon, Sep 20, 2010 at 09:18, Tim Toast <toasty256 at yahoo.com> wrote:
> Hi All
>
> It's great to see someone has put a kit together. That is sure to
> spark some interest in optical coms. In the interest of a little
> fun competition, it would be nice to have a simple kit for laser
> com's too. One obvious advantage (or not so obvious) for laser
> over LED, is size and power consumption. A simple laser transceiver
> could be made very small and portable, even pocket-sized and
> battery powered. Under 90 ma. for most 5 mw diodes.
>
> It would help if everyone could start with the same size, easy to
> obtain, enclosure. One that comes to mind is the old "Tuna Tin 2"
> kits. You could actually use a tuna can (Tuna Tin THZ or
> Tetrazzini?) but someone suggested to me to use one of those
> "Altoids" candy tins. They have an easy access door and complete
> sheilding, plus plenty of room for a circuit board and batteries
> inside. These are the large 5" x 3" x 1" inch size boxes. They
> also come in a couple smaller sizes and even round ones, all with
> resealable metal lids or doors.
>
> I was looking at some amplifier circuits today and saw this high
> gain hearing-aid design that uses 3 transistors and one battery
> (1.5v). If you switch the microphone with a photo detector front
> end, you have a high-gain receiver plus part of the transmitter
> too. A laser transceiver could be made very small and energy
> efficient using a low voltage like 3 volts (2 cells). A 3, 6 or
> 9 volt design for the small light-weight battery sizes. With a
> dual 555 timer chip, you can have a simple high quality PWM AM
> for the laser and a tone generator for MCW or alignment. The
> goals being low cost, light wieght, easy to put together etc..
>
> Relatively cheap optics that work well:
> If you are willing to take apart some junk equipment you can find
> lots of optical goodies. The old VHS Camcorders can supply most of
> the optical parts. An old DVD player will get you a 5 milliwat red
> laser diode (these are often dual wavelength visible/IR diodes with
> three pins, or four pins if it has a monitor diode) and some small
> lenses to use. These even have one lens you can use to collimate
> the laser fairly well (the laser pickup "output" lens is a 5mm or
> 6mm f0.9 or faster type) or it can adapt the beam for use with a
> larger lens. The main large glass lens on the camcorder is usually
> a 25 to 50mm f1.0 type when used by itself. It can work for either
> transmitter or receiver. Some of the older ones have a fine
> adjustment twist focus.
> For short range use, it might be nice to be able to defocus the
> transmitter and receiver some - up to 10 degrees or more maybe -
> these twist focusing lenses would be great for that.
> Inside the camera zoom lens are a few smaller glass lenses in both
> positive and negative types plus a special "eyepeice" type assembly
> - similar to a 15 - 20mm Kellner telescope eyepiece. This could
> make a nice finder when paired with a larger objective lens and a
> cross-hair. The video viewfinder eyepiece is also adjustable and
> could be used for either one or a finder. It is usually a 20mm F1
> or F2 plano convex plastic lens.
> The performance won't be excellent obviously with these small
> lenses but should work for the shorter ranges ok. (under 50 miles
> or so?? :) you can always break out the big optics for better
> performance.
>
>
I wonder how easy it would be to add data to it so it could do anything
that can supply a digital stream, voice, images, you name it. It would
not have to be high speed, a 128Kb data stream would be a good start
even a 64kb data stream.
-- 

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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