[Laser] stable audio oscillator?
David D. Rea
[email protected]
Thu, 10 Apr 2003 19:08:40 -0400
If you only need a few hundred Hz, you could use a microcontroller with
a crystal oscillator. You could just program it to clock an I/O pin on
and off every [insert desired number here] machine cycles.
If you're using a pen pointer, you can then just use a NPN transistor to
pull down the input rail of the pointer, providing MCW at whatever rate
you want.
If you wanted to get real spiffy, you could hook a keyboard and display
up to the microcontroller, and have it do everything for ya!
Dave Rea
RIT
Rochester, NY
On Thu, 2003-04-10 at 18:38, Andrew T. Flowers, K0SM wrote:
> I'm not really sure whom to ask about this, but I'm guessing that
> someone has run into a similar problem at one time or another...
>
> I'm building a laser communication system and I'm looking at different
> modulation schemes for the transmitter. I'd like to try QRSS CW--that's
> CW in 0.5wpm or even less, using DSP to show the elements on the screen
> using spectran or other analysis program. I thought about keying the
> laser on and off into a 12vdc fan to create a squarewave tone. It works
> fine for normal speed CW, but the frequency drift is +/- 10Hz or so.
> For QRSS to be effective, I need rock-solid stability, preferably less
> than 100 millihertz/min or better. Any ideas here? I'd like to keep it
> cheap. Is there some version of the 555 timer do this with good
> components? I was also thinking of getting some ovenized xtal thing in
> the low RF range and then dividing down.
>
> Ideas??
>
> Andy, K0SM
>
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