[Laser] more strobelight stuff

Tue Feb 8 05:25:29 EST 2005

Hello anyone doing Laser stuff coupled with WLAN 802.11b,g?

Berns
University of the Philippines

----- Original Message ----- 
From: "Tim Toast" <toasty256 at yahoo.com>
To: "laser mailinglist" <laser at mailman.qth.net>
Sent: Sunday, February 06, 2005 6:37 PM
Subject: [Laser] more strobelight stuff

> Here is some more info about this and keep in 
> mind this is just in the planning stages and 
> evolving a bit. I made a block diagram today 
> of some possible systems: 
> http://aladal.net/toast/xbpsk.gif
> 
> I'm tending to go with the idea of using the 
> audio output from the computer software now 
> instead of trying to generate part of the psk 
> signal.
> 
> In the case of BPSK, it needs to be demodulated 
> partially first in order to get the raw digital 
> "control waveform", unless it's already available 
> from the software. Then that is used to drive a 
> one-shot multivibrator that has a suitable width 
> output pulse. The output of the one-shot is used 
> to drive the strobe trigger circuit which will 
> in turn make the high voltage pulses to trigger 
> the strobe. 
> 
> Some problems with this:
> I'm not clear right off hand how to demodulate a 
> PSK signal partially or whether the one-shot needs 
> to produce a pulse on both low-high and high-low 
> transitions. Also i was thinking with a "baseband" 
> psk31 signal, the output of the one-shot will be 
> 31.25~Hz? If thats true then the strobe is only 
> going to fire at that rate... and that would 
> probably be a problem on the receive end when 
> trying to use it with existing PSK software. But 
> maybe it can be driven somehow from a higher 
> frequency carrier in the 80-90 Hz range or above 
> the 120 Hz buzz ..but not too far above. 
> loose edges. Any thoughts on this?
> 
> On the other hand, using the LaserScatter audio 
> seems a bit easier. You would only need to "limit" 
> the signal to square it up and condition it for 
> the one-shot (if it's a sinewave). The one-shot 
> triggers on one of the transitions - low-high or 
> high-low of the input. As long as the input 
> frequency remains the same, the trigger pulses 
> will be created at that rate. Then when the 
> frequency changes to the next character, the 
> trigger pulses follow along in step at the new 
> rate. And if this is all in the range of 10-30 Hz 
> or so, then no problems for firing the strobe at 
> those rates. 
> This seems like it should work and i'm leaning 
> towards it for now although i'd like to get the 
> psk kinks worked out as well somehow. 
> Any feedback is appreciated.
> 
> 
> =====
> Tim Toast
> http://www.aladal.net/toast/
> 
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